Superabsorbent polymer-containing wound dressings have a beneficial effect on wound healing by reducing PMN elastase concentration and inhibiting microbial growth

Research Advances in Superabsorbent Polymers

Superabsorbent polymers are new functional polymeric materials that can absorb and retain liquids thousands of times their masses. This paper reviews the synthesis and modification methods of different superabsorbent polymers, summarizes the processing methods for different forms of superabsorbent polymers, and organizes the applications and research progress of superabsorbent polymers in industrial, agricultural, and biomedical industries. Synthetic polymers like polyacrylic acid, polyacrylamide, polyacrylonitrile, and polyvinyl alcohol exhibit superior water absorption properties compared to natural polymers such as cellulose, chitosan, and starch, but they also do not degrade easily. Consequently, it is often necessary to modify synthetic polymers or graft superabsorbent functional groups onto natural polymers, and then crosslink them to balance the properties of material. Compared to the widely used superabsorbent nanoparticles, research on superabsorbent fibers and gels is on the rise, and they are particularly notable in biomedical fields like drug delivery, wound dressing, and tissue engineering.

[Treatment of 52 patients with a self-adhesive siliconised superabsorbent dressing: a multicentre observational study]

OBJECTIVE

To provide 'in use' clinical data to support exudate management in patients with moderately to highly exuding wounds with bordered superabsorbent wound dressing with a silicone adhesive interface Zetuvit Plus Silicone Border (Paul Hartmann Ltd., Germany).

MATERIALS AND METHODS

This study was an open-labelled non-comparative study. Patients included in the study were selected by the clinical investigator(s) according to whether the patient required a dressing for the management of moderately to highly exuding wounds such as pressure ulcers, diabetic foot ulcers, venous leg ulcer and arterial ulcers The patients were treated with A superabsorbent sterile wound dressing with bordered superabsorbent wound dressing with a silicone adhesive interface Zetuvit Plus Silicone Border (Paul Hartmann Ltd., Germany).

RESULTS

The Zetuvit Plus Silicone Border dressing had met the clinical objectives relating to exudate management, affirmed by the health professionals with a yes response in 94% of cases. Additionally, the health professionals rated the handling of exudate as excellent/good (78%) and most (80%) reported that they would use the superabsorbent wound dressing with a silicone adhesive interface again. Allied to this was the fact that the dressing improved the wound edge and periwound skin conditions (29% and 36% of patients, respectively). The dressing retained its position in 72% of patients. For wear time, the largest proportion of dressing changes, both pre-study and during the evaluation period, was every third day (45% and 44%, respectively). But there was a shift to extended wear time with use of the superabsorbent wound dressing with a silicone adhesive interface with 72% of patients' dressing changes being every third day or longer.

CONCLUSION

The superabsorbent silicone border dressing was successful in managing wound exudate in moderately to highly exuding wounds and consequently this had a beneficial impact on the wound edge and periwound skin. Overall, there was a positive effect on wound bed preparation and in turn the healing response was progressive.

An observational study of wounds treated with hydro-responsive wound dressings

OBJECTIVE

Acute and hard-to-heal wounds are a significant burden to both a patient's quality of life and resources in healthcare systems. Here, we evaluate the outcomes of a non-comparative case series study in which Ringer's solution-preactivated polyacrylate dressings were used to treat acute and hard-to-heal wounds (the presence of Ringer's solution provides a wound dressing that allows, upon application, the immediate hydration of the underlying wound tissue).

METHOD

Patients with acute and hard-to-heal wounds were enrolled into an open-labelled, non-comparative observational study. Patients were treated with Ringer's solution-preactivated polyacrylate dressings to enable wound debridement and wound cleansing for up to 12 weeks.

