In class this week we discussed the types of biomaterials that can be used tissue engineering and recent advancements in the field. There appears to be little published research that examines the use of tissue engineering to deliver contraceptive drugs. As a result, I examined how tissue engineering has been used in women’s reproductive health. I found that female reproductive tissue is an interesting application for tissue engineering because properties of the tissues may change due to the menstrual cycle and due to puberty, pregnancy, and menopause. As a result, finding biomaterials that can mimic the biological function of tissue is essential for creating effective solutions. Women suffering from reproductive organ failure due to acquired disorders, congenital defects, or trauma have few options currently besides surgical transplantation. Reproductive organ failure may cause infertility and loss of function.

In the article, “Efficient Biomaterials for Tissue Engineering of Female Reproductive Organs”, the authors review current biomaterials that are being investigated to create female reproductive tissues and reproductive organs. Restoring normal function of reproductive organs is extremely challenging because the bioengineering materials must restore structure and function, including the excretion of hormones.

One of the applications for tissue engineering was in the construction of ovaries. Ovaries store oocytes and secrete reproductive hormones, including estrogen, testosterone, and progesterone. The endocrine function of the ovaries involves complex signaling between follicles and their environment, which relies on mechanical signaling with the ECM and endocrine and paracrine signaling pathways. The signals begin folliculogenesis, which causes the reproductive cycle. Current techniques for treating dysfunctional ovaries include hormone therapy, uterine auto-transplantation and xeno-transplantation, ex-vivo fertilization, and, as discussed in the review, the development of artificial ovaries. Ovaries could be constructed by applying scaffolds with necessary cells and pharmaceutical agents. Scaffolds may be made with natural or synthetic materials, both of which were discussed in the article.

Creating biomaterials that can mimic the ovaries ECM is critical for restoring the complex signaling and interactions that occur with the human follicles. The ECM in ovarian tissue contains proteins such as collagen and glycoproteins such as fibronectin and lamin. During follicular development, the amount of and location of fibronectin and laminin. In order to create an artificial ovary, biomaterials must support the growth and attachment of follicles and ovarian stromal cells to the ECM. The biomaterial must mimic the ovarian tissue in order to maintain biological signals and mechanical strength. Currently natural materials being used in tissue engineering include alginate, fibrin, collagen, gelatin and hyaluronic acid and synthetic materials such as silica, polyethylene glycol, and polydimethylsiloxane. As we’ve learned in class, natural materials can be beneficial because they are more similar to the human ECM and have greater biocompatibility and bioactivity than synthetic polymers, which can be toxic when degraded in the body.

The review discusses the advantages and disadvantages of each of the materials that have been investigated for this application. They first identify five ideal properties: biocompatibility, degradation kinetics (ie allow growth of ovarian follicles), degradation by productions not toxic, mechanical properties, and biomimicry.

Alginate is a polysaccharide derived from algae that can form a hydrophilic and biocompatible stable matrix that can handle isolated follicles. Alginate combined with ascorbic acid has been shown to improve the survival of mouse follicles and in vitro tests demonstrated vascularization and low inflammation.

Fibrin is another popularly studied biomaterial for ovaries. Fibrin matrixes encapsulated ovarian mice follicles and then transplanted into the mice. After a week, angiogenesis and follicular development had occurred. Fibrin can be degraded, so researchers have examined a matrix made of fibrin and alginate because alginate is not degradable. The combination matrices were used for the ovarian cells and showed more dynamic mechanical properties.

The article also discusses research that’s been done to create a decelluarized ovary. The the ECM of the ovary can then be reseeded with ovarian cells. Recellularized ovaries with reseeded with ovarian cell where able to initiate puberty in in vivo mice studies. In conclusion, extensive work is still required before engineered ovaries will be able to be used in humans. Most likely a combination of biomaterials will have to be utilized in order to create the unique structure found in ovaries.

Source: Tamadon, A., et al. Efficient biomaterials for tissue engineering of female reproductive organs. Tissue Eng. Regener. Med. 13(5):447–454, 2016.

