Comparison of different cationic polymers efficacy in fabrication of alginate multilayer microcapsules

Abstract

In past decades, alginate-based multilayer microcapsules have been given important attention in various pharmaceutical investigations. Alginate-poly l lysine-alginate (APA) is studied the most. Due to the similarity between the structure of polyethyleneimine (PEI) and poly-L-lysine (PLL) and also lower price of PEI than PLL, this study was conducted to compare the efficacy of linear (LPEI) and branch (BPEI) forms of PEI with PLL as covering layers in fabrication of microcapsules. The microcapsules were fabricated using electrostatic bead generator and their shape/size, surface roughness, mechanical strength, and interlayer interactions were also investigated using optical microscopy, AFM, explosion test and FTIR, respectively. Furthermore, cytotoxicity was evaluated by comparing the two anionic final covering layers alginate (Alg) and sodium cellulose sulphate (NCS) using MTT test. BPEI was excluded from the rest of the study due to its less capacity to strengthen the microcapsules and also the aggregation of the resultant alginate-BPEI-alginate microcapsules, while LPEI showed properties similar to PLL. MTT test also showed that NCS has no superiority over Alg as final covering layer. Therefore, it is concluded that, LPEI could be considered as a more cost effective alternative to PLL and a promising subject for future studies.

Keywords: Alginic acid; Extrusion; Microencapsulation; Poly electrolyte complexes; Poly l-lysine; Polyethylene imine.

Graphical abstract

Fig. 1

Structure of alginic acid and egg-box model (Reproduced with permission from . Copyright 2002 John Wiley and Sons).

Fig. 2

Structure of PEI; up, linear, down, branched (Reproduced with permission from . Copyright 2008 Elsevier B.V.).

Fig. 3

Schematic of electrostatic bead generator used for fabrication of alginate microcapsules.

Fig. 4

Microscopic images of alginate microcapsules made from different concentrations of alginate solution. (A) 1%, (B) 1.5%, and (C) 2% (magnification, 4×).

Fig. 5

Different appearance of microcapsules as a result of the application of different cationic polymers. (A) ABA, (B) ALA, and (C) APA(magnification, 4×).

Fig. 6

FTIR spectra of multilayer microcapsules, (A) ABA, (B) ALA and (C) APA.

Fig. 7

Microcapsules size growth (%), after explosion test. Comparison of different types and concentrations of cationic polymers (*P < 0.05, n = 3).

Fig. 8

Microscopic images of multilayer microcapsules. (A) ABA, (B) ALA and (C) APA (magnification, 4×).

Fig. 9

Size growth in different types of microcapsules. Incubation temperature, (A) 2 to 8 °C and (B) 37 °C (mean ± SD, n = 3).

Fig. 10

Microscopic images of the multilayer microcapsules. Upper panel shows the microcapsules at the day of fabrication, lower panel shows the microcapsules after incubation for 49 days in 0.9% NaCl. (A) ALA, (B) ALN, (C) APA and (D) APN (magnification, 4×). Black spots in B and D series are NCS precipitates.