The ‘Back-to-nature’ concept has currently been adopted intensively in various industries, especially the pharmaceutical industry. In the past few decades, the overuse of synthetic chemicals has caused severe damage to the environment and ecosystem. One class of natural materials developed to substitute artificial chemicals in the pharmaceutical industries is the natural polymers, including cellulose and its derivatives. The development of nanocelluloses as nanocarriers in drug delivery systems has reached an advanced stage. Cellulose nanofiber (CNF), nanocrystal cellulose (NCC), and bacterial nanocellulose (BC) are the most common nanocellulose used as nanocarriers in drug delivery systems. Modification and functionalization using various processes and chemicals have been carried out to increase the adsorption and drug delivery performance of nanocellulose. Nanocellulose may be attached to the drug by physical interaction or chemical functionalization for covalent drug binding. Current development of nanocarrier formulations such as surfactant nanocellulose, ultra-lightweight porous materials, hydrogel, polyelectrolytes, and inorganic hybridizations has advanced to enable the construction of stimuli-responsive and specific recognition characteristics. Thus, an opportunity has emerged to develop a new generation of nanocellulose-based carriers that can modulate the drug conveyance for diverse drug characteristics. This review provides insights into selecting appropriate nanocellulose-based hybrid materials and the available modification routes to achieve satisfactory carrier performance and briefly discusses the essential criteria to achieve high-quality nanocellulose.

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In this study, a metal–organic framework, namely, Zn3(BTC)2 (BTC = 1,3,5-benzenetricaboxylic acid), was solvothermally synthesized and employed as a catalyst for biodiesel production from degummed vegetable oil via a one-step transesterification and esterification reaction. The resulting Zn3(BTC)2 particles exhibit a well-defined triclinic structure with an average size of about 1.2 μm, high specific surface area of 1176 m2/g, and thermal stability up to 300 °C. The response surface methodology–Box–Behnken design (RSM–BBD) was employed to identify the optimal reaction conditions and to model the biodiesel yield in relation to three important parameters, namely, the methanol/oil molar ratio (4:1–8:1), temperature (45–65 °C), and time (1.5–4.5 h). Under the optimized reaction conditions (i.e., 6:1 methanol/oil molar ratio, 65 °C, 4.5 h), the maximum biodiesel yield reached 89.89% in a 1 wt % catalyst, which agreed very well with the quadratic polynomial model’s prediction (89.96%). The intrinsic catalytic activity of Zn3(BTC)2, expressed as the turnover frequency, was found to be superior to that of other MOF catalysts applied in the transesterification and esterification reactions. The reusability study showed that the as-synthesized Zn3(BTC)2 catalyst exhibited good stability upon three consecutive reuses without a noticeable decrease in the methyl ester yield (∼4%) and any appreciable metal leaching (<5%). Furthermore, a preliminary technoeconomic analysis showed that the total direct operating cost for the kilogram-scale production of Zn3(BTC)2 is estimated to be US$50, which may sound economically attractive.

The utilization of natural gum polysaccharides as the vehicle for drug delivery systems and other biomedical applications has increased in recent decades. Their biocompatibility, biodegradability, and price are much cheaper than other materials. It is also renewable and available in massive amounts, which are the main reasons for its use in pharmaceutical applications. Gum can be easily functionalized with other natural polymers to enhance their applications. Various aspects of the utilization of natural gums in the forms of polyelectrolyte complexes (PECs) for drug delivery systems are discussed in this review. The application of different mathematical models were used to represent the drug release mechanisms from PECs; these models include a zero-order equation, first-order equation, Higuchi, simplified Higuchi, Korsmeyer–Peppas, and Peppas–Sahlin.