Copper-containing intrauterine contraceptive devices are one of the most commonly used forms of contraceptive in the world. Copper IUDs have grown in popularity because they offer many benefits over hormonal IUDs and oral contraceptives including a longer half-life (12 years), high corrosion resistance, low failure rate, and high cost-effectiveness. Still, relatively little is known about the exact mechanism of action that prevents pregnancy with the device, but there are two leading hypotheses. First, the dissolution of copper ions may interact with the sperm, preventing their movement. Alternatively, the copper causes inflammation, which prevents the movement of the sperm. After Cu-IUDs are inserted, a layer of cuprous oxide covers the surface preventing further corrosion. Continued corrosion, or the dissolution of the material into the surrounding solution, is a property of metals that is allows the release of copper from IUDs. Different metals corrode at different rates, so understanding how copper reacts to the intrauterine environment is necessary to create an optimal device.

The paper “Corrosion Behavior and Mechanical Properties of Ultrafine-Grained Pure Copper with Potential as a Biomaterial” discusses the effects that grain size of copper has on mechanical properties of the material and release of copper ions. The research uses swaging to study how grain size can affect strength and ductility as well as the corrosive behavior of the material in physiological conditions.

Originally, course-grained copper was used, but this resulted in a high release of copper ions and corrosion failure. Modifications of the shape and size of course grained Cu-IUDs resulted in little improvement. Copper tubes instead of wire resulted in an unnecessarily high release of copper ions, reducing the life span of the device. The authors believe that an ultrafine-grained Cu-IUDs offers better corrosion properties than previous materials, and therefore is suited for future contraceptive devices.

In order to generate ultrafine-grained Cu, swaging, a severe plastic deformation technique, was utilized to create non-uniform ultrafine-grains and further swaging resulted in homogenous ultrafine-grains throughout the copper bar. These techniques create a high density of dislocations with high-angle grain boundaries. As we learned in class, the application of stress created dislocations allowing the metal to deform. In class we discussed how cold working could cause plastic deformation and alter the properties of the metal. In this paper, swaging was utilized to generate more grains and dislocations. The finer grain improves ductility, increases strength, increases workability, and increases failure resistance compared to course-grained Cu.

The researchers used commercial copper, which was rotary swaged to decrease the cross-sectional area of the bar. The image below shows optical micrographs of the copper at increasing small areas and finer grain sizes.

Next the ultimate tensile strength and yield strength were tested. As we learned in class, smaller grain size resulted in higher tensile strength and higher yield strength, as shown in the graph below. After a point, the tensile strength begins to decline which suggests there’s an optimum grain size to achieve maximum strength. Ductility – measured by elongation – decreased with decreased grain size.

Finer grains resulted in lower corrosion resistance and a higher corrosion rate because high dislocation density occurred due to the plastic deformation. The high density of grain boundaries in finer grained copper were associated with greater number of electrons and resulted in more immediate formation of a surface layer of Cu2O. They further investigated the corrosion resistance using electrochemical impedance spectroscopy. They found that the fine grain had a more homogenous nanocrystalline microstructure, which resulted in a more uniform distribution of grain boundaries, which created a more compact protective layer and reduced polarization. Larger grains were found to be less resistant to corrosion.

The thick oxide layer found in fine grain copper was found to facilitate the release of soluble copper ions necessary for infertility. Finer grains are seen to generate more uniform corrosion. In conclusion, the authors believe that fine-grain copper led to improved mechanical properties and more uniform corrosion, making it a promising material for Cu-IUDs. The paper is significant because optimizing Cu-IUDs can provide more effective and longer lasting contraceptive devices. Creating a more even dissolution of copper ions could minimize negative side effects by providing only the necessary amount of ions necessary to prevent sperms movement. Providing better contraceptive devices has the potential to improve quality of life by minimizing unplanned pregnancies and decreasing physician visits.

Source: Gholami M, Mhaede M, Pastorek F, Altenberger I, Hadzima B, et al. 2015. Corrosion Behavior and Mechanical Properties of Ultrafine-Grained Pure Copper with Potential as a Biomaterial. Advanced Engineering Materials. 18(4):615–23

In our unit on glasses and ceramics, we learned about bulk metallic glasses, which are amorphous metallic alloys. BMGs have beneficial properties, such as enhanced corrosion resistance, high strength, and high flexibility. Furthermore, the material has high processibility and its unique blow molding fabrication technique allows the shape, size, and surface pattern to be tightly controlled and easily replicated. Bulk metallic glasses can be designed to contain surface modifications and micro and nanopatterns. These surface modifications give the material the unique ability to decrease fusion of foreign body giant cells thereby decreasing the resulting immune response.

