Bio-based polymers containing traditional medicinal fillers for wound healing applications - An evaluation of neoteric development and future perspectives

In recent years, health-care providers have seen more patients with difficult-to-treat wounds and burns. The biopolymer-based wound dressing protects the wounded area while assisting in the recovery of dermal and epithelial tissues throughout the healing process. The overall number of patients with chronic lesions has been expanding due to developing society, over weight, and cardiovascular illness. For the treatment of chronic wounds, there is an increasing demand for the development of ideal wound dressing materials with excellent properties such as antibacterial activity, biocompatibility, free radical scavenging capacity, non-adherent property, hydrophilicity, and so on. Nevertheless, owing to the above mention properties, natural polymers are being used for several key functions of biomedicine like narcotic distribution systems, tissue manufacturing, bandages, and so on. Accordingly, the significance of these bio-based polymers interfered with healing functions that lead to informing and inspiring youth and scientist researchers worldwide to grab with these far-reaching areas of medicine and biology. The review highlights the physiochemical properties of natural polymers, the biological evaluation of various materials as wound dressings, their synthesis and mechanical properties, clinical status, challenges, and future perspectives.

Inflammatory Microenvironment of Skin Wounds

Wound healing is a dynamic and highly regulated process that can be separated into three overlapping and interdependent phases: inflammation, proliferation, and remodelling. This review focuses on the inflammation stage, as it is the key stage of wound healing and plays a vital role in the local immune response and determines the progression of wound healing. Inflammatory cells, the main effector cells of the inflammatory response, have been widely studied, but little attention has been paid to the immunomodulatory effects of wound healing in non-inflammatory cells and the extracellular matrix. In this review, we attempt to deepen our understanding of the wound-healing microenvironment in the inflammatory stage by focusing on the interactions between cells and the extracellular matrix, as well as their role in regulating the immune response during the inflammatory stage. We hope our findings will provide new ideas for promoting tissue regeneration through immune regulation.

Efficacy of MMP-inhibiting wound dressings in the treatment of chronic wounds: a systematic review

OBJECTIVE

Matrix metalloproteinases (MMPs) substantially contribute to the development of chronicity in wounds. Thus, MMP-inhibiting dressings may support healing. A systematic review was performed to determine the existing evidence base for the treatment of hard-to-heal wounds with these dressings.

METHODS

A systematic literature search in databases and clinical trial registers was conducted to identify randomised controlled trials (RCTs) investigating the efficacy of MMP-inhibiting dressings. Studies were analysed regarding their quality and clinical evidence.

RESULTS

Of 721 hits, 16 relevant studies were assessed. There were 13 studies performed with collagen and three with technology lipido-colloid nano oligosaccharide factor (TLC-NOSF) dressings. Indications included diabetic foot ulcers, venous leg ulcers, pressure ulcers or wounds of mixed origin. Patient-relevant endpoints comprised wound size reduction, complete wound closure, healing time and rate. Considerable differences in the quality and subsequent clinical evidence exist between the studies identified. Substantial evidence for significant improvement in healing was identified only for some dressings.

CONCLUSION

Evidence for the superiority of some MMP-inhibiting wound dressings exists regarding wound closure, wound size reduction, healing time and healing rate. More research is required to substantiate the existing evidence for different types of hard-to-heal wounds and to generate evidence for some of the different types of MMP-inhibiting wound dressings.

Resting TcPO2 levels decrease during liner wear in persons with a transtibial amputation

Background

In our clinic, a substantial number of patients present with transtibial residual limb pain of no specific somatic origin. Silicone liner induced tissue compression may reduce blood flow, possibly causing residual limb pain. Thus, as a first step we investigated if the liner itself has an effect on transcutaneous oxygen pressure (TcPO2).