RESULTS

A total of 303 patients were enrolled in the study and 278 were included in the analysis. Wound size decreased, from a median of 3.6cm² (interquartile range (IQR): 1.2-9.3] at baseline to a median of 2.6cm² (IQR: 1.1-7.8] at 84 days. Relative wound area reduction (WAR) was 43.1% at 84 days and estimated probability of achievement of a WAR of ≥40% and ≥60% was 68.7% and 53.4%, respectively. Median time to achieve a WAR of ≥40% and ≥60% was 54 days and 75 days, respectively. The median percentage of wound area covered by fibrin had decreased from 50.0% to 10% and granulation tissue had increased from 25% to 50% after 84 days. In addition, periwound skin condition, local signs of infection and pain all showed improvement. The majority of the wounds were assessed as 'healed' or 'better' at the conclusion of the evaluation period.

CONCLUSION

Based on the findings of this study, the use of Ringer's solution-preactivated polyacrylate dressings in daily practice has the potential to improve clinical outcomes, including healing, in patients with acute and hard-to-heal wounds.

Antimicrobial effects of bacterial binding to a dialkylcarbamoyl chloride-coated wound dressing: an in vitro study

OBJECTIVE

Wound dressings that inactivate or sequestrate microorganisms, such as those with a hydrophobic, bacteria-binding dialkylcarbamoyl chloride (DACC) surface, can reduce the risk of clinical infections. This 'passive' bioburden control, avoiding bacterial cell wall disruption with associated release of bacterial endotoxins aggravating inflammation, is advantageous in hard-to-heal wounds. Hence, the full scope of DACC dressings, including the potential impact of higher inoculum densities, increased protein load and different pH on antibacterial activity, needs to be evaluated.

METHOD

The Japanese Industrial Standard (JIS) L 1902 challenge test was used to evaluate the antimicrobial activity of the DACC-coated dressing against several World Health Organization (WHO)-prioritised wound pathogens (e.g., meticillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, microorganisms with extended-spectrum beta-lactamases and Acinetobacter baumannii), the effect of repeated bacterial challenge in an adverse wound environment, and antimicrobial performance at wound-related pH.

RESULTS

High antibacterial activity of the DACC-coated dressing against the WHO-prioritised bacteria strains by its irreversible binding and inhibition of growth of bound bacteria was confirmed using JIS L 1902. At increased inoculation densities, compared to standard conditions, the DACC-coated dressing still achieved strong-to-significant antibacterial effects. Augmenting the media protein content also affected antibacterial performance; a 0.5-1 log reduction in antibacterial activity was observed upon addition of 10% fetal calf serum. The pH did not influence antibacterial performance. The DACC-coated dressing also sustained antibacterial activity over subsequent reinfection steps.

CONCLUSION

It can be assumed that the DACC-coated dressing exerts beneficial effects in controlling the wound bioburden, reducing the overall demand placed on antibiotics, without using antimicrobial substances.

Investigating the microbial and metalloprotease sequestration properties of superabsorbent wound dressings

Exudate production is a natural part of the wound healing process, however levels of exudate need to be appropriately managed to maintain a moist wound environment which supports healing. An overly-exuding wound creates an environment favourable to bacterial growth. In recent years, a significant increase in commercially available superabsorbent dressings have become available which claim to absorb and retain excess exudate and its components. However, the effectiveness of these dressings in sequestering and retaining bacteria and host-derived proteins has not been compared. We have therefore investigated several superabsorbent dressings for their ability to absorb and retain bacteria (Staphylococcus aureus and Pseudomonas aeruginosa), their impact on bacterial viability, and their ability to sequester matrix metalloproteinases (MMP)-2 and 9 over 7 days. Whilst all dressings could sequester bacteria, some dressings internalised bacteria more effectively. There was considerable variation in bacterial viability within the dressings’ core, as well as differences in bacterial retention. Some dressings effectively internalised and retained bacteria over time, whereas other dressings retained significantly less. These differences were reflected visually using scanning electron microscopy. Most dressings fully sequestered MMP-2 and 9. These data illustrate differences in the ability of superabsorbent dressings to absorb and retain exudate and its components.

