Formulation, characterization and biological evaluation of injectable nanocrystals from stem exudate gel of Caralluma retrospiciens (Ehrenb) – Part C

Abstract

The purpose of this study was to develop injectable nanocrystals (NC) from stem exudate gel (EG) from Caralluma retrospiciens (Ehrenb) using the technique of nanoprecipitation. The NC had a zeta potential of −5.58 ± 4.27 mV. Size distribution analysis showed that it ranged in size from 100 to 300 nm. The polydispersity index (PDI) was 0.467, while its percentage PDI was 68.4. Scanning electron microscopic analysis and transmission electron microscopy studies revealed the morphological features of NC as discrete crystals with rough surfaces. The mobility of NC was 5.5 µm.cm/Vs, while its conductivity was 0.16 mS/cm. Antibacterial studies showed broad activity against both Gram-positive and Gram-negative bacteria. The minimum inhibitory concentrations (MICs) of NC against Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), Streptococcus pyogenes (S. pyogenes), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were 6, 8, 8, 4, 8, and 6 % (w/v), respectively. The antibacterial effect was highest against K. pneumoniae (25.6 ± 1.5 mm), followed by E. coli (25.5 ± 1.8 mm), P. aeruginosa (24.1 ± 1.2 mm), S. pyogenes (22.2 ± 1.2 mm), S. aureus (21.83 ± 1.2 mm) and B. subtilis (20.33 ± 1.8 mm). In this study, the cytotoxicity properties of NC were determined against MCF-7 breast cancer cells ATCC. The NC failed to inhibit the proliferation of MCF-7 cells against the even at 300 µg/mL concentration. These results indicated that the NC is a promising antibacterial injectable dosage form.