Agro-Industrial Waste Valorization: Transformation of Starch from Mango Kernel into Biocompatible, Thermoresponsive and High Swelling Nanogels

Abstract

Mango industry processing disposes 40-60% of this fruit as residues, such as peels and kernels. The exploration of bioproducts from these industrial rejects can reduce environmental impact besides of producing high value-added materials. In this scenario, carboxymethyl starch nanoparticles were produced from mango (Mangifera indica L.) kernel starch. These nanoparticles were then decorated with thermoresponsive chains of the amino terminated poly(N-isopropylacrylamide) (PNIPAM‑NH2), with the intention of evaluating their applicability in the biomedical area. Elemental analysis, Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopy confirmed successful grafting of PNIPAM-NH2 onto the carboxymethyl starch backbone. Scanning electron microscopy (SEM) images and dynamic light scattering (DLS) data showed sizes of 100 and 112 nm in the dry state and of 744 and 598 nm in the hydrated state, when the grafting degree (GD) was of 6 and 14.3%, respectively. The degree of swelling was of 41,100 and 15,100% for GD of 6 and 14.3% respectively, suggesting that the nanogels are suitable for drug incorporation. The toxicity of the nanogels to human adipose-derived stem cells (ADSCs) and red blood cells (RBCs) was evaluated by lactate dehydrogenase (LDH), alamarBlue and hemolysis assays. Both nanogels were non-cytotoxic and non-hemolytic, suggesting the suitability of these biomaterials for cell- and blood-contacting applications.