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Polymer-clay nanocomposite hydrogel films (PCNCHFs) were prepared from caboxymethyl cellulose, polyvinylpyrrolidone, agar and nanosepiolite clay (0, 0.3, 0.5, 0.7, 0.9 and 1.5% reinforcement) by treating thermally in a simple, rapid, and inexpensive route. The PCNCHFs and its 5-fluorouracil (FU)-loaded composites (PCNCHFs@FU) were tested for FU release and characterized by FTIR, XRD, FE-SEM, EDX, DSC, and TGA analyses to investigate their structural, morphological, and thermal properties. The nanosepiolite-loaded polymer composites (PCNCHF1 to PCNCHF5) exhibited higher tensile strength than the pristine polymer hydrogel (PCNCHF0); consequently, the thermal properties (glass- and melting-transition) were improved. The PCNCHFs@FU demonstrated prolonged FU release at pH 7.4 for 32 h. The biocompatibility of PCNCHFs was tested against human skin fibroblast (CCDK) cells. The viability of cells exposed to all PCNCHFs was >95% after 72 h of culture. The live/dead assay show the proliferation of fibroblast cells, confirming the biocompatibility of the hydrogels. The pH-sensitive PCNCHFs@FU release could be suitable for drug release in cancer therapy, and the developed PCNCHFs may also be useful for tissue engineering, food packaging, and other biological applications., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2021. Published by Elsevier B.V.)

Gelatin methacryloyl (GelMA) is a versatile biomaterial that has been used in various biomedical fields. Thus far, however, GelMA is mostly obtained from mammalian sources, which are associated with a risk of transmission of diseases, such as mad cow disease, as well as certain religious restrictions. In this study, we synthesized GelMA using fish-derived gelatin by a conventional GelMA synthesis method, and evaluated its physical properties and cell responses. The lower melting point of fish gelatin compared to porcine gelatin allowed larger-scale synthesis of GelMA and enabled hydrogel fabrication at room temperature. The properties (mechanical strength, water swelling degree and degradation rate) of fish GelMA differed from those of porcine GelMA, and could be tuned to suit diverse applications. Cells adhered, proliferated, and formed networks with surrounding cells on fish GelMA, and maintained high initial cell viability. These data suggest that fish GelMA could be utilized in a variety of biomedical fields as a substitute for mammalian-derived materials., Competing Interests: This commercial affiliation (Samsung Electronics) does not alter our adherence to PLOS ONE policies on sharing data and materials.

The stiffness of hydrogels has been reported to direct cell fate. Here, we found that the stiffness of hydrogels promotes the reprogramming of mouse embryonic fibroblasts into induced pluripotent stem cells (iPSCs). We prepared cell culture substrates of various stiffnesses (0.1, 1, 4, 10, and 20 kPa) using a polyacrylamide hydrogel. We found that culture on a soft hydrogel plays an important role in inducing cellular reprogramming into iPSCs via activation of mesenchymal-to-epithelial transition and enhancement of stemness marker expression. These results suggest that physical signals at the interface between cell and substrate can be used as a potent regulator to promote cell fate changes associated with reprogramming into iPSCs, which may lead to effective and reproducible iPSC-production., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To achieve the task of fabricating functional tissues, scaffold materials that can be sufficiently vascularized to mimic functionality and complexity of native tissues are yet to be developed. Here, we report development of synthetic, biomimetic hydrogels that allow the rapid formation of a stable and mature vascular network both in vitro and in vivo. Hydrogels were fabricated with integrin binding sites and protease-sensitive substrates to mimic the natural provisional extracellular matrices, and endothelial cells cultured in these hydrogels organized into stable, intricate networks of capillary-like structures. The resulting structures were further stabilized by recruitment of mesenchymal progenitor cells that differentiated into a smooth muscle cell lineage and deposited collagen IV and laminin in vitro. In addition, hydrogels transplanted into mouse corneas were infiltrated with host vasculature, resulting in extensive vascularization with functional blood vessels. These results indicate that these hydrogels may be useful for applications in basic biological research, tissue engineering, and regenerative medicine., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Micropatterning techniques that control three-dimensional (3D) arrangement of biomolecules and cells at the microscale will allow development of clinically relevant tissues composed of multiple cell types in complex architecture. Although there have been significant developments to regulate spatial and temporal distribution of biomolecules in various materials, most micropatterning techniques are applicable only to two-dimensional patterning. We report here the use of two-photon laser scanning (TPLS) photolithographic technique to micropattern cell adhesive ligand (RGDS) in hydrogels to guide cell migration along pre-defined 3D pathways. The TPLS photolithographic technique regulates photo-reactive processes in microscale focal volumes to generate complex, free from microscale patterns with control over spatial presentation and concentration of biomolecules within hydrogel scaffolds. The TPLS photolithographic technique was used to dictate the precise location of RGDS in collagenase-sensitive poly(ethylene glycol-co-peptide) diacrylate hydrogels, and the amount of immobilized RGDS was evaluated using fluorescein-tagged RGDS. When human dermal fibroblasts cultured in fibrin clusters were encapsulated within the micropatterned collagenase-sensitive hydrogels, the cells underwent guided 3D migration only into the RGDS-patterned regions of the hydrogels. These results demonstrate the prospect of guiding tissue regeneration at the microscale in 3D scaffolds by providing appropriate bioactive cues in highly defined geometries.

