Silver-resistance, allergy, and blue skin: Truth or urban legend?

Lignin-Cobalt Nano-Enabled Poly(pseudo)rotaxane Supramolecular Hydrogel for Treating Chronic Wounds

Chronic wounds (CWs) are a growing issue for the health care system. Their treatment requires a synergic approach to reduce both inflammation and the bacterial burden. In this work, a promising system for treating CWs was developed, comprising cobalt-lignin nanoparticles (NPs) embedded in a supramolecular (SM) hydrogel. First, NPs were obtained through cobalt reduction with phenolated lignin, and their antibacterial properties were tested against both Gram-negative and Gram-positive strains. The anti-inflammatory capacity of the NPs was proven through their ability to inhibit myeloperoxidase (MPO) and matrix metalloproteases (MMPs), which are enzymes involved in the inflammatory process and wound chronicity. Then, the NPs were loaded in an SM hydrogel based on a blend of α-cyclodextrin and custom-made poly(ether urethane)s. The nano-enabled hydrogel showed injectability, self-healing properties, and linear release of the loaded cargo. Moreover, the SM hydrogel's characteristics were optimized to absorb proteins when in contact with liquid, suggesting its capacity to uptake harmful enzymes from the wound exudate. These results render the developed multifunctional SM material an interesting candidate for the management of CWs.

A Randomized Controlled Trial of Three Advanced Wound Dressings in Split-Thickness Skin Grafting Donor Sites-A Personalized Approach?

Background: Split-thickness skin grafting (STSG) is a frequently used reconstructive technique, and its donor site represents a standardized clinical model to evaluate wound dressings. We compared hydroactive nanocellulose-based, silver-impregnated and ibuprofen-containing foam wound dressings. Methods: A total of 46 patients scheduled for elective surgery were evaluated on the STSG donor site for wound healing (time-to-healing, Hollander Wound Evaluation Scale), pain level (Visual Analogue Scale), and handling (ease of use), as well as scar quality (Patient Scar Assessment Scale, Vancouver Scar Scale) after 3, 6 and 12 months. Results: Almost all dressings compared equally well. We observed statistically relevant differences for pain level favoring the ibuprofen-containing dressing (p = 0.002, ΔAIC = 8.1), and user friendliness in favor of nanocellulose (dressing removal: p = 0.037, ΔAIC = 2.59; application on patient: p = 0.042, ΔAIC = 2.33; wound adhesion: p = 0.017, ΔAIC = 4.16; sensation on skin: p = 0.027, ΔAIC = 3.21). We did not observe any differences for wound healing across all groups. Treatment with hydroactive nanocellulose and the ibuprofen-containing foam revealed statistically relevant better scar appearances as compared to the silver wound dressing (p < 0.001, ΔAIC = 14.77). Conclusion: All wound dressings performed equally well, with the detected statistical differences hinting future directions of clinical relevance. These include the reserved use of silver containing dressings for contaminated or close to contaminated wounds, and the facilitated clinical application of the nanocellulose dressing, which was the only suitable candidate in this series to be impregnated with a range of additional therapeutic agents (e.g., disinfectants and pain-modulating drugs). Personalized donor site management with the tested dressings can meet individual clinical requirements after STSG and improve management strategies and ultimately patient outcomes.

Topical Wound Therapy Products With Ionic Silver: A Technologic Analysis

PURPOSE

The purpose of this technologic analysis was to review use of ionic silver as a component of topical wound therapy products.

APPROACH

Published literature from a variety of fields related to ionic silver and its use in topical wound therapy products was reviewed and a summary of common commercially available wound care products containing ionic silver was generated, along with general recommendations for use. Safety information from both manufacturer guidelines and the Manufacturer and User Facility Device Experience (MAUDE) database is summarized.

CONCLUSIONS

Various formulations of ionic silver products are used for topical treatment of wounds. Antimicrobial activity varies according to the specific silver formulation and type of microorganisms in the wound bed. In vitro evidence suggests that some bacterial strains may be developing resistance to ionic silver. Improved knowledge of the benefits and safety precautions associated with topical silver preparations can guide its application to topical therapy for wound healing.