Methods

Persons with unilateral transtibial amputation and residual limb pain of unknown origin were included. Medical history, including residual limb pain, was recorded, and the SF-36 administered. Resting TcPO2 levels were measured in the supine position and without a liner at 0, 10, 20 and 30 minutes using two sensors: one placed in the Transverse plane over the tip of the Tibia End (= TTE), the other placed in the Sagittal plane, distally over the Peroneal Compartment (= SPC). Measurements were repeated with specially prepared liners avoiding additional pressure due to sensor placement. Statistical analyses were performed using SPSS.

Results

Twenty persons (9 women, 11 men) with a mean age of 68.65 years (range 47–86 years) participated. The transtibial amputation occurred on average 43 months prior to study entry (range 3–119 months). With liner wear, both sensors measured TcPO2 levels that were significantly lower than those measured without a liner (TTE: p < 0.001; SPC: p = 0.002) after 10, 20 and 30 minutes. No significant differences were found between TcPO2 levels over time between the sensors. There were no significant associations between TcPO2 levels and pain, smoking status, age, duration of daily liner use, mobility level, and revision history.

Conclusion

Resting TcPO2 levels decreased significantly while wearing a liner alone, without a prosthetic socket. Further studies are required to investigate the effect of liner wear on exercise TcPO2 levels.

The significance of collagen dressings in wound management: a review

Clinical experience and research has improved our understanding of wound healing which, in turn, has enabled health professionals to aid wound healing and manufacturers to develop modern wound dressings. The significant role of collagen in wound healing has led to the development of numerous products on the basis of this biological material. The main focus of this review is to provide a critical appraisal of publications about collagen and acellular collagen dressings with a fleece-like or spongy structure. It is intended for clinicians and researchers, and aims to keep them up-to-date in the complex field of interactive, collagen-based wound dressings, including their manufacture, combination possibilities, mechanisms of action, performance in the promotion of wound healing and indications. Despite the small number of clinical studies, the importance of acellular collagen dressings with a fleece- or sponge-like structure is likely to increase in the future. As there is no ideal wound dressing, the knowledge attained is meant to support health professionals in selecting the right product, and pave the way for new applications and clinical studies.

Dressings and topical agents for treating venous leg ulcers

BACKGROUND

Venous leg ulcers are open skin wounds on the lower leg which can be slow to heal, and are both painful and costly. The point prevalence of open venous leg ulcers in the UK is about 3 cases per 10,000 people, and many people experience recurrent episodes of prolonged ulceration. First-line treatment for venous leg ulcers is compression therapy, but a wide range of dressings and topical treatments are also used. This diversity of treatments makes evidence-based decision-making challenging, and a clear and current overview of all the evidence is required. This review is a network meta-analysis (NMA) which assesses the probability of complete ulcer healing associated with alternative dressings and topical agents.

OBJECTIVES

To assess the effects of (1) dressings and (2) topical agents for healing venous leg ulcers in any care setting and to rank treatments in order of effectiveness, with assessment of uncertainty and evidence quality.

SEARCH METHODS

In March 2017 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also scanned reference lists of relevant included studies as well as reviews, meta-analyses, guidelines and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting. We updated this search in March 2018; as a result several studies are awaiting classification.

SELECTION CRITERIA

We included published or unpublished randomised controlled trials (RCTs) that enrolled adults with venous leg ulcers and compared the effects of at least one of the following interventions with any other intervention in the treatment of venous leg ulcers: any dressing, or any topical agent applied directly to an open venous leg ulcer and left in situ. We excluded from this review dressings attached to external devices such as negative pressure wound therapies, skin grafts, growth factors and other biological agents, larval therapy and treatments such as laser, heat or ultrasound. Studies were required to report complete wound healing to be eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction. We conducted this NMA using frequentist meta-regression methods for the efficacy outcome; the probability of complete healing. We assumed that treatment effects were similar within dressings classes (e.g. hydrocolloid, foam). We present estimates of effect with their 95% confidence intervals (CIs) for individual treatments focusing on comparisons with widely used dressing classes, and we report ranking probabilities for each intervention (probability of being the best, second best, etc treatment). We assessed the certainty (quality) of the body of evidence using GRADE for each network comparison and for the network as whole.