Hotspots, Frontiers, and Emerging Trends of Superabsorbent Polymer Research: A Comprehensive Review

Superabsorbent polymer (SAP) is a kind of functional macromolecule with super-high water absorption and retention properties, which attracts extensive research and has wide application, especially in the areas of hygiene and agriculture. With reference to the Web of Science database, the SAP research literature from 2000 to 2019 is reviewed both quantitatively and qualitatively. By examining research hotspots, top research clusters, the most influential works, the representative frontier literature, and key emerging research trends, a visual panorama of the continuously and significantly increasing SAP research over the past 2 decades was presented, and issues behind the sharp increase in the literature were discovered. The findings are as follows. The top ten keywords/hotspots headed by hydrogel highlight the academic attention on SAP properties and composites. The top ten research themes headed by clay-based composites which boast the longest duration and the strongest impact have revealed the academic preference for application rather than theoretical study. Academically influential scholars and research studies have been acknowledged, and the Wu group was at the forefront of the research; however, more statistically significant works have been less detected in the last 10 years despite the sharper increase in publications. Hydrogel, internal curing, and aerogel are both current advances and future directions.

Superabsorbent polymers: A state-of-art review on their classification, synthesis, physicochemical properties, and applications

Superabsorbent polymers (SAP) and modified natural polymer hydrogels are widely and increasingly used in agriculture, health care textiles, effluent treatment, drug delivery, tissue engineering, civil concrete structure, etc. However, not many comprehensive reviews are available on this class of novel polymers. A review covering all the viable applications of SAP will be highly useful for researchers, industry persons, and medical, healthcare, and agricultural purposes. Hence, an attempt has been made to review SAPs with reference to their classifications, synthesis, modification by crosslinking, and physicochemical characterization such as morphology, swellability, thermal and mechanical properties, lifetime prediction, thermodynamics of swelling, absorption, release and transport kinetics, quantification of hydrophilic groups, etc. Besides, the possible methods of fine-tuning their structures for improving their absorption capacity, fast absorption kinetics, mechanical strength, controlled release features, etc. were also addressed to widen their uses. This review has also highlighted the biodegradability, commercial viability and market potential of SAPs, SAP composites, the feasibility of using biomass as raw materials for SAP production, etc. The challenges and future prospects of SAP, their safety, and environmental issues are also discussed.

Use of a superabsorbent dressing in the management of exudate in hard-to-heal wounds

With the shift in demographics towards an ageing population with multimorbidity, the number of hard-to-heal (chronic) wounds is increasing each year. This poses a challenge for both health professionals, for whom wound management is becoming more complex, and for patients, who have to cope with exudate production, malodour and pain. This article summarises understanding of healing in such wounds and how best to meet the challenge of exudate, which is a ubiquitous hallmark of hard-to-heal wounds. The role of superabsorbent dressings is considered, with particular reference to Kliniderm superabsorbent in the management of people with these challenging wounds.

New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

Development of sustainable bio-based materials for removal of toxic contaminants from water is a high priority goal. Novel bio-based binary and ternary copolymers with enhanced ion-exchange, adsorption and antibacterial properties were obtained by using plant biomass-derived diallyl esters of furandicarboxylic acid (FDCA) as crosslinking agents and easily available vinyl monomers. The synthesized copolymer materials showed higher sorption capacities for Ni^II , Co^II and Cu^II compared to the commercial ion-exchange resins, and they maintained their high metal adsorption capacities for over 10 cycles of regeneration. The synthesized copolymer gels containing 1-5 wt % of the crosslinker showed excellent water absorption capacities. The synthesized copolymers with 1 % crosslinker content showed swelling ratios high enough to also act as moisture absorbents. Synthesized copolymers with crosslinker content of 10 wt % performed as contact-active antibacterials by inhibiting the growth of Gram-positive (S. aureus) and Gram-negative bacteria (E. coli, K. pneumonia) in suspension tests.

