Ultraviolet light-irradiated photocrosslinkable chitosan hydrogel to prevent bone formation in both rat skull and fibula bone defects

Abstract

In the field of orthopaedic surgery, an orthopaedic surgeon sometimes requires to suppress excessive bone formation, such as ectopic bone formation, ossifying myositis and radio-ulnar synostosis, etc. Ultraviolet (UV) light irradiation of a photocrosslinkable chitosan (Az-CH-LA) generates an insoluble hydrogel within 30 s. The purpose of this study was to evaluate the ability of the photocrosslinked chitosan hydrogel (PCH) to inhibit bone formation in an experimental model of bone defect. Rat calvarium and fibula were surgically injured and PCH was implanted into the resultant bone defects. The PCH implants significantly prevented bone formation in the bone defects during the 4 and 8 week observation periods. In the PCH-treated defects, fibrous tissues infiltrated by inflammatory cells were formed by day 7, completely filling the bone defects. In addition to these findings, expression of osteocalcin and runt-related gene 2 (RUNX2) mRNA, both markers of bone formation, was lower in the PCH-treated defects than in the controls. In contrast, collagen type 1α2 and α-smooth muscle actin (α-SMA) mRNA levels were significantly higher in the PCH-treated defects after 1 week. PCH stimulated the formation of fibrous tissue in bone defects while inhibiting bone formation. Thus, PCH might be a promising new therapeutic biomaterial for the prevention of bone formation in orthopaedic surgery.

Nano Textured PEEK Surface for Enhanced Osseointegration

“…The histological sections post 8-week implantation are processed by methylene-fuchsin staining, and the results are shown in Figure d,e. At a defect site, once the bone defect is occupied by fibrous tissue, it is hard to have further bone formation. − The fibrous tissue, in addition, contributes to the weak bone-bonding between the samples and tissue. A thick covering of fibrous tissue encompassing the PEEK samples can be observed and the tissue is easy to peel off from the PEEK surface, which indicates a weak osseointegration of flat surface.…”

Chitosan Hydrogels for Regenerative Engineering

“…Chitosan hydrogel has also been investigated to prevent excessive bone formation. Using a photocrosslinkable chitosan hydrogel (Az-CS-LA), Tsuda et al demonstrated the ability of the hydrogel to effectively prevent ectopic bone formation for up to 8 weeks in a rat model with calvarium and fibula defects [79]. In native ECM, the presence of sulfated polysaccharides such as chondroitin sulfate plays an essential role to bind and retain growth factors to support cell functions.…”

“…The lactose group made the Az-CS-LA polymer water soluble. Briefly, the hydrogels were prepared by exposing a solution of Az-CH-LA 20 mg/mL to UV light for 30 s [79]. Gelation time was dependent on the intensity of UV radiation; the higher the intensity, the lower the gelation time.…”

Study of the Contribution of the State of Water to the Gel Properties of a Photocrosslinked Polyacrylic Acid Hydrogel using Magnetic Resonance Imaging

“…To date, various photocrosslinked hydrogels have been investigated as materials that can be used as drug‐delivery systems and tissue engineering. These hydrogels were prepared via a photochemical reaction using mono‐, di‐, or multifunctional vinylated monomers or macromers, including HEMA, poly(ethylene glycol) dimethacrylate, poly(ethylene glycol) diacrylate, methacrylated sebacic acid, azide and lactose moieties introduced in chitosan, and styrenated gelatin …”