Sterilizing tissue-materials using pulsed power plasma.

This paper investigates the potential of pulsed power to sterilize hard and soft tissues and its impact on their physico-mechanical properties. It hypothesizes that pulsed plasma can sterilize both vascular and avascular tissues and the transitive layers in between without deleterious effects on their functional characteristics. Cartilage/bone laminate was chosen as a model to demonstrate the concept, treated at low temperature, at atmospheric pressure, in short durations and in buffered environment using a purposed-built pulsed power unit. Input voltage and time of exposure were assigned as controlling parameters in a full factorial design of experiment to determine physical and mechanical alteration pre- and post-treatment. The results demonstrated that, discharges of 11 kV sterilized samples in 45 s, reducing intrinsic elastic modules from 1.4 ± 0.9 to 0.9 ± 0.6 MPa. There was a decrease of 14.1 % in stiffness and 27.8 % in elastic-strain energy for the top quartile. Mechanical impairment was directly proportional to input voltage (P value < 0.05). Bacterial inactivation was proportional to treatment time for input voltages above 32 V (P < 0.001; R Sq = 0.98). Thermal analysis revealed that helix-coil transition decelerated with exposure time and collagen fibrils were destabilized as denaturation enthalpy reduced by 200 µV. We concluded by presenting a safe operating threshold for pulsed power plasma as a feasible protocol for effective sterilization of connective tissues with varying level of loss in mechanical robustness which we argue to be acceptable in certain medical and tissue engineering application.

The microRNA expression signature on modified titanium implant surfaces influences genetic mechanisms leading to osteogenic differentiation.

Topographically and chemically modified titanium implants are recognized to have improved osteogenic properties; however, the molecular regulation of this process remains unknown. This study aimed to determine the microRNA profile and the potential regulation of osteogenic differentiation following early exposure of osteoprogenitor cells to sand-blasted, large-grit acid-etched (SLA) and hydrophilic SLA (modSLA) surfaces. Firstly, the osteogenic characteristics of the primary osteoprogenitor cells were confirmed using ALP activity and Alizarin Red S staining. The effect of smooth (SMO), SLA and modSLA surfaces on the TGF-ß/BMP (BMP2, BMP6, ACVR1) and non-canonical WNT/Ca(2+) (WNT5A, FZD6) pathways, as well as the integrins ITGB1 and ITGA2, was determined. It was revealed that the modified titanium surfaces could induce the activation of TGF-ß/BMP and non-canonical WNT/Ca(2+) signaling genes. The expression pattern of microRNAs (miRNAs) related to cell differentiation was evaluated. Statistical analysis of the differentially regulated miRNAs indicated that 35 and 32 miRNAs were down-regulated on the modSLA and SLA surfaces respectively, when compared with the smooth surface (SMO). Thirty-one miRNAs that were down-regulated were common to both modSLA and SLA. There were 10 miRNAs up-regulated on modSLA and nine on SLA surfaces, amongst which eight were the same as observed on modSLA. TargetScan predictions for the down-regulated miRNAs revealed genes of the TGF-ß/BMP and non-canonical Ca(2+) pathways as targets. This study demonstrated that modified titanium implant surfaces induce differential regulation of miRNAs, which potentially regulate the TGF-ß/BMP and WNT/Ca(2+) pathways during osteogenic differentiation on modified titanium implant surfaces.

Preliminary evaluation of the capacity of surface-active phospholipids to provide semipermeability in a saline filtration environment.

BACKGROUND: Semipermeability to fluid transport is one of the principal attributes of a tissue like articular cartilage. Consequently, this characteristic can be exploited in attempts to understand the functional roles of the biological layer of Surface Active Phospholipids (SAPL) which form on its surfaces. A previous study, relevant to peritoneal SAPL was carried out in which hypertonic glucose solution was dialysed against physiological saline through SAPL membrane and concluded that SAPL possessed semipermeability. Our analysis extends this previous study by dialysing hypertonic and hypotonic saline solutions against physiological saline via SAPL membranes which is more relevant to the articular joint environment. MATERIAL/METHODS: Membranes were produced from either synthetic or bovine cartilage SAPL and used to carry out tests involving the dialysis of hypotonic and hypertonic sodium chloride solutions against physiological saline, using an Ussing chamber to hold both the membranes and dialysis fluids. RESULTS: The dialysis produced osmotic pressures which are commensurate with our experimental constraints, but strongly indicated that it is indeed possible to generate osmotic pressures using SAPL membranes, indicating the semipermeability of this lipid structure. CONCLUSIONS: It is widely accepted that the collagen-proteoglycan membrane provides the semipermeability of articular cartilage despite the low levels of osmotic pressure recorded in our experiments, our results demonstrate that SAPL aggregation can constitute a semipermeable layer with a strong capability to contribute to the semipermeablity of the collagen-proteoglycan system especially on the surface of the tissue. Consequently its deficiency, as seen in osteoarthritis could lead/contribute to cartilage dysfunction.