Online Webinar: Recent advances in sorption analysis of biomaterials

Hello everyone and thank you for joining us for today's Surface Measurement Systems webinar where we are very lucky to be joined by Tian tian Yin from McGill University to share some of their recent research with us. The topic of today's webinar is Recent Advances in Sorption Analysis of Biomaterials. We will be having two speakers today and as always there will be a live Q and A after each presentation where the audience will have an opportunity to place their queries and questions to the speaker directly, whether about something concerning the topic discussed in the presentation or on a wider implication of the subject discussed that the speaker may be able to assist on. To take part in this live Q and A is very simple. Simply submit your written questions at any time in the Questions tab on the webinar panel and then during the Q and A session at the end of the presentation I will ask the question myself. Our first talk today is from Tian Tian Yin of McGill University who has very kindly offered to take some time out of her schedule to be with us today to share the their research. The title of this topic is Characterization of Sodium and Calcium Addition on Immediate Aqueous Interactions of Binary Borate Glasses by Dynamic Vapor Sorption within Situ Raman. So without further ado, I would like to invite Tian Tian to begin their presentation.

Thanks a lot for your introduction. Good morning everyone. I'm Tian Tian from McGill University, Canada. I am supervised by Professor Najat and Professor Waters. I just passed my thesis defense last Tuesday. Today I would like to present one chapter of my thesis that is the characterization of sodium and calcium addition on the immediate aqueous interaction of binary Borate glasses by Dynamic Wave Absorption with in situ Raman. For today's presentation to begin with, the background of the project will be introduced followed by the project objectives. Then the methodology and results will be discussed. Finally, the main funding of this project will be summarized. Now let's move to the background of this project. Glasses are in the subfamily of the ceramic and are characterized by their amorphous nature. Means they lack crystallinity that is Long ranging periodic arrangement. Glass also show a range of glass transition behavior such as glass transition temperature. Glass transition temperature is the temperature above which solid glass begin to behave as a viscoelastic one. It can be used to indicate the bound strength and network connectivity of the glasses. Glasses are often made of oxide including network format and network modifier. The network modifier is the oxide that forms the highly cross linked network of chemical bonds. The network modifier are the oxides that disrupt disrupt the network connectivity and influence the final properties of the glasses. The structure of the glasses is also represented by the number of the bridging oxygens and non bridging oxygens. Bridging oxygens are the oxygens that link the network polyhydro. The non bridging oxygens are those oxygens that don't link to the network. Polyhedral Bioactive Glass Bioactive glass are the glasses with the ability to form hydroxycarbonate peptide in physiological solution to bond with hard and soft tissue to release ion to stimulate tissue regeneration. They have long been applied in the mineral tissue regeneration such as bone and teeth and recently they have demonstrated great promise in soft tissue repair such as for wound healing. Bioactive silicate glasses are the most common bioactive glasses. Two kinds of silicate glasses have been in clinical use. However Boris glasses silicate glasses have slow dissolution rate and incomplete conversion to hydroxy carbonate aldehyde which limits their wider application. Due to the structure difference, the boiled glasses have lower chemical durability and higher dissolution and bioactivity than the silicate glasses. Therefore, boiled glasses have a greater advantage in the mineral tissue regeneration and in the wound healing. When bullet glasses has obtained FDA clearance as a wound dressing, the properties of Borit glasses are much dependent on their structure so the structural feature of boreht glasses will be revealed. First as shown in this slide boreality glasses has have five basic structure units. B4 is the unit with Tetrahydroboro and four bridging oxygen B3 B1, B2, B1 B0 are the unit with Trigonoboro and 3210 brilliant oxygens. Four is the molecular fraction of B4 unit. It is an important parameter to reflect the structural feature of Boris glasses indicating their network connectivity. From the literature we can see the initial modifier addition and for increase with the increasing modifier content due to the conversion of B3 unit to B4 unit. Then after N4 reaches the maximum with further modifier addition, N4 decrease with further modifier addition because the B4 unit convert to other borate units such as B2 and B1. N4 is affected not only by the modifier content but also by the modifier types. We can say at the low modifier content N4 of sodium borate is higher than that of calcium borate. N4 also impacts the properties of borate glasses. For example, for sodium borage glasses with the initial modifier addition an increase in N4 leads to an increase in their glass transition temperature. Then with further modifier addition a decrease in N4 results in a decrease in their glass transition temperature. Furthermore, n 4 also impacts the dissolution behavior of boried glasses. For example, for the lisse and borate glasses, as M4 increase with increasing modifier content, there is a decrease in their dissolution rate. Understanding the dissolution behavior of glasses is essential in tailoring their properties to a specific biomedical application since the dissolution of glasses including hydration and hydrolysis reaction serves as the first reaction stage leading to the appetite formation in the physiological solution. Moreover, the ability to dissolve and release ion is crucial for their use in the soft tissue repair such as wound healing and is also critical to evaluate the solubility of glasses. Therefore, it is important to understand the glass dissolution mechanism and to study the effect of modified addition on their aqueous reactivity and reactions. Therefore, our fourth objective is to study the sodium and calcium addition on their structure as well as mechanism and reactivities of aqueous interactions of Boris glasses. Calcium and sodium are the crucial and typical network modifier for the glasses. Understanding the component, structure and property relationship is essential in tailoring borate glasses for desired properties. Therefore, binary calcium borate and sodium borate formulations have been selected in this study. Additionally, the reactivity of the glasses with water has been determined by measuring the weight change or ion release or or long term submersion of glasses in the DI water. This method is time consuming and the results are and the results are not transferable since this method is complex to keep consistent. Moreover, by using this traditional method, the initial reaction between glass and water may be too rapid to detect and the weight loss of glasses in the water make it difficult to characterize any immediate structure change. To understand the reaction between glass and water. DVS is the dynamic vapor sorption that is a technique can measure the vapor sorption of a material under controlled relative humidity. Traditional vapor sorption method is commonly used in the pharmaceutical and food science field. We believe the dynamic wafer suction can be used to simulate the glass reaction in the water, avoiding the weight loss. DVS has been applied to study the reactivity of the bioactive and soluble phosphate glasses where their vaporsorption rates has been correlated linearly with their dissolution rate in the DI water. As for the Boris glasses, due to the potential correlation between dissolution and