ALGINATE versus NPWT in the Preparation of Surgical Excisions for an STSG: ATEC Trial

Are All Alginate Dressings Equivalent?

Alginate dressings are widely used in wound treatment for their healing and hemostatic properties and their capacity to drain exudate. However, a clear understanding of the heterogeneity within this class of dressings is lacking. Numerous sources of variability exist between alginate dressings: their composition (% of calcium alginate relative to other components), the ratio of D-Mannuronic and L-Guluronic acids in the alginate fraction, their purity (presence of toxic contaminants), and the shape of their fibers (surface and thickness). These parameters affect the performance and safety of alginate dressings, which may thus not be interchangeable in clinical practice. Therefore, clinicians must be aware of these differences to ensure optimal treatment and avoid complications or suboptimal healing. The objective of this study was to compare six alginate dressings to conclude or not on their equivalence. The results obtained demonstrate considerable variability between alginate dressings in the assessed characteristics: composition, Ca2+ release, level of cytotoxicity, fiber shape, draining capacity, and their resistance to traction. Algostéril, the only pure calcium alginate rich in G, releases a specific dose of Ca2+ and is the only non-cytotoxic dressing. With its multilobed fibers that are statistically the thickest, it provides the best draining capacity and greatest resistance to traction. These results demonstrate that alginate dressings are not equivalent. Each dressing is distinct, and consequently the clinical performance of one cannot be transposed to the others. Therefore, each alginate dressing should demonstrate its own efficacy, in a given indication, through a clinical trial.

In vitro effects of wound-dressings on key wound healing properties of dermal fibroblasts

Healing of complex wounds requires dressings that must, at least, not hinder and should ideally promote the activity of key healing cells, in particular fibroblasts. This in vitro study assessed the effects of three wound-dressings (a pure Ca2+ alginate: Algostéril®, a Ca2+ alginate + carboxymethylcellulose: Biatain alginate® and a polyacrylate impregnated with lipido-colloid matrix: UrgoClean®) on dermal fibroblast activity. The results showed the pure calcium alginate to be non-cytotoxic, whereas the other wound-dressings showed moderate to strong cytotoxicity. The two alginates stimulated fibroblast migration and proliferation, whereas the polyacrylate altered migration and had no effect on proliferation. The pure Ca2+ alginate significantly increased the TGF-β-induced fibroblast activation, which is essential to healing. This activation was confirmed by a significant increase in Vascular endothelial growth factor (VEGF) secretion and a higher collagen production. The other dressings reduced these fibroblast activities. The pure Ca2+ alginate was also able to counteract the inhibitory effect of NK cell supernatants on fibroblast migration. These in vitro results demonstrate that tested wound-dressings are not equivalent for fibroblast activation. Only Algostéril was found to promote all the fibroblast activities tested, which could contribute to its healing efficacy demonstrated in the clinic.

Modulation of NK cell activation by exogenous calcium from alginate dressings in vitro

Natural Killer (NK) cells participate in the defense against infection by killing pathogens and infected cells and secreting immuno-modulatory cytokines. Defects in NK cell activity have been reported in obese, diabetic, and elderly patients that are at high risk of developing infected chronic wounds. Calcium alginate dressings are indicated for the debridement during the inflammatory phase of healing. Since calcium ions are major activators of NK cells, we hypothesized that these dressings could enhance NK functions, as investigated in vitro herein. Primary human blood NK cells were freshly-isolated from healthy volunteers and exposed to conditioned media (CM) from two alginate dressings, Algosteril® (ALG, pure Ca2+ alginate) and Biatain® Alginate (BIA, Ca2+ alginate with CMC), in comparison with an exogenous 3mM calcium solution. Our results demonstrated that exogenous calcium and ALG-CM, but not BIA-CM, induced NK cell activation and enhanced their capacity to kill their targets as a result of increased degranulation. NK cell stimulation by ALG depended on the influx of extracellular Ca2+via the SOCE Ca2+ permeable plasma membrane channels. ALG-CM also activated NK cell cytokine production of IFN-γ and TNF-α through a partly Ca2+-independent mechanism. This work highlights the non-equivalence between alginate dressings for NK cell stimulation and shows that the pure calcium alginate dressing Algosteril® enhances NK cell cytotoxic and immuno-modulatory activities. Altogether, these results underline a specific property of this medical device in innate defense that is key for the cutaneous wound healing process.

Preparation, biocompatibility, and wound healing effects of O-carboxymethyl chitosan nonwoven fabrics in partial-thickness burn model

This study was aimed at preparing O-carboxymethyl chitosan (CM-CTS) fabrics, and examining the wound healing effects on partial-thickness burn. The functional polysaccharides were produced from chitosan needle-punched nonwovens reacted with chloroacetic acid. Then the biocompatibility and biological functions were evaluated through fibroblast L-929 and SD rats. CM-CTS fabrics were obtained with elongation at break more than 42%, tensile strength reaching 0.65 N/mm², and water vapor transmission rate about 2600 g/m²∙24 h. Moreover, CM-CTS fabrics could effectively promote the mouse L-929 migration in vitro. CM-CTS fabrics yielded satisfactory results in angiogenesis, collagen deposition, interleukin-6 content, transforming growth factor level and healing rate, which were superior to the positive control and model groups after rats suffering with partial-thickness burn. In conclusion, CM-CTS fabrics possessed proper mechanical properties, air permeability, favorable biocompatibility, acceleration on fibroblasts migration and healing capacity for partial-thickness burn injury, and owned good potential as high-quality wound dressing.

[ALGINATE versus negative-pressure therapy: Comparison of the clinical effectiveness, tolerance and costs in management of patients after surgical excision. Multicenter, randomized non-inferiority clinical trial on 113 patients]

INTRODUCTION

Pure calcium alginate dressing (ALGINATE) and Negative Pressure Wound Therapy (NPWT) are frequently used for the preparation of skin excisions for a split thickness skin graft take. The trial compared the healing efficacy, safety and cost of patient care for these two treatments.

PATIENTS AND METHODS

This randomized, non-inferiority trial enrolled 113 patients who underwent skin excision (>30 cm²) and received ALGINATE or NPWT. The primary outcome was the time to obtain optimal granulation tissue for a split thickness skin graft take. Secondary outcomes were the occurrence of adverse events (AEs) and the impact of the patient care cost on the Social Security budget.

RESULTS

The mean time to optimal granulation was similar between ALGINATE and NPWT: approximately 20 days. No AE was reported with ALGINATE while 24 % of patients treated with NPWT presented an AE. Following hospitalization, 94 % of ALGINATE patients were cared for at home by a private nurse, while 90 % of NPWT patients were followed up in aftercare and rehabilitation facilities or home hospitalization. Therefore, the cost of treatment per patient for the French Social Security was 498 € with ALGINATE and 2104 € with NPWT.

CONCLUSION

This trial has demonstrated that ALGINATE has a similar healing efficacy to that of NPWT, and that it is markedly better with regard to patient safety and cost savings. ALGINATE should therefore be preferred to NPWT in this indication.