Novel electrospun materials for bone tissue engineering were obtained by blending biodegradable polyhydroxybutyrate (PHB) or polyhydroxybutyrate valerate (PHBV) with the anionic sulfated polysaccharide κ-carrageenan (κ-CG) in varying ratios. In both systems, the two components phase separated as shown by FTIR, DSC and TGA. According to the contact angle data, κ-CG was localized preferentially at the fiber surface in PHBV/κ-CG blends in contrast to PHB/κ-CG, where the biopolymer was mostly found within the fiber. In contrast to the neat polyester fibers, the blends led to the formation of much smaller apatite crystals (800 nm vs 7 μm). According to the MTT assay, NIH3T3 cells grew in higher density on the blend mats in comparison to neat polyester mats. The osteogenic differentiation potential of the fibers was determined by SaOS-2 cell culture for 2 weeks. Alizarin red-S staining suggested an improved mineralization on the blend fibers. Thus, PHBV/κ-CG fibers resulted in more pronounced bioactive and osteogenic properties, including fast apatite-forming ability and deposition of nanosized apatite crystals.

This review explores the potential of electrospun nanofibers for drug delivery applications. In the first section, some of the key challenges in drug delivery as well as the promise of electrospun drug loaded nanofibers are highlighted. Techniques of drug incorporation into nanofibers such as blending, surface modification and co-axial electrospinning are detailed. The major requirements of drug eluting scaffolds such as biocompatibility and biodegradability, efficient drug control and release, and adequate mechanical performance are addressed. Drug release kinetics, biodegradability and mechanical properties can be controlled by careful selection of polymers and electrospinning processing parameters while biocompatibility of electrospun mats may be enhanced through surface modification of the nanofibers. The major applications as well as the routes of administration of the drug-loaded electrospun nanostructures are discussed. Currently available drug eluting nanofibrous mats for applications ranging from cancer therapy to wound dressings as well as their preclinical trials are also reviewed.

Bone tissue engineering based on scaffolds is quite a complex process as a whole gamut of criteria needs to be satisfied to promote cellular attachment, proliferation and differentiation: biocompatibility, right surface properties, adequate mechanical performance, controlled bioresorbability, osteoconductivity, angiogenic cues, and vascularization. Third generation scaffolds are more of composite types to maximize biological-mechanical-chemical properties. In the present review, our focus is on the performance of micro-organism-derived polyhydroxyalkanoates (PHAs)-polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV)-composite scaffolds with ceramics and natural polymers for tissue engineering applications with emphasis on bone tissue. We particularly emphasize on how material properties of the composites affect scaffold performance. PHA-based composites have demonstrated their biocompatibility with a range of tissues and their capacity to induce osteogenesis due to their piezoelectric properties. Electrospun PHB/PHBV fiber mesh in combination with human adipose tissue-derived stem cells (hASCs) were shown to improve vascularization in engineered bone tissues. For nerve and skin tissue engineering applications, natural polymers such as collagen and chitosan remain the gold standard but there is scope for development of scaffolds combining PHAs with other natural polymers which can address some of the limitations such as brittleness, lack of bioactivity and slow degradation rate presented by the latter. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1667-1684, 2017.

The promise of tissue engineering is the combination of a scaffold with cells to initiate the regeneration of tissues or organs. Engineering of scaffolds is critical for success and tailoring of polymer properties is essential for their good performance. Many different materials of natural and synthetic origins have been investigated, but the challenge is to find those that have the right mix of mechanical performance, biodegradability and biocompatibility for biological applications. This article reviews key polymeric properties for bone and vascular scaffold eligibility with focus on biopolymers, synthetic polymers and their blends. The limitations of these polymeric systems and ways and means to improve scaffold performance specifically for bone and vascular tissue engineering are discussed.