vapor soption, DVS potentially can be developed as a more convenient and accurate method to evaluate the reactivity of the borate glasses. Moreover, in situ Raman coupled with the DVS can monitor the real time structure of glasses on the vapor environment. Avoiding the structure change causes the bio drying process compared to the FTIR and XRD analysis that can only be used to analyze the structure of the glasses post expansion to aqueous environment and drying. Therefore, our second objective is to explore the correlation of reaction and reactivities of boiled glasses with vapor and the water in order to validate the device within city Raman as a technique to evaluate aqueous interactions of borate gases. Here is the methodology for our project. First of all, the binary calcium borate and sodium borate formulation was fabricate were made by the MALE quenching method. Their glass transition temperature was analyzed by the dsc. Their borrow coordination and structure prey and post exposure to aqueous environment was analyzed by xrd, FTIR and in situ Raman. Their dissolution and release behavior was studied by immersing the glass glasses in the DI water and analyzed by SAT. Their weight change on the vapor was determined by DVS. These are estimate compositions 1Ca30 and 1 Sodium Borate Sodium 30 were produced by MALE quenching method. The precise final composition was determined by icp. The difference between initial formulation and the final composition is attributed to the evaporation of boro. At a high boro concentration when the temperature is above 1200 degrees centigrade we can say both calcium 30 and sodium 30 have same initial modifier content, similar final modifier content and similar particle size. XRD and FTL analysis were used to study the structure of Ca30 and Sodium30. The XRD diffractions indicates their morphos glass nature in the FTLR spectrum. The relative intensity for the B4 unit of calcium 30 is lower than that of sodium 30, indicating the lower N4 of the Ca30 which is also in line with the previous study. Furthermore, the thermal analysis shows calcium 30 has a higher glass transition temperature than the sodium 30. Although the calcium 30 has lower N4 than the sodium 30. It indicates the replacement of sodium by calcium ion reduces the network mobility because the divergent feature of calcium ions results in the tighter bonds and strong stronger network linkage of Boris glasses. This slide shows the vapor sorption and ion release behavior of Casium 30 and Sodium 30. DVS was used to measure the weight change of the sample when exposed to vapor at 90% relative humidity for 24 hours followed by the desorption at 0% relative humidity for another 24 hours. In the left figure, the left Y axis is for the weight change of calcium 30 and empty sample pan while the red y axis is for weight change of sodium 30. We can say at 90% relative humidity calcium 30 only shows transitory and very small weight change which can be attributed to the vapor adsorption on the sample surface and sample pump. While sodium 30 has a rapid weight increase under 90% relative humidity even after sufficient desorption at the 0% relative humidity there is a 32% weight increase remaining in the sodium 30 from the red figure that's for the glass dissolution. The ICP measurements reveal the release calcium sodium borough concentration in the DI water over various times. Calcium 30 shows less ion release than the sodium 30. This table summarizes the wage increase of calcium 30 and sodium 30 after vaporsorption desorption as well as their weight change after dissolving the water. The weight loss of the glass in the DI water was calculated by the converting the ion concentration in the DI water measured by the ICP. It is found the calcium 30 showed less vapor sorption and ion release comparing to the sodium 30, although the CA 30 has lower than sodium 30. Moreover, it can be found that the more vapor sorption weight change corresponds to the more weight loss in the water indicating the faster vapor reaction corresponds to faster water reaction. This demonstrated the correlation between vapor sorption and dissolution reaction rates. For Casim 30 there is almost no weight change at 90% relative humidity so it is not surprised to find from ECL, RAM, FTL and XRD there is no structure change for Casium 30 post espancial to vapor. Furthermore from FTI and XRD there is also no structure change for calcium 30 post expansion to water well for sodium 30 it has much more weight change after its functional to vapor and from in situ Raman and FTL analysis there is new phase formation after expansion to vapor for two hours and this new phase was identified to be crystal by xrd. We can also say the same crystallization also occurred when immersed in water for 30 minutes. We can see calcium 30 has no structure change for both pulse expansion to water or vapor while sodium 30 forms the same crystal when exposed to water and vapor. The same crystal formation post expansion to water and vapor for the both glasses demonstrate the correlation between the reaction in the water and the reaction in the vapor. This means aqueous reaction in the water and in the vapor appear to occur by the similar mechanism. Actually the glasses reacting with vapor is the glasses reacting with the water from vapor liquidation. Therefore the glasses undergo the same aqueous reaction when immersed in the water and exposed to vapor. Therefore the glass states with rapid vapor reaction rates should have rapid ion release and dissolution rates such as sodium 30. Otherwise if vapor can't induce glass reaction. It is expected that their dissolving the water should be very slow due to the slow water induced reaction such as calcium 30. Therefore, DVs can be used to evaluate the reactivity of Boris glasses with water, that is to predict how difficult the boric glasses is to initiate the reaction in the water and how rapid the water reaction is. However, there is a difference between the dissolution and the vapor solption. For example, for the sodium 30 pulse is spatial to vapor for 30 minutes. There is only small change in the FT and XRD spectrum indicating the sodium 30 only begin to form crystal. However, there is more new crystal formation when dissolving in the water for 30 minutes. This indicates the glass have more rapid reaction with water than with vapor. This is because there is weight loss and ion release when immersing in the water. This ion release and weight loss of glasses in the water decrease the diffusion distance between glass and water. Glass reaction in the water has a smaller diffusion distance and larger contact area and no liquidation time like a vapor induced reaction. This results resulting in a faster dissolution rate than the vapor sorption reaction rate. Therefore, based on the experimental result we conclude concisely that although calcium 30 has lower N4 than the sodium 30, calcium 30 has a lower dissolution ion release and the vapor sorption rates and the higher glass transition temperature than the Sodium 30. Secondly, Casium 30 has no new phase 4 formation poses partial to vapor and water while Sodium 30 shows crystallization positively sponge to vapor and water. Thirdly, based on the structure change and reaction rate of vapor and water induced reaction, the correlation between vapor sorption and dissolution was demonstrated which validates DVS and in situ Raman as more sensitive tools to characterize aqueous reactivity and the reactions of Boris glasses. Finally, I would like to thank my supervisor, Professor Najad and Professor Waters as well as my group members and collaborators for their contribution to this work and to acknowledge this study was supported by the Canada Natural Science and Engineering Research Council, Canada foundation for the Innovation, as well as McGill Faculty of Engineering for supporting me through the McGill Engineering Doctor Award. That's all. Thank you for your attention. And this is my email address. Please fill. Feel free to contact me if you have any questions.

