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1. 3D printing of drug-eluting bioactive multifunctional coatings for orthopedic applications

   https://doi.org/10.18063/ijb.v9i2.661  

   Adarkwa, Eben ; Roy, Abhijit ; Ohodnicki, John ; Lee, Boeun ; Kumta, Prashant N. ; Desai, Salil ( December 2022 , International Journal of Bioprinting)

   Three-dimensional (3D) printing is implemented for surface modification of titanium alloy substrates with multilayered biofunctional polymeric coatings. Poly(lactic-coglycolic) acid (PLGA) and polycaprolactone (PCL) polymers were embedded with amorphous calcium phosphate (ACP) and vancomycin (VA) therapeutic agents to promote osseointegration and antibacterial activity, respectively. PCL coatings revealed a uniform deposition pattern of the ACP-laden formulation and enhanced cell adhesion on the titanium alloy substrates as compared to the PLGA coatings. Scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed a nanocomposite structure of ACP particles showing strong binding with the polymers. Cell viability data showed comparable MC3T3 osteoblast proliferation on polymeric coatings as equivalent to positive controls. In vitro live/dead assessment indicated higher cell attachments for 10 layers (burst release of ACP) as compared to 20 layers (steady release) for PCL coatings. The PCL coatings loaded with the antibacterial drug VA displayed a tunable release kinetics profile based on the multilayered design and drug content of the coatings. Moreover, the concentration of active VA released from the coatings was above the minimum inhibitory concentration and minimum bactericidal concentration, demonstrating its effectiveness against Staphylococcus aureus bacterial strain. This research provides a basis for developing antibacterial biocompatible coatings to promote osseointegration of orthopedic implants. 

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2. Thermogelling, ABC Triblock Copolymer Platform for Resorbable Hydrogels with Tunable, Degradation‐Mediated Drug Release

   https://doi.org/10.1002/adfm.201704107  

   Gupta, Mukesh K. ; Martin, John R. ; Dollinger, Bryan R. ; Hattaway, Madison E. ; Duvall, Craig L. ( October 2017 , Advanced Functional Materials)

   Clinical application of injectable, thermoresponsive hydrogels is hindered by lack of degradability and controlled drug release. To overcome these challenges, a family of thermoresponsive, ABC triblock polymer‐based hydrogels has been engineered to degrade and release drug cargo through either oxidative or hydrolytic/enzymatic mechanisms dictated by the “A” block composition. Three ABC triblock copolymers are synthesized with varying “A” blocks, including oxidation‐sensitive poly(propylene sulfide), slow hydrolytically/enzymatically degradable poly(ε‐caprolactone), and fast hydrolytically/enzymatically degradable poly(d,l‐lactide‐co‐glycolide), forming the respective formulations PPS₁₃₅‐b‐PDMA₁₅₂‐b‐PNIPAAM₂₂₅(PDN), PCL₈₅‐b‐PDMA₁₅₀‐b‐PNIPAAM₁₅₀(CDN), and PLGA₆₀‐b‐PDMA₁₄₈‐b‐PNIPAAM₁₅₂(LGDN). For all three polymers, hydrophilic poly(N,N‐dimethylacrylamide) and thermally responsive poly(N‐isopropylacrylamide) comprise the “B” and “C” blocks, respectively. These copolymers form micelles in aqueous solutions at ambient temperature that can be preloaded with small molecule drugs. These solutions quickly transition into hydrogels upon heating to 37 °C, forming a supra‐assembly of physically crosslinked, drug‐loaded micelles. PDN hydrogels are selectively degraded under oxidative conditions while CDN and LGDN hydrogels are inert to oxidation but show differential rates of hydrolytic/enzymatic decomposition. All three hydrogels are cytocompatible in vitro and in vivo, and drug‐loaded hydrogels demonstrate differential release kinetics in vivo corresponding with their specific degradation mechanism. These collective data highlight the potential cell and drug delivery use of this tunable class of ABC triblock polymer thermogels.

