Right. Very close. Thank you so I thought I would do a little bit about me first. So you all know who I am so I am as press are close and in bioengineering there is my e-mail address if you have any questions feel free to contact me so I have I lead has a wide range of projects which I will try to do a quick survey of some of the ones that might be of interest to people today. But in general were interested in kind of nano and micro mechanics and interactions of biological systems and how those scale up to the whole tissue properties and so I suppose in a nano type seminar people should know this but people often think about biological processes in the phenomena as being kind of at the cell level which is a micro scale organism. But the cell interacts with its environment on very small length scales in very small forces and so we're kind of trying to understand how those interactions end up scaling up in the tissue. I mean we look at a wide variety of tissues have a lot of projects on cardiovascular system which I'll discuss as well as some orthopedics. To. Mostly we do measurements and modeling in the lab in the Stockholm mostly focuses some of the kind of more experimental work. And we use a lot of atomic force microscopy which you know can be used for imaging as well as mechanical probing of samples. We're currently we have a new system that's a P. three D. Af-Am and it's on top of the Olympus con focal optical microscope so we can do mechanical probing with the F.M. and then optical imaging with the consequence system. So in the lab we have projects that kind of span nano to micro scale. Interactions. I have a couple projects kind of looking at the lead killer mechanics of quite a bit of work in the cell mechanics kind of area and then some work looking at small. And in Taishan of tissue and how that affects mechanical properties so I thought I would start with the orthopedics because that's what I started in so when I was at MIT I was in a car ledge mechanics lab and our work was focusing on how so cartilage is a very hierarchical structure tissue. It's on the end of your joints it cushions your joints during loading. And it doesn't have very many cells so most of the function of the tissue is this extracellular mite matrix which is made up of college and and these large proteome like an aggregate or you have a core protein with very charge gag chains on the side. So that's kind of a more schematic representation. And because the gag chains are highly charged when you compress the tissue the like charges repel and that contributes to about fifty percent of the tissue modulus and the other fifty percent is from college and. During diseases such as arthritis you actually see a loss of previous. Like ants from tissue and so we're trying to understand kind of what happens to these molecules with age and disease and how their interactions change on the molecular scale and if that when we scale it up could explain some of the changes we're seeing in the tissue. So we actually did some modeling work both at a kind of molecular scale all the way up to Continuum models to kind of scale up the interaction forces we would measure at the small scale to large scale tissue properties and in the end we found that the molecule itself if you kind of put a kind of biomimetic layer on a substrate as well as on an A.F.M. probe you could actually compress these molecules together and get forces that translate to a stress strain kind of behavior that's on the order of fifty percent of what you measure on tissue The other thing we noticed is that if you take molecules these are from a cow. So this is a fetal bovine Nagra can and this is a mature agrah can. And by bio chemical composition of these two aren't all that different. There's just some changes and like consolation as well as a few less gag chains on this molecule you can see that they actually have very different force behavior which translates to much smaller responses so as you get older the molecule doesn't give back as much force. So that's kind of paralleling what we see and the whole tissue. Unfortunately as we get older our tissue doesn't work quite as well as it did when we were little. The studies were looking at now and cartilage in the lab are focused on how radiation affects cartilage tissue mechanics. So this is important. So this actually is funded by NASA. So NASA is interested in this because when the astronauts go in space and they're outside the Earth's protective atmosphere. They actually have a lot of radiation but also for radiotherapy of cancer treatments radiation patients receive something like two grade doses continually for a while for their. Treatment and this works great at shrinking out a tumor and maybe even getting rid of the tumor but people have started noticing that now that we can kind of cure the patient. There are some long term side effects of the radiotherapy. So. Why do we care about how radiation effects skeletal tissues kind of the old logic was that the more proliferated of the cells. The more they were affected by radiation and so. A cartilage and bone don't proliferate that much and so they were often thought to be rather radiation insensitive. But recent studies showed that at least in bone radiation at clinically relevant doses make Actually actual large differences and cause osteoporosis like symptoms and so this was from collaborators work and so he sent us these joints. So before they analyzed the bone. They sent us the cartilage tissue to measure. And so these are mice models. I don't know how many people have worked with mice but mice are