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Wound healing disorders frequently occur due to biofilm formation on wound surfaces requiring conscientious wound hygiene. Often, the application of conventional liquid antiseptics is not sufficient and sustainable as (1) the borders and the surrounding of chronic wounds frequently consist of sclerotic skin, impeding an effectual penetration of these products, and (2) the hair follicles representing the reservoir for bacterial recolonization of skin surfaces are not affected. Recently, it has been reported that tissue-tolerable plasma (TTP), which is used at a temperature range between 35 and 45°C, likewise has disinfecting properties. In the present study, the effectivity of TTP and a standard liquid antiseptic was compared in vitro on porcine skin. The results revealed that TTP was able to reduce the bacterial load by 94%, although the application of the liquid antiseptic remained superior as it reduced the bacteria by almost 99%. For in vivo application, however, TTP offers several advantages. On the one hand, TTP enables the treatment of sclerotic skin as well, and on the other hand, a sustainable disinfection can be realized as, obviously, also the follicular reservoir is affected by TTP.
Contaminated surfaces have been discussed as a possible source of severe acute respiratory
syndrome coronavirus-2 (SARS-CoV-2). Under experimental conditions, SARS-CoV-2 can remain
infectious on surfaces for several days. However, the frequency of SARS-CoV-2 detection on surfaces
in healthcare settings and the public is currently not known. A systematic literature review was
performed. On surfaces around COVID-19 cases in healthcare settings (42 studies), the SARS-CoV2 RNA detection rates mostly were between 0% and 27% (Ct values mostly > 30). Detection of
infectious SARS-CoV-2 was only successful in one of seven studies in 9.2% of 76 samples. Most of the
positive samples were obtained next to a patient with frequent sputum spitting during sampling.
Eight studies were found with data from public surfaces and RNA detection rates between 0% and
22.1% (Ct values mostly > 30). Detection of infectious virus was not attempted. Similar results
were found in samples from surfaces around confirmed COVID-19 cases in non-healthcare settings
(7 studies) and from personal protective equipment (10 studies). Therefore, it seems plausible to
assume that inanimate surfaces are not a relevant source for transmission of SARS-CoV-2. In public
settings, the associated risks of regular surface disinfection probably outweigh the expectable health
benefit
The objective of the present investigation was to examine the residual antimicrobial activity after a topical exposure of reconstructed human epidermis (RHE) to equimolar solutions of either chlorhexidine digluconate (CHG, 0.144% w/v) or octenidine dihydrochloride (OCT, 0.1% w/v) for 15 min. RHE-associated antiseptic agents were more effective on Staphylococcus aureus than on Pseudomonas aeruginosa. S. aureus was not detected after 24 h of contact, which demonstrated a microbicidal efficacy of greater than 5-log<sub>10</sub> reduction. In contrast, P. aeruginosa was reduced by approximately 2 log<sub>10</sub> at the same incubation time, which parallels the growth of the initial inoculum. This result could be interpreted either as a microbiostatic effect or as an adherence of P. aeruginosa to a low positively charged surface. Small amounts of CHG and OCT can penetrate the stratum corneum. Using these antiseptic agents, the viability of keratinocytes was reduced to 65-75% of that of the untreated RHE control following 24 h incubation in the presence of test microorganisms. With consideration of antimicrobial activity and cytotoxic effect, OCT corresponds better to a biocompatible antiseptic agent than CHG.
Cold physical plasmas, especially noble gas driven plasma jets, emit considerable amounts of ultraviolet radiation (UV). Given that a noble gas channel is present, even the energetic vacuum UV can reach the treated target. The relevance of UV radiation for antimicrobial effects is generally accepted. It remains to be clarified if this radiation is relevant for other biomedical application of plasmas, e.g., in wound care or cancer remediation. In this work, the role of (vacuum) ultraviolet radiation generated by the argon plasma jet kINPen for cysteine modifications was investigated in aqueous solutions and porcine skin. To differentiate the effects of photons of different wavelength and complete plasma discharge, a micro chamber equipped with a MgF2, Suprasil, or Borosilicate glass window was used. In liquid phase, plasma-derived VUV radiation was effective and led to the formation of cysteine oxidation products and molecule breakdown products, yielding sulfite, sulfate, and hydrogen sulfide. At the boundary layer, the impact of VUV photons led to water molecule photolysis and formation of hydroxyl radicals and hydrogen peroxide. In addition, photolytic cleavage of the weak carbon-sulfur bond initiated the formation of sulfur oxy ions. In the intact skin model, protein thiol modification was rare even if a VUV transparent MgF2 window was used. Presumably, the plasma-derived VUV radiation played a limited role since reactions at the boundary layer are less frequent and the dense biomolecules layers block it effectively, inhibiting significant penetration. This result further emphasizes the safety of physical plasmas in biomedical applications.