MAIN RESULTS

We included 78 RCTs (7014 participants) in this review. Of these, 59 studies (5156 participants, 25 different interventions) were included in the NMA; resulting in 40 direct contrasts which informed 300 mixed-treatment contrasts.The evidence for the network as a whole was of low certainty. This judgement was based on the sparsity of the network leading to imprecision and the general high risk of bias in the included studies. Sensitivity analyses also demonstrated instability in key aspects of the network and results are reported for the extended sensitivity analysis. Evidence for individual contrasts was mainly judged to be low or very low certainty.The uncertainty was perpetuated when the results were considered by ranking the treatments in terms of the probability that they were the most effective for ulcer healing, with many treatments having similar, low, probabilities of being the best treatment. The two most highly-ranked treatments both had more than 50% probability of being the best (sucralfate and silver dressings). However, the data for sucralfate was from one small study, which means that this finding should be interpreted with caution. When exploring the data for silver and sucralfate compared with widely-used dressing classes, there was some evidence that silver dressings may increase the probability of venous leg ulcer healing, compared with nonadherent dressings: RR 2.43, 95% CI 1.58 to 3.74 (moderate-certainty evidence in the context of a low-certainty network). For all other combinations of these five interventions it was unclear whether the intervention increased the probability of healing; in each case this was low- or very low-certainty evidence as a consequence of one or more of imprecision, risk of bias and inconsistency.

AUTHORS' CONCLUSIONS

More research is needed to determine whether particular dressings or topical agents improve the probability of healing of venous leg ulcers. However, the NMA is uninformative regarding which interventions might best be included in a large trial, largely because of the low certainty of the whole network and of individual comparisons.The results of this NMA focus exclusively on complete healing; whilst this is of key importance to people living with venous leg ulcers, clinicians may wish to take into account other patient-important outcomes and factors such as patient preference and cost.

Protease-modulating matrix treatments for healing venous leg ulcers

BACKGROUND

Venous leg ulcers (VLUs) are open skin wounds on the lower leg that occur because of poor blood flow in the veins of the leg; leg ulcers can last from weeks to years, and are both painful and costly. Prevalence in the UK is about 2.9 cases per 10,000 people. First-line treatment for VLUs is compression therapy, but around 60% of people have unhealed ulcers after 12 weeks' treatment and about 40% after 24 weeks; therefore, there is scope for further improvement. Limited evidence suggests non-healing leg ulcers may have persisting elevated levels of proteases, which is thought to deter the later stages of healing; thus, timely protease-modulating matrix (PMM) treatments may improve healing by physically removing proteases from the wound fluid.

OBJECTIVES

To determine the effects of protease-modulating matrix (PMM) treatments on the healing of venous leg ulcers, in people managed in any care setting.

SEARCH METHODS

In September 2016 we searched: the Cochrane Wounds Specialised Register; CENTRAL; Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

We searched for published or unpublished randomised controlled trials (RCTs) that evaluated PMM treatments for VLUs. We defined PMM treatments as those with a purposeful intent of reducing proteases. Wound healing was the primary endpoint.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, risk of bias assessment and data extraction.

