Characterization of Polymeric Microcapsules Containing a Low Molecular Weight Peptide for Controlled Release

Abstract

A need exists to prolong the release of rapidly metabolized peptides of a low molecular weight, while delivering this peptide without environmental interference. Previous studies have used bovine serum albumin (BSA) as a model peptide to study release characteristics from alginate microcapsules. BSA is 66 kDa in size, while the peptide of interest here, connexin-43 carboxyl-terminus mimetic peptide (αCT1), is only 3.4 kDa. Such a change in size results in a much different set of release parameters. Our overall goal is a sustained release over a 24+ h period. Prolonged application of the peptide to a wound site to investigate therapeutic effects is ideal. As a result, a diffusion method using alginate microcapsules, along with the addition of poly-l-lysine and poly-l-ornithine, has been explored. We first aimed to establish and characterize our parameters through a set of parametric tests. Variations in polymer coating, change in pH, and changes in loading ratio have previously been shown to effect release using model compounds. Here we test specific changes in these parameters to show effects on the release of αCT1. Additionally, the microcapsules were attached to several biomaterials and surgical implants by ultraviolet cross-linking to study the effectiveness of attachment and delivery. Analysis and measurements using phase contrast microscopy, scanning electron microscopy, and atomic force microscopy were used to characterize changes in microcapsule morphology.

Targeting the tight junction protein, zonula occludens-1, with the connexin43 mimetic peptide, αCT1, reduces VEGF-dependent RPE pathophysiology

“…In addition, it has been reported that Cx43 expression in the choroid co-localizes with markers of oxidative stress and inflammation [75]. And finally, the effects on tight junction stability may occur indirectly, by the well-characterized anti-inflammatory effect of αCT1 (inflammation causes tight junction disassembly) [76–78], These additional mechanisms will be investigated in future studies; although the dynamic range of the animal models may not allow for an assignment of relative contributions between the different mechanisms.…”

A synthetic connexin 43 mimetic peptide augments corneal wound healing

“…Sterile sodium alginate (Sigma-Aldrich catalog#A0682, high maluronic acid content, low viscosity) poly-l-ornithine (Alfa Aesar L-ornithine hydrochloride 99%) microcapsules were synthesized and release of αCT1 was measured according to a previously published protocol (Moore et al, 2013). All microcapsules were synthesized with a 2% alginate/0.5% PLO concentration and gelled in 0.15M calcium chloride (CaCl 2 ) (Sigma-Aldrich) solution 12 minutes.…”

“…Microcapsule solutions were buffered to pH 4.3 using 0.1M HEPES and 0.1M hydrochloric acid (HCL) to control pore size and release rate. A-PLO microcapsules were loaded with αCT1 according to previous studies (Moore et al 2013), with an initial concentration of 200μM. To determine the peptide release profile, synthesized capsules were rinsed three times in deionized water, incubated at 37°C, and the released peptide concentration determined with a microBCA Assay kit (Thermo Scientific).…”

“…Previous studies from our laboratory using alginate poly-l-ornithine and alginate poly-l-lysine microcapsules loaded with 200μM concentrations of αCT1 detailed the release profiles of the microcapsules (Moore et al, 2013). Release characteristics were adjusted using different polymer coatings and reduction in pore size by adjusting pH to 4.3 from a biologically neutral 7.4.…”

New Insights into Acrylic Polymer Precipitation by Supercritical Fluids

“…Micro-and nanoencapsulation processes have been developed in order to encapsulate active agents in many fields, and polymers, gums, carbohydrates, proteins, lipids and inorganic materials have been used as coating materials. Polymers have been widely used as coating material [1][2][3][4] because they can preserve the properties and activities of the active substances; they are nontoxic, biocompatible, and easy to process. Furthermore, polymers can increase patient compliance by masking tastes and odors.…”