Thank you so much Tiantian. That was a great presentation. Very in depth. Yes. So now we have an opportunity for our audience to submit any questions they may have for Tiantian based on the presentation they just heard. You can submit these in the questions tab. We have one here just to get us started and they ask could you Use DVS as a way to screen bioglasses faster. Hello? Tiantian, can you hear us?

Hi. Hi. Yes, that's the question.

Yes.

Yes. Could you use dynamic vapor absorption as a way to screen bioglasses faster?

Yes. Yes. Our project is to build the correlation between the vapor sorption and and vapor subtraction and dissolution behavior of glasses and in order to develop DVS as a more convenient and sensitive method to characterize the aqueous interaction of the glasses. And we found that there is a correlation between the wafersorption and the dissolution behavior of glasses based on their structure change and also reaction rates. And so we think DVS can be characterized the reactivity of the bioactive glasses. Yeah. As a valid method.

Great, thank you. And we have another question here. And they ask what impact would the higher water uptake and reactivity have on the performance of the Sodium 30 bioglass glass compared to a CA30 sample?

Sorry, can you repeat your question? Hello. Hi, can you repeat the question?

Sorry, I had a microphone on mute. That's my mistake. Apologies. Tiantian. Yes, the question is what impacts would the higher water uptake and reactivity have on the performance of the Sodium 30 bioglass compared to the Calcium 30 sample?

Yes. And there is a water and vapor induced crystallization in the sodium 30 and that's very different from the calcium 30 that is without any structure change post exponential to water and vapor. And due to there is a crystallization of Sodium 30. So Sodium 30 has. Is more. React. More reactive, more active than the calcium 30 when reacting with the water and with the vapor. And also this is the one part today I only show the one publication actually we have another paper that is. That will be soon in price that about to apply us to characterize a range of the sodium borate glasses. And in that work we can say this the water and the vapor induced crystallization will have impact on their dissolution behavior. Yeah.

Thank you. It looks like that's all the questions we have for now. Tian Tian. So once again thank you so much for being here with us today to share your the results and findings from your thesis. It's really appreciated and just a big thank you from everyone for myself and the audience.

It's my pleasure. Thanks a lot.

Thank you. So we will move on to the second presentation of the day. This is being delivered by Dr. Dan Burnett, the Vice President of Surface Measurement Systems North America. And Dan is here to speak with us about the importance of surface energy and wettability in biomaterials. Again there will be a live Q and A at the end of this session. So if you have any questions for Dan at the end of the session, please do submit these in the Questions tab. So without further ado, I will now hand over to Dr. Burnett.