In the article “Bulk Metallic Glasses for Biomedical Applications” the authors discuss the versatility of BMGs for implant applications. They examined the biological responses to BMGs in vitro and in vivo and found the material promoted cell adhesion and improved immune responses. Because of the material’s good processing capability and good biocompatibility, the authors proposed that the material could be used to improve a variety of bioengineered medical devices.

One application of BMGs that was discussed in class is a reservoir for controlled drug release. Applied to reproductive health, BMGs could be used to design better drug delivery systems such as IUDs or birth control arm implants. Currently, most IUDs and arm implants are made of very flexible polymers, although BMGs are extremely ductile, which may pose an issue. Some types of  IUDs, such as the ParaGuard, are made with coils of copper. BMGs have been created with copper, as demonstrated by Xu et al. IUDs made of bulk metallic glasses containing copper could provide several advantages over traditional copper IUDs. First, the casting method to create BMGs allows for intricate designs and may simplify the production of the device, which is typically t-shaped. Furthermore, BMGs have higher wear resistance and greater compressive strength, making them potentially safer devices. The use of surface nano- and micropatterns may provide an additional benefit to create IUDs. The copper interferes with sperm movement through the release of copper ions. Increasing the exposed surface area potentially could increase the effectiveness of the IUD, and/or interfere with the sperm. One aspect that must be considered is copper IUDs rely on the immune response to kill sperm. Decreasing the immune response by using more biocompatible material such as the BMG, has the potential to decrease the efficacy of the device. There was no information on designing IUDs with copper BMGs in the literature, although the beneficial characteristics of BMGs make it an interesting application to look into.

Sources:

Schroers J, Kumar G, Hodges TM, Chan S, Kyriakides TR. 2009. Bulk metallic glasses for biomedical applications. Jom. 61(9):21–29

How PARAGARD Works. PARAGARD® (intrauterine copper contraceptive). https://www.paragard.com/how-paragard-works.aspx

Xu D, Lohwongwatana B, Duan G, Johnson WL, Garland C. 2004. Bulk metallic glass formation in binary Cu-rich alloy series – Cu100−xZrx (x=34, 36, 38.2, 40 at.%) and mechanical properties of bulk Cu64Zr36 glass. Acta Materialia. 52(9):2621–24

The student polymer presentations discussed the potential for hyaluronic acid scaffolds for drug delivery, which may be applicable for the development of contraceptive devices. Hyaluronic acid, the class learned was a natural polymer that played various roles in the body including wound healing, tissue repair, and the mediation of cell proliferation. Hyaluronic acid hydrogels are increasingly being used to deliver drugs because they are biocompatible, biodegradable, and non-immunogenic. Furthermore, HA hydrogels are highly tunable which allows the rate of degradation to be modified to fit various drug delivery needs. As the presentation in class discussed, HA-based hydrogels hold great potential for tissue repair and regeneration, such as in the in the repair of the lumbar disc through the administration of growth factors and mesenchymal stem cells.

I was interested to see whether HA-based hydrogel technology had been explored for contraceptives, and found little research on the topic. There were several patents for HA-based drug delivery devices that included the use of their technology for contraceptives in their claims (US5616568A). As the guest lecturer in class discussed, these claims will prevent others from infringing on the researchers intellectual property but may prevent research. Interestingly there was very little research that specifically examined a HA-based solution to deliver contraceptive drugs, although Gupta et al. discussed HA as a potential intravaginal delivery mechanism for contraception (Gupta & Prabha, 2017). Nowak et al. examined how preactivated hyaluronic acid could be used as a vaginal delivery system. They stabilized and enhanced mucoadhesive properties by thiolating and preactivating hyaluronic acid. It was found that the preactivated HA-CYS-MNA demonstrated beneficial bio adhesion allowing for increased retention time of vaginally administered drugs and could be a potentially advantageous biomaterial for the delivery of various drugs, including contraceptive (Nowak, 2015).

In women’s health, HA has been commonly used for the treatment of de novo dyspareunia in women using hormonal oral contraceptive. Hyaluronic acid has been been found to be a very effective treatment for dyspareunia, which is associated with the long-term use of oral hormonal contraceptive (Serati, 2015). The biomaterial has a proven track record of being tolerated by women and may confer additional benefits outside of drug delivery. While there may be limitations to HA-based delivery drugs that have deterred research in a contraceptive application, it appears to hold promising possibilities for a new route of administration. If a HA-based hydrogel could hold contraceptives and release them over long time periods, it could be an additional option for women.

