Exploring the potential of redispersible nanocomplex-in-microparticles for enhanced oral insulin delivery

Muco-Adhesive and Muco-Penetrative Formulations for the Oral Delivery of Insulin

Insulin, a pivotal anabolic hormone, regulates glucose homeostasis by facilitating the conversion of blood glucose to energy or storage. Dysfunction in insulin activity, often associated with pancreatic β cells impairment, leads to hyperglycemia, a hallmark of diabetes. Type 1 diabetes (T1D) results from autoimmune destruction of β cells, while type 2 diabetes (T2D) stems from genetic, environmental, and lifestyle factors causing β cell dysfunction and insulin resistance. Currently, insulin therapy is used for most of the cases of T1D, while it is used only in a few persistent cases of T2D, often supplemented with dietary and lifestyle changes. The key challenge in oral insulin delivery lies in overcoming gastrointestinal (GI) barriers, including enzymatic degradation, low permeability, food interactions, low bioavailability, and long-term safety concerns. The muco-adhesive (MA) and muco-penetrative (MP) formulations aim to enhance oral insulin delivery by addressing these challenges. The mucus layer, a hydrogel matrix covering epithelial cells in the GI tract, poses significant barriers to oral insulin absorption. Its structure, composition, and turnover rate influence interactions with insulin and other drug carriers. Some of the few factors that influence mucoadhesion and mucopenetration are particle size, surface charge distribution, and surface modifications. This review discusses the challenges associated with oral insulin delivery, explores the properties of mucus, and evaluates the strategies for achieving excellent MA and MP formulations, focusing on nanotechnology-based approaches. The development of effective oral insulin formulations holds the potential to revolutionize diabetes management, providing patients with a more convenient and patient-friendly alternative to traditional insulin administration methods.

Comparison of virus-capsid mimicking biologic-shell based versus polymeric-shell nanoparticles for enhanced oral insulin delivery

Virus-capsid mimicking mucus-permeable nanoparticles are promising oral insulin carriers which surmount intestinal mucus barrier. However, the impact of different virus-capsid mimicking structure remains unexplored. In this study, utilizing biotin grafted chitosan as the main skeleton, virus-mimicking nanoparticles endowed with biologic-shell (streptavidin coverage) and polymeric-shell (hyaluronic acid/alginate coating) were designed with insulin as a model drug by self-assembly processes. It was demonstrated that biologic-shell mimicking nanoparticles exhibited a higher intestinal trans-mucus (>80%, 10 min) and transmucosal penetration efficiency (1.6-2.2-fold improvement) than polymeric-shell counterparts. Uptake mechanism studies revealed caveolae-mediated endocytosis was responsible for the absorption of biologic-shell mimicking nanoparticles whereas polymeric-shell mimicking nanoparticles were characterized by clathrin-mediated pathway with anticipated lysosomal insulin digestion. Further, in vivo hypoglycemic study indicated that the improved effect of regulating blood sugar levels was virus-capsid structure dependent out of which biologic-shell mimicking nanoparticles presented the best performance (5.1%). Although the findings of this study are encouraging, much more work is required to meet the standards of clinical translation. Taken together, we highlight the external structural dependence of virus-capsid mimicking nanoparticles on the muco-penetrating and uptake mechanism of enterocytes that in turn affecting their in vivo absorption, which should be pondered when engineering virus-mimicking nanoparticles for oral insulin delivery.

Synthesis of an insulin-loaded mucoadhesive nanoparticle designed for intranasal administration: focus on new diffusion media

Intranasal administration is a drug delivery approach to provide a non-invasive pharmacological response in the central nervous system with relatively small peripheral side effects. To improve the residence time of intranasal drug delivery systems in the nasal mucosa, mucoadhesive polymers (e.g., chitosan) can be used. Here, insulin-loaded chitosan nanoparticles were synthesized and their physiochemical properties were evaluated based on requirements of intranasal administration. The nanoparticles were spherical (a hydrodynamic diameter of 165.3 nm, polydispersity index of 0.24, and zeta potential of +21.6 mV) that granted mucoadhesion without any noticeable toxicity to the nasal tissue. We applied a new approach using the Krebs-Henseleit buffer solution along with simulated nasal fluid in a Franz's diffusion cell to study this intranasal drug delivery system. We used the Krebs-Henseleit buffer because of its ability to supply glucose to the cells which serves as a novel ex vivo diffusion medium to maintain the viability of the tissue during the experiment. Based on diffusion rate and histopathological endpoints, the Krebs-Henseleit buffer solution can be a substituent solution to the commonly used simulated nasal fluid for such drug delivery systems.

Insulin-loaded nanoparticles based on acetylated cashew gum/chitosan complexes for oral administration and diabetes treatment

Insulin is one of the most important drugs in the clinical treatment of diabetes. There is growing interest in oral insulin administration as it mimics the physiological pathway and potentially reduces side effects associated with subcutaneous injection. In this study, a nanoparticulate system was developed using acetylated cashew gum (ACG) and chitosan by the polyelectrolyte complexation method, for oral administration of insulin. The nanoparticles were characterized by size, zeta potential and encapsulation efficiency (EE%). And they had a particle size of 460 ± 11.0 nm, PDI of 0.2 ± 0.021, zeta potential of 30.6 ± 0.48 mV, and an EE% of 52.5 %. Cytotoxicity assays were performed for HT-29 cell lines. It was observed that ACG and nanoparticles did not have a significant effect on cell viability, verifying their biocompatibility. Hypoglycemic effects of the formulation were analyzed in vivo, noting that the nanoparticles reduced blood glucose by 51.0 % of baseline levels after 12 h, not inducing signs of toxicity or death. Biochemical and hematological profiles were not clinically modified. Histological study indicated no signs of toxicity. Results showed that the nanostructured system presented itself as a potential vehicle for oral insulin release.

In situ rearranged multifunctional lipid nanoparticles via synergistic potentiation for oral insulin delivery

Oral administration of therapeutic peptides/proteins (TPPs) is confronted with multiple gastrointestinal (GI) barriers such as mucus and intestinal epithelium, and the first-pass metabolism in the liver is also responsible for low bioavailability. In situ rearranged multifunctional lipid nanoparticles (LNs) were developed to overcome these obstacles via synergistic potentiation for oral insulin delivery. After the reverse micelles of insulin (RMI) containing functional components were gavaged, LNs formed in situ under the hydration effect of GI fluid. The nearly electroneutral surface generated by the rearrangement of sodium deoxycholate (SDC) and chitosan (CS) on the reverse micelle core facilitated LNs (RMI@SDC@SB12-CS) to overcome mucus barrier and the sulfobetaine 12 (SB12) modification further promoted epithelial uptake of LNs. Subsequently, chylomicron-like particles formed by the lipid core in the intestinal epithelium were easily transported to the lymphatic circulation and then into the systemic circulation, thus avoiding hepatic first-pass metabolism. Eventually, RMI@SDC@SB12-CS achieved a high pharmacological bioavailability of 13.7% in diabetic rats. In conclusion, this study provides a versatile platform for enhanced oral insulin delivery.