David Haddow

Characterization of sol-gel surfaces for biomedical applications

The aim of the present study was to characterize sol-gel derived titania coatings prepared by dipping. The surface characterization was carried out using X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF SIMS), combined with X-ray diffraction (XRD) and thermal analysis. Sol-gel derived titania surfaces mimicked the surface chemistry of the natural oxide layer found on commercial titanium implants. These surfaces could be used to develop an in vitro model of the osseointegration process. Similar analytical techniques were applied to apatite-like coatings and preliminary results suggest that hydroxyapatite coatings can be produced from a sol-gel route.

A new autologous keratinocyte dressing treatment for non‐healing diabetic neuropathic foot ulcers

Aims   To evaluate the use of a new cell‐tailored carrier surface (TranCell) for delivery of autologous keratinocytes to promote wound healing in patients with chronic neuropathic foot ulcers.

Clinical experience using cultured epithelial autografts leads to an alternative methodology for transferring skin cells from the laboratory to the patient

We report a 10-year audit using cultured epithelial autografts (CEAs) for patients with extensive burns. Clinical take using CEAs averaged only 45% (as has been reported by others) but over half of all cells cultured for these patients had to be discarded owing to difficulties of timing the production of CEA sheets to the needs of the patients. CEAs could not be used until they had reached confluence and formed an integrated sheet, which took, on average, 12 days. However, once formed, they needed to be used within 2-3 days or they lost the ability to attach to wound beds. In response to this we developed a simpler carrier dressing methodology for transferring cultured subconfluent keratinocytes from the laboratory to the wound bed. This methodology offers an increase in speed of delivery but its major contribution is the greater flexibility in timing the transfer of cells from the laboratory to the changing needs of the patients.

Randomized, controlled, single-blind study on use of autologous keratinocytes on a transfer dressing to treat nonhealing diabetic ulcers

AIM To compare the rate of healing of diabetic neuropathic ulcers using cultured autologous keratinocytes delivered on chemically defined transfer discs (Myskin) (active treatment) versus healing obtained with cell-free discs (placebo). MATERIALS AND METHODS After a 4-week lead-in period patients (randomly assigned) received active or placebo treatments weekly for 6 weeks. All patients then received active treatments for a maximum of 12 treatments where required. Altogether, 16 patients with a total of 21 ulcers resistant to conventional therapy were recruited from four specialist diabetic centers in three cities. RESULTS All 21 ulcers were treated and of these ten healed and eight improved, with two failing to respond (one ulcer was lost due to autoamputation). For analysis according to the study criteria, however, only the 12 patients with 12 index ulcers who completed treatment protocols were eligible - five in the placebo group and seven in the active group. Of these, five ulcers healed completely and seven were reduced by more than 50%. Complete healing took a median of ten active applications. CONCLUSIONS Repeated regular applications of the patients keratinocytes, delivered on the carrier dressing, initiated wound healing in ulcers resistant to conventional therapy, with 18 out of 21 ulcers responding. The healing observed did not appear attributable to patient recruitment or the cell-free carrier dressing but to the delivery of the cultured cells.

Sol-Gel Derived Calcium Phosphate Coatings for Biomedical Applications

Hydroxyapatite (HA) coatings have received considerable attention because they exhibit bone bonding capabilities. Unfortunately the common forms of coating production result in cracking and degradation of HA due to the thickness of the coatings and the elevated temperatures employed. This study demonstrates the production of sub-micron, crack-free calcium phosphate coatings on quartz glass substrates using a sol-gel dip-coating technique and firing temperatures below 1000°C.Coatings fired at 1000°C comprised a mixture of hydroxyapatite (HA) and tricalcium phosphate (TCP). XPS analysis of the coating surface showed that the Ca/P ratio lay in the range 1.5–1.67, and that there was a contribution from carbon in the form of carbonate.It is proposed that the sol-gel coatings comprising a resorbable (TCP) and an insoluble (HA) phase have potential benefits in certain implant applications.

Development of a calcium-chelating hydrogel for treatment of superficial burns and scalds

AIMS Superficial burns and scalds are usually managed conservatively with traditional dressings. Failure to heal within 3 weeks leads to their management by skin grafting. Our aim was to develop a biomaterial to actively promote keratinocyte migration in superficial burns by modulating local cation concentrations to accelerate keratinocyte migration and deter wounds from contracting, thus potentially reducing the number of such wounds requiring grafting. MATERIALS & METHODS We investigated polymeric hydrogels for their Ca(2+) chelating properties and enhancement of keratinocyte migration in human tissue-engineered skin models. RESULTS Dimethylaminoethyl methacrylate:methacrylic acid hydrogel coupled with elevated [Mg(2+)] reduced media [Ca(2+)], potentiating keratinocyte migration in tissue-engineered skin models, it also significantly reduced wound model contraction. CONCLUSION Dimethylaminoethyl methacrylate:methacrylic acid hydrogels could promote wound healing and reduce wound contraction, a significant complication in burn wound healing.