Sources:

Gupta, S., & Prabha, V. (2017). Intravaginal Delivery Approaches for Contraception: An Overview with Emphasis on Gels. Journal of Pharmacy & Pharmaceutical Sciences,20, 270. doi:10.18433/j3fm06

Nowak, J., Laffleur, F., & Bernkop-Schnürch, A. (2015). Preactivated hyaluronic acid: A potential mucoadhesive polymer for vaginal delivery. International Journal of Pharmaceutics,478(1), 383-389. doi:10.1016/j.ijpharm.2014.11.048

Serati, M., Bogani, G., Dedda, M. C., Braghiroli, A., Uccella, S., Cromi, A., & Ghezzi, F. (2015). A comparison between vaginal estrogen and vaginal hyaluronic for the treatment of dyspareunia in women using hormonal contraceptive. European Journal of Obstetrics & Gynecology and Reproductive Biology,191, 48-50. doi:10.1016/j.ejogrb.2015.05.026

In the last decade, there has been an increased push to develop male contraceptives. So far there have been no approved therapies, but researchers continue to explore different approaches to contraceptives. There have been significant advances developing hormonal contraceptives for men, but these have been shown to produce side effects. There has been a more recent need to develop non-hormonal drugs, such as adjudin, that can be delivered locally.

Delivering drugs locally poses significant challenges because the blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in the body. The BTB divides the function unit of the testis where spermatogenesis occurs and allows for spermatogenesis to occur in a region where the immune system is not present. Tight junctions between Sertoli cells at the BTB prevent the drugs from entering from the microvessels into the adluminal compartment. Drug transporters also actively pump molecules out of the testis posing an additional barrier. Recent advances, such as the advancement of nanotechnology, have increased the solubility of particles and decreased their size, which may allow for greater penetration across impermeable barriers.

The paper “Effective Delivery of(BTB) – Lesson from Adjudin” explores the potential of developing non-hormonal male contraceptives and using nanoparticles to deliver adjudin. Adjudin is a molecule that is known to cause reversible germ cell exfoliation by disrupting the adherens junction between germ cells and Sertoli cells in the testes. Unfortunately naturally adjudins show poor bioavailability.

In class, we discussed the barriers to drug delivery including the barriers faced by nanoparticles. In order for the nanoparticles to be effective, they must travel to the target cell and cross the cell membrane while avoiding non-specific uptake. There is a variety of pathways through which molecules can be transported; for example phagocytosis, macropinocytosis, endocytosis, and passive diffusion. Ultimately, interactions between the cells and participles take place which regulate these behaviors so it’s crucial to understand how target cells uptake particles and how cells recognize biomaterials. Furthermore, surface properties of the cell can modulate cellular interactions and affect the circulating half-life by evading the immune system. One way for this to occur is through the presence of surface proteins.

The article examines different mechanisms to allow cellular uptake of the drug, adjudin, into the target cells within the testis. The researchers considered mesoprous silica nanoparticles (MSN) because adjudin can be loaded into them and allow for oral administration. Furthermore, MSN may be magnetized by surrounding a magnetic Fe₃O₄ core with mesopores. Magnets can be placed strategically to increase delivery to target organs. For example, the article suggests placing “permanent magnets in men’s shorts to generate a strong magnetic field”. To further increase delivery to the Sertoli cell, an anti-FSH receptor antibody can be added to the surface of the MSN. MSN uses endocytosis vesicle-mediated pathways or GTPase-mediated macropinocytosis to enter cells and has been shown to be able to cross the BTB in mouse models.

While it appears there is much more research to be conducted in this space and the ideas are very general, this paper offers interesting and novel mechanisms to deliver contraceptives. I would like to explore more the actually effectiveness of the magnetic delivery of the MSN particles. I thought it was interesting that the authors were focused on non-hormonal drugs for men because the majority of contraceptives offered for women are hormonal and present significant side effects. I would be interested to see whether non-hormonal options are being explored for women’s use as well.

Chen H, Mruk D, Xia W, Bonanomi M, Silvestrini B, Cheng C-Y. 2016. Effective Delivery of Male Contraceptives Behind the Blood-Testis Barrier (BTB) – Lesson from Adjudin. Current Medicinal Chemistry23:701–713. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4845722/.

