Polyurethane/poly(d,l-lactic acid) scaffolds based on supercritical fluid technology for biomedical applications: Studies with L929 cells

Medical applications and prospects of polylactic acid materials

Polylactic acid (PLA) is a biodegradable and bio-based polymer that has gained significant attention as an environmentally friendly alternative to traditional petroleum-based plastics. In clinical treatment, biocompatible and non-toxic PLA materials enhance safety and reduce tissue reactions, while the biodegradability allows it to breakdown over time naturally, avoiding a second surgery. With the emergence of nanotechnology and three-dimensional (3D) printing, medical utilized-PLA has been produced with more structural and biological properties at both micro and macro scales for clinical therapy. This review summarizes current applications of the PLA-based biomaterials in drug delivery systems, orthopedic treatment, tissue regenerative engineering, and surgery and medical devices, providing viewpoints regarding the prospective medical utilization.

The three-dimensional culture of L929 and C2C12 cells based on SPI-SA interpenetrating network hydrogel scaffold with excellent mechanical properties

Cell-cultured meat, which is obtained by adsorbing cells on the three-dimensional scaffold, is considered a potential solution to animal welfare issues. Edible and safe cell-cultured meat scaffolds are a key part of its research. Soy protein isolate (SPI) hydrogel has a three-dimensional network structure and has been studied for L929 cell culture because of its non-toxicity and biocompatibility. However, the toughness and mechanical properties of SPI hydrogel are not enough to bear the requirements of cell cultivation. In this paper, sodium alginate (SA) was added to SPI hydrogel, and the interpenetrating network (IPN) technology was used to construct SPI-SA IPN hydrogel by transglutaminase and Ca2+ double crosslinking method. SPI-SA IPN hydrogel has excellent mechanical properties, structural stability and biodegradable performance than SPI hydrogel. The bio-compatibility and degradability of L929 and C2C12 cells on SPI-SA IPN hydrogel were studied by cytotoxicity, trypan blue and living/dead cell staining, and the growth law of the hydrogel as a scaffold for cell culture was analyzed. The results showed that L929/C2C12 cells can proliferate normally and adhere in hydrogel and have good bio-compatibility. L929 cells with size about 20-50 µm have better adhesion and growth abilities on SPI-SA IPN hydrogel than C2C12 cells with 100-300 µm. Therefore, the SPI-SA IPN hydrogel is non-toxic and supports the growth of cells in the pores of the material. This study provides a reference for the application of SPI-SA IPN hydrogels in vitro cell growth.

A Brief Introduction to the Polyurethanes According to the Principles of Green Chemistry

Polyurethanes are most often called “green” when they contain natural, renewable additives in their network or chemical structure, such as mono- and polysaccharides, oils (mainly vegetable oils), polyphenols (e.g., lignins, tannins), or various compounds derived from agro-waste white biotechnology (Principle 7). This usually results in these polyurethanes obtained from less hazardous substrates (Principle 4). Appropriate modification of polyurethanes makes them susceptible to degradation, and the use of appropriate processes allows for their recycling (Principle 10). However, this fulfilment of other principles also predisposes them to be green. As in the production of other polymer materials, the synthesis of polyurethanes is carried out with the use of catalysts (such as biocatalysts) (Principle 9) with full control of the course of the reaction (Principle 11), which allows maximization of the atomic economy (Principle 2) and an increase in energy efficiency (Principle 6) while minimizing the risk of production waste (Principle 1). Moreover, traditional substrates in the synthesis of polyurethanes can be replaced with less toxic ones (e.g., in non-isocyanate polyurethanes), which, at the same time, leads to a non-toxic product (Principle 3, Principle 5). In general, there is no need for blocking compounds to provide intermediates in the synthesis of polyurethanes (Principle 8). Reasonable storage of substrates, their transport, and the synthesis of polyurethanes guarantee the safety and the prevention of uncontrolled reactions (Principle 12). This publication is a summary of the achievements of scientists and technologists who are constantly working to create ideal polyurethanes that do not pollute the environment, and their synthesis and use are consistent with the principles of sustainable economy.

Comparative study of lactic acid production from date pulp waste by batch and cyclic-mode dark fermentation

Biowaste valorization into lactic acid (LA) by treatment with indigenous microbiota has recently gained considerable attention. LA production from date pulp waste provides an opportunity for resource recovery, reduces environmental issues, and possibly turns biomass into wealth. This study aimed to compare the performance of batch and cyclic fermentation processes in LA production with and without enzymatic pretreatment. The fermentation studies were conducted in the absence of an external inoculum source (relying on indigenous microbiota) and without the addition of nutrients. The highest LA volumetric productivity (3.56 g/liter/day), yield (0.07 g/g-TS), and concentration (21.66 g/L) were attained with enzymatic pretreated date pulp in the cyclic-mode fermentation at the optimized conditions. The productivity rate of LA was enhanced in the cyclic-mode as compared to the batch process. Enzymatic pretreatment increased the digestibility of cellulose that led to higher LA yield. An Artificial Neural Network model was developed to optimize the process parameters and to predict the LA concentration from date pulp waste in both fermentation processes. The main advantage of the ANN approach is the ability to perform quick predictions without resource-consuming experiments. The model predicted optimal conditions well and demonstrated good agreement between experimental and predicted data.

Formation of oriented fishbone-like pores in biodegradable polymer scaffolds using directional phase-separation processing

The scaffold is a dreamed biomaterial of tissue engineers which can culture cells three-dimensionally outgrowing the two-dimensional cell culture in a petri dish to repair or regenerate tissues and organs. To maximize the performance of this dreamed material, complex three-dimensional (3D) structures should be generated with a simple technique and nontoxic ingredients. Many tissues have tubular or fibrous bundle architectures such as nerve, muscle, tendon, ligament, blood vessel, bone and teeth. The concept of mimicking the extracellualr matrix in real tissue has recently been applied to scaffold development. In this study, a novel method for preparing the poly(L-lactic acid) (PLLA) scaffold with a tubular architecture is presented. Solid-liquid phase-separation was applied to form tubular pores in the scaffold using the directional freezing apparatus. Pores formed in this manner exhibited a fishbone like morphology due to the two crystalline phases of 1,4-dioxane. A tubular diameter of ca. 60-250 μm was achieved by regulating the PLLA concentration and the cooling rate. The compressive modulus of the fishbone-like porous scaffold showed higher values than that of non-directional porous scaffold.