very small and we were interested in kind of the functional property of the tissue. So in a larger animal model like a pig or a cow. You can take your traditional mechanical testing device and test the mechanical properties but with a mouse you're kind of limited to a technique like A.F.M. and so we took the tissue. From these mice and we did a mechanical indentation test. And the so this is the results we got so the control had modulus that was kind of what we expected and the radiated tissue was really low and I have to be honest that when I first got this data I didn't actually believe it and I told my students to do it again and and I told my collaborator for the next set of samples to blind them so we wouldn't know. Because I don't know if you've all done fm indentation test but you don't know where the contact point is so there's models to figure out where contact is and that actually influences your measurements but what we did. Again we pretty much got the same data. So we felt pretty confident about this result. Now one question we started getting asked is if I'm we're only probing a couple microns into the tissue are these effects kind of surface effects or does is it representative of the whole tissue property. Now it's hard to test in a mouse. We can't really do that in a mouse because there's it's very small the geometries strange so we did a set of poor sign xpand. So first our hypothesis was that this is actually due to a loss of produce like and so I don't know if it's coming out very well but there's pink color is like CAD and the radiated tissue almost has not. And so we did as I said a study on porcelain explanted So we took porcelain cartilage and cultured it and then you radiated the cartilage by itself. So not the whole animal and then ran an experiment using my current intonation and then also Danno inundation with a half hour which is this is the measurement we could do on the mice and what we found was that with the poor sign. Issue. We still got a very similar result. So that seems to indicate that it's a kind of a hole tissue effect as opposed to just a surface layer effect. Since it's not really like scale dependent for what we're seeing. So we're currently following up on that try to look at molecular mechanisms of what happened so gags are coming out in the media we've actually made those measurements and tried to now look at what's the structure of the the fragments coming off to kind of go back to look at is it normal is it getting clipped and things like that. So that's kind of an example of a project where we kind of start at the small scale go to large scale but since this is a nanotechnology kind of audience I thought I would focus a little bit on some of our nanoparticle work. So we're trying to understand how nano particles interact with cells I have several collaborators in chemical engineering and materials science and they're making particles for a wide range of applications. And eventually you even if you're making it for an industrial application you need to know whether or not this particle is really safe to be released. Definitely. If you're making it for a vial medical application you need to know whether or not you're going to kill whatever it is. And unless you put it specifically against on the on the surface of your particle the cells are going to interact with your particle using nonspecific kind of interactions initially and then eventually maybe the cell will engulf the particle or not depending on the type of interaction. So we've all seen these kinds of papers so these are some in literature you can make a lovely particles This is from literature. They come in different sizes and compositions I can change their color based on their sizes. Users. From our lab. I think these are still the gold particles and you can change the surface tapping. And that's great but you've got these nicely synthesized particles and you've characterized them and you know their size and then you're going to put them on cells and so when you put them on cells or if you're going to inject them in the body. You're going to have to deal with a couple different things. So they're physiological ionic strength is something like point one five. So the water properties might not be exactly what you're looking for in addition media and serum are full of proteins another sticky things and as soon as you put your nice pristine particle in that environment proteins will. Aggregate on the surface and so this is important to keep in mind and you might have particles that look very similar in your initial synthesis but when you put them in media actually behave quite differently. So this actually we just got accepted for this paper but my collaborator Chris kitchens in material chemical engineering developed a green synthesis for silver nanoparticles using garlic extract So these are garlic silver nanoparticles They're like the anti vampire nanoparticle. And then he compared them to sit citrate stabilized silver particles. So these are both it. You can both do them in water and the interesting thing is the garlic stabilized particles remain much more stable in need in cell media compared to the citrate particles would very quickly kind of fell out of solution. Over time. So for a biological application this might not be a bad idea. So at this. In time we also did some cited toxicity measurements so we took in our case these are vascular smooth muscle cells and that's just a sampling of data we've done lots of different types of particles but basically we found that the particles when they're water soluble and of the