We have developed collagenase-sensitive hydrogels by incorporating a collagenase-sensitive fluorogenic substrate (CS-FS) within the backbone of a polyethylene glycol (PEG) copolymer to visualize collagenase activity during three-dimensional cell migration. CS-FS was synthesized by conjugating Bodipy dyes to a peptide with collagenase-sensitive sequence, Leu-Gly-Pro-Ala (LGPA), and the products were grafted into the collagenase-sensitive PEG hydrogels. CS-FS both in solution and hydrogels had an increase in the fluorescence intensity after proteolytic degradation by collagenase, but not by non-targeted proteases nor in the absence of an enzyme. Fibroblasts inside the hydrogels conjugated with CS-FS spread and extended lamellipodia in three dimensions over several days, and their pericellular collagenase-mediated proteolysis of the hydrogel was visualized via confocal microscopy. A matrix metalloproteinase inhibitor, served as a negative control, significantly reduced the degradation rate of CS-FS by collagenase and prevented cell migration and cell-mediated collagenase activity inside these hydrogels. In summary, we have fabricated collagenase-sensitive hydrogels incorporated with CS-FS and successfully visualized the collagenase activity during three-dimensional cell migration.

We have developed a dual-sensitive composite hydrogel network from guar gum grafted polyacrylamidoglycolic acid (graft polymer) using sodium borohydride, which induces cross-linking and growth of silver nuclei by reduction reaction through a fast and easy route. The cross-linked graft polymer (GGAA) and its silver nanocomposite (GGAA@SNC) hydrogels have been successfully utilized to explore sustained release of 5-fluorouracil (5-FU), an anticancer drug, and antibacterial activity was evaluated. The composite hydrogels exhibit sol-gel behavior due to pH and temperature effect. To identify the functional interactions of pure guar gum (GG), graft polymer, 5-FU loaded GGAA and GGAA@SNC hydrogels, the synthesized materials are characterized by FTIR, DSC, and XRD analysis. In addition, the growth of silver nanoparticles (SNPs), its size, and stability in the hydrogel network were verified by UV-vis spectra, FE-TEM, and TGA-DTA analysis. Additionally, the structural morphology and porosity of polymer structures were observed by FE-SEM analysis. The different polymer network parameters (Mc, χ, 휉 and ϕ) and diffusion constant (D) were calculated by using swelling data and evaluated to assess the drug release profile. The diffusion exponents (n) were determined by studying 5-FU release behavior of the composite hydrogels in phosphate buffer solution (pH = 1.2 & 7.4); in vitro release data indicated that, maximum 5-FU release was significantly achieved in pH 7.4 rather than pH 1.2. The GGAA@SNC hydrogels showed excellent antibacterial activity towards Bacillus subtilis and Salmonella ebony using zone of inhibition test. A versatile strategy has been developed to prepare GGAA@SNC hydrogels to enhance 5-FU release over 16 h for its effective anticancer drug release applications. [ABSTRACT FROM AUTHOR]

