Healing wounds is a multifaceted process posing a significant healthcare hurdle.
While traditional medical dressings, typically crafted from cotton gauze, offer biocompatibility, breathability, absorbency, and softness, they lack the capacity to enhance healing or combat infection. What's imperative is the development of intelligent dressings that accelerate the healing journey while actively addressing infection.
At Cornell University, a research team is tackling this obstacle by enhancing the effectiveness of cotton dressings through the application of a biologically active layer of nanofibers. These nanofibers leverage the antioxidant, anti-inflammatory, and antibacterial attributes of lawsone, a botanical compound plentifully present in henna leaves.
The therapeutic attributes of lawsone render it a compelling option for wound care, yet its restricted solubility poses a challenge for integration into dressings. Consequently, researchers opted to utilize cyclodextrins, natural oligosaccharides derived from starch, to form inclusion complexes that encapsulate lawsone molecules. This method enhances lawsone's solubility, stability, and bioavailability, potentially amplifying its therapeutic. efficacy. Importantly, cyclodextrins are compatible with electrospinning, facilitating the creation of nanofiber coatings on cotton substrates.
The excessive and prolonged utilization of synthetic antibiotics at elevated levels has played a role in the emergence of the perilous epidemic of multidrug-resistant microorganisms," stated Tamer Uyar, head of the NanoFibers and NanoTextiles Laboratory, in a press release. "The incorporation of natural and potent antibacterials like lawsone could offer a viable alternative to synthetic counterparts.
Uyar and his team utilized two cyclodextrins, namely HP-β-CD and HP-γ-CD, to form inclusion complexes with CD/lawsone ratios of 2:1 and 4:1 M. Subsequently, they employed electrospinning technology to produce CD/lawsone nanofibrous webs with an average fiber diameter ranging from approximately 300 to 700 nm.
An effective approach to promote healing involves mitigating oxidative stress within the wound microenvironment. The team explored the antioxidant characteristics of the nanofibers through a DPPH radical scavenging assay. This assay entailed incorporating the nanofibrous webs into distilled water, introducing a methanolic DPPH solution, and subsequently employing UV-visible spectroscopy to monitor the reduction in DPPH absorption over a period of time.
Nanofibers featuring a 2:1 M CD/lawsone ratio exhibited elevated antioxidant activity, attributed to the higher concentration of lawsone. Among the cyclodextrins tested, HP-β-CD demonstrated superior activity compared to HP-γ-CD. Over time, the antioxidant activity progressively heightened, rising from approximately 20% at 1 hour to about 65% at 24 hours for HP-β-CD/lawsone 2:1 nanofibers.
The researchers highlight that the nanofibrous samples displayed notably greater antioxidant activity, suggesting a potential for accelerated wound healing compared to pure lawsone. They attribute this enhancement to the heightened solubility facilitated by CD inclusion and the substantial surface-to-volume ratio of the nanofibrous web.
In addition to promoting wound healing, an intelligent dressing should effectively prevent and eliminate infections. Therefore, the researchers assessed the activity of the nanofibers against two prevalent bacterial strains: gram-negative E. coli and gram-positive S. aureus. They dissolved nanofibrous samples in bacterial solutions, incubated them at 37°C for 24 hours, and subsequently plated them for colony counting.
The untreated negative control samples exhibited no antimicrobial activity, allowing bacteria to persist and proliferate. Conversely, all four types of nanofibers displayed robust antimicrobial effectiveness, completely eliminating both E. coli and S. aureus bacteria, as evidenced by the absence of colonies on the culture plates. Interestingly, there was no discernible distinction in the efficacy between nanofibers with 4:1 and 2:1 molar ratios, suggesting that even those with lower lawsone content possessed adequate antibacterial activity.
Opting for HP-β-CD/lawsone 4:1 and HP-γ-CD/lawsone 4:1 as prime choices for dressing fabrication, the researchers applied nanofibrous samples onto cotton substrates to examine their capacity for lawsone release. Subsequently, they submerged the nanofiber-coated samples in a PBS solution and subjected them to agitation on an orbital shaker at 37°C. The cumulative release of lawsone was evaluated by analyzing small samples extracted at designated time intervals.
The majority of the lawsone content, around 84% in HP-β-CD/lawsone 4:1 and 77% in HP-γ-CD/lawsone 4:1, was discharged within the first 30 seconds. This significant initial release is linked to the swift dissolution of the nanofiber coating, which concluded within 3 minutes, releasing all of the lawsone at that point. The researchers observed that the release pattern observed in the cotton-coated samples closely resembled that of free-standing fibers.
The team is currently exploring additional bioactive agents. "Our next objectives involve assessing their cytotoxicity, conducting anti-inflammatory evaluations, and initiating in vivo studies for wound healing," Uyar informs Physics World.
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