size range we're looking at which is between five and fifteen nanometers they're relatively not cytotoxic So if I do your so standard MT T.N.T.'s type ass A's it comes out looking like this. So not really cytotoxic by. Classical definition. And so at this point you're asking yourself why are these particle safe. So they seem to be stable and we had doesn't kill the cells. So obviously are they safe. But the definition of safe is very different depending on what your eventual application is so if you're going to have something that becomes an environmental waste. You need to know how it interacts with the usually Marine and aquatic life forms and if it's an industrial setting. It's different than if it's in medical settings if it's going to be injected in a person one issue that's come up a lot recently is cosmetic start having nano type particles and they're not very regulated so trying to come up with a test for safety are important and standard side of toxicity assaye is haven't shown to be very predictive of safety. Once you actually get in the animal. So that brings us back to what the heck am I doing doing these measurements right so we do a lot of cell mechanics work. And so when we started this particle experiment. I had vascular some muscle cells and Chris just wanted to know whether night killed some cells so I did the essay on the cells we had in the lab which happened to be the vascular small. Cells and what was interesting is that while it was totally not cytotoxic according to the essay we could definitely see that the cells were changing and so that kind of led us down this other path. So for those of you not familiar with biology. We look at two different types of vascular cardiovascular muscle cells and in the lab we have cardio meiosis which are the primary constituent of the myocardial mean your heart. They're the contract in cells that make the heart work in vivo they kind of look like this in their biggest things and they synchronize in the contract and if you have them in a cell culture dish they will spontaneously contract vascular smooth muscle cells are the muscle layer in your artery over here and they regulate blood pressure. So they all expand and contract making the blood pressure change. And in the body they can be found along a continuum of you know types from a synthetic proliferative type you know type to a quiet contract. You know type. All healthy arteries have cells in kind of this continuum. However when you have an injury or disease you tend to shift the cells towards more of a proliferative synthetic you know type and that causes all sorts of problems. So this kind of a blow up so you can see there's where the vascular skin cells are that's a contract tile kind of looking cell and this is a big fat flat. Synthetic cell. And that's actually one of the main problems in atherosclerosis the cells proliferate and then they get into areas that they're not supposed to get into and that causes inflammatory responses to all sorts of things. The other thing to note is if you culture vascular some muscle cells over time. You'll tend to shift things and because your keep proliferating and making passages you're going to end up with more and more kind of proliferative synthetic cells and less and less contract tiles cells. So they're so important to keep in mind when you're doing your experiment. So this is actually what happened with the nano particles these are control cells and this is the particles that were treated the cells that were treated with nano particles so on the ass say it looks like the particles didn't do anything but obviously if you look these cells don't look anything like the control cells. So that led us to look at kind of their mechanical properties since the main function of these cells is mechanical and. So we did some in addition tests to poke the cell come back my grad student made this. Nice and then you can also do stress realize sation you can push down in the cell hold and come back up so stress relaxation experiments kind of look at more of the viscous response of the cell. And one of the first studies we did looked at just the normal quiescent contract all phenotype versus the proliferative synthetic pheno type and what you saw is that the proliferative synthetic cells were softer than the contract I'll cells. This is a problem because if you have all these proliferate of cells in one area they're going to be softer. And then that whole area might stretch out more and they'll get larger strains and then it will shift more of the cells down that way. So it's kind of a positive feedback. And so this is actually for the cells I showed in the picture of the result so some of the particles we treated the cells with tended to shift the part of the cell the cells towards a more contract Tyler stiffer if you know type some of the other ones we tested actually went the other way and caused more. The cells to become. For live for it is. And so again they're not showing up a side of toxic on kind of standard assayed but they're obviously shifting the self you know types and so if you're going to inject these into an animal Sure it might not kill the cells in the area but you could have long term damaging effects. If you start messing around with vascular muscle. Particularly if you're shifting the other way which most of the particles were doing so most of the particles we were seeing were shifting the cells to were more proliferate if you know type that's kind of the precursor to things like atherosclerosis So that would be bad. This was not totally unexpected as you probably know