The usage of gelatin hydrogel is limited due to its instability and poor mechanical properties, especially under physiological conditions. Divalent metal ions present in gelatin such as Ca2+ and Fe2+ play important roles in the gelatin molecule interactions. The objective of this study was to determine the impact of divalent ion removal on the stability and mechanical properties of gelatin gels with and without chemical crosslinking. The gelatin solution was purified by Chelex resin to replace divalent metal ions with sodium ions. The gel was then chemically crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Results showed that the removal of divalent metal ions significantly impacted the formation of the gelatin network. The purified gelatin hydrogels had less interactions between gelatin molecules and form larger-pore network which enabled EDC to penetrate and crosslink the gel more efficiently. The crosslinked purified gels showed small swelling ratio, higher crosslinking density and dramatically increased storage and loss moduli. The removal of divalent ions is a simple yet effective method that can significantly improve the stability and strength of gelatin hydrogels. The in vitro cell culture demonstrated that the purified gelatin maintained its ability to support cell attachment and spreading.
Native tissues are endowed with a highly organized nanofibrous extracellular matrix (ECM) that directs cellular distribution and function. The objective of this study is to create a purely natural, uniform, and highly aligned nanofibrous ECM scaffold for potential tissue engineering applications. Synthetic nanogratings (130 nm in depth) were used to direct the growth of human dermal fibroblasts for up to 8 weeks, resulting in a uniform 70 μm–thick fibroblast cell sheet with highly aligned cells and ECM nanofibers. A natural ECM scaffold with uniformly aligned nanofibers of 78 ± 9 nm in diameter was generated after removing the cellular components from the detached fibroblast sheet. The elastic modulus of the scaffold was well maintained after the decellularization process because of the preservation of elastin fibers. Reseeding human mesenchymal stem cells (hMSCs) showed the excellent capacity of the scaffold in directing and supporting cell alignment and proliferation along the underlying fibers. The scaffold’s biocompatibility was further examined by an in vitro inflammation assay with seeded macrophages. The aligned ECM scaffold induced a significantly lower immune response compared to its unaligned counterpart, as detected by the pro-inflammatory cytokines secreted from macrophages. The aligned nanofibrous ECM scaffold holds great potential in engineering organized tissues.
Our innovative curriculum improved medical student comfort level discussing HPV vaccination with hesitant parents and increased the perceived likelihood of recommending HPV vaccination. The intervention is easy to implement, scalable, and requires minimal resources. Educating future providers on this important topic has the potential to improve vaccination rates nationwide and thus should be considered for all medical students.
Nitric oxide (NO) plays an important role in cardiovascular homeostasis, immune responses, and wound repair. The pro-angiogenic and antimicrobial properties of NO has stimulated the development of NO-releasing materials for wound dressings. Gelatin, an abundant natural biodegradable polymer derived from collagen, is able to promote wound repair. S-Nitroso-N-acetylpenicillamine (SNAP) can release NO under physiological conditions and when exposed to light. The objective of this project was to fabricate a NO-releasing gelatin-based nanofibrous matrix with precise light-controllable ability. Results showed that under controlled phase separation fabrication conditions, the gelatin formed a highly porous matrix with the nanofiber diameter ranging from 50 to 500 nm. Importantly, the removal of the trace amount of divalent metal ions within gelatin generated a more stable nanofibrous structure. N-acetyl-D-penicillamine (NAP) was functionalized onto the matrix and nitrosated with t-butyl nitrite, yielding a SNAP-gelatin matrix. Analysis of the photoinitiated NO-release showed that the SNAP-gelatin matrices released NO in a highly controllable manner. Application of increasing light intensities yielded increased NO flux from the matrices. In addition, the dried matrices stored in dark at 4 °C maintained stable NO storage capacity, and the purified (ion-removed) gelatin preserved higher NO-releasing capacity than nonpurified gelatin. The antibacterial effect from the SNAP-gelatin matrices was demonstrated by exposing Staphylococcus aureus ( S. aureus ) to a light-triggered NO flux. This controllable NO-releasing scaffold provides a potential antibacterial therapeutic approach to combat drug resistant bacteria.
Nitric oxide plays important roles in cardiovascular homeostasis, immune responses and wound repair. Therefore, polymers that release nitric oxide locally at the surface exhibit improved biocompatibility for biomedical implants through reducing neointimal hyperplasia and thrombosis caused by blood vessel wall damage. The objective of this article was to fabricate a nitric oxide–releasing gelatin hydrogel that can continuously generate nitric oxide at a physiologically relevant level and inhibit cell attachment and proliferation. The nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP), was successfully conjugated to the gelatin hydrogel, which showed a rapid nitric oxide release in the first 2 h and then a slower but sustained release in the next 70-h period. Human mesenchymal stem cells (hMSCs), as a model cell line with wide biomedical applications, were used to examine the cell attachment and proliferation of the nitric oxide–releasing gelatin hydrogel. Compared with the control gelatin, the nitric oxide–releasing gelatin hydrogel demonstrated a 0·35 times lower hMSCs attachment at 6 h and a 3·15 times lower hMSCs proliferation after 72-h incubation. Moreover, hMSCs on nitric oxide–releasing gelatin exhibited a rounder cell shape and covered less cellular area than their counterparts on the control gelatin hydrogel. This gelatin hydrogel with local nitric oxide release at physiological level provides a promising therapeutic approach in enhancing the performance of biomedical implants.
Introduction: Current bioinks for 3D bioprinting, such as gelatin-methacryloyl, are generally low viscosity fluids at room temperature, requiring specialized systems to create complex geometries. Methods and Results: Adding decellularized extracellular matrix microparticles derived from porcine tracheal cartilage to gelatin-methacryloyl creates a yield stress fluid capable of forming self-supporting structures. This bioink blend performs similarly at 25 °C to gelatin-methacryloyl alone at 15 °C in linear resolution, print fidelity, and tensile mechanics. Conclusion: This method lowers barriers to manufacturing complex tissue geometries and removes the need for cooling systems.
Engineered skeletal muscle grafts have made great progress during the past decades, benefiting from a growing understanding of mechanobiology and stem cell differentiation. Current techniques are widely varied, ranging from in vitro methods following the classical tissue engineering paradigm to in situ approaches such as host cell recruitment. In different ways, all of these try to supply mechanical toughness while providing the necessary signals for differentiation and maturation of the engineered skeletal muscle.
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