Synthesis, Characterization and Modification of Gum Arabic Microgels for Biomedical and Environmental Applications

Abstract

In this study, Gum Arabic (GA) microgels were successfully synthesized via reverse micellization method with a high yield (78±5.0%) in 5-100 μm size range using divinyl sulfone (DVS) as a crosslinker. The as synthesized GA microgels show 22.8±3.5% biodegradability property at stomach condition (pH 1) in 20 days, whereas no degradation was observed at pH 7.4 and pH 9 conditions at 37 oC. By using diethylenetriamine (DETA) and taurine (TA) as chemical modifying agents, GA microgels were chemically modified as GA-DETA and GA-TA microgels. Remarkably, GA-DETA and GA-TA microgels show zeta potential values of 5.23±4.07 and -24.85±1.33 mV in comparison to GA microgels which give -27.31±4.20 mV overall surface charge. Moreover, blood compatibility of GA, GA-TA, and GA-DETA microgels was tested via in vitro protein adsorption, % hemolysis ratio and blood clotting index. Interestingly, GA based microgels were hemocompatible with % hemolysis ratio between 0.23 and 2.05; and the GA microgels were found highly compatible with a blood clotting index of 81±40. The biocompatibility of GA, GA-DETA and GA-TA microgels against L929 fibroblast cells also indicate 84.4%, 89.1% and 67.0% cell viability respectively at 25.0 μg/mL concentration; suggesting a great deal of potential in vivo biomedical applications up to this concentration. In addition, 5 and 10 mg/mL minimum inhibition concentration (MIC) of protonated GA-DETA microgels (GA-DETA-HCl) was determined against E. coli and S. aureus respectively. The bare and GA-TA microgels present good loading capability of 160 and 57 mg.g-1 for phenylephrine (PHP) whereas, in case of Trimethoprim(TMP), GA-DETA and GA-TA microgels show a relatively higher loading capacity of 80 and 52 mg.g-1 respectively. Contrarily, 39.27 ±1.20, 18.40 ±3.130 and 3.10 ±1.140 mg.g-1 release of PHP was observed in case of GA, GA-TA and GA-DETA microgels respectively to the BPS medium in 8 Hrs. Likewise, GA and GA-TA microgels exhibits upto 4.5 ±3.32 and 9.80 ±4.10 mg.g-1 release respectively and an unexpectedly low release amount of 3.3 ±1.94 mg.g-1 from GA-DETA microgels was monitored in case of TMP. Besides, Zeta potential measurements in this study suggest that GA-DETA microgels denote a positively charged surface in DI water. Due to this fact, GA-DETA microgels were used as micro reactor in removal study of some negatively charged pollutants such as; chromate(Cr(III)), dichromate(Cr(VI)), arsenate(As(V)), methyl orange(MO), eosin Y(EY) and Congo red(CR) from aqueous media. Thus, 0.05 g feed of GA-DETA microgels show upto 69.80, 99.30 %, 40.0 %, 91.0%, 84.10 % and 73.0 % removal capability for As(V), Cr(VI), Cr(III), MO, EY and CR respectively in 2 Hrs. mixing time. Moreover, kinetic models such as; the Langmuir, the Fruendlich and modified Fruendlich isotherms were applied to the obtained adsorption data and it was concluded that modified Fruendlich model exhibits relatively practical fit for almost all pollutants giving R2 value nearer to unity. Moreover, maximum adsorption capacity (Qm) was determined for all the six pollutants with the numerical values of 217, 256, 271, 143, 130 and 116 mg.g-1 for As (V) Cr(III), Cr(VI), MO, EY and CR respectively. Further, it was observed that the modified Fruendlich isotherm give inclusively best fit for all pollutants showing R2 values of 0.9962, 0.9926, 0.9972, 0.9988, 0.9988 and 0.980 in case of adsorption As(V), Cr(VI), Cr(III), MO, EY and CR respectively.