cells kind of interact with their micro environment and take cues from the and micro and Vironment and lots of things affect the cells. You know type in mechanical properties things like Matrix composition orientation and things like that. So we had done some previous experiments looking at how the microenvironment affected these cells and what we were trying to show is that if you change the orientation of what substrate the cells sit on. So if you are on just college inverses aligned college in fibers do the cells change shift to one phenotype or the other and also do we reduce some of the variability we're seeing. So if you go back like these standard deviation bars are relatively large and that's not a typical If you look at cell mechanics literature. If it's F.M. or any other technique there's actually quite a large cell to cell variability. That's much larger than the repeated point measure. So it's not the experimental technique it's actually a difference between cells. And so we thought that if the micro environment is affecting the cell and changing how the cell interacts. The mechanics of the cell then maybe if we more tightly control the micro environment we could get more uniform cells. So if the cells are seeing just one alignment of fiber they might all kind of be more similar. So one of the issues we had was how to align college and fibers the cell biologists we worked with. Put the college in solution on the slide and then you take a cell scraper and you scrape it down and then you kind of hold it and have gravity work its way down to make aligned fibers and this is kind of what they look like so. They're sort of aligned but they're not very aligned and we get slightly better alignment using an inkjet printer. So we actually print collagen onto a substrate in lines and that causes slightly better alignment and one issue we had is that to get really really well aligned substrates like something you might actually see in biology. You have to use techniques like microfluidics and things like that which we do have in the lab so. That's what we were limited with. But this is kind of what they look like. So here's your vascular smooth muscle cells on an alliance substrate you can see they're kind of all in a line they're big long contract AILA looking cells. Whereas on a randomly oriented substrate they're big and spread so they definitely have more of the contract out phenotype on the aligned substrate than the random substrate. That's just to show the nucleus acting. This also works with cardio my ascites and this is well known for cardio Miles said that's how you kind of try to keep your cardiac cells in a more in vivo like condition so that they're all kind of lined up and to and instead of. Being randomly oriented like over here. And what we found is that. The cells on the line substrates tended to be stiffer than the cells on the Unaligned substrate one thing that was interesting was that it actually took almost a week for the cells to kind of stabilize. I mean everyone knows you put your cells down you have to wait a day for them to really adhere to the Matrix but they're obviously still remodelling and changing and in the first five days of culture and then once they hit that five day mark it kind of plateaus. Cells also obviously are influenced by their matrix composition so. The cells on fiber Nekton were significantly stiffer than those on college and. On stress or life station measures. This was interesting. This is a cardiac cell. So you compress and you hold and as I said the cardiac cells they spontaneously contract so as you're holding in the cells relaxing it still contracts and you can see the beats that the cell is doing and actually most of the beats are all the same size and it doesn't matter how compressed the cell is it's always the same size. So I guess that's good. You don't want it to as I'm moving around my cells not contracting the same amount raise. It is actually a relatively complex behavior it doesn't just have a single exponential relaxation it has a kind of a fast initial response and a slow decay. If you looked at the relaxation measures there wasn't quite as much of a trend. They tended to relax more on college and then on fiber Nekton but. Now one thing we were surprised by is that the cell to cell variability on all the substrate was about the same and we had expected that if you made you. Substrate much more aligned and uniform the cells themselves would come out much more uniform and that wasn't the case and most likely that's because our line substrings aren't that well aligned. We've done some follow on studies where we actually block cell matrix interactions as well as cell cell interactions and you can actually get these cells cell. Variability measures to drop significantly so if you limit the cells ability to interact with this micro environment then they all will look relatively the same because they can only interact in so many ways. So. That's fully differentiated cells and so you. You have cells these change a little bit but of course everyone's interested in stem cells you want to cure heal diseases and there's this whole paradigm in tissue engineering you take yourselves out. You put them on a you know a side a matrix and then you put them back in. And there's an initial preconditioning step maybe where you give them some forces or you add some flow and you start the differentiation process before you stick them back in. And so we were kind of looking at it as for making vascular smooth muscle cells. Vessel or smooth muscle cells are relatively stiff. And if I take a stem