MAIN RESULTS

We included 12 studies (784 participants) in this review; sample sizes ranged from 10 to 187 participants (median 56.5). One study had three arms that were all relevant to this review and all the other studies had two arms. One study was a within-participant comparison. All studies were industry funded. Two studies provided unpublished data for healing.Nine of the included studies compared PMM treatments with other treatments and reported results for the primary outcomes. All treatments were dressings. All studies also gave the participants compression bandaging. Seven of these studies were in participants described as having 'non-responsive' or 'hard-to-heal' ulcers. Results, reported at short, medium and long durations and as time-to-event data, are summarised for the comparison of any dressing regimen incorporating PMM versus any other dressing regimen. The majority of the evidence was of low or very low certainty, and was mainly downgraded for risk of bias and imprecision.It is uncertain whether PMM dressing regimens heal VLUs quicker than non-PMM dressing regimens (low-certainty evidence from 1 trial with 100 participants) (HR 1.21, 95% CI 0.74 to 1.97).In the short term (four to eight weeks) it is unclear whether there is a difference between PMM dressing regimens and non-PMM dressing regimens in the probability of healing (very low-certainty evidence, 2 trials involving 207 participants).In the medium term (12 weeks), it is unclear whether PMM dressing regimens increase the probability of healing compared with non-PMM dressing regimens (low-certainty evidence from 4 trials with 192 participants) (RR 1.28, 95% CI 0.95 to 1.71). Over the longer term (6 months), it is also unclear whether there is a difference between PMM dressing regimens and non-PMM dressing regimens in the probability of healing (low certainty evidence, 1 trial, 100 participants) (RR 1.06, 95% CI 0.80 to 1.41).It is uncertain whether there is a difference in adverse events between PMM dressing regimens and non-PMM dressing regimens (low-certainty evidence from 5 trials, 363 participants) (RR 1.03, 95% CI 0.75 to 1.42). It is also unclear whether resource use is lower for PMM dressing regimens (low-certainty evidence, 1 trial involving 73 participants), or whether mean total costs in a German healthcare setting are different (low-certainty evidence, 1 trial in 187 participants). One cost-effectiveness analysis was not included because effectiveness was not based on complete healing.

AUTHORS' CONCLUSIONS

The evidence is generally of low certainty, particularly because of risk of bias and imprecision of effects. Within these limitations, we are unclear whether PMM dressing regimens influence venous ulcer healing relative to dressing regimens without PMM activity. It is also unclear whether there is a difference in rates of adverse events between PMM and non-PMM treatments. It is uncertain whether either resource use (products and staff time) or total costs associated with PMM dressing regimens are different from those for non-PMM dressing regimens. More research is needed to clarify the impact of PMM treatments on venous ulcer healing.

A 'test and treat' strategy for elevated wound protease activity for healing in venous leg ulcers

BACKGROUND

Venous leg ulcers are a common and recurring type of complex wound. They can be painful, malodorous, prone to infection and slow to heal. Standard treatment includes compression therapy and a dressing. The use of protease-modulating treatments for venous leg ulcers is increasing. These treatments are based on some evidence that a proportion of slow to heal ulcers have elevated protease activity in the wound. Point-of-care tests which aim to detect elevated protease activity are now available. A 'test and treat' strategy involves testing for elevated proteases and then using protease-modulating treatments in ulcers which show elevated protease levels.

OBJECTIVES

To determine the effects on venous leg ulcer healing of a 'test and treat' strategy involving detection of high levels of wound protease activity and treatment with protease-modulating therapies, compared with alternative treatment strategies such as using the same treatment for all participants or using a different method of treatment selection.

SEARCH METHODS

We searched the following electronic databases to identify reports of relevant randomised clinical trials: The Cochrane Wounds Group Specialised Register (January 2016), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) Issue 12, 2015); Ovid MEDLINE (1946 to January 2016); Ovid MEDLINE (In-Process & Other Non-Indexed Citations January 2016); Ovid EMBASE (1974 to January 2016); EBSCO CINAHL (1937 to January 2016). We also searched three clinical trials registers, reference lists and the websites of regulatory agencies. There were no restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

Published or unpublished RCTs which assessed a test and treat strategy for elevated protease activity in venous leg ulcers in adults compared with an alternative treatment strategy. The test and treat strategy needed to be the only systematic difference between the groups.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection; we planned that two authors would also assess risk of bias and extract data.

MAIN RESULTS

We did not identify any studies which met the inclusion criteria for this review. We identified one ongoing study; it was unclear whether this would be eligible for inclusion.

AUTHORS' CONCLUSIONS

Currently there is no randomised evidence on the impact of a test and treat policy for protease levels on outcomes in people with venous leg ulcers.