All right, thanks, John. I'm going to share my screen. Hopefully this will everybody can see the presentation. Yeah. So thanks again for the presentation. I'm going to take a little bit of a step back and just do kind of a general application base. So it's going to just highlight some recent applications and or uses for both DVS and IGC for looking at different properties of biomaterials, in particular the surface energy and the wettability. So this will be a little bit of an overview. I won't get very in depth to the different applications, but just give a sampling of what can be done. And as I like to start a lot of my presentations, many if you've seen any webinar I've given previously, I often start with this to kind of lay the groundwork of how surface measurement systems products are typically used and how we can characterize materials. In particular, we play in the space of where we use a molecule as a probe molecule. So as opposed to using heat response or energy or optical or X ray response of a material, we study material properties by using absorption techniques. So we use how a molecule, like the previous presentation in dvs, how a water molecule may interact with the material. We can use a range of different molecules. And how these molecules will interact with the material can tell us about, you know, how they adsorb, which is just looking at the surface, how they absorb, which they get into the bulk. Or even as the previous presentation, how these may induce some sort of chemical or structural change, whether it be crystallization, phase change, swelling, glass transitions, all sorts of things. So we're going to use how these molecules, as in the cartoon here shows a water molecule, how those molecules may interact with the surface or the bulk, or even chemically change a material. And then we can learn about the chemistry of the material, the structure of the material, the surface properties of that material, and then that can be used for a wide range of applications. So the title of the presentation mentions surface energy. Not everybody is completely familiar with surface energy. It's basically the excess energy at a surface relative to the bulk. So there's some free energy at the surface because there's no nearest neighbors at the top. And it's analogous to the surface tension of a liquid. So you can think of a liquid like the meniscus of a water droplet or in a capillary that's due to the surface tension of water. For a solid material, it's called the surface energy. And we can basically use this to look at things like how surface interactions will occur and also things like the thermodynamic work of adhesion. So the surface energy is classically divided into a dispersive, which is also called a long, a non polar or long range interactions, then a Lewis acid base. This is electron donor, electron acceptor component. So essentially we can look at the total surface energy, which is a combination of the dispersive or nonpolar and then the acid base or sometimes called the polar component of the surface energy, and how this surface energy can affect lots of material properties. This is just showing some of those things. So we can look at, as I mentioned, adhesion and cohesion. We can look at how different processes might induce surface changes to a material or aging or weathering. All sorts of things can change the surface properties. It is a very sensitive technique. So it could look at batch to batch variability. If I have impurities or different vendors or different suppliers, or slightly differences in particle size, shape or habit, they can affect the surface energy and then just general material properties. Looking at the, maybe the surface reactivity, the acidity or basicity. How if I do a surface modification or if I want to coat a sample and I'm going to look at how that affects the interfacial properties, we can use that by monitoring and controlling the surface energy. So just a few quick cartoon slides. Again, I apologize if you've seen an SMS talk. You might have seen these slides before, but they do a good job of illustrating what surface energy can do. So if I increase the surface energy of a surface like I show here in this pink rectangle, I can increase the wettability. The higher the energy, the more likely, let's say a droplet of water might wet that surface. If I'm thinking of a powder or granules, if I increase the surface energy, keeping everything else similar, I can increase the cohesive forces because those particles will then want to stick together because of the surface energy is increasing. I'm thinking about milling or process induced disorder. Although I'm often doing these things to maybe change the particle size, I'm also going to change the surface chemistry, not just the size of the molecule or if I'm thinking of like grinding or plasma etching or some sort of surface treatment, those can often expose buried interfaces, create surface disorder, create amorphous sites at the surface, and that can be tracked and monitored. By the surface energy. Then if we look at composites, or binary or tertiary, or any type of composite material, where I have multiple components, it could be different powders, it could be fibers and a polymer, it could be a polymer with powders. Anytime I have a multi component system, how those different materials interact with each other is going to be partially controlled and defined by the work of adhesion, which is defined by the surface energy of the materials. So for instance, if I have these large particles, and let's say I increase the surface energy of these large particles, I can overcome the cohesive forces of these smaller ones, then I can increase the adhesion between the two surfaces. So surface energy can be important in lots of different processes. And as I mentioned, if we know the surface energy of different materials, we can predict their adhesive or cohesive properties based on the adhesive