Ion-doped Brushite Cements for Bone Regeneration

Decades of research in orthopaedics has culminated in the quest for formidable yet resorbable biomaterials using bioactive materials. Brushite cements most salient features embrace high biocompatibility, bioresorbability, osteoconductivity, self-setting characteristics, handling, and injectability properties. Such type of materials is also effectively applied as drug delivery systems. However, brushite cements possess limited mechanical strength and fast setting times. By means of incorporating bioactive ions, which are incredibly promising in directing cell fate when incorporated within biomaterials, it can yield biomaterials with superior mechanical properties. Therefore, it is a key to develop fine-tuned regenerative medicine therapeutics. A comprehensive overview of the current accomplishments of ion-doped brushite cements for bone tissue repair and regeneration is provided herein. The role of ionic substitution on the cements physicochemical properties, such as structural, setting time, hydration products, injectability, mechanical behaviour and ion release is discussed. Cell-material interactions, osteogenesis, angiogenesis, and antibacterial activity of the ion-doped cements, as well as its potential use as drug delivery carriers are also presented. STATEMENT OF SIGNIFICANCE: Ion-doped brushite cements have unbolted a new era in orthopaedics with high clinical interest to restore bone defects and facilitate the healing process, owing its outstanding bioresorbability and osteoconductive/osteoinductive features. Ion incorporation expands their application by increasing the osteogenic and neovascularization potential of the materials, as well as their mechanical performance. Recent accomplishments of brushite cements incorporating bioactive ions are overviewed. Focus was placed on the role of ions on the physicochemical and biological properties of the biomaterials, namely their structure, setting time, injectability and handling, mechanical behaviour, ion release and in vivo osteogenesis, angiogenesis and vascularization. Antibacterial activity of the cements and their potential use for delivery of drugs are also highlighted herein.

Magnetic Nanoparticle-Based Drug Delivery Approaches for Preventing and Treating Biofilms in Cystic Fibrosis

Biofilm-associated infections pose a huge burden on healthcare systems worldwide, with recurrent lung infections occurring due to the persistence of biofilm bacteria populations. In cystic fibrosis (CF), thick viscous mucus acts not only as a physical barrier, but also serves as a nidus for infection. Increased antibiotic resistance in the recent years indicates that current therapeutic strategies aimed at biofilm-associated infections are “failing”, emphasizing the need to develop new and improved drug delivery systems with higher efficacy and efficiency. Magnetic nanoparticles (MNPs) have unique and favourable properties encompassing biocompatibility, biodegradability, magnetic and heat-mediated characteristics, making them suitable drug carriers. Additionally, an external magnetic force can be applied to enhance drug delivery to target sites, acting as “nano-knives”, cutting through the bacterial biofilm layer and characteristically thick mucus in CF. In this review, we explore the multidisciplinary approach of using current and novel MNPs as vehicles of drug delivery. Although many of these offer exciting prospects for future biofilm therapeutics, there are also major challenges of this emerging field that need to be addressed.

Are Antimicrobial Peptide Dendrimers an Escape from ESKAPE?

Significance: The crisis of antimicrobial resistance (AMR) increases dramatically despite all efforts to use available antibiotics or last resort antimicrobial agents. The spread of the AMR, declared as one of the most important health-related issues, warrants the development of new antimicrobial strategies. Recent Advances: Antimicrobial peptides (AMPs) and AMP dendrimers (AMPDs), as well as polymer dendrimers are relatively new and promising strategies with the potential to overcome drug resistance issues arising in ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) colonizing chronic wounds. Critical Issues: AMPs-AMPDs suffer from limited efficacy, short-lasting bioactivity, and concerns of toxicity. To circumvent these drawbacks, their covalent coupling to biopolymers and/or encapsulation into different drug carrier systems is investigated, with a special focus on topical applications. Future Directions: Scientists and the pharmaceutical industry should focus on this challenging subject to either improve the activity of existing antimicrobial agents or find new drug candidates. The focus should be put on the discovery of new drugs or the combination of existing drugs for a better synergy, taking into account all kinds of wounds and existing pathogens, and more specifically on the development of next-generation antimicrobial peptides, encompassing the delivery carrier toward improved pharmacokinetics and efficacy.

Risk and clinical impact of bacterial resistance/susceptibility to silver-based wound dressings: a systematic review

Objective:

To perform a systematic review of the literature on bacterial resistance, tolerance and susceptibility of silver within the context of wound therapy using silver-based dressings.

Methods:

A literature search was carried out using PubMed, Embase and Cochrane Library databases, the focus was whether results from microbiological experimental in vitro tests with reference strains and clinical wound isolates are reflected in clinical practice with regards to their ‘resistance’ profiles, comparable with those observed for antibiotics. The search results were allocated to six categories: resistance and resistance mechanism, in vitro tests with standard strains and wound isolates, prevalence and incidence, impact on clinical practice and impact on antibiotic therapy as well as reviews, expert opinions and consensus.

Results:

Based on all findings of the literature, it cannot be confirmed that a related clinical resistance to silver-ions in silver-based dressings has clinical impact, although endogenous and exogenous genetic resistance patterns have been described and intensively investigated. A translation of these genetic resistance-expression structures to phenotypic appearances, similar to those known for antibiotics, has not been demonstrated for silver in the literature.

Conclusion:

It can be concluded that there is no definitive evidence available and further studies should be conducted.

Spatiotemporal distribution and speciation of silver nanoparticles in the healing wound

First observation of AgNPs dynamics in the wounds of real patients through elemental imaging and speciation.

