Carboxymethyl-starch: iodine anti-infective complexes: expanded v-helix and increased mucoadhesion

There is a major need of novel approaches to limit contamination with respiratory viruses such as SARS-CoV-2 (Covid 19) and inluenza.

Since the viral transmission is by aerosols, the oral and nasopharyngeal decontamination seems of relevance to prevent virus spreading. The hypothesis was that CMS, grafted with polar carboxylic groups, may present expanded V-helices, helping to load higher amounts of iodine.

Carboxymethylstarch (CMS) having a degree of substitution between 0.15-0.30, microspheres of CMS cross-linked with Sodium TriMetaPhosphate (STMP), and high amylose starch cross-linked (CL) with epichlorohydrin HAS-CL(5,10) were proposed as matrices for iodine inclusion complexes for application as anti-infective agents. The sublimated iodine vapor was spontaneously included in the CMS matrices with no interventions during loading. This was found for CMS only and did not occur with non-derivatized starch. The morphology and the corresponding iodine-loaded formulations have been characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy.

X-ray diffraction patterns of CMS, showed the peaks characteristic of B-type helices vanished whereas peaks (at 20° and 22°) characteristic of the V-type (simple helix) have been strengthened. Furthermore, by hydrolysis of CMS matrix with alpha-amylase, the released iodine would act against infective agents (i.e. respiratory viruses). The iodine complexation induced some structural modifications on the CMS network. CMS:I₂ presented an enhanced mucoadhesion, a markedly increased sprayability, and a higher susceptibility at amylolysis with alpha-amylase, when compared to unloaded CMS.

The novel CMS:I₂ complexes appear as potential virucidal agents (supported by a recent investigation).