Wound care in venous ulcers

Wound dressings: ulcer dressings should create and maintain a moist environment on the ulcer surface. It has been shown that in an ulcer with a hard crust and desiccated bed, the healing process is significantly slowed and sometimes completely blocked so favouring infection, inflammation and pain. In contrast a moist environment promotes autolytic debridement, angiogenesis and the more rapid formation of granulation tissue, favours keratinocytes migration and accelerates healing of wounds. Apart from these common characteristics, wound dressings are completely different in other aspects and must be used according to the ulcer stage. In necrotic ulcers, autolytic debridement by means of hydrogel and hydrocolloids or with enzymatic paste is preferred. In case of largely exuding wounds alginate or hydrofibre are indicated. When bleeding occurs alginate is indicated due to its haemostatic power. Where ulcers are covered by granulation tissue, polyurethane foams are preferred. When infection coexists antiseptics are necessary: dressing containing silver or iodine with large antibacterial spectrum have proved to be very effective. In the epithelization stage polyurethane films or membranes, thin hydrocolloids or collagen based dressings are very useful to favour advancement of the healing wound edge. Despite these considerations, a Cochrane review failed to find advantages for any dressing type compared with low-adherent dressings applied beneath compression. Surgical debridement and grafting of wounds, negative wound pressure treatment: surgical and hydrosurgical debridement are indicated in large, necrotic and infected wounds as these treatments are able to get rid of necrotic, infected tissue very quickly in a single surgical session, thereby significantly accelerating wound bed preparation and healing time. Negative wound pressure treatment creating a negative pressure on ulcer bed is able to favour granulation tissue and shorten healing time. In case of hard-to-heal leg ulcers such as large, deep, infected and long-lasting venous ulcers, sharp debridement and skin grafting may favour and shorten ulcer healing.

Foam dressings for venous leg ulcers

BACKGROUND

Venous leg ulcers are a common and recurring type of chronic or complex wound that are associated with considerable cost to patients and to healthcare providers. Primary wound contact dressings are usually applied beneath compression devices with the aim of aiding healing. Foam dressings are used frequently, and a variety of foam products is available on the market. The evidence base to guide dressing choice, however, is sparse. 

OBJECTIVES

To determine the effects of foam dressings on the healing of venous leg ulcers.

SEARCH METHODS

In October 2012 we searched The Cochrane Wounds Group Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); the Database of Abstracts of Reviews of Effects (DARE) (The Cochrane Library); the Economic Evaluation Database (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; EBSCO CINAHL. There were no restrictions based on language or date of publication.

SELECTION CRITERIA

We included published or unpublished randomised controlled trials (RCTs) that evaluated the effects of any type of foam dressing in the treatment of venous ulcers.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, data extraction and risk of bias assessment. Meta-analysis was undertaken when deemed feasible and appropriate.

MAIN RESULTS

Twelve RCTs (1023 participants) reporting 14 comparisons were included in this review. There was no difference in healing outcomes between hydrocellular foam dressings and polyurethane foam dressings (three RCTs). Pooled data across five RCTs (418 participants) showed no statistically significant difference between foam dressings and hydrocolloid dressings in the proportion of ulcers healed at 12 to 16 weeks (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.81 to 1.22). No statistically significant between-group differences in healing outcomes were detected when foam dressings were compared with: paraffin gauze (two RCTs); hydrocapillary dressing (one RCT); knitted viscose dressing (one RCT); and protease modulating matrix (one RCT). No statistically significant between-group differences in the proportion of participants experiencing adverse events were detected when hydrocellular foam dressings were compared with polyurethane foam dressings, or when foam dressings were compared with hydrocapillary, hydrocolloid, or knitted viscose dressings (one RCT for each comparison). Six RCTs were considered as being at overall high risk of bias, and the remaining six RCTs were considered to be at overall unclear risk of bias. No included RCT had an overall low risk of bias.

AUTHORS' CONCLUSIONS

The current evidence base does not suggest that foam dressings are more effective in the healing of venous leg ulcers than other wound dressing treatments. The evidence in this area is of low quality. Further evidence is required from well-designed and rigorously-conducted RCTs, that employ methods to minimise bias and report them clearly, before any definitive conclusions can be made regarding the efficacy of foam dressings in the management of venous leg ulcers.