Nowadays, there are still numerous challenges for well-known biomedical applications, such as tissue engineering (TE), wound healing and controlled drug delivery, which must be faced and solved. Hydrogels have been proposed as excellent candidates for these applications, as they have promising properties for the mentioned applications, including biocompatibility, biodegradability, great absorption capacity and tunable mechanical properties. However, depending on the material or the manufacturing method, the resulting hydrogel may not be up to the specific task for which it is designed, thus there are different approaches proposed to enhance hydrogel performance for the requirements of the application in question. The main purpose of this review article was to summarize the most recent trends of hydrogel technology, going through the most used polymeric materials and the most popular hydrogel synthesis methods in recent years, including different strategies of enhancing hydrogels’ properties, such as cross-linking and the manufacture of composite hydrogels. In addition, the secondary objective of this review was to briefly discuss other novel applications of hydrogels that have been proposed in the past few years which have drawn a lot of attention.

Several studies have shown the influence of the physical properties of scaffolds on their mechanical properties. An initial characterization of a type of collagen protein was carried out by studying its composition andits solubility at different pH values and infrared spectroscopy. Subsequently, porosity and scaffold pore size were studied, assessing how varying the composition of the initial solution (increasing the protein concentration or adding glutaraldehyde) changed the properties of the final scaffolds obtained. Lastly, rheological measurements were performed to evaluate the mechanical strength of the scaffolds. The initial characterization revealed that the type I collagen protein used is considerably denatured. In addition, increasing the protein content in the scaffold decreases the porosity, related to an increase in the elastic modulus producing an enhancement of its mechanical strength, while adding glutaraldehyde to the scaffold increases its mechanical strength without lowering its pore size or porosity. The results obtained are useful in that they demonstrate that it is possible to design a scaffold with specific properties, by just controlling the collagen concentration or adding glutaraldehyde to the initial solution. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1462-1468, 2016.

Biomaterials have been used since ancient times. However, it was not until the late 1960s when their development prospered, increasing the research on them. In recent years, the study of biomaterials has focused mainly on tissue regeneration, requiring a biomaterial that can support cells during their growth and fulfill the function of the replaced tissue until its regeneration. These materials, called scaffolds, have been developed with a wide variety of materials and processes, with the polymer ones being the most advanced. For this reason, the need arises for a review that compiles the techniques most used in the development of polymer-based scaffolds. This review has focused on three of the most used techniques: freeze-drying, electrospinning and 3D printing, focusing on current and future trends. In addition, the advantages and disadvantages of each of them have been compared.

The creation of skeletal muscle tissue in vitro is a major topic of interest today in the field of biomedical research, due to the lack of treatments for muscle loss due to traumatic accidents or disease. For this reason, the intrinsic properties of nanofibrillar structures to promote cell adhesion, proliferation, and cell alignment presents an attractive tool for regenerative medicine to recreate organized tissues such as muscle. Electrospinning is one of the processing techniques often used for the fabrication of these nanofibrous structures and the combination of synthetic and natural polymers is often required to achieve optimal mechanical and physiochemical properties. Here, polycaprolactone (PCL) is selected as a synthetic polymer used for the fabrication of scaffolds, and the effect of protein addition on the final scaffolds' properties is studied. Collagen and gelatin were the proteins selected and two different concentrations were analyzed (2 and 4 wt/vol%). Different PCL/protein systems were prepared, and a structural, mechanical and functional characterization was performed. The influence of fiber alignment on the properties of the final scaffolds was assessed through morphological, mechanical and biological evaluations. A bioreactor was used to promote cell proliferation and differentiation within the scaffolds. The results revealed that protein addition produced a decrease in the fiber size of the membranes, an increase in their hydrophilicity, and a softening of their mechanical properties. The biological study showed the ability of the selected systems to harbor cells, allow their growth and, potentially, develop musculoskeletal tissues.