The evaluation of the effect of probiotics on the healing of equine distal limb wounds

The effect of dressings saturated with either a standardized suspension of probiotic bacteria or saline on healing of traumatic distal limb wounds in horses was evaluated for 24 days, and the systemic inflammatory effect was assessed. The wounds were divided in two groups based on the phase of healing: wounds with an incomplete (ICGB) or a complete granulation bed (CGB). The wound area was expressed as percentage of the wound area at day 0 and defined as relative wound area. The mean relative wound area decreased faster in probiotic than saline treated wounds. The difference was most obvious in CGB and increased rapidly from day 0 until day 12 up to 30%, and stabilized around 25% thereafter until the end of the observation period, but it was not statistically significant because of the large variation within the treatment groups. The mean wound area of CGB decreased to 28.4% (range: 6.3 to 49.3) with probiotic and to 51.9% (range: 29.3 to 81.7) with saline treatment at day 24. Additionally, the rate to 50% healing in CGB was 3.4 faster with probiotic compared to saline treatment, whereas in ICGB this was 1.9 faster. Topical probiotics did not increase serum amyloid A and white blood cell counts. Although the mentioned differences were not statistically significant, the clinical relevance of the effect of treatment with probiotics in CGB wounds is clear, supported by the differences in mean wound area in course of time and the time required to reach 50% healing (day 12 for probiotic vs more than day 24 for saline treated wounds). Thus the probiotic treated wounds reached 50% reduction in wound area in half of the time of the saline treated wounds. The topical use of probiotics can be considered as safe as it did not cause a systemic effect.

Treatment of 52 patients with a self-adhesive siliconised superabsorbent dressing: a multicentre observational study

Objective:

To provide ‘in use’ clinical data to support exudate management in patients with moderately to highly exuding wounds with bordered superabsorbent wound dressing with a silicone adhesive interface.

Method:

This study was an open-labelled non-comparative study. Patients included in the study were selected by the clinical investigator(s) according to whether the patient required a dressing for the management of moderately to highly exuding wounds.

Results:

The primary aim of this study was to evaluate the clinical objective in relation to exudate handling (moderate to high) with a superabsorbent silicone border dressing (Zetuvit Plus Silicone Border; SAP silicone border dressing; designated RespoSorb Silicone Border in some countries). The SAP border dressing had met the clinical objectives relating to exudate management, affirmed by the health professionals with a yes response in 94% of cases. Additionally, the health professionals rated the handling of exudate as excellent/good (78%) and most (80%) reported that they would use the SAP silicone border dressing again. Allied to this was the fact that the SAP silicone border dressing improved the wound edge and periwound skin conditions (29% and 36% of patients, respectively). Regarding dressing retention, the SAP silicone border dressing retained its position in 72% of patients. For wear time, the largest proportion of dressing changes, both pre-study and during the evaluation period, was every third day (45% and 44%, respectively). But there was a shift to extended wear time with use of the SAP silicone border dressing with 72% of patients' dressing changes being every third day or longer.

Conclusion:

The SAP silicone border dressing was successful in managing wound exudate in moderately to highly exuding wounds and consequently this had a beneficial impact on the wound edge and periwound skin. Overall, there was a positive effect on wound bed preparation and in turn the healing response was progressive. This study has shown that the SAP silicone border dressing successfully controlled exudate and provided positive benefits when used in the treatment of patients with moderately to highly exuding wounds.

Exudates absorption and proteases trapping in venous leg ulcers

OBJECTIVE

In venous leg ulcer (VLU), the impaired healing has been shown to be associated with excessive levels of protease activities such as matrix metalloproteinases (MMPs) and elastases found in exudates. The present study focused on exudates absorption and proteases trapping capacity of a new generation of polyacrylate superabsorbent, Tegaderm superabsorber (TS), compared with a traditional dressing such as Zetuvit.

METHOD

We studied the proteases implicated in VLU (MMP-1, MMP-2, MMP-9 and PMN elastase). Absorption was tested using an artificial exudate like fluid, over 30 minutes. The protein trapping ability was obtained using ELISA assays (enzyme-linked immunosorbent assay) to determine the amount retained by the dressings from spiked fluid samples.

