Regenerative materials that facilitate wound healing

Design and characterization of 3D printed, neomycin-eluting poly-L-lactide mats for wound-healing applications

This study evaluates the suitability of 3D printed biodegradable mats to load and deliver the topical antibiotic, neomycin, for up to 3 weeks in vitro. A 3D printer equipped with a hot melt extruder was used to print bandage-like wound coverings with porous sizes appropriate for cellular attachment and viability. The semicrystalline polyester, poly-l-lactic acid (PLLA) was used as the base polymer, coated (post-printing) with polyethylene glycols (PEGs) of MWs 400 Da, 6 kDa, or 20 kDa to enable manipulation of physicochemical and biological properties to suit intended applications. The mats were further loaded with a topical antibiotic (neomycin sulfate), and cumulative drug-release monitored for 3 weeks in vitro. Microscopic imaging as well as Scanning Electron Microscopy (SEM) studies showed pore dimensions of 100 × 400 µm. These pore dimensions were achieved without compromising mechanical strength; because of the "tough" individual fibers constituting the mat (Young's Moduli of 50 ± 20 MPa and Elastic Elongation of 10 ± 5%). The in vitro dissolution study showed first-order release kinetics for neomycin during the first 20 h, followed by diffusion-controlled (Fickian) release for the remaining duration of the study. The release of neomycin suggested that the ability to load neomycin on to PLLA mats increases threefold, as the MW of the applied PEG coating is lowered from 20 kDa to 400 Da. Overall, this study demonstrates a successful approach to using a 3D printer to prepare porous degradable mats for antibiotic delivery with potential applications to dermal regeneration and tissue engineering. Illustration of the process used to create and characterize 3D printed PLLA mats.

Development, characterization and pre-clinical trials of an innovative wound healing dressing based on propolis (EPP-AF®)-containing self-microemulsifying formulation incorporated in biocellulose membranes

The considerable role of pristine bacterial cellulose membranes (BC) as ideal dressings have been widely demonstrated to treat wounds and burns. Nevertheless, drawbacks regarding antimicrobial spectrum and frequent dressing replacement are still present. Based on this, the present work proposes an innovative dressing by incorporating a technological self-microemulsifying formulation (SMEF) encapsulating propolis (BC/PP). BC/PP was fully chemically and biologically characterized employing in vitro and in vivo models. Antimicrobial studies demonstrated BC/PP high efficiency against both gran-negative and gran-positive bacteria. Release studies evidenced propolis markers sustained release for up to 7 days. In vivo wound healing activity was assessed by wound healing rate, anti-inflammatory and tissue formation events and the results evidenced the pro-inflammatory activity of BC/PP, which could promote improved healing results. To conclude, BC/PP presented an outstanding antibacterial activity in vitro with weekly replacement and promotion of healing, offering, for the first time, a broad-spectrum biomembrane potential to treat infected wounds.

Simplifying the Forehead Flap for Nasal Reconstruction: A Review of 420 Consecutive Cases

BACKGROUND

The forehead flap is an important tool in nasal reconstruction. The authors present objective data and recommendations based on over a decade of consecutive forehead flap nasal reconstructions performed by the senior author (J.F.T.). In addition, the authors separate the technique into its individual steps and provide details of the senior author's approach to each.

METHODS

The authors performed a retrospective analysis of patients who underwent nasal reconstruction with the forehead flap over a 10-year period performed by the senior author (J.F.T.). Each case was evaluated for defect location, pedicle design, time of division, number of stages, use of cartilage grafts, lining reconstruction, donor-site closure, and complications.

RESULTS

Four hundred twenty patients underwent forehead flap nasal reconstruction. Average time to pedicle division was 32 days. Three-fourths of patients completed reconstruction in two stages. Defects most commonly involved the nasal ala and tip. Approximately half of patients received cartilage grafts and half underwent lining reconstruction. There were 16 complications, ranging from partial flap loss to postoperative death (n = 1).

CONCLUSIONS

Confidently grasping the nuances of forehead flap nasal reconstruction arms the reconstructive surgeon with a reliable tool that can effectively treat a variety of defects. It is safe to use in an outpatient setting even in elderly patients. Recommendations include ipsilateral flap design and turn-in component as the first choice for lining replacement.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Comparison of collagen content in skin wounds evaluated by biochemical assay and by computer-aided histomorphometric analysis

CONTEXT

The quantification of total collagen is of major importance in a wide range of research areas, including the study of cutaneous wound healing and new drugs trials.

OBJECTIVE

The total collagen content in skin biopsies was compared by biochemical hydroxyproline assay and by two computer-aided histomorphometric analyses of histological sections.

MATERIALS AND METHODS

Two methods were used to evaluate collagen formation: the hydroxyproline assay, as the gold standard and histomorphometric image analysis of the filled areas by corresponding stained collagen fibres, using picrosirius and Gomori's trichrome staining. The image analyses were determined by digital densitometry recognition using computer-aided ImageJ software. One-way ANOVA, simple linear regression and ANCOVA were applied for the statistical analysis and correlation.

RESULTS

In a simple linear regression analysis carried out on the 14th day period after the induction of skin injury, three techniques, picrosirius red (F = 33.57, p = 0.00), Gomori's trichrome (F = 81.61, p = 0.00) and hydroxyproline content (F = 16.85, p = 0.00) were able to detect collagen production. After scale adjustment, there were no significant differences among either the slopes (F = 1.17, p = 0.32) or the intercepts (F = 0.69, p = 0.51) of the estimated regression lines. It seems that a highly significant correlation exists between the histomorphometrical analysis and hydroxyproline assay.