cell stem cells are pretty much as soft as you can get for a cell and if I was to take that cell and stick it in a very mechanically active environment. It wouldn't get the same signals that an adult cell would so we were trying to understand how far along the differentiation path or how long it would take for these cells to reach something that looked like an adult cell. And so we tried two different types of cells bone marrow and adipose derived stem cells and we did stand. Or differentiation protocol so you start adding growth factors. And bone marrow stem cells about a week into the protocol they actually hit modulus values that are on the order of what an adult cell looks like at this point they're nowhere near fully differentiated by all the biological markers. But they actually have a more organized cytoskeleton and therefore they're able to bear more load and interestingly that adipose derive some cells also gets to for over time in culture but you can see it does so much more slowly. This is day fourteen. And it's still not quite as high. So the cell source. Even though these are both. Kind of very similar. So in terms of their differentiation potential actually makes a big difference and actually at day fourteen and day seven These cells have similar markers. So it's known that they kind of the Adipose cells kind of go a little bit more slowly down a vascular muscle so lineage. But it was surprising to us that they were that much lower in modulus than in the bone marrow stromal cells so we're kind of following up on that and looking at which particular markers are most indicative of kind of mechanical properties for these cells. And we have a bunch of modeling work in that area which I don't have time to get into. So that's cardiovascular I thought I would pause here and see if there are any questions at this point. Yes. Carla is just the party of like an SIA. Yeah. Yes So the cartilage that's irradiated has less than content and control tissue. It's kind of qualitative in his stall a G. picture but we've actually done some biochemical ass's now to kind of show that so you get a massive loss of pretty well I can into the media day two so after your radiation a lot of the like ants come out. It actually kind of stabilizes after a week but yes. So not so much aging but definitely disease so in arthritis you definitely get significant loss of. Can there's actually a sense items that come in clipped out the Agora can from it's large aggregate and it comes out of the tissue and so one thing we're following up on is looking at what size fragments are coming off. To kind of figure out which of the enzymes is it that's responsible for the radiation effect certain fragments are worse to lose than others in particular there's the third clip site basically clips off the whole molecule and the whole thing comes out as opposed to one of the earlier ones which is just the end. So they have different effects on the whole mechanical properties in the end. Yes So that's that's what we're looking at now kind of what. What what are the cans that are coming out and which ones are left in there. What size of the fragments are in there and hopefully So with that we actually so my collaborator does bone and he actually got pretty lucky in that the bones response to radiation is similar to osteoarthritis and they've actually shown that if you give patients not to your theory I said sorry osteoporosis. If you give the patients and osteoporosis drug before you give them radiation you can actually stop some of the effects that we're seeing now I don't think we can do that with correlation mostly because there aren't very many good arthritis drugs but I'm assuming it's a similar inflammatory mechanism. And. So that Chris kitchens and chemical engineering. I forgot how he came up with a I think he had it for some other study where they were looking at. Anti-oxidants stuff and then his grad student was trying to come up with this green synthesis and thought it might work. So it's one of those happy coincidences. But I don't think they know fully they did a bunch of characterisation as in that paper so we know kind of some of the groups but it's not it's not like citrate where it's a pristine surface where you know what's on the surface and that actually might be why they're more stable and media because there is a heterogeneous surface that. Yes. Yeah yeah yeah. How long it takes. Yeah. So the bone they did look at that and I actually I don't remember how long it took but it didn't really come back. Very well but it eventually did cartilage. Well I mean when we've looked at it's not really coming back but that's not surprising. Carla doesn't really heal. It's really a cellular So so that's a that's an issue with Scarlett if you start messing with the matrix it takes a long time for those few cells to like with plenty of the pretty alike and content in the Matrix. So we haven't done really young animals people have done growth plate cartilage and they've shown that that actually is a long term issue patients kids that have had like radiation on one leg have a shorter leg on that side than the ones. That's not your radiated so that's more of a proliferative kind of concept so that one more changes. Yeah. Yes that's a great question and. So the two part. It's all sort of the second part. So we actually asked the raw data is a position of Z. sensor so like how far the Piazza has moved and then versus deflection of the tip. So to convert the data you take your deflection and you multiply by your spring constant That's your force and then to get distance. It's