Designing forms of birth control that eliminate the need to take a pill daily not only improves quality of life but also greatly increases the efficacy of the drug due to higher rates of adherence. Currently there are several drug delivery devices, such as the intravaginal ring (IVR), intrauterine device, and birth control implants, that allow for long-term release of birth control. These devices are made of a variety of biomaterials that offer a wide range of characteristics that allow each to be effective in a given environment.

The article “Influence of Process Route on the Mechanical Properties of Polymer Based Intravaginal Drug Delivery System” discusses the necessary characteristics of an IVR for constant drug release in the vaginal cavity. In order to deliver the same drug dosage over time, the chosen polymer must allow the pharmaceutical agent to be released at a consistent rate, while not degrading itself. The paper specifically examined matrix IVRs, in which the pharmaceutical agent is homogenously distributed throughout the entire ring, rather than reservoir systems, in which the drug is only in the inside of the ring. The mechanical properties of the polymer are also important, so that the device is flexible enough to be inserted into the vaginal cavity and then rigid enough regain its shape and remain in place over time. The paper looked at the five existing IVR devices but focused on EVA rather than silicone devices. The authors examined how polymer composition and the process parameters affected the proprieties of a matrix based IVR.

In class we discussed the mechanical properties of polymers such as their tensile strength and elasticity and the tests utilized to measure these properties. We discussed that optimizing these properties were crucial for the success of devices because the devices must withstand the forces of the body without deforming or fracturing. Furthermore, devices should not exert strong forces on their environment but rather should show similar properties as their surroundings.

The authors of the paper varied the polymer vinyl acetate (VA) content and hydrophilic polymer (HP) in the EVA rings and recorded changes in compression and relaxation using a Z005 tester. For tensile strength testing, the ring was pulled until failure occurred and the net extension and net load were recorded. The maximum tensile stress could be calculated using the equation:

Ultimately their goal was to determine what the optimal VA content was that would allow the ring to remain within the vaginal cavity without damaging the endothelial tissue. Specifically the VA and HP content was varied to investigate the effects on the mechanical properties of the device. The effect of temperature of the melt was also examined.

Increasing the VA content reduced the cyrstallinity, which created greater drug permeability and increased elasticity. The authors found that at VA content of 18% or below yielded an unacceptable elasticity, but VA content had little effect on the tensile strength. Furthermore, HP content greater than 10% proved to have very low fracture points, which made them unsuitable for devices. The ideal IVR must have HP content less than 10% and a VA content greater than 18%. The applied hot channel temperature appeared to have a significant impact on tensile strength. Below 190°C the tensile strength decrease.

The paper found that matrix IVRs can be produced out of EVA and the VA and HP content should be optimized for effective mechanical properties so that individuals can utilize the drug device. While the paper examines the tensile force and compression and relaxation of the materials, many other properties of the device should be taken into account when optimizing the ration of the two materials or choosing an additional material. Changing the VA and HP content changed the crystalline structure of the device which might effect the rate at which the pharmaceutical agent is being released in the body. In addition the researchers should examine if the yield point changes. Because the devices are compressed during insertion and then expected to return to their original shape, the ring cannot experience plastic deformation from the forces.

While the intravaginal ring offers many benefits, the risk of falling out is still substantial so its critical to develop a ring that demonstrate necessary mechanical properties. The ring has been shown to very effectively release birth control and is more effective than oral medications due to the elimination of the burden of daily pills.

Source: Eggenreich, K., S. Schrank, G. Koscher, K. Nickisch, E. Roblegg, and J. Khinast. Influence of process route on the mechanical properties of polymer based intravaginal drug delivery systems. AIP Conference Proceedings , 2017.doi:10.1063/1.5016734

Over the semester, I hope to explore the application of different biomaterials to address unmet needs in women’s health. While many popular women’s health products (such as the Pill) have experienced little innovation since the sixties, recently there has been an increase in interest and investment in women’s health related research and technology. This blog is going to examine a variety of products for women’s health, specifically relating to contraception. The use of novel materials and delivery systems holds exciting possibilities for the future because designing new and improved forms of birth control will allow women to have more options. As of now, there’s a tremendous unmet need because many forms produce negative side effects and the burden of a daily pill reduces adherence and efficacy. Biomaterials play an integral role in the delivery mechanism of many novel options.