Interactions between chitosan and cells measured by AFM

The integration of peri-implant soft tissues around zirconia abutments: Challenges and strategies

Stable soft tissue integration around the implant abutment attenuates pathogen penetration, protects underlying bone tissue, prevents peri-implantitis and is essential in maintaining long-term implant stability. The desire for "metal free" and "aesthetic restoration" has favored zirconia over titanium abutments, especially for implant restorations in the anterior region and for patients with thin gingival biotype. Soft tissue attachment to the zirconia abutment surface remains a challenge. A comprehensive review of advances in zirconia surface treatment (micro-design) and structural design (macro-design) affecting soft tissue attachment is presented and strategies and research directions are discussed. Soft tissue models for abutment research are described. Guidelines for development of zirconia abutment surfaces that promote soft tissue integration and evidence-based references to inform clinical choice of abutment structure and postoperative maintenance are presented.

Dual-Functional Polyetheretherketone Surface with an Enhanced Osteogenic Capability and an Antibacterial Adhesion Property In Vitro by Chitosan Modification

A chitosan layer was covalently bonded to a polyetheretherketone (PEEK) surface using a simple facile self-assembly method to address inadequate biological activity and infection around the implant. The surface characterization, layer degradation, biological activity, and antibacterial adhesion properties of chitosan-modified PEEK (PEEK-CS) were studied. Through chitosan grafting, the surface morphology changed, the surface roughness increased, and the contact angle decreased significantly. PEEK-CS boosted cell adhesion, proliferation, increased alkaline phosphate activity, extracellular matrix mineralization, and expression of osteogenic genes. PEEK-CS demonstrated less adhesion to Porphyromonas gingivalis as well as less bacterial adhesion to P. gingivalis and Streptococcus mutans. According to our findings, chitosan modification significantly improved the osteogenic ability and antibacterial adhesion of PEEK in vitro.

Novel anti-infective activities of chitosan immobilized titanium surface with enhanced osteogenic properties

We have covalently immobilized chitosan onto a titanium (Ti) surface to manage implant-related infection and poor osseointegration, two of the major complications of orthopedic implants. The Ti surface was first treated with sulfuric acid (SA) and then covalently grafted with chitosan. Surface roughness, contact angle and surface zeta potential of the samples were markedly increased by the sulfuric acid treatment and the subsequent chitosan immobilization. The chitosan-immobilized Ti (SA-CS-Ti) showed two novel antimicrobial roles: it (a) prevented the invasion and internalization of bacteria into the osteoblast-like cells, and (b) significantly increased the susceptibility of adherent bacteria to antibiotics. In addition, the sulfuric acid-treated Ti (SA-Ti) and SA-CS-Ti led to significantly increased (P<0.05) osteoblast-like cell attachment, enhanced cell proliferation, and better osteogenic differentiation and mineralization of osteoblast-like cells.

In vitro and in vivo evaluation of osteoporosis therapeutic peptide PTH 1-34 loaded pegylated chitosan nanoparticles

Oral formulation of human parathyroid hormone 1-34 (PTH 1-34) is an alternative patient compliant route in treating osteoporosis. PTH 1-34 loaded chitosan nanoparticles were PEGylated (PEG-CS-PTH NPs) and characterized by DLS, SEM, TEM and FTIR. PEG-CS-PTH NP aggregates of 200-250 nm which in turn comprised 20 nm individual nanoparticles were observed in SEM and TEM images respectively. The PEG-CS-PTH NP with 40% encapsulation efficiency was subjected to an in vitro release in simulated rat body fluids. PEG-CS-PTH NP treated human primary osteoblast cells, upon PTH 1-34 receptor activation, produced second messenger-cAMP, which downstream stimulated intracellular calcium uptake, production of bone specific alkaline phosphatase, osteocalcin etc., which substantiates the anabolic effect of the peptide. PEG-CS-PTH NPs showed an oral bioavailability of 100-160 pg/mL PTH 1-34 throughout 48 h, which is remarkable compared to the bare PTH 1-34 and CS-PTH NPs. The NIR image of gastrointestinal transit of ICG conjugated PEG-CS-PTH NPs supports this significant finding.

Determinants of cell-material crosstalk at the interface: towards engineering of cell instructive materials

The development of novel biomaterials able to control cell activities and direct their fate is warranted for engineering functional biological tissues, advanced cell culture systems, single-cell diagnosis as well as for cell sorting and differentiation. It is well established that crosstalk at the cell-material interface occurs and this has a profound influence on cell behaviour. However, the complete deciphering of the cell-material communication code is still far away. A variety of material surface properties have been reported to affect the strength and the nature of the cell-material interactions, including biological cues, topography and mechanical properties. Novel experimental evidence bears out the hypothesis that these three different signals participate in the same material-cytoskeleton crosstalk pathway via adhesion plaque formation dynamics. In this review, we present the relevant findings on material-induced cell response along with the description of cell behaviour when exposed to arrays of signals-biochemical, topographical and mechanical. Finally, with the aid of literature data, we attempt to draw unifying elements of the material-cytoskeleton-cell fate chain.