Colloids and Surfaces A: Physicochemical and Engineering Aspects
Hydrogels incorporated with silver nanocolloids prepared from antioxidant rich Aerva javanica as disruptive agents against burn wound infections
Graphical abstract
Introduction
Thermally injured patients experience remarkable mortality and morbidity despite prominent developments in the controlling severe burn injury and its related complications [1]. The major reason of infections and related complications in burn wound patients is the thermal destruction of the skin barrier leading to depression of local and systemic host cellular and humoral immune response [2]. Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is the dominant cause of sepsis in patients who are immunosuppressed by their burns [3]. Generally, 40% of wounds develop microbial infection of some kind, and out of these almost 14–17% of burn wounds patients are specifically infected with MRSA. Present antimicrobial drugs and disinfectants are not very effective against Multiple Drug Resistant (MDR) bacterial strains [4]. This is partly due to changing bacterial populations in hospitals and also due to the use of unsterilized surgical instruments and excessive use of antibiotic drugs [5]. The multiple drug resistant Pseudomonas aeruginosa (PA) strains isolated from wounds, skin and burn are the most common cause of hospital acquired infections [6].
Green synthesis approach in nanotechnology has opened up new dimensions for rapid self-assembly of non-toxic antimicrobial nanomaterials to cure such bacterial infections. Regardless of nanoparticles polydispersity issue in biologically synthesized nanoparticles, the potential of these nano-materials in wound healing as a potent disinfectant is exceptional [7]. Biosynthesized silver nanoparticles (AgNPs) in particular have shown excellent therapeutic potential as a potent bactericidal and antibiofilm formulation against MDR bacterial species [8]. Their use in topical creams, ointments and in gels is an effective way to prevent the spread of nosocomial infections in thermally injured patients [9], [10], [11], [12].
Hydrogels because of their biocompatible, biodegradable and viscoelastic nature can be used as topical agents in burn wounds to control bacterial infections [13]. These properties of hydrogels are excellent for wound dressings and facilitate cell viability, proliferation and differentiation [14], [15], [16]. Due to their high-water content, hydrogels provide moist, heavily hydrated environment to the wound area and support cellular immunological activity which is essential for the wound healing process. However, this hydrated environment can facilitate invasive microbial infection, the extent of which is dependent on the type of wound (first degree, second degree, third degree and fourth degree) [17]. Inflammation is essential to wound healing but presence of microbial contamination prolongs the process of inflammation (cytokines including IL-1 and TNF- α are pro-inflammatory) which may lead for a wound to the chronic state as a result of healing failure. This in turn up-regulates the matrix metalloproteases, to degrade extracellular matrix of the skin tissues, that reduces the level of natural protease inhibitors and prolongs the wound inflammation [18]. Thus, gels capable of imparting antimicrobial action in addition to serving their primary functional role are desirable [14]. Their conjugation with antimicrobial nanomaterials for better wound healing are at the nascent stages of research, especially the extent to which biosynthesized AgNPs are studied for their efficacy is very limited and further research is needed to identify their potential toxicity and use in hydrogels [15], [19], [20].
The current study focuses on the green synthesis approach for assembly of antimicrobial silver nano-fluids utilizing wound healing properties of Aerva javanica. The study also addresses the safety concern by evaluation of in vitro and in vivo toxicity of synthesized AgNPs prior to their incorporation into the chitosan hydrogels.
Section snippets
Synthesis of silver nanoparticles
Aerva javanica was collected from cholistan desert, Pakistan. The whole plant was grinded into the fine powder, dissolved in deionized water and the extract solution was filtered using Whatman filter paper number No. 1. The aqueous extract was added in 1 mM solution of AgNO3 (Sigma Aldrich, St. Louis, MO, USA) in a ratio of 1:10 (w/w) and shake at 200 rpm for 50 min at room temperature. The complete reduction of Ag ions to nano-silver was observed in 2 h. The color change from colorless to light
AgNPs synthesis and characterization
Aerva javanica was selected for the synthesis of AgNP’s because of its inherent antioxidant properties. This plant has been studied for the presence of flavonoids and their characterization and various properties including their potential as antifungal, antibacterial properties as well as their Antihelminthic properies [29]. Aerva javanica was chosen to counter the cytotoxicity of AgNPs where uncapped AgNPs excessively produce reactive oxygen species that limit their biocompatibility. To
Discussion
Despite advances in burn wound treatment, occurrence of high mortality and morbidity rates in thermally injured patients is a consequence of sepsis and its associated complications [1]. One of the main reasons of non-healing of wounds is the presence of MRSA and P. aeruginosa biofilm that cause delay in the healing process [17], [23]. Different strategies have been proposed to prevent the spread of burn wound infections followed by immediate healing [24]. AgNPs exhibit broad spectrum
Conclusion
The current study demonstrates the potential use of antioxidant rich Aerva javanica for efficient synthesis of antimicrobial AgNPs showing minimum in vitro and in vivo toxicity. These AgNPs increased the healing and antibacterial activity in burn wound infections upon incorporation in chitosan hydrogels. These results effectively exhibited the role of AgNPs as disinfectants and to be used as drug delivery vehicle owing to their safety profile, antioxidant properties and excellent antimicrobial
Acknowledgements
Authors are thankful to ASAB-NUST for administrative and technical support, SCME-NUST for SEM, AFM and FTIR analysis. Portion of this research project performed on mouse models was part of Muhammad Uzair Hashmi MSc Thesis ‘Safety and efficiency evaluation of biosynthesized nanoparticles’. IRB Approval Letter is attached.
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