YOUR how far the Piazza has traveled minus the deflection of the tip. That's how far you've gone only thing that's left is finding what the contact point is so there's multiple ways of finding that if you look at literature the easiest one is kind of look for the point where the forest goes above noise meaning you've hit something you can actually do to region models were before you hit and after you hit they have different shaped curves and you fit in till you find the point that works. We've actually tried to several of those and they all come out with about the same point for cells which is nice. So that's that answer your second part and then the first part. So that's a great question. Most people doing cell indentation with a half hour. Will use the Hertz linear elastic model which assumes contact. Like a very small indentation that your probe is much larger than the intimidation. Which isn't too bad for our studies. Most of these we did with a five micron radius probe and we're only indenting about a micron but we're fitting only the first two hundred nanometers to five hundred nanometers are the imitation curve. But in parallel to this we've actually done some finite element models of the cell that actually included some of the structural fibers that you can see so we have a lot of work on taking imaging data and converting that into a finite element model that then can more accurately simulate what's. Going on an experiment. So. But it's a big ongoing area of research in terms of the Hertz analytical model is nice in that it's analytical and it's easy to pull out a number and everybody uses it. So you can actually compare but it has a lot of shortcomings. So I have one last thing which kind of changes gears that's why I stopped but kind of doing a little bit more of the tissue level things and talking about teeth which is actually good from the question about bone healing and things like that so bone as anyone who's broken a bone knows it heals unless you have a really large gap at which point it doesn't heal but your tooth won't heal you. If you crack your tooth. If you especially if it's a vertical crack that's it you get the tooth taken out. And so. There's been work on trying to understand how to make the cells that are in your teeth. Kind of. Re do some remodelling So if you if you crack your now well it's not getting repaired we can't. There's no repair at all if you cracked the dent in which is the inside part of your tooth which you get some very minimal repair but it's not the same quality tissue and usually it ends up giving all sorts of problems with bacteria being able to get in and then you have cavities. So there are cells in your teeth dental pulp cells and it's very similar to the bone marrow so it's inside the teeth in kind of the same way the bone marrow is inside your bone these cells have been shown to be able to be induced to go along all sorts of different lineages. In particular they're pretty good at go. Going into Osteogenesis or odd Odone to generate the lineages meaning they can make mineralized tissue. How do you put a general and Connor genic lineages. Mostly probably because in this area where it connects back to the jaw. That's kind of the cell types that you might need. Rips. So we kind of started looking at how these cells respond to their substrate. So with the goal of eventually making something that a material that when you say have a cavity. You could stuff it in there and then and eventually over time the cells could rebuild the tooth for you and then you wouldn't you know lose your to eventually. And so this is been done with bone marrow cells where you take the cells and you culture them on different stiffness substrates and look at their response and what we found was actually that you do get some differentiation in all the different substrate environments but that this is much more the cells the blasts of the the dental cells prefer remarked stiffer substrate and bone marrow cells did when we did him in culture. So they really didn't like the really soft gels and so now we're working on looking at how we can actually do some substrate guidance and patterning of substrates to see if we can actually get them to become more Odone to blast like as opposed to BO so we would like them to make teeth not bone and so were making pattern substrates of different types. We've tried lines. We're trying to hexagons because that mimics the. Crystal an orientation of the dentin and we're kind of looking that now at that. Now one thing we noticed was that they. Tend to migrate off the patterns parts onto the flat part of the substrate. So we have had a lot of trouble getting to them to stay on to the patterned areas which was different than what we've had before. So that's kind of software starting. And this actually all started because we were looking at Dental micro mechanics. So this all gets back to it would be nice if we could repair cracks in teeth. But you know be nice if your teeth didn't crack in the first place and in particular if you do have a repair done so if you have a cavity filled there's a mismatch in mechanical properties between the dental tissue and the filler. And so that's where cracks happen and then your crack happens more bacteria gets in and then you have to get it refilled and eventually you'll have enough to still left. The other problem is it's impressive if you look at teeth and see. So you've got your Denton inside and you're now will and Denton has roughly the same mechanical properties as bone. But now all is really really really strong rate that we all know it's