Hyaluronic Acid-Based Shape-Memory Cryogel Scaffolds for Focal Cartilage Defect Repair.

Traumatic joint injuries can result in significant cartilage defects, which can greatly increase the risk of osteoarthritis development. Due to the limited self-healing capacity of avascular cartilage, tissue engineering approaches are required for filling defects and promoting cartilage regeneration. Current approaches utilize invasive surgical procedures for extraction and implantation of autologous chondrocytes; therefore, injectable biomaterials have gained interest to minimize the risk of infection as well as patient pain and discomfort. In this study, we engineered biomimetic, hyaluronic acid (HA)-based cryogel scaffolds that possess shape-memory properties as they contract and regain their shape after syringe injection to noninvasively fill cartilage defects. The cryogels, fabricated with HA and glycidyl methacrylate at -20°C, resulted in an elastic, macroporous, and highly interconnected network that provided a conducive microenvironment for chondrocytes to remain viable and metabolically active after injection through a syringe needle. Chondrocytes seeded within cryogels and cultured for 15 days exhibited enhanced cell proliferation, metabolism, and production of cartilage extracellular matrix glycosaminoglycans compared with HA-based hydrogels. Furthermore, immunohistochemical staining revealed production of collagen type II from chondrocyte-seeded cryogels, indicating the maintenance of cell phenotype. These results demonstrate the potential of chondrocyte-seeded, HA-based, injectable cryogel scaffolds to promote regeneration of cartilage tissue for nonsurgically invasive defect repair. Impact statement Hyaluronic acid-based shape-memory cryogels provide a conducive microenvironment for chondrocyte adhesion, proliferation, and matrix biosynthesis for use in repair of cartilage defects. Due to their sponge-like elastic properties, cryogels can fully recover their original shape back after injection while not impacting metabolism or viability of encapsulated cells. Clinically, they provide an opportunity for filling focal cartilage defects by using a single, minimally invasive injection of a cell encapsulating biocompatible three-dimensional scaffold that can return to its original structure to fit the defect geometry and enable matrix regeneration.

Needle-injectable microcomposite cryogel scaffolds with antimicrobial properties.

Porous three-dimensional hydrogel scaffolds have an exquisite ability to promote tissue repair. However, because of their high water content and invasive nature during surgical implantation, hydrogels are at an increased risk of bacterial infection. Recently, we have developed elastic biomimetic cryogels, an advanced type of polymeric hydrogel, that are syringe-deliverable through hypodermic needles. These needle-injectable cryogels have unique properties, including large and interconnected pores, mechanical robustness, and shape-memory. Like hydrogels, cryogels are also susceptible to colonization by microbial pathogens. To that end, our minimally invasive cryogels have been engineered to address this challenge. Specifically, we hybridized the cryogels with calcium peroxide microparticles to controllably produce bactericidal hydrogen peroxide. Our novel microcomposite cryogels exhibit antimicrobial properties and inhibit antibiotic-resistant bacteria (MRSA and Pseudomonas aeruginosa), the most common cause of biomaterial implant failure in modern medicine. Moreover, the cryogels showed negligible cytotoxicity toward murine fibroblasts and prevented activation of primary bone marrow-derived dendritic cells ex vivo. Finally, in vivo data suggested tissue integration, biodegradation, and minimal host inflammatory responses when the antimicrobial cryogels, even when purposely contaminated with bacteria, were subcutaneously injected in mice. Collectively, these needle-injectable microcomposite cryogels show great promise for biomedical applications, especially in tissue engineering and regenerative medicine.

Oxygen-Releasing Antibacterial Nanofibrous Scaffolds for Tissue Engineering Applications.