    

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3. Comparison of endothelial cell attachment on surfaces of biodegradable polymer-coated magnesium alloys in a microfluidic environment

   https://doi.org/10.1371/journal.pone.0205611  

   Liu, Lumei Liu ; Ye, Sang-Ho ; Gu, Xinzhu ; Russel, Teal ; Xu, Zhigang ; Wagner, William R. ; Lee, Young-Choon ( October 2018 , PloS one)

   Polymeric coatings can provide temporary stability to bioresorbable metallic stents at the initial stage of deployment by alleviating rapid degradation and providing better interaction with surrounding vasculature. To understand this interfacing biocompatibility, this study explored the endothelial-cytocompatibility of polymer-coated magnesium (Mg) alloys under static and dynamic conditions compared to that of non-coated Mg alloy surfaces. Poly (carbonate urethane) urea (PCUU) and poly (lactic-co-glycolic acid) (PLGA) were coated on Mg alloys (WE43, AZ31, ZWEKL, ZWEKC) and 316L stainless steel (316L SS, control sample), which were embedded into a microfluidic device to simulate a vascular environment with dynamic flow. The results from attachment and viability tests showed that more cells were attached on the polymer-coated Mg alloys than on non-coated Mg alloys in both static and dynamic conditions. In particular, the attachment and viability on PCUU-coated surfaces were significantly higher than that of PLGA-coated surfaces of WE43 and ZWEKC in both static and dynamic conditions, and of AZ31 in dynamic conditions (P<0.05). The elementary distribution map showed that there were relatively higher Carbon weight percentages and lower Mg weight percentages on PCUU-coated alloys than PLGA-coated alloys. Various levels of pittings were observed underneath the polymer coatings, and the pittings were more severe on the surface of Mg alloys that corroded rapidly. Polymer coatings are recommended to be applied on Mg alloys with relatively low corrosion rates, or after pre-stabilizing the substrate. PCUU-coating has more selective potential to enhance the biocompatibility and mitigate the endothelium damage of Mg alloy stenting. 

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4. Polymeric coatings for applications in electrocatalytic and photoelectrosynthetic fuel production

   https://doi.org/10.1039/C8TA05805A  

   Wadsworth, B. L. ; Khusnutdinova, D. ; Moore, G. F. ( November 2018 , Journal of Materials Chemistry A)

   Applications of polymeric coatings have emerged as a promising direction for preparing multilayered assemblies and controlling surface properties. In addition to providing a foundation for interfacing soft materials onto solid supports, polymers afford opportunities to develop hybrid constructs with properties difficult to achieve using monolayer-based chemical modification methods. In particular, the microenvironments of polymers are proposed to facilitate charge transfer to redox-active sites, manage delivery of chemical substrates, improve product specificity during catalytic transformations, and lend chemical protection to underpinning solid-state supports as well as embedded components. In this article, we highlight selected examples of polymeric materials utilized in electrocatalytic and photoelectrosynthetic fuel production. 

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5. Sustained release of N ‐acetylcysteine by sandwich structured polycaprolactone/collagen scaffolds for wound healing

   https://doi.org/10.1002/jbm.a.36656  

   Hou, Jinfei ; Chen, Lifeng ; Liu, Zhirong ; Li, Jialun ; Yang, Jie ; Zhong, Aimei ; Zhou, Muran ; Sun, Yang ; Guo, Liang ; Yang, Yanqing ; et al ( March 2019 , Journal of Biomedical Materials Research Part A)

   PCL (poly‐caprolactone) nanofibers have good biocompatibility and high porosity, which are usually utilized for application in wound dressings. However, wound healing could be hindered by the overproduction of reactive oxygen species (ROS) and different factors. Pure nanofibers cannot satisfy these requirements of wound healing.N‐acetylcysteine (NAC), as an antioxidant, meets the requirements for wound healing by resisting the overproduction of ROS and by promoting angiogenesis and maturation of the epidermis. In this study, we prepared a sandwich structured PCL‐Col/NAC scaffold using the molding method, which consisted of PCL nanofibers at the core and NAC‐loaded collagen on both sides. The hydroscopicity and tensile modulus of PCL‐Col/NAC scaffolds showed best performance of these properties among groups. Meanwhile, the drug release profiles of PCL‐Col/NAC scaffolds were investigated using the HPLC method and the results suggested a sustained drug release of NAC for PCL‐Col/NAC scaffolds. In addition, PCL‐Col/NAC scaffolds presented better properties than the control groups in cell migration and proliferation. The in vivo wound healing therapy effect was studied using an oval (2 × 1 cm) full‐thickness skin defect wound model for SD rats. After 21 days, gross view and histological analysis showed a favorable beneficial therapeutic effect as well as better epidermal maturation compared with the control groups. CD31 immunohistology results revealed relatively more new vessels in the PCL‐Col/NAC group than the control groups. This study developed novel PCL‐Col/NAC scaffolds with an excellent hydroscopicity, tensile modulus and the ability to promote epidermal maturation and angiogenesis, demonstrating its promising potential in wound healing treatment. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

    

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