A Novel Polymer Insect Repellent Conjugate for Extended Release and Decreased Skin Permeation of Para-Menthane-3,8-Diol

Abstract

Background: We developed a novel polymer insect repellent conjugate for extended release and decreased skin permeation of the volatile insect repellent p-menthane-3,8-diol (PMD). Methods: PMD was conjugated with acryloyl chloride via an ester bond to form acryloyl–PMD, which was subsequently copolymerised with acrylic acid at varying molar ratios. Copolymer structures were characterised by 1H NMR and FT-IR, analysed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), molecular weights and reactivity ratios determined, and repellent loading assessed. Results: Using porcine liver esterases, ~45% of the insect repellent was released over five days. Penetration and permeation studies of the copolymer and free repellent using excised, full-thickness porcine ear skin showed no detectable permeation of the copolymer through skin compared to the PMD. Moreover, tape stripping revealed that over 90% of the copolymer remained on the outer surface of the skin, whereas free PMD was within all skin layers. A planarian toxicity fluorescence assay indicated that that the copolymer is unlikely to be a significant irritant when applied topically. Conclusions: this study demonstrates the feasibility of the copolymer approach to develop extended-release insect repellents while reducing skin uptake and transdermal permeation of the small-molecular-weight active ingredient, in order to minimise any adverse effects.

Functional Coatings by Natural and Synthetic Agents for Insect Control and Their Applications

“…The authors determined that the copolymer released around 45% of PMD over a period of 5 days. This had the potential to prolong repellent efficacy as well as reducing PMD associated allergic reactions since skin uptake was reduced [74]. A study by Maguranyi et al found that eucalyptus essential oils were least effective at repelling Aedes aegypti, providing only 10 min to 25 min of protection.…”

Long-Term Insect Repellent Electrospun Microfibers from Recycled Poly(ethylene terephthalate)

“…The vapor barrier of picaridin disrupts the insect’s olfactory sense and taste, preventing contact . Encapsulation of repellents has been shown to enable the extended release of repellents. , For example, solid lipid nanoparticles (SLN) have a high capacity of repellent loading but require direct contact with the skin . Polymer-based encapsulations have proven to be most effective while limiting contact with the skin.…”

Host-Guest Inclusion Complexes of Natural Products and Nanosystems: Applications in the Development of Repellents

“…In addition to DEET, other repellents of synthetic origin have been applied in commercial formulations, such as picaridin (icaridin, hydroxy-ethyl isobutyl piperidine carboxylate, Figure 2A) and N-acetyl-n-butyl-3-amino propionate (IR3535, Figure 2A). Currently, several natural compounds from essential oils have been also used in commercial repellent formulations due to their satisfactory repellent activity, such as the p-menthane-3, 8-diol (PMD) [18,27] (Figure 2B) and citronellal (Figure 2B) [28,29]. Some repellents act as competitive inhibitors of attractant molecules that are exhaled by the mammalian hosts.…”