RESULTS

TS had a higher exudate absorption capacity (72.8±1.7%) compared with the standard dressing (36.5±1.6%), and was also able to trap and retain proteases while the standard dressing released them. The difference was shown to be much larger for MMP-2 and PMN elastase.

CONCLUSION

In our knowledge, this is the first comparative in vitro study evaluating absorption capacity as well as protease trapping capacity of a polyacrylate dressing for the four most implicated proteases in VLU. TS could be an appropriate alternative to improve the management of VLU by trapping MMPs and PMN elastse with a particularly high affinity for MMP-2 and PMN elastase.

Microbial alginate dressings show improved binding capacity for pathophysiological factors in chronic wounds compared to commercial alginate dressings of marine origin

Marine alginates are well established in wound management. Compared with different modern wound dressings, marine alginates cannot prove superior effects on wound healing. Alginates from bacteria have never been studied for medical applications so far, although the microbial polymer raises expectations for improved binding of wound factors because of its unique O-acetylation. Due to its possible positive effects on wound healing, alginates from bacteria might be a superior future medical product for clinical use. To prove the binding capacity of microbial alginates to pathophysiological factors in chronic wounds, we processed microbial alginate fibres, produced from fermentation of the soil bacterium Azotobacter vinelandii ATCC 9046, into needle web dressings and compared them with commercial dressings made of marine alginate. Four dressings were assessed: Marine alginate dressings containing either ionic silver or zinc/manganese/calcium, and microbial alginate dressings with and without nanosilver. All dressings were tested in an in vitro approach for influence on chronic wound parameters such as elastase, matrix metalloproteases-2, tumour necrosis factor-α, interleukin-8, and free radical formation. Despite the alginate origin or addition of antimicrobials, all dressings were able to reduce the concentration of the proinflammatory cytokines TNF-α and IL-8. However, microbial alginate was found to bind considerable larger amounts of elastase and matrix metalloproteases-2 in contrast to the marine alginate dressings. The incorporation of zinc, silver or nanosilver into alginate fibres did not improve their binding capacity for proteases or cytokines. The addition of nanosilver slightly enhanced the antioxidant capacity of microbial alginate dressings, whereas the marine alginate dressing containing zinc/manganese/calcium was unable to inhibit the formation of free radicals. The enhanced binding affinity by microbial alginate of Azotobacter vinelandii to pathophysiological factors may be interesting to support optimal conditions for wound healing.

Extracellular Bacterial Proteases in Chronic Wounds: A Potential Therapeutic Target?

Significance: Bacterial biofilms are considered to be responsible for over 80% of persistent infections, including chronic lung infections, osteomyelitis, periodontitis, endocarditis, and chronic wounds. Over 60% of chronic wounds are colonized with bacteria that reside within a biofilm. The exaggerated proteolytic environment of chronic wounds, more specifically elevated matrix metalloproteinases, is thought to be one of the possible reasons as to why chronic wounds fail to heal. However, the role of bacterial proteases within chronic wounds is not fully understood. Recent Advances: Recent research has shown that bacterial proteases can enable colonization and facilitate bacterial immune evasion. The inhibition of bacterial proteases such as Pseudomonas aeruginosa elastase B (LasB) has resulted in the disruption of the bacterial biofilm in vitro. P. aeruginosa is thought to be a key pathogen in chronic wound infection, and therefore, the disruption of these biofilms, potentially through the targeting of P. aeruginosa bacterial proteases, is an attractive therapeutic endeavor. Critical Issues: Disrupting biofilm formation through the inhibition of bacterial proteases may lead to the dissemination of bacteria from the biofilm, allowing planktonic cells to colonize new sites within the wound. Future Directions: Despite a plethora of evidence supporting the role of bacterial proteases as virulence factors in infection, there remains a distinct lack of research into the effect of bacterial proteases in chronic wounds. To assess the viability of targeting bacterial proteases, future research should aim to understand the role of these proteases in a variety of chronic wound subtypes.