strength or the cohesive strength, the work of adhesion and the work of cohesion. So we can use it as a screening tool to measure the properties of individual materials and then predict how they might interact. And I'll show you an example of that later on. So an inverse gas chromatography is one way to measure surface energy. It's actually the preferred method for measuring surface energies of powders and particulates and fibers. And essentially you put the sample into a sample column, you elute the different probe molecules, and we measure the retention time. This retention time is related to how strongly or how weakly those molecules interact with the surface. And for those of you not familiar with cerf, with inverse gas chromatography, it is a relatively new technique. If I track the number of citations in Google Scholar, you can see that prior to 1980, there were very few published per year. It's invented around the 1960s, but as I can see, the last 20 to 30 years, there has been a pretty significant increase in the number of publications. So although it's not as mainstream as some other techniques, it is becoming more and more widely available and used to study surface properties of materials. As I mentioned, you simply inject different probe molecules, you measure the retention time. From that retention time, I can get the retention volume, which is related to the free energy, and then that gives us access to the surface energy. I won't go into the weeds of all the calculations. We'll be happy to provide that if necessary. But essentially what you need to do is you inject a few non polar probe molecules to get the non polar or dispersive component of the surface energy. We typically use a series of straight chain alkanes and then we can get the gamma D, which is the dispersive component of the surface energy. Likewise, you can use some Lewis acid base probe molecules to get the Lewis acid base contribution to the surface energy. So essentially you inject a few nonpolar or dispersive probe molecules and then you inject a few Lewis acid base probe molecules. Then I can get the total surface energy of the material. Moving on to just some case studies or some examples. You can see here we're looking at some glycine oligomers. And we were studying the surface energy and also the surface energy of these materials as a function of relative humidity. So it is possible to humidify this column such that I can have both Acarya gas and water molecules. So I can look at the effect of relative humidity. And that's what's being done. Pardon me, as I move to the next slide. That's what's being done in this study. We're looking at glycine, diglycine, triglycine, tetraglycine and pentaglycine. And we're looking at both the dispersive component, which is in red, and the acid base component, which is in blue. And as we go from glycine, you can see here predominantly the surface energy is dominated by the nonpolar or dispersive component. And as we can see, as we go from 0 to 10 to 30 to 50% relative humidity, basically no change in the surface energy. Water is not affecting the surface energy significantly. However, as we increase the glycine chain length, we go to triglycine tetraglycine dependent glycine. We can see two things happen. Number one, the polar contribution becomes more and more significant relative to the total surface energy. So we can see a much higher polar contribution. And then as we increase the relative humidity, we can see that the surface energy is affected dramatically by the water. Not surprising. As we increase the polar functionality of the surface, the surface is more sensitive to water and water vapor. So we can see that again, as we go up in glycine chain length, we're seeing an increase in the surface polarity or the surface acid base nature. And that makes it more sensitive to water molecules. So we can show here again, this is the acid base portion of the surface energy plotted versus the glycine chain length. And we can see that as we increase, we're seeing an increase in polar peptide bonds, which is why we see this increase in acid base surface energy that's related to the crystal structure of these different glycines. And just to show you an example this is diglycine and triglycine. So some modeling suggests that the increase in the glycine chain length causes a change in what major crystal habits are exposed. So now when we go to larger and larger chain lengths, we can see that we get more and more hydrophilic surfaces that are exposed, which explains both the increase in the polar nature and the increased sensitivity to moisture. So just showing an example how I can use surface energy to look at very subtle differences in surface chemistry. Even though it's essentially glycine, as we add the chain length, we can see the surface chemistry changes significantly. We can also look at what's called surface energy heterogeneity. As most materials are energetically heterogeneous, describing it by a single value is not always show the full picture. So inverse gc, unlike other surface energy techniques, is not able, is able to show an energetic heterogeneity. So just as this cartoon might show, if I have two surfaces, if I look at the average surface energy, they might be similar. But if I then cover the entire surface, I can maybe get a more fuller picture of the energetic distribution of the distribution of surface energy sites. So if I only look at one singular, what we call surface coverage, which is where we vary the ratio of the probe molecule to the surface, I might get the same answer. But these two surfaces are different. But if we investigate the entire surface, we can see that these two surfaces look quite different. And how we do that is we do a series of experiments where essentially we do them at fixed, what we call surface coverages. Essentially, we inject enough molecules to theoretically interact with different fractions of the surface. And we can do