Silver nanoparticles selectively treat triple-negative breast cancer cells without affecting non-malignant breast epithelial cells in vitro and in vivo

Silver nanoparticles (AgNPs) show promise for treatment of aggressive cancers including triple-negative breast cancer (TNBC) in preclinical cancer models. For clinical development of AgNP-based therapeutics, it will be necessary to clearly define the specific physicochemical features of the nanoparticles that will be used, and to tie these properties to biological outcomes. To fill this knowledge gap, we performed thorough structure/function, mechanistic, safety, and efficacy studies to assess the potential for AgNPs to treat TNBC. We establish that AgNPs, regardless of size, shape, or stabilizing agent, are highly cytotoxic to TNBC cells at doses that are not cytotoxic to non-malignant breast epithelial cells. In contrast, TNBC cells and non-malignant breast epithelial cells are similarly sensitive to exposure to silver cation (Ag+), indicating that the nanoparticle formulation is essential for the TNBC-specific cytotoxicity. Mechanistically, AgNPs are internalized by both TNBC and non-malignant breast cells, but are rapidly degraded only in TNBC cells. Exposure to AgNPs depletes cellular antioxidants and causes endoplasmic reticulum stress in TNBC cells without causing similar damage in non-malignant breast epithelial cells. AgNPs also cause extensive DNA damage in 3D TNBC tumor nodules in vitro, but do not disrupt the normal architecture of breast acini in 3D cell culture, nor cause DNA damage or induce apoptosis in these structures. Lastly, we show that systemically administered AgNPs are effective at non-toxic doses for reducing the growth of TNBC tumor xenografts in mice. This work provides a rationale for development of AgNPs as a safe and specific TNBC treatment.

Silver-containing dressing for surgical site infection in clean and clean-contaminated operations: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Silver-containing dressings for the prevention of surgical site infections (SSIs) remained controversial, and accumulating evidence was lacking, so a meta-analysis was conducted to systematically assess the effectiveness and safety of silver-containing dressings for clean and clean-contaminated surgical incisions.

METHODS

Pubmed, Embase, and the Cochrane Library were searched from the inception to February 2016 for randomized controlled trials (RCTs), which explored silver-containing dressings for the prevention of SSIs in clean and clean-contaminated operations. Relative risk (RR) with 95% confidence interval (CI) was pooled using random effects model. Predefined subgroup analyses, sensitivity analyses, and influence analyses were further undertaken.

RESULTS

Nine RCTs totaling 2196 patients (1141 in silver-containing group and 1055 in control group) were included. Silver-containing dressings did not effectively prevent the incidence of SSIs (9 RCTs; RR: 0.92; 95% CI: 0.66-1.29; I2 = 40%), superficial SSIs (5 RCTs; RR: 0.67; 95% CI: 0.36-1.24; I2 = 36%), and deep SSIs (5 RCTs; RR: 0.78; 95% CI: 0.41-1.49; I2 = 0). Subgroup analyses, sensitivity analyses, and influence analyses confirmed the robustness of the pooled estimate.

CONCLUSIONS

The current available evidence indicated that silver-containing dressing as compared with silver-free dressing was not associated with lower incidence of SSIs. Considering the quality of evidence ranking very low, further studies with higher quality should be warranted.

Antimicrobial coated implants in trauma and orthopaedics-A clinical review and risk-benefit analysis

Implant-associated infections remain a major issue in orthopaedics and antimicrobial functionalization of the implant surface by antibiotics or other anti-infective agents have gained interest. The goal of this article is to identify antimicrobial coatings, for which clinical data are available and to review their clinical need, safety profile, and their efficacy to reduce infection rates. PubMed database of the National Library of Medicine was searched for clinical studies on antimicrobial coated implants for internal fracture fixation devices and endoprostheses for bone surgery, for which study design, level of evidence, biocompatibility, development of resistance, and effectiveness to reduce infection rates were analyzed. Four different coating technologies were identified: gentamicin poly(d, l-lactide) coating for tibia nails, one high (MUTARS^®) and one low amount silver (Agluna) technology for tumor endoprostheses, and one povidone-iodine coating for titanium implants. There was a total of 9 published studies with 435 patients, of which 7 studies were case series (level IV evidence) and 2 studies were case control studies (level III evidence). All technologies were reported with good systemic and local biocompatibility, except the development of local argyria with blue to bluish grey skin discoloration after the use of silver MUTARS^® megaendoprostheses. For the local use of gentamicin, there is contradictory data on the risk of emergence of gentamicin-resistance strains, a risk that does not seem to exist for silver and iodine based technologies. Regarding reduction of infection rates, one case control study showed a significant reduction of infection rates by Agluna silver coated tumor endoprostheses. Based on socio-economic data, there is a strong need for improvement of infection prevention and treatment strategies, including implant coatings, in fracture care, primary and revision arthroplasty, and bone tumor surgery. The reviewed gentamicin, silver Agluna, and povidone-iodine technologies have shown a good risk benefit ratio for patients. Further data from randomized control trials are desirable, although this will remain challenging in the context of infection prevention due to the required large sample size of such studies.