The importance of hydration in wound healing: reinvigorating the clinical perspective

Balancing skin hydration levels is important as any disruption in skin integrity will result in disturbance of the dermal water balance. The discovery that a moist environment actively supports the healing response when compared with a dry environment highlights the importance of water and good hydration levels for optimal healing. The benefits of 'wet' or 'hyper-hydrated' wound healing appear similar to those offered by moist over a dry environment. This suggests that the presence of free water may not be detrimental to healing, but any adverse effects of wound fluid on tissues is more likely related to the biological components contained within chronic wound exudate, for example elevated protease levels. Appropriate dressings applied to wounds must not only be able to absorb the exudate, but also retain this excess fluid together with its protease solutes, while concurrently preventing desiccation. This is particularly important in the case of chronic wounds where peri-wound skin barrier properties are compromised and there is increased permeation across the injured skin. This review discusses the importance of appropriate levels of hydration in skin, with a particular focus on the need for optimal hydration levels for effective healing. Declaration of interest: This paper was supported by Paul Hartmann Ltd. The authors have provided consultative services to Paul Hartmann Ltd.

Study on the Antimicrobial Properties of Citrate-Based Biodegradable Polymers

Citrate-based polymers possess unique advantages for various biomedical applications since citric acid is a natural metabolism product, which is biocompatible and antimicrobial. In polymer synthesis, citric acid also provides multiple functional groups to control the crosslinking of polymers and active binding sites for further conjugation of biomolecules. Our group recently developed a number of citrate-based polymers for various biomedical applications by taking advantage of their controllable chemical, mechanical, and biological characteristics. In this study, various citric acid derived biodegradable polymers were synthesized and investigated for their physicochemical and antimicrobial properties. Results indicate that citric acid derived polymers reduced bacterial proliferation to different degrees based on their chemical composition. Among the studied polymers, poly(octamethylene citrate) showed ~70-80% suppression to microbe proliferation, owing to its relatively higher ratio of citric acid contents. Crosslinked urethane-doped polyester elastomers and biodegradable photoluminescent polymers also exhibited significant bacteria reduction of ~20 and ~50% for Staphylococcus aureus and Escherichia coli, respectively. Thus, the intrinsic antibacterial properties in citrate-based polymers enable them to inhibit bacteria growth without incorporation of antibiotics, silver nanoparticles, and other traditional bacteria-killing agents suggesting that the citrate-based polymers are unique beneficial materials for wound dressing, tissue engineering, and other potential medical applications where antimicrobial property is desired.

An evaluation of KerraMax Care in the management of moderate to heavily exuding wounds

Highly exuding wounds are common and can result in malodour, pain, maceration, infection and unsightly soiled dressings, as well as having a negative impact on an individual's quality of life. This communication reports on the findings from an evaluation by nurses regarding the clinical effectiveness and safety of superabsorbent dressing KerraMax Care and the patient experience of KerraMax Care in the management of moderate to highly exuding wounds. A total of 54 evaluations were completed. Nurses commented on the main benefits seen clinically with KerraMax Care as being reduced maceration, exudate managed and improved wound appearance. Other changes observed in wound appearance noted were visible granulation tissue and reduced pain. The evaluation demonstrates the positive impact that good dressing selection can have on the lives of patients, improving their wound-care experience and outcome.

A superabsorbent polymer-containing wound dressing efficiently sequesters MMPs and inhibits collagenase activity in vitro

Superabsorbent polymer (SAP)-containing wound dressings present a valuable and unique category of wound management products. An in vitro approach was used to assess the effects of a new SAP dressing in treatment of non-healing wounds. It was shown that the SAP dressing possesses a significant binding capacity for MMP-2 and MMP-9 in vitro (P\0.001). The inclusion of the bound proteases was so strong that no MMP-2 and only marginal amounts of MMP-9 were released from the dressing samples in a subsequent elution step. In addition, the SAP dressing was able to take up collagenase and reduce its activity in vitro. However, collagenase was not completely inactivated upon binding and enzyme-mediated substrate turnover could be observed at the dressings. In conclusion, in vitro data confirm the positive effect of the SAP wound dressing observed in vivo. The findings suggest that it should be specifically useful for highly exuding wounds with an elevated proteolytic activity that needs to be reduced to support healing.