Lack of suitable auto/allografts has been delaying surgical interventions for the treatment of numerous disorders and has also caused a serious threat to public health. Tissue engineering could be one of the best alternatives to solve this issue. However, deficiency of oxygen supply in the wounded and implanted engineered tissues, caused by circulatory problems and insufficient angiogenesis, has been a rate-limiting step in translation of tissue-engineered grafts. To address this issue, we designed oxygen-releasing electrospun composite scaffolds, based on a previously developed hybrid polymeric matrix composed of poly(glycerol sebacate) (PGS) and poly(ε-caprolactone) (PCL). By performing ball-milling, we were able to embed a large percent of calcium peroxide (CP) nanoparticles into the PGS/PCL nanofibers able to generate oxygen. The composite scaffold exhibited a smooth fiber structure, while providing sustainable oxygen release for several days to a week, and significantly improved cell metabolic activity due to alleviation of hypoxic environment around primary bone-marrow-derived mesenchymal stem cells (BM-MSCs). Moreover, the composite scaffolds also showed good antibacterial performance. In conjunction to other improved features, such as degradation behavior, the developed scaffolds are promising biomaterials for various tissue-engineering and wound-healing applications.

Autoclavable and Injectable Cryogels for Biomedical Applications.

Prior to any clinical application, terminal sterilization of biomaterials is a critical process imposed by the Food and Drug Administration. Of all the methods available for sterilization, high-pressure steam sterilization such as autoclaving is the most widely used. While autoclave sterilization minimizes pathogen contamination, it can dramatically impact both structural and biological properties of biomaterials. It has recently been reported that injectable cryogels with shape memory properties hold great promises as 3D macroporous biomimetic scaffolds for biomedical applications including tissue engineering. In this study, the impact of autoclave sterilization on properties of a series of cryogels is measured. Unlike conventional hydrogels, cryogels made of natural polymers demonstrate a strong resilience to autoclave sterilization. This process does not alter either their macrostructural or unique physical properties including syringe injectability. The scaffolds' bioactive sites are preserved and autoclaved cryogels retain their excellent cytological compatibility post-autoclaving. Furthermore, autoclaved cryogels do not trigger a notable activation of primary murine bone marrow-derived dendritic cells suggesting a minimal risk for biomaterial-induced inflammation, which is further confirmed by an in vivo histologic analysis. In summary, these results further demonstrate the huge potential of cryogels in the biomedical field and their capacity to be translated into clinical applications.

Latest Progress in Electrospun Nanofibers for Wound Healing Applications.

Electrospinning is a versatile technique used to create native tissue-like fibrous scaffolds. Recently, it has gained a large amount of attention for generation of bioactive dressing materials suitable for treatment of both chronic and acute wounds. In this Review, we focus on the latest advances made in the application of electrospun scaffolds for bioactive wound healing. We first provide a brief overview of the wound healing process and electrospinning approaches. We then discuss fabrication of scaffolds made from natural and synthetic polymers via electrospinning for effective wound treatment and management. Natural polymers used for wound healing included in our Review cover protein based polymers such as collagen, gelatin, and silk and polysaccharide based polymers such as chitosan, hyaluronic acid, and alginate. In addition, we discuss aliphatic polyesters, super hydrophilic polymers, and polyurethanes as some of the most commonly used synthetic polymers for wound healing and wound dressing applications. Next, we review multifunctional and "smart" scaffolds developed by electrospinning based approaches. We place an emphasis on how flexibility of the electrospinning process enables production of advanced scaffolds such as core-shell fibrous scaffolds, multilayer scaffolds, and surface modified scaffolds. Taken together, it is clear that electrospinning is an emerging technology that provides a unique opportunity for engineering more effective wound dressing, management, and care products.

A biosurfactant-sophorolipid acts in synergy with antibiotics to enhance their efficiency.