Abstract
Antimicrobial coating of implant material with poly(hexamethylene biguanide) hydrochloride (PHMB) may be an eligible method for preventing implant‐associated infections. In the present study, an antibacterial effective amount of PHMB is adsorbed on the surface of titanium alloy after simple chemical pretreatment. Either oxidation with 5% H2O2 for 24 hr or processing for 2 hr in 5 M NaOH provides the base for the subsequent formation of a relatively stable self‐assembled PHMB layer. Compared with an untreated control group, adsorbed PHMB produces no adverse effects on SaOs‐2 cells within 48 hr cell culture, but promotes the initial attachment and spreading of the osteoblasts within 15 min. Specimens were inoculated with slime‐producing bacteria to simulate a perioperative infection. Adsorbed PHMB reacts bactericidally against Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa after surface contact. Adhered SaOs‐2 cells differentiate and produce alkaline phosphatase and deposit calcium within 4 days in a mineralization medium on PHMB‐coated Ti6Al4V surfaces, which have been precontaminated with S. epidermidis. The presented procedures provide a simple method for generating biocompatibly and antimicrobially effective implant surfaces that may be clinically important.
Multiple evidence in animal models and in humans suggest a beneficial role of cold physical
plasma in wound treatment. Yet, risk assessment studies are important to further foster therapeutic
advancement and acceptance of cold plasma in clinics. Accordingly, we investigated the long-term
side effects of repetitive plasma treatment over 14 consecutive days in a rodent full-thickness ear
wound model. Subsequently, animals were housed for 350 days and sacrificed thereafter. In blood,
systemic changes of the pro-inflammatory cytokines interleukin 1β and tumor necrosis factor α
were absent. Similarly, tumor marker levels of α-fetoprotein and calcitonin remained unchanged.
Using quantitative PCR, the expression levels of several cytokines and tumor markers in liver,
lung, and skin were found to be similar in the control and treatment group as well. Likewise,
histological and immunohistochemical analysis failed to detect abnormal morphological changes
and the presence of tumor markers such as carcinoembryonic antigen, α-fetoprotein, or the neighbor
of Punc 11. Absence of neoplastic lesions was confirmed by non-invasive imaging methods such as
anatomical magnetic resonance imaging and positron emission tomography-computed tomography.
Our results suggest that the beneficial effects of cold plasma in wound healing come without apparent
side effects including tumor formation or chronic inflammation.
The effect of water-filtered infrared-A radiation (wIRA) on normal skin flora was investigated by generating experimental wounds on the forearms of volunteers utilizing the suction blister technique. Over 7 days, recolonization was monitored parallel to wound healing. Four groups of treatment were compared: no therapy (A), dexpanthenol cream once daily (B), 20 min wIRA irradiation at 30 cm distance (C), and wIRA irradiation for 30 min once daily together with dexpanthenol cream once daily (D). All treatments strongly inhibited the recolonization of the wounds. Whereas dexpanthenol completely suppressed recolonization over the test period, recolonization after wIRA without (C) and in combination with dexpanthenol (D) was suppressed, but started on day 5 with considerably higher amounts after the combination treatment (D). Whereas the consequence without treatment (A) was an increasing amount of physiological skin flora including coagulase-negative staphylococci, all treatments (B–D) led to a reduction in physiological skin flora, including coagulase-negative staphylococci. In healthy volunteers, wIRA alone and in combination with dexpanthenol strongly inhibited bacterial recolonization with physiological skin flora after artificial wound setting using a suction-blister wound model. This could support the beneficial effects of wIRA in the promotion of wound healing.
Aim
Periprosthetic joint infections are a devastating complication after arthroplasty, leading to rejection of the prosthesis. The prevention of septic loosening may be possible by an antimicrobial coating of the implant surface. Poly (hexamethylene) biguanide hydrochloride [PHMB] seems to be a suitable antiseptic agent for this purpose since previous studies revealed a low cytotoxicity and a long-lasting microbicidal effect of Ti6Al4V alloy coated with PHMB. To preclude an excessive activation of the immune system, possible inflammatory effects on macrophages upon contact with PHMB-coated surfaces alone and after killing of S. epidermidis and P. aeruginosa are analyzed.
Methods
THP-1 monocytes were differentiated to M0 macrophages by phorbol 12-myristate 13-acetate and seeded onto Ti6Al4V surfaces coated with various amounts of PHMB. Next to microscopic immunofluorescence analysis of labeled macrophages after adhesion on the coated surface, measurement of intracellular reactive oxygen species and analysis of cytokine secretion at different time points without and with previous bacterial contamination were conducted.
Results
No influence on morphology of macrophages and only slight increases in iROS generation were detected. The cytokine secretion pattern depends on the surface treatment procedure and the amount of adsorbed PHMB. The PHMB coating resulted in a high reduction of viable bacteria, resulting in no significant differences in cytokine secretion as reaction to coated surfaces with and without bacterial burden.
Conclusion
Ti6Al4V specimens after alkaline treatment followed by coating with 5–7 μg PHMB and specimens treated with H2O2 before PHMB-coating (4 μg) had the smallest influence on the macrophage phienotype and thus are considered as the surface with the best cytocompatibility to macrophages tested in the present study.