pH response of pollen paper for drug delivery

Abstract

Pollen is one of the most durable natural materials known to mankind. This is attributed to sporopollenin, a component of the pollen grain’s outer walls. There has been much development on pollen paper as a sustainable biomaterial. Pollen paper has kept the ability to undergo reversible shape changes induced by the environment from its microgel form. pH responsive studies on pollen paper have been focused on shape morphing, while little is done on the pH response with regards to drug delivery. When compared to traditional transdermal patches which operate by releasing drugs at a steady rate, pollen paper shows potential in varying the release rate of drugs. This is achieved by leveraging pollen paper’s ability to control swelling through changes in pH, which would allow a change in drug release rate. This study takes some reference from previous research which studied the pH responsive drug delivery of sporopollenin exine capsules.

This study investigates the effect of pH as an environmental stimulus on the drug release rate across three types of pollen paper, namely, Camellia, Lotus, and Sunflower pollen paper. The study also investigates the microscopic behavior of micropores on the surface of flattened sporopollenin, in which pollen paper is made of. This study covers the processing of pollen paper, which is done using previously established protocols. These include steps such as washing with deionized water, defatting using acetone and diethyl ether, cytoplasmic removal using 10%(wt.vol) Potassium hydroxide solution, gelation using deionized water, and paper formation through the evaporation of water.

The results of this study find that as pH increases, the drug release rate and total drug released by the pollen paper increases, with the highest being Sunflower, followed by Camellia, and lastly, Lotus. Through Scanning Electron Microscopy imaging and analysis, the study observes that by placing pollen paper in buffers of increasing pH, the mean size of micropores on the flattened sporopollenin surface increases. This draws a possible relationship between the increased micropore size and an increase in drug loading capacity, as well as drug delivery rate.