DISCUSSION AND CONCLUSION

The morphometric analysis proved to be adequate and can be used as a simple, rapid, low-cost technology for evaluating total collagen in cutaneous wound specimens, compared with the gold standard hydroxyproline assay.

Recent advances in acellular regenerative tissue scaffolds

The management of chronic wounds is a considerable challenge for foot and ankle surgeons. The well-established tenets of adequate vascular supply, debridement with eradication of infection, and offloading must be employed in the management of all extremity wounds. Regenerative scaffolds are a viable means of reestablishing a favorable wound environment. The matrix facilitates cell migration, chemoattraction, angiogenesis, wound bed granulation, and expedited wound closure. Although studies have demonstrated success with acellular matrices, a multimodal approach should always be employed to improve healing success. Negative pressure wound therapy, compression, offloading, and antibiotics are advocated to improve outcomes. Acellular graft selection requires a multifactorial analysis, taking into consideration the specific patient and wound characteristics as well as the differences between acellular matrices. Patient age, comorbidities, activity level, and ability to comply with protocol as well as wound etiology, duration, depth, surface area, exudate, bacterial burden, location, vascular status, ischemic status, and presentation are all critical components. To effectively choose a matrix, the clinician must have a comprehensive understanding of the products available and the data validating their use. The mechanisms by which the acellular matrix accelerates wound healing and increases the likelihood of wound healing continue to be investigated. However, it is clear that these acellular biologic tissue scaffolds are incorporating into the host tissue, with resultant revascularization and cellular repopulation. Moving forward, additional investigations examining the effectiveness of acellular biologic tissue scaffolds to improve healing in complex, nondiabetic wounds are warranted.

Development of a silk fibroin/HTCC/PVA sponge for chronic wound dressing

A sponge wound dressing comprising silk fibroin, N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan chloride, and polyvinyl alcohol was developed for chronic wound healing. These composite sponges were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The composite sponge had a fluid uptake of 80% of its weight, and the water vapor transmission rate of 2974 ± 684 g/m2/day, indicating that the sponge could keep a moist environment around the wound bed. The Wistar rats were used to evaluate these composites for the treatment of chronic wounds. Wound healing was monitored through the macroscopic and immunological analyses. Although the wound area reduction rates were similar for the composite dressings compared to the non-woven fabrics containing wax-oil, the new composite dressings were found to be capable of improving the formation of blood vessels inside the wound beds by promoting the regrowth of skin tissues. Based on these results, using aqueous composite sponges in wound dressings, instead of oil-containing fabrics, promotes healing of chronic wounds in clinical applications.

An algorithmic approach for managing orthopaedic surgical wounds of the foot and ankle

BACKGROUND

Wound breakdown after orthopaedic foot and ankle surgery may necessitate secondary soft tissue coverage. The foot and ankle region is challenging to reconstruct for orthopaedic and plastic surgeons owing to its complex bony anatomy and unique functional demands. Therefore, identifying strategies for plastic surgery of these wounds may help guide surgeons in defining the best treatment plan.

QUESTIONS/PURPOSES

We evaluated our current algorithmic approach for managing orthopaedic surgical wounds of the foot and ankle with respect to whether (1) prophylactic or simultaneous soft tissue coverage affected wound-healing complications (secondary plastic surgery, orthopaedic hardware removal, malunion, further orthopaedic surgery, ultimate failure) and (2) postoperative referral for soft tissue management was associated with wound location, size, and orthopaedic procedure.

METHODS

We retrospectively reviewed 112 patients who underwent elective orthopaedic foot or ankle surgery and required concomitant plastic surgery at our institution. Study end points included secondary plastic surgery procedures, hardware removal for infection, foot or ankle malunion, further orthopaedic surgery, and wound-healing failure as defined by a chronic nonhealing wound or need for amputation. Minimum followup was 0.6 months (mean, 24.9 months; range, 0.6-197 months). Four patients were lost to complete followup. We developed an algorithm that centers on two critical points of care: preoperative evaluation by the orthopaedic surgeon and evaluation and treatment by the plastic surgeon after referral.

RESULTS

Compared with postoperative intervention, prophylactic or simultaneous soft tissue coverage did not lead to differences in frequency of secondary plastic surgery procedures (p = 0.55), hardware removal procedures (p = 0.13), malunions (p = 0.47), further orthopaedic surgery (p = 0.48), and ultimate failure (p = 0.27). Patients referred postoperatively for soft tissue management most frequently had dorsal ankle wounds (p < 0.001) of smaller size (p = 0.03), most commonly associated with total ankle arthroplasty (p = 0.004).

CONCLUSIONS

Using our algorithmic approach, prophylactic or simultaneous soft tissue coverage did not improve the study end points. In addition, unexpected postoperative wound breakdown necessitating a plastic surgery consultation most commonly occurred on the dorsal ankle after total ankle arthroplasty. Our algorithm facilitates early identification of skin instability and enables prompt soft tissue coverage before or concurrently with orthopaedic procedures. The effect of prophylactic or simultaneous soft tissue coverage on postoperative wound healing requires further investigation.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.