Aylin Ziylan Albayrak

Biocompatibility of plasma-treated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanofiber mats modified by silk fibroin for bone tissue regeneration

The objective of this study was to produce biocompatible plasma-treated and silk-fibroin (SF) modified poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofiber mats. The mats were plasma-treated using O2 or N2 gas to increase their hydrophilicity followed by SF immobilization for the improvement of biocompatibility. Contact angle measurements and SEM showed increased hydrophilicity and no disturbed morphology, respectively. Cell proliferation assay revealed that SF modification together with N2 plasma (PS/N2) promoted higher osteoblastic (SaOs-2) cell viability. Although, O2 plasma triggered more mineral formation on the mats, it showed poor cell viability. Consequently, the PS/N2 nanofiber mats would be a potential candidate for bone tissue engineering applications.

Novel phosphorus-containing cyclopolymers from ether dimer of tert-butyl α-hydroxymethyl acrylate

A new acrylate monomer with phosphonic acid ester groups was synthesized from the reaction of the acid chloride derivative of the ether dimer of tert-butyl α-(hydroxymethyl) acrylate with diethyl hydroxymethyl phosphonate. Bulk polymerization of this monomer at 75-77°C with 2,2′-azobisisobutyronitrile (AIBN) gave soluble cyclopolymers. The T g value of the cyclopolymer was 44°C, and produced a char yield of 36% at 580°C. The phosphonate monomer was copolymerized with the ether dimer of tert-butyl α-(hydroxymethyl) acrylate in different ratios. The T g of the copolymers decreased with increasing amounts of the phosphonate monomer in the copolymers, with the values of 148, 105 and 93°C for the copolymers containing 10, 30 and 50 mol% phosphonate monomer in feed, respectively. The char residues of the copolymers increased with the incorporation of the phosphonate monomer. The selective hydrolysis of the phosphonate monomer with trimethylsilyl bromide (TMSBr) gave a monomer with two phosphonic acid groups. The polymerization of this monomer at 70-75°C with AIBN was unsuccessful; however, this monomer was copolymerized with the ether dimer of tert-butyl α-(hydroxymethyl) acrylate and its carboxylic acid derivative.

In Vitro Biocompatibility and Antibacterial Activity of Electrospun Ag Doped HAp/PHBV Composite Nanofibers

The authors report herein in vitro antibacterial property and osteoblast biocompatibility of electrospun Ag doped HAp/PHBV (Ag-HAp/PHBV) composite nanofibers as an osteoconductive and antibacterial material for bone tissue engineering applications. Ag-HAp powders were synthesized and stable composite suspensions of Ag-HAp/PHBV were prepared with the aid of a cationic surfactant DTAB for the electrospinning process. Continuous and uniform composite nanofibers were generated within a diameter range of 400–900 nm. Obtained nanocomposite scaffolds provide a favorable environment for bone mineralization, SaOS-2 osteoblastic cell attachment and growth as well as they present antibacterial activity against E. coli and S. aureus bacteria without any noticeable cytotoxic effect. GRAPHICAL ABSTRACT

Three-dimensional silk impregnated HAp/PHBV nanofibrous scaffolds for bone regeneration

ABSTRACT Three-dimensional silk fibroin impregnated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibrous scaffolds with or without hydroxyapatite (HAp) were prepared by wet-electrospinning method followed by freeze-drying. Scaffolds with cotton wool-like structure have the average fiber diameter of 450–850 nm with 80–85% porosity. In-vitro cell culture tests using MG-63 osteosarcoma human cells revealed improved cell viability, alkaline phosphatase (ALP) activity and total cellular protein amount on the silk impregnated scaffolds compared to PHBV and HAp/PHBV scaffolds after 10 days of cell culture. Immunohistochemical analyses on the silk impregnated scaffolds showed that HAp triggered cell penetration and type I collagen production. Besides, HAp mineralization tendency increased with a decrease in percent crystallinity of the scaffolds comprising HAp and silk after 4 weeks of incubation in simulated body fluid. Consequently, cotton wool-like HAp/PHBV-SF scaffold would be a promising candidate as a bone-filling material for tissue regeneration. GRAPHICAL ABSTRACT