Photo cross-linked biodegradable hydrogels for enhanced vancomycin loading and sustained release

Application of photocrosslinked gelatin, alginate and dextran hydrogels in the in vitro culture of testicular tissue

Testicular tissue culture in vitro is considered an important tool for the study of spermatogenesis and the treatment of male infertility. Although agarose hydrogel is commonly used in testicular tissue culture, the efficiency of spermatogenesis in vitro is limited. In this study, testicular tissues from adult mice were cultured using a gas-liquid interphase method based on agarose (Agarose), gelatin methacryloyl (GelMA), alginate methacryloyl (AlgMA), dextran methacryloyl (DexMA), and mixture GelMA-Agarose, AlgMA-Agarose, and DexMA-Agarose hydrogels, respectively, for 32 days in vitro. The integrity of the seminiferous tubules, the density and proportions of spermatogonia, spermatocytes, Sertoli cells, and testosterone concentrations were quantified and compared between groups. Properties of different hydrogels including compression modulus, Fourier Infrared Spectroscopy (FITR) spectra, pore size, water absorption, and water retention were tested to investigate how biochemical and physical properties of hydrogels affect the results of testicular tissue culture. The results indicate that testicular tissues cultured on AlgMA exhibited the highest seminiferous tubule integrity rate (0.835 ± 0.021), the presence of a high density of spermatocytes (2107.627 ± 232.082/mm2), and a high proportion of SOX9-positive well-preserved seminiferous tubules (0.473 ± 0.047) compared to all remaining experimental groups on day 32. This may be due to the high water content of AlgMA reducing the toxic effect of oxygen on testicular tissue. In the later period of culture, testicular tissues cultured on DexMA, not DexMA-Agarose, produced significantly more testosterone (18.093 ± 3.302 ng/mL) than the other groups, suggesting that DexMA is friendly to Leydig cells. Our study provides a new idea for the optimization of the gas-liquid interphase method for achieving in vitro spermatogenesis, facilitating the future achievement of efficient in vitro spermatogenesis in more species, including humans.

New antibacterial hydrogels based on sodium alginate

Nowadays, the combined knowledge and experience in biomedical research and material sciences results in the innovation of smart materials that could efficiently overcome the problems of microbial contaminations. Herein, a new drug delivery platform prepared by grafting sodium alginate with β-carboxyethyl acrylate and acrylamide was described and characterized. 9-Aminoacridine (9-AA), and kanamycin sulfate (KS) were separately loaded into the hydrogel in situ during graft polymerization. The grafting efficiency for the resulting hydrogels was 70.01-78.08 %. The chemical structure of the hydrogels, thermogravimetric analysis, and morphological features were investigated. The swelling study revealed that the hydrogel without drugs achieved a superior swelling rate compared to drug-loaded hydrogels. The hydrogel tuned the drug-release rate in a pH-dependent manner. Furthermore, the antibacterial study suggested that the hydrogels encapsulating 9-AA (88.6 %) or KS (89.3 %) exhibited comparable antibacterial activity against Gram-positive and Gram-negative bacterial strains. Finally, the cytocompatibility study conducted on normal lung cell line (Vero cells) demonstrated neglectable to tolerable toxicity for the drug-loaded hydrogel. More interestingly, the cell viability for the blank hydrogel was 92.5 %, implying its suitability for biomedical applications.

Inherent and Composite Hydrogels as Promising Materials to Limit Antimicrobial Resistance

Antibiotic resistance has increased significantly in the recent years, and has become a global problem for human health and the environment. As a result, several technologies for the controlling of health-care associated infections have been developed over the years. Thus, the most recent findings in hydrogel fabrication, particularly antimicrobial hydrogels, could offer valuable solutions for these biomedical challenges. In this review, we discuss the most promising strategies in the development of antimicrobial hydrogels and the application of hydrogels in the treatment of microbial infections. The latest advances in the development of inherently and composite antimicrobial hydrogels will be discussed, as well as hydrogels as carriers of antimicrobials, with a focus on antibiotics, metal nanoparticles, antimicrobial peptides, and biological extracts. The emergence of CRISR-Cas9 technology for removing the antimicrobial resistance has led the necessity of new and performant carriers for delivery of the CRISPR-Cas9 system. Different delivery systems, such as composite hydrogels and many types of nanoparticles, attracted a great deal of attention and will be also discussed in this review.

Antibacterial Hydrogels

Antibacterial materials are recognized as important biomaterials due to their effective inhibition of bacterial infections. Hydrogels are 3D polymer networks crosslinked by either physical interactions or covalent bonds. Currently, hydrogels with an antibacterial function are a main focus in biomedical research. Many advanced antibacterial hydrogels are developed, each possessing unique qualities, namely high water swellability, high oxygen permeability, improved biocompatibility, ease of loading and releasing drugs, and structural diversity. Here, an overview of the structures, performances, mechanisms of action, loading and release behaviors, and applications of various antibacterial hydrogel formulations is provided. Furthermore, the prospects in biomedical research and clinical applications are predicted.

Tuning the phase transition temperature of thermal-responsive OEGylated poly-L-glutamate via random copolymerization with L-alanine

Two series of copolymers were prepared by ring-opening polymerization (ROP) of γ-(2-methoxyethoxy)esteryl-L-glutamate (L-EG2Glu) N-carboxyanhydride (NCA) and L-alanine (L-Ala) using HMDS and PEG-NH2 as initiator, respectively. Poly-(L-EG2Glu-co-L-Ala) displayed lower critical solution temperature (LCST) behavior but had a lower phase transition temperature than poly-L-EG2Glu at similar molecular weight (MW). The clouding point (CP) of random copolypeptides can be tuned by altering the alanine content and overall MW. Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) indicated that the thermal-responsive properties depended on the content of ordered conformations. PEG-b-poly-(L-EG2Glu-co-L-Ala) can spontaneously form hydrogels in water at room temperature. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that these hydrogels were formed by nanoribbons. The intermolecular hydrogen bonding among copolypeptide blocks accounted for the nanoribbon assemblies and hydrogel network formation.