a range of experiments over a range of fractional surface coverages. That allows us to build up what we call an energetic heterogeneity profile. So as this plot, we can plot the surface energy as a function of surface coverage. This essentially means that at low surface coverages, let's say on the left hand side of the graph, we are measuring the surface energy of the top 1% of surface sites. Then we can do higher concentration experiments where now we're measuring the top 5%, the top 10%, 15 and 20%, and so on, and we can build up this profile. And then although maybe the average surface energy, as I coat more and more the surface, these two protein samples might look very similar. But if I look at the lower concentrations or lower coverages, we can see that these two are quite different. So this is basically a solid dispersion with a drug and a binder and then one has a drug binder plus a protein. And we can see that the sample with the, with the protein has a lower surface energy. Most like this is just the drug with the binder is in green. When we add the protein, we can see we've changed what's available on the surface. So the surface chemistry has changed significantly. Maybe the protein is coating the drug in the binder. So therefore it's no longer on the surface, it's now buried into maybe the bulk of the sample. And we can do these again experiments at different relative humidities. And we can see these are looking at the polarity, which is the ratio of the dispersive component to the acid base component, which I didn't show all the details, but if you want the full details, we can show that, ask for that, we can provide the study for you. And so we can look at 0% relative humidity, 40%, 50, 60, 70, 80% and so on and so on. And we can see that the polarity changes as I have moisture present or under dry conditions. So we can see initially as the wettability increases, but then decreases. The dvs or moisture absorption data does show that there could be some evidence of some sort of structural change when I get to very high relative humidity. Just showing another example. This is looking at a small flexible membrane for protein separation. And we can look at the both dispersive and acid base contribution. So again, this is the polarity which is the acid base contribution divided by the total. And you can see for three different membranes, membrane 1, membrane 2 and membrane 3. We can see that the very significant increase in the surface polarity as we change the surface chemistry of the material. We can see that the protein was separated into the lowest polarity membrane. So then we can see how that the higher the polarity is, the more hydrophilic it is. The lower the polarity, the more hydrophobic the sample is. Here's a study that was done with Ethicon and was published several years ago where we're looking at the, the ability of blood clotting agents. So there was five different samples of control starch based spheres and then some different hemostat aggregates. And we can see here, this is the blood, this is the blood clotting agent put in there over time. And you can see that the control, you know, no clotting, this is just the starch based spheres, you know, minimum to no. And then eventually you can see very good clotting ability with that. So we wanted to look at the surface properties of these different materials to see if surface energy could shed some light on the mechanism of this, you know, interaction with the blood. So we measured the total surface energy, the dispersive, the acid base and the wettability. Again, this red is the starch based spheres which did not do a good job of clotting the blood. And then the hemostat aggregates did a much better job of that. And we can clearly see that there's some subtle differences in here, which is explained further in the paper. But the starch based had a very high dispersive surface energy which made it and a very high acid base surface energy which increased the wettability. So it has a more hydrophilic. It wanted to stick to the hydrophilic but not the hydrophobic blood. The lipids in the blood are more hydrophobic. So we actually did a work of adhesion versus work of cohesion calculation where we use the surface energy of the aggregates of the clotting agents and then we use the surface tension of blood that is a known value that's been measured before and we can measure this work of adhesion to cohesion ratio. Does the aggregate or the clotting agent want to stick to itself or want to stick to the blood? And the closer that is to one, the better the adhesion would be. And we can see from the starch base spheres this is much lower than 1, which means the starch base would rather stick to itself than stick to the lower energy and lipophilic blood as opposed to the other materials which had a lower surface energy and a more hydrophobic nature that interacted more strongly with that and what's made them to better clotting agents. And here's the full reference if you want to see that paper. There's also been some other recent publications on looking at surface energetics and IGC on biomaterials. A few of them are shown here for reference. Just to show you some of the other applications in terms of things like solubility parameters and different glass ionomer cements and adhesion and surface energetics. So moving very quickly and to wrap up my presentation, I wanted to give some examples related to DVS as well. Those of you familiar with DVS know what it does. It measures the weight change as a function of relative humidity essentially. And this is what Tian Tian did a very nice job of showing how that can be coupled with things like in situ ramen to look at both weight gain and weight loss with along with structural changes. Typically what's done in a DBS is you increase or decrease the relative humidity. You measure the mass gain or the mass loss. You can construct an isotherm which is the equilibrium uptakes at each