Development and Application of Magnesium Citrate-Functionalized Starch-Based Nanomaterials in Enhancing the Fortification of Vitamin D3: Batch and Release Performance Studies

Recently, diverse strategies have been developed to formulate food micronutritional supplements like magnesium (Mg²⁺) and vitamin D₃ (VD₃). Nevertheless, the progress in food supplement formulations is limited, due to their undesirable interactions with various food ingredients. In the last few decades, starch has been widely used to prepare micro or nano-carriers for different micronutrients following diverse physical and chemical methods, due to its excellent surface features, the possibility of derivation from various reagents, biodegradability, and biocompatibility. However, most of these methods have not yet been tested in the laboratory scales, failed partially or completely in producing uniform particles in nanoscale domains, and require multiple formulation steps. Herein, starch nanomaterials (SNMs) are fabricated as an effective carrier for VD₃ and Mg²⁺ by ultrasonication under moderate conditions. Initially, the SNMs were prepared by ultrasonication using equal masses of native corn starch (NCS) and high amylose corn starch (HACS). The generated materials were then grafted with magnesium, in citrate form at room conditions, as a primary functionalization step, forming magnesium citrate-grafted SNM (MNM-Mg), which were used as sorbents for VD₃. Experimentally, a set of analytical methods including atomic force microscopy (AFM), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared spectroscopy (FT-IR), Zeta sizer, and X-ray diffraction analysis (XRD) were used to determine the size, surface properties, functionality, stability, and morphology of the prepared nanomaterials. The adsorptive behavior of VD₃ on MNM-Mg surfaces was investigated by analyzing the equilibrium adsorptive data using various isotherm models including Langmuir, BET, Toth, and Redlich–Peterson. Furthermore, the release kinetics for the MNM-Mg after adsorbing VD₃ (MNM-Mg-VD₃) were tested in a phosphate buffer solution at pH 7.4, mimicking human bloodstream conditions. Our results showed the successful synthesis of stable MNM-Mg (Z potential of −36 mV) with an estimated average size of 10 nm and a BET surface area of 28 m²/g. To the best of our knowledge, the VD₃ that was loaded on our primarily modified nanomaterials with magnesium citrate, compared with the physically mixed VD₃ MNM-Mg with VD₃(MNM-Mg+VD₃ (PM)) and directly administrated, tended to be completely released after 5 h with lower diffusivity and greater controlled release performance.