(LR-010) A Model to Evaluate the Biomechanical Strain Modalities Delivered to Tissue by a Novel tNPWT+DL Dressing

Runi Brownhill, PhD – Director, Science & Research Group, Advanced Wound Management R&D, Smith + Nephew; Louise France, PhD – Lecturer in Mechanical and Medical Engineering, Faculty of Science and Engineering, University of Hull; Matthew Hardman, PhD – Director of Research, Hull York Medical School; Xuanyuan Zhang, BSc (Hons) – PhD Researcher, Hull York Medical School

Introduction:

Whilst traditional Negative Pressure Wound Therapy (tNPWT) systems have demonstrated efficacy in managing hard-to-heal wounds¹, they are limited by their localized pressure delivery. In contrast, an advanced single-use NPWT^† system has shown accelerated healing outcomes², attributed to its ability to distribute negative pressure across a wider therapeutic zone. To bridge this gap, a novel tNPWT dressing, enhanced with a distribution layer (tNPWT+DL*) has been developed.

 

This study investigated the biomechanical effects of NPWT in vitro. Peri-wound dermal strain range of interest (3.5-6.5%) was assessed for its influence on injured primary human dermal fibroblasts (HDFs) using a bespoke cell culture model.

Methods:

Wounded (~3 cm diameter, ~1.5 cm depth) porcine tissue models (n=3) were treated with tNPWT^‡ and tNPWT+DL* (both with foam filler). Tissue strain was quantified using Finite Element Analysis (FEA) based on displacement data from micro-CT imaging of metallic markers embedded at various depths. Strain range of interest was identified within the peri-wound region. A bespoke cell stretching device (CSD) was developed to deliver the strain to cultured HDFs on collagen I-coated elastic membranes. HDFs from five donors with full informed consent (NHS REC 17/SC/0220) were cultured to confluence, injured via scratch assay, and then subjected to strain (3.5-4.5% and 5.5-6.5%) using the CSD for 24 h. Post-treatment, scratch closure was quantified using crystal violet staining and image analysis. Statistical analysis was performed using Welch’s t-test.

Results:

The peri-wound tissue region experiences a 6.3-fold (528%) increase in coverage in the strain range of interest (3.5-6.5%) with tNPWT+DL* compared to tNPWT^‡ at a sub-dermal depth of 2 cm. Strain application significantly enhanced HDF migration: 3.5-4.5% strain improved scratch closure by 7.29% (p< 0.0001), and 5.5-6.5% strain by 7.97% (p< 0.01), compared to no-strain controls.

Discussion: The strain ranges of interest correlated with increased cell migration in vitro. These results suggest that by delivering beneficial mechanotransductive strains more broadly to the peri-wound region compared to tNPWT^‡, the novel tNPWT+DL* dressing may further improve cellular responses and accelerate wound healing.