relative humidity stage. So I can get the mass uptake and the mass loss and I can also get the kinetics. How quickly or how slowly does that water come on or come off the sample? Once I understand and measure the isotherm, there are wide range, I won't get into those. There's another webinar on isotherm models if you're interested. We can provide that for you. But once I measure the isotherm, which is the uptake as a function of relative humidity, there are a wide range of surface based and kind of polymer solvent based isotherm models that could give you an indication of how that moisture or that vapor is interacting with the sample. Sometimes you could have cluster based models. It doesn't actually wet the entire surface. This is just showing a visual illustration of that. So I might have hydrophilic regions, I might have hydrophobic regions, and sometimes that can be related and determined from the isotherm shape, whether it's what's considered like a classic type 2 or a classic type 3 isotherm where I might get islanding or clumping on the surface as opposed to completely wetting the surface. So this is a visual illustration of what an isotherm model might be able to tell you about how water or other vapor interacts with the material. As the previous presentation mentioned, you can use DVS in conjunction with things like Raman or Video. You can also use near ir. And just to show you a very quick illustration, I won't go over Raman because the previous talk went over that. But here it's just looking at a pellet that's used as an osmotic pump delivery system. And this is at 0% relative humidity. This is at 95% relative humidity. You can see a very significant structural and physical change to the sample. And you can actually use this to quantify the degree of swelling. There is a scale bar here. So I can look at this. So for instance, we can look at the pellet length and the pellet diameter and we can measure that as a function of relative humidity, as a physical measurement, actually measuring the dimensions of that. Or you could use image J or some image analysis to look at the area of this. But you can clearly see we skipped some points, but it shows very little. Almost no change up to 60%, 50% relative humidity. Once you get above a critical relative humidity, you can see that the material swells significantly. There's obviously a phase change that's occurring once I get to very high relative humidity. So I can actually look at structural and physical dimensional changes using the dbs. What was shown previously was mostly on powders or pellets. You can use a wide range of geometries. And looking at not only the uptake, which we showed previously, but I mentioned the kinetics, which is how quickly or how slowly something goes in and out of a material. You can do that with a thin film. So we can measure the fusion rates in and out of a sample. This is just showing on some synthetic skin, which is called a vitro skin. We can make step changes in relative humidity and then measure how quickly water goes in and out of those samples. And we can do that with different surface treatments. So this is looking at, you know, basically the change in mass as we change. And then we can get the diffusion coefficients here, what you see here at each step, change in relative humidity. And I can do that with different surface treatments, different coatings, different humectants, different maybe oils or creams or emulates that might be put onto the sample. And look at skin transport properties as a function of Rh and modification. You can also look at membrane permeation. This is typically done through a permeation or diffusion cell. We also call it a pain cell. You can put the sample and then measure the flux going across the sample. As I have a humidity or concentration gradient, I can put, let's say a zeolite or getter on the inside, So I have 0% relative humidity and then control and then a separate relative humidity on the outside. And I can measure the flux going across this. To look at permeation rates through or across a membrane or film. That can be done with a wide range of materials. This is just an electrospun polymer. You can see at different relative humidities, I will get different rates going across that membrane, different thicknesses. I can change that as well. You can even do it with skin samples. You can do it with vitro skin or synthetic skin, which is what we're looking at here. And here you can see this is different vitro skin samples treated with different creams or glycerols or humectants. And we can look at the change in water loss or water flux across that membrane as we treat that with different materials. We can also look at different medical or micro needles or delivery. This is looking at microneedle on coated versus uncoated. So we have microneedles with drug either on these or not on these and even though the uptake and the amount of drug is very, very small, it's in the less than a milligram. For this patch, we can do a baseline correction to measure the uptake of just the device itself and then the uptake with the microneedle on. And we can get very, very sensitive differences between looking at uncoated versus coated samples, see if we see the water uptake or any phase changes that might be observed or any amorphous content that we might see. So I know that was a very quick and brief overview of biomaterials and how we can study them with DBS and IGC looking at surface energetics and wetability. If there are any questions, I'd be happy to answer them. Also, you can send us a chat or message us and I can provide full details on all of these studies. I just wanted to give you an overview to follow up on the very detailed and excellent presentation by Tianjin earlier on the bioactive glasses. So with that I'll pause and if there's any questions before our time runs out, I'm happy to answer them. So John, I'll turn it over to you to see if there's any questions.

