[Show abstract][Hide abstract] ABSTRACT: Current methods used for the detection of residual proteinaceous contamination vary in sensitivity and specificity. This is of concern because it increases the risk for transmission of neurodegenerative diseases such as spongiform encephalopathies.
To determine the effectiveness of electrolysis-assisted sonication (EAS) for removing residual proteinaceous contamination from surgical grade stainless steel.
EAS was used to clean surgical grade 316L stainless steel that had been contaminated with the protein bovine serum albumin. Using nitrogen, an abundant element in proteins, as a marker for the presence of protein, X-ray photoelectron spectroscopy (XPS) was used to quantify the amount of protein remaining on the substrate surface. Cathodic, anodic and dual polarization modes of EAS were investigated using 0.1% NaCl solution (w/v, in deionized water) as the electrolyte medium and 13 V as the polarization voltage.
EAS under dual polarization was found to be the most effective method for removing the residual protein layer down to an estimated XPS detection limit of 10 ng/cm(2). Surface roughness and hardness of the stainless steel remained unchanged following EAS treatment, indicating that the procedure does not compromise the material's properties.
This relatively inexpensive and quick method of cleaning medical devices using an easily accessible salt-based electrolyte solution may offer a cost-effective strategy for cleaning medical and dental devices made of stainless steel in the future.
The Journal of hospital infection 03/2012; 81(1):41-9. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Established methods for cleaning and sterilising biomedical devices may achieve removal of bioburden only at the macroscopic level while leaving behind molecular levels of contamination (mainly proteinaceous). This is of particular concern if the residue might contain prions. We investigated at the molecular level the removal of model and real-life proteinaceous contamination from model and practical surfaces by air plasma (ionised air) treatment. The surface-sensitive technique of X-ray photoelectron spectroscopy (XPS) was used to assess the removal of proteinaceous contamination, with the nitrogen (N1s) photoelectron signal as its marker. Model proteinaceous contamination (bovine serum albumin) adsorbed on to a model surface (silicon wafer) and the residual proteinaceous contamination resulting from incubating surgical stainless steel (a practical biomaterial) in whole human blood exhibited strong N1s signals [16.8 and 18.5 atomic percent (at.%), respectively] after thorough washing. After 5min air plasma treatment, XPS detected no nitrogen on the sample surfaces, indicating complete removal of proteinaceous contamination, down to the estimated XPS detection limit 10ng/cm(2). Applying the same plasma treatment, the 7.7at.% nitrogen observed on a clinically cleaned dental bur was reduced to a level reflective of new, as-received burs. Contact angle measurements and atomic force microscopy also indicated complete molecular-level removal of the proteinaceous contamination upon air plasma treatment. This study demonstrates the effectiveness of air plasma treatment for removing proteinaceous contamination from both model and practical surfaces and offers a method for ensuring that no molecular residual contamination such as prions is transferred upon re-use of surgical and dental instruments.
The Journal of hospital infection 11/2010; 76(3):234-42. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hydroxyapatite (HA) thin-film coatings grown biomimetically using simulated body fluid (SBF) are desirable for a range of applications such as improved fixation of fine- and complex-shaped orthopedic and dental implants, tissue engineering scaffolds and localized and sustained drug delivery. There is a dearth of knowledge on two key aspects of SBF-grown HA coatings: (i) the growth kinetics over short deposition periods, hours rather than weeks; and (ii) possible difference between the coatings deposited with and without periodic SBF replenishment. A study centred on these aspects is reported. X-ray photoelectron spectroscopy (XPS) has been used to study the growth kinetics of SBF-grown HA coatings for deposition periods ranging from 0.5 h to 21 days. The coatings were deposited with and without periodic replenishment of SBF. The XPS studies revealed that: (i) a continuous, stable HA coating fully covered the titanium substrate after a growth period of 13 h without SBF replenishment; (ii) thicker HA coatings about 1 μm in thickness resulted after a growth period of 21 days, both with and without SBF replenishment; and (iii) the Ca/P ratio at the surface of the HA coating was significantly lower than that in its bulk. No significant difference between HA grown with and without periodic replenishment of SBF was found. The coatings were determined to be carbonated, a characteristic desirable for improved implant fixation. The atomic force and scanning electron microscopies results suggested that heterogeneous nucleation and growth are the primary deposition mode for these coatings. Primary osteoblast cell studies demonstrated the biocompatibility of these coatings, i.e., osteoblast colony coverage of approximately 80%, similar to the control substrate (tissue culture polystyrene).
[Show abstract][Hide abstract] ABSTRACT: We aimed to improve implant osseous integration by developing a novel bisphosphonate (BP) loading technique to improve BP release from hydroxyapatite grown by simulated body fluid (SBF) deposition. Orally administered BPs have been used to inhibit osteoclast activity at the implant/bone interface. Ideally, these drugs should be delivered locally at the hydroxyapatite (HA) – bone interface for maximum effect. Plasma-sprayed HA-coated substrates were exposed to a co-precipitate solution containing the BP pamidronate, dissolved in SBF, for 1 hour. Surface analysis of BP-HA-coated substrates was employed using X-ray photoelectron spectroscopy (XPS) to confirm the presence of the adsorbed BP on the HA surface. Cell culture experiments using primary osteoclasts were undertaken to determine the biological activity of the adsorbed BP. The biological effectiveness of the adsorbed BP was confirmed by a 30-fold decrease in osteoclast survival observed on the BP-exposed substrates when compared to the non-BP containing HA-coated substrate (p < 0.002). The co-deposition of a BP rich HA matrix ensures the presence of BP at the implant-bone interface to reduce local osteoclast activity. Our findings are likely to lead to improved bony integration of the implant by local osteoclast inhibition.
XII International Conference on Biomedical Engineering,, Singapore; 12/2005
[Show abstract][Hide abstract] ABSTRACT: The uses of alginate hydrogels for several applications in drug delivery and tissue engineering due to its good compatibility, low toxicity, relative low cost and simple gelation with divalent cations were discussed. A hydrogel based system was found to be advantageous due to its intrinsic elasticity and water retention ability. It was observed that the loading level of the active biomolecule could be controlled and different hydrogels allowed tuning of other properties such as viscosity and degradation time. The results show that the delivery system could be used for bone implants and could be used in conjunction with a porous hydroxyapatite coating, into the pores of which hydrogel layer can intercalate.
[Show abstract][Hide abstract] ABSTRACT: The effects of physical and chemical factors of the substrate chemistry and oligonucleotide chemistry on the immobilization process and efficiency were studied. The oligonucleotides terminated by various functional groups were immobilized to functionalized substrates prepared by plasma polymerization. The surface analysis of the propanol surface, immobilized oligonucleotides and immobilized control were performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight- secondary ion mass spectrometry (TOF-SIMS). The effectiveness of oligonucleotides over antibodies as recognition elements in microarrays for high throughput screening were recognized and applied to medical diagnosis and plant pathogen detection.