Poly(acrylamide- co -acrylamidoglycolic acid)/guar gum@ Ag-nanocomposite (AgNC@PAAG) hydrogels has been fabricated by a green protocol utilizing rhubarb stem-extract as bioreductant. The prepared nanocomposites (NCs) are formulated by varying guar gum (GG) polymer and cross-linker content, and used remarkably to study the release of an anticancer drug, 5-fluorouracil (FU). The AgNC@PAAG has demonstrated its potential in bacterial inactivation and p -nitrophenol (PNP) reduction. The AgNC@PAAG hydrogels showed extended FU release time, which was up to 23 h in pH 7.4. The higher zone of inhibition was documented for AgNC@PAAG against B. subtilis and E. coli. It was noticed that, the inhibition activity of AgNC@PAAG, was directly proportional to cross-linker content than the GG polymer. The efficiency of AgNC@PAAG as a nanocatalyst was evaluated for a model reduction reaction of p -nitrophenol (PNP) reduction by aqueous sodium borohydride (NaBH 4), with an apparent rate constant of 121.8 × 10−3 min−1 at ambient temperature. The proposed nanocatalysts are reliable and recyclable, demonstrated its catalytic recycle efficacy of 85% after the third successive run. These NCs robust its biological and catalytic activity after embedding silver nanoparticles (AgNPs) by the bioreduction process; these optimized nanocatalysts can be remarkably used in biomedical healthcare sectors and industrial catalysis. Unlabelled Image • Guar gum silver-nanocomposites (AgNC@PAAG) were prepared from rhubarb extract. • AgNC@PAAG showed extended FU release (23 h) with superior EE (62%) than PAAG. • AgNC@PAAG showed significant zone of inhibition against B. subtilis and E. coli. • AgNC@PAAG showed potential catalytic activity toward p-nitro phenol (<14 min). • AgNC@PAAG evinced notable catalytic behavior with recyclable efficiency of 85%. [ABSTRACT FROM AUTHOR]

Human skin is made up of multiple layers and is designed to protect the human body. The stratum corneum (SC), specifically, is a keratinized layer of skin through which molecules heavier than 500 Da cannot penetrate. Traditional methods of transdermal drug delivery through the SC, such as hypodermic needles, are less than ideal because their size and appearance can cause fear and pain, creating hesitation, limiting self-administration, and preventing their use in some patients altogether. A new technology has been developed to address these limitations, in which an array of needles, each microns in diameter and length, called microneedles, are able to pierce the skin’s SC to deliver therapeutic agents without stimulating the proprioceptive pain nerves. These needles provide a strong advantage because they are capable of being incorporated into patches that can be conveniently self-administered by patients, while also offering the same bioabsorption and bioavailability currently provided by hypodermic needles. There have been many advancements in microneedle fabrication, and there are currently many variations of microneedle technology. Therefore, the purpose of this review is to provide a broad, introductory summary of current microneedle technology. [ABSTRACT FROM AUTHOR]

The effect of cross-linking density of hyaluronic acid (HA) hydrogels on mechanical properties and degradation behaviors has been investigated. HA hydrogels were prepared by the covalent cross-linking of HA with poly(ethylene glycol)-diamine with two different molecular weights at various cross-linking densities. The elastic modulus increased gradually as the theoretical cross-linking density of HA hydrogels increased from 0% to 20%. However, as the theoretical cross-linking density increased above 20%, the elastic modulus decreased. At a theoretical cross-linking density of 20%, the elastic modulus increased as the molecular weight of the cross-linking molecule decreased. In vitro degradation rates of HA hydrogels decreased as the molecular weight of the cross-linking molecule decreased at a theoretical cross-linking density of 20%. The degradation rate of the cross-linked HA hydrogels decreased with increases in the theoretical cross-linking density from 0% to 20%. However, there was no significant difference in the degradation rate as the theoretical cross-linking density increased above 30%. With controllable mechanical properties and degradation rates, the developed HA hydrogels would be further investigated for various medical applications. [Copyright &y& Elsevier]