Thank you, Dan. Yes, we'll just give the audience a few minutes to submit any questions. You can do so in the questions tab, everyone. So please, any questions for Dr. Burnett, please submit them there.

Now if there's no questions, that means I either put everybody asleep or did a very good job explaining it. I'll choose the latter on that one. But you know, hopefully if there's any questions, please, please feel free to ask them at this time. Well, as we wrap up, before I turn it back over to John, I mean, please reach out to us. I should have put our email, but you can email us@scienceurfacemeasurementsystems.com if you have any questions or comments or queries afterwards or if you're watching this webinar after it's uploaded to our site later on, not live, please contact us@scuritiesurfacemeasurementsystems.com thanks John.

Thank you Dan. Yes, I don't think we have any questions for now, so I think we can wrap up there. Thank you once again Dan for that presentation and a massive thank you to TNTN for being with us today on this recent take on this webinar. So and of course thank you to our audience for joining us today. Please don't forget we have a brand new website live@surface measurementsystems.com which features our full catalog of webinars going all the way back to 2015 2016. So please do check in there. You can search them by keyword and by key applications. So it is a very useful way to get up to date on recent knowledge, as well as a full catalog of application notes, which you can also filter by keyword and application term. So please do visit our website@Surfacemeasurementsystems.com webinars to view our webinars and stop in the Knowledge hub in the website to view all of the recent application notes and product brochures. So thank you once again to our speakers for today, and a special thank you to our audience and we hope you enjoy the rest of the day wherever you are. Thank you.