SAP-containing dressings exhibit sustained antimicrobial effects over 7 days in vitro

OBJECTIVE

To investigate the antimicrobial activity of SAP-containing wound dressings in vitro over a prolonged period of time (7 days) and to assess their ability to sustain the antimicrobial effect.

METHOD

SAP dressings were tested according to the JIS L 1902:2002 against the pathogens Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Candida albicans.Additionally, effect on S. aureus and P. aeruginosa growth was investigated after a prolonged incubation period of 7 days. Furthermore, both SAP dressings were repeatedly inoculated with P. aeruginosa suspension and, after 7 days, microbial growth under the dressings was evaluated.

RESULTS

Both SAP-containing wound dressings tested exhibited a significant to strong antimicrobial activity against Staphylococcus aureus, MRSA, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Candida albicans in vitro. Moreover, it could be shown that they were able to sustain antibacterial efficacy over a prolonged period of time. Using a direct incubation method with repeated re-inoculation of the dressing samples, it could be shown that growth of P. aeruginosa was reduced after 4 days of treatment and completely inhibited after 7 days. No significant differences were observed between the two SAP-dressings tested.

CONCLUSION

These in vitro experiments impressively demonstrated the antimicrobial mechanism of SAP-containing wound dressings: rapid up-take of fluid, binding of microorganisms to the SAP-core, and retention of the bacteria inside the dressing. Moreover, it could be shown that they are able to exhibit their antimicrobial activity over a prolonged period of time unless the amount of fluid present exceeds their fluid-handling capacity.

Citrate-linked keto- and aldo-hexose monosaccharide cellulose conjugates demonstrate selective human neutrophil elastase-lowering activity in cotton dressings

Sequestration of harmful proteases as human neutrophil elastase (HNE) from the chronic wound environment is an important goal of wound dressing design and function. Monosaccharides attached to cellulose conjugates as ester-appended aldohexoses and ketohexoses were prepared on cotton gauze as monosccharide-citrate-cellulose-esters for HNE sequestration. The monosaccharide-cellulose analogs demonstrated selective binding when the derivatized cotton dressings were measured for sequestration of HNE. Each monosaccharide-cellulose conjugate was prepared as a cellulose citrate-linked monosaccharide ester on the cotton wound dressing, and assayed under wound exudate-mimicked conditions for elastase sequestration activity. A series of three aldohexose and four ketohexose ester cellulose conjugates were prepared on cotton gauze through citric acid-cellulose cross linking esterification. The monosaccharide portion of the conjugate was characterized by hydrolysis of the citrate-monosaccharide ester bond, and subsequent analysis of the free monosaccharide with high performance anion exchange chromatography. The ketohexose and aldohexose conjugate levels on cotton were quantified on cotton using chromatography and found to be present in milligram/gram amounts. The citrate-cellulose ester bonds were characterized with FTIR. Ketohexose-citrate-cellulose conjugates sequestered more elastase activity than aldohexose-citrate-cellulose conjugates. The monosaccharide cellulose conjugate families each gave distinctive profiles in elastase-lowering effects. Possible mechanisms of elastase binding to the monosaccharide-cellulose conjugates are discussed.