Sophorolipids (SLs), biosurfactants with antimicrobial properties, have been tried to address the problem of antibiotic resistance. The synergistic action of SL and antibiotics was checked using standard microdilution and spread plate methods. With Staphylococcus aureus, SL-tetracycline combination achieved total inhibition before 4 h of exposure while tetracycline alone couldnot achieve total inhibition till the end of 6 h. The inhibition caused by exposure of bacterium to SL-tetracycline mixture was ~25% more as compared to SL alone. In spite of known robustness of gram-negative bacteria, SL-cefaclor mixture proved to be efficient against Escherichia coli which showed ~48% more inhibition within 2 h of exposure as compared to cefaclor alone. Scanning electron microscopy of the cells treated with mixture revealed bacterial cell membrane damage and pore formation. Moreover, SLs being a type of asymmetric bola, they are expected to form self-assemblies with unique functionality. This led to the speculation that SLs being amphiphilic in nature can span through the structurally alike cell membrane and facilitate the entry of drug molecules.

Crystalline xylitol production by a novel yeast, Pichia caribbica (HQ222812), and its application for quorum sensing inhibition in gram-negative marker strain Chromobacterium violaceum CV026.

Xylitol, a sugar alcohol, is fast gaining ground over other artificial sugar substitutes owing to its advantageous properties. Xylitol is a safer alternative for diabetics because of insulin-independent metabolism. It has beneficial properties suitable to form an important part of odontological formulations. Conventional commercial production of xylitol involves harsh chemical method operating at high temperature and pressure. Thus, microbial production of xylitol is preferred over chemical method, and yeasts have been extensively exploited for this purpose. In the present manuscript, quantitative production of xylitol from D-xylose with the yield of 0.852 gm/gm and volumetric productivity of 1.83 gm/l/h in crystalline form, using novel yeast Pichia caribbica is reported. Also, a mild, safe procedure for product extraction is described. The ability of xylitol to act as a quorum sensing antagonist in gram-negative marker strain Chromobacterium violaceum CV026 has been demonstrated for the first time.

Jatropha oil derived sophorolipids: production and characterization as laundry detergent additive.

Sophorolipids (SLs) are glycolipidic biosurfactants suitable for various biological and physicochemical applications. The nonedible Jatropha oil has been checked as the alternative raw material for SL synthesis using C. bombicola (ATCC22214). This is useful towards lowering the SL production cost. Through optimization of fermentation parameters and use of resting cell method, the yield 15.25 g/L could be achieved for Jatropha oil derived SL (SLJO) with 1% v/v oil feeding. The synthesized SL displayed good surfactant property. It reduced the surface tension of distilled water from 70.7 mN/m to 33.5 mN/m with the Critical Micelle Concentration (CMC) value of 9.5 mg/L. Keeping the prospective use of the SL in mind, the physicochemical properties were checked along with emulsion stability under temperature, pH stress, and in hard water. Also antibacterial action and stain removal capability in comparison with commercial detergent was demonstrated. SLJO enhanced the detergent performance. Based on the results, it can be said that SLs have utility as fabric cleaner with advantageous properties such as skin friendly nature, antibacterial action, and biodegradability. Therefore SLs are potential green molecules to replace synthetic surfactants in detergents so as to reduce harm caused to environment through detergent usage.

Differentiation-inducing ability of sophorolipids of oleic and linoleic acids using a glioma cell line.

Sophorolipids are biosurfactants produced by non-pathogenic yeasts. They show structural similarity with the membrane components of mammalian cells, i.e., glycosphingolipids and gangliosides, which are involved in processes such as signaling, oncogenesis, and differentiation. Sophorolipids have been reported to induce differentiation in several leukemic cell lines, cell death via apoptosis in a human liver cancer cell line, and necrosis in a pancreatic adenocarcinoma cell line. Here we report, for the first time, the effects of precursor fatty acids and sophorolipids of oleic and linoleic acids in pure acidic and crude forms on LN-229, a glioma cell line. In response to different sophorolipid forms, various morphological changes were observed, such as formation of long thread-like extensions arising from the ends of the cells, cell alignment, cell elongation and bundle formation in a dose-dependent manner. In this study we present the morphological evidence of the potential of sophorolipids as differentiation inducers.