kind of strong material and so the transition between Denton and an animal happens over really really short distances and so it's impressive that. At that point where you have this mismatch it goes it's changes mechanical properties really fast and that you're not getting stuff cracking all over the place so we sorry. So that's what we looked at but we also wanted to look at how when you were in your teeth how the heck that half of fx these properties. So this all came about because we had teeth in the lab and I had a summer student who was getting married and I wanted to know if she should write her teeth before the wedding. So this is this is the studies and. He asked her dentist friend so she asked the collaborator who's a dentist. And he told her that sure he could widen her teeth but that no he would never do it on himself. So we were trying to understand why the heck the dentist would never ever why in their own teeth but they will be willing to widen people. So we got some teeth. And we treated them with Crest why strips opalescent which is a whitening true you can go at the dentist to get and then we did. Now no indentation along the dentin enamel junction. So as I said you know the dentin if you look at say the modulus. Is much softer than an ample and this changes over something like about ten microns. In distance. And what we found was not that bad. So this is a percentage different from the control. So the opalescent didn't change things too much. It made the dentin slightly harder crust white strips actually made both the dentin and the enamel harder and then our kind of positive control was phosphoric acid which eats away at the mineral component so we were expecting that to go down. So the conclusion from this was well it's not that bad and the reason is the whitening people know that peroxides would be bad. So they add fluoride into the whitening products and so the idea being that the peroxide might make the properties go down. So we're going to stick some fluoride in there to like replace some of hydroxy appetite into floor appetite. But this isn't great either. So. What's happening here is that your dentist is getting stiffer. But you're now. Getting actually significantly stiffer more so than in the dent and so now you've got an even bigger mismatch between the an adult and the dentin So this is only after one treatment if you keep doing this over time. Perhaps that is actually not great and that actually might cause more likelihood of cracking later. Later after a while so. So that's kind of the significant conclusions from that study. So my my student didn't get her teeth whitened before the wedding that was. The end of that thing so kind of in the lab we've looked at all sorts of different areas the T.V. stuff actually wanted to mention because I know you all have like nice my crew fabrication and thing facilities and we're trying to make the substrate that look like a dental materials to grow ourselves on so people have suggestions I would be great. And but we're doing all sorts of different projects I actually have a bunch of projects that I don't want to talk about here but that are looking at instrumentation designed for developing country medical devices. So it's a great area to be in. And I couldn't have done it without the help of all these students so these are the alum So these are my first two Ph D. students and these are the two Master's students Sandy and Scott worked on the cardiac and vascular cells. Laura did the teeth and Will did the nanoparticles these are my current grad students. I have a huge army of undergrads working for me but these are the students that have worked on the projects that I mentioned Laura I did some work on the nanoparticles with Elliot Herschel worked on some of the cartilage and James did some of the dental materials and of course these are my collaborators and you can't run the lab Well funding. So thank you for the funding and thank you for your time. More questions than yeah yeah. It depends on the particles so I kind of showed a few of them but some particles definitely increase full of ration as they did they typically don't decrease it that much but the ones where the particles increase proliferation rate that's where we saw decreases in mechanical properties so it kind of goes with shifting to more of a synthetic proliferative you know type. Yeah. So I think it's some of it's about the initial interaction in that most of the particles they were the same size and the same core materials was either gold or silver that we've mostly been working with it's just the surface that changed and so the fact that some part of. Ols didn't see a change in proliferation rates and some particles you had a huge change in proliferation rate. Once the particles are inside the cell they're in the same kind of environment so it's I think it's that initial kind of interaction at the beginning we didn't test long term I think we looked at mostly of two weak. Mostly because vascular smooth muscle cells after a while they start proliferating so it's hard to look at those. Yes. Yeah but we're trying to use college and so I was yeah it's hard to do with kind of those things but that would be one way of getting a nice like a much more aligned substrate. But we don't really have that really. And yet make a nice straight. Excellent. OK with you because that's actually one of the issues we've had so that you chip printer is good for kind of like it's better than just scraping but it's still not it's not like electricity in terms of how a line the fibers get Yeah yeah. So I'm very thankful.