In vitro protoscolicidal effects of high-intensity focused ultrasound enhanced by a superabsorbent polymer

Echinococcus granulosus, the etiologic agent of cystic echinococcosis in humans and other animal hosts, is distributed worldwide. Echinococcosis is an increasing public health and socioeconomic concern. The present work evaluated whether or not a superabsorbent polymer (SAP) could enhance the damage efficacy of high-intensity focused ultrasound (HIFU) on the viability of E. granulosus protoscolices in vitro. HIFU of 100 W acoustic power and 0.01 g superabsorbent polymer were used to treat 5,000 protoscolices in 2-ml protoscolices suspension. After different HIFU exposure time (5, 10, 20, 30, 40, 50, and 60 s, respectively), the temperature of protoscolices suspension was taken, and the treated protoscolices were stained by trypan-blue exclusion assay, and their structures were observed by light microscopy. To better understand the biological mechanisms responsible for the deaths of protoscolices, the activity of succinate dehydrogenase (SDH) of the protoscolices treated with HIFU was examined. The temperature of protoscolices suspension treated with HIFU rose slowly, and the death rate of protoscolices was 73.7 % in the group of HIFU treatment time of 40 s; however, with the same HIFU treatment time of 40 s, the temperature of protoscolices suspension in the group of HIFU combined with SAP rose quickly, and the death rate of protoscolices was 100 %. The same protoscolicidal effect (100 %) of HIFU of 100 W acoustic power combined with SAP was also observed in the groups of HIFU treatment time of 50 and 60 s, respectively. The dead protoscolices were stained to blue, shrunken and black calcareous corpuscles, and disordered and decreasing hooks though of intact membrane, as well as some protoscolices lost hooks and tore open on membrane were observed. In the group of HIFU combined with SAP, it was found that the superabsorbent polymer was surrounded by the spoiled, and the destruction of protoscolices was much stronger than in the group of HIFU. The dead protoscolices exhibited the reduction or absence of SDH staining intensity in the parenchymal cell and calcareous corpuscles after HIFU irradiation, where a large number of necrotic cells were evident. These results suggested that HIFU could induce the damage and loss of viability of protoscolices; SAP could enhance the HIFU energy focused and cause more severe destruction efficacy on protoscolices; and mitochondrial energetic function is involved in the regulation of cell-death pathways of protoscolices.

Superabsorbent dressings for copiously exuding wounds

Exudate control is important in the management of both acute and chronic wounds. A new category of absorbent dressings that contain superabsorbent particles promises high absorbency. The aim of this multicentre, prospective, non-comparative observational study was to evaluate the clinical efficacy and absorbent capacity of a superabsorbent dressing. Fifteen inpatients and outpatients with highly exuding wounds were included. Most patients (n=8) (53%) had chronic wounds; 20% (n=3) had ulcerating tumours. The superabsorbent dressing was used as a primary or a secondary dressing. Assessment was on day 0 (start), day 3 and day 7 (end of study). The study looked at wound bed and periwound skin condition, exudate production, pain upon dressing removal, reason for dressing removal, and frequency of dressing changes. A clinical visual scoring tool was used, together with digital photographs, which were assessed by the same experienced clinician. All 15 patients completed the study, during which no adverse events were noted. At day 7, maceration had reduced from 46.7% (n=7) at day 0 to 6.7% (n=1). After only 3 days, dressing change frequency was reduced from once daily to twice weekly in 80% (n=12) of patients. The superabsorbent dressing seems to reduce complications associated with exudate production, stimulate wound healing and increase patient comfort; it may also save time and costs for caregivers.

The effect of biomaterials and antifungals on biofilm formation by Candida species: a review

Candida albicans, C. glabrata, C. parapsilosis, and C. tropicalis are able to form biofilms on virtually any biomaterial implanted in a human host. Biofilms are a primary cause of mortality in immunocompromised and hospitalized patients, as they cause recurrent and invasive candidiasis, which is difficult to eradicate. This is due to the fact that the biofilm cells show high resistance to antifungal treatments and the host defense mechanisms, and exhibit an excellent ability to adhere to biomaterials. Elucidation of the mechanisms of antifungal resistance in Candida biofilms is of unquestionable importance; therefore, this review analyzes both the chemical composition of biomaterials used to fabricate the medical devices, as well as the Candida genes and proteins that confer drug resistance.