Melatonin and the nervous system: nanomedicine perspectives

The mechanism of action of melatonin on the nervous system, sleep, cognitive deficits, and aging is not fully understood. Neurodegenerative diseases (ND) are one of the leading causes of disability and mortality worldwide. Sleeping and cognitive impairments also represent common and serious public health problems, particularly deteriorating with the aging process. Melatonin, as a neuromodulatory hormone, regulates circadian rhythms and the sleep-wake cycle, with functions extending to antioxidant, anti-inflammatory, neuroprotective, and anti-aging properties. However, melatonin is a hydrophobic compound with relatively low water solubility and a short half-life. While melatonin can cross the blood-brain barrier, exogenous melatonin administered orally or intravenously has poor bioavailability, undergoes rapid metabolism in the circulation, and shows limited brain accumulation, ultimately compromising its therapeutic efficacy. In recent years, the convergence of melatonin research with nanomedicine ensures safe therapeutic uses, limited drug degradation, and perspectives for targeted drug delivery to the central nervous system. Here we outline the promising neurotherapeutic properties of nanomaterials as carriers loaded with melatonin drug alone or in combinations with other active molecules.

Synthesis of Novel Acrylamide Graft Copolymer of Acacia nilotica Gum for the Stabilization of Melatonin Nanoparticles for Improved Therapeutic Effect: Optimization Using (3)2 Factorial Design

The objective of the present study was to optimize the microwave-assisted synthesis of the acrylamide graft copolymer of Acacia nilotica gum (AM-co-ANG). Furthermore, graft copolymer was used for the formulation of a nanoparticulate system using a novel top to bottom solvent antisolvent technique for the delivery of melatonin. Grafting of ANG was optimized by using 32 factorial design, where concentrations of polymer and monomer (acrylamide) were used as independent variables and swelling index in acidic (0.1 N HCl) and basic (1 N NaOH) pH. Grafted polymers were further used to develop and optimize nanoparticulate system using concentration of the graft copolymer and concentration of drug as independent variables. The size of the nanoformulation and entrapment efficiency were selected as dependent variables. Difference in infrared spectrum and absorbance maxima in the ultraviolet region confirm that grafting has taken place. Porous structure and a higher contact angle confirmed hydrophobic nature of AM-co-ANG as compared with the native polymer. Acrylamide graft copolymers show more swelling in 1 N NaOH as compared with 0.1 N HCl. In vitro toxicity studies in hepatic (HepG2 cell line), brain (SHSY5Y cell line), and skin (HaCaT cell line) cells easily predict that synthesized polymer have no cytotoxicity. The entrapment efficiency ranged from 55.24 ± 1.35% to 73.21 ± 1.83%. A nonlinear correlation was observed between independent and dependent variables, as confirmed by multivariate analysis of variance, surface regression, and the correlation report. The prepared formulations were able to release drug up to 12 h. The regression coefficient easily predicted that most of the formulations followed Baker-Lonsdale drug release kinetics.

Melatonin and metformin co-loaded nanoliposomes efficiently attenuate liver damage induced by bile duct ligation in rats

In the current study, the therapeutic effectiveness of the metformin (Met) and melatonin (Mel) co-loaded liposomes was investigated on cholestasis induced by bile duct ligation (BDL) in male rats. Histopathological analysis, biochemical analysis, and oxidative stress markers were assayed to determine the therapeutic effect of Met and Mel co-loaded liposomes on cholestasis. Histopathological analysis revealed that the simultaneous administration of Met and Mel, whether in the free (C-Mel-Met) or liposomal (C-Lipo-Mel-Met) forms, reduced inflammation as well as proliferation of bile ducts; however, results were more prominent in the liposomal form of Mel and Met. Additionaly, serum levels of aspartate aminotransferase (AST) were significantly (p < 0.001) higher in (C-Mel-Met) treated rats compared with (BDL) rats; however, (C-Lipo-Mel-Met) treated rats exhibited significant (p < 0.05) lower AST rates in comparison to (BDL) rats. Moreover, a significant (p < 0.0001) drop in bilirubin levels was detected in (C-Lipo-Mel-Met) treated rats in comparison to (BDL) rats; it is noteworthy mentioning that bilirubin levels in (C-Lipo-Mel-Met) treated rats were insignificant in comparison to sham-control (SC) rats. Furthermore, rats concomitantly administered Met and Mel, exhibited significant downregulation in the expression levels of inflammatory cytokine genes such as TNF-α and IL-1 gene expression, where the downregulation was more prominent in the liposomal from. Our findings demonestrate that the concomitant administration of metformin and melatonin in the liposomal form had more therapeutic effect on liver injury than their free forms through improving histological changes, reducing biochemical markers and favoring oxidant- antioxidant balance.

Solid lipid nanoparticles loading with curcumin and dexanabinol to treat major depressive disorder

Dexanabinol (HU-211) is an artificially synthesized cannabinoid derivative that exerts neuroprotective effects through anti-inflammatory and antioxidant effects. Curcumin exhibits antidepressant effects in the treatment of major depressive disorder. To investigate the antidepressant effects of solid lipid nanoparticles loaded with both curcumin and dexanabinol, and the underlying mechanisms associated with this combination, we established wild-type (CBR1^+/+) and cannabinoid receptor 1 (CBR1) knockout (CBR1^–/–) mouse models of major depressive disorder, through the intraperitoneal injection of corticosterone, for 3 successive days, followed by treatment with intraperitoneal injections of solid lipid nanoparticles loading with curcumin (20 mg/kg) and dexanabinol (0.85 mg/kg), for 2 successive days. Our results revealed that solid lipid nanoparticle loading with curcumin and dexanabinol increased the mRNA and protein expression levels of the mature neuronal markers neuronal nuclei, mitogen-activated protein 2, and neuron-specific beta-tubulin III, promoted the release of dopamine and norepinephrine, and increased the mRNA expression of CBR1 and the downstream genes Rasgef1c and Egr1, and simultaneously improved rat locomotor function. However, solid lipid nanoparticles loaded with curcumin and dexanabinol had no antidepressant effects on the CBR1^–/– mouse models of major depressive disorder. This study was approved by the Institutional Ethics Committee of Tongji Hospital of Tongji University, China (approval No. 2017-DW-020) on May 24, 2017.

Potential and Applications of Nanocarriers for Efficient Delivery of Biopharmaceuticals

During the past two decades, the clinical use of biopharmaceutical products has markedly increased because of their obvious advantages over conventional small-molecule drug products. These advantages include better specificity, potency, targeting abilities, and reduced side effects. Despite the substantial clinical and commercial success, the macromolecular structure and intrinsic instability of biopharmaceuticals make their formulation and administration challenging and render parenteral delivery as the only viable option in most cases. The use of nanocarriers for efficient delivery of biopharmaceuticals is essential due to their practical benefits such as protecting from degradation in a hostile physiological environment, enhancing plasma half-life and retention time, facilitating absorption through the epithelium, providing site-specific delivery, and improving access to intracellular targets. In the current review, we highlight the clinical and commercial success of biopharmaceuticals and the overall applications and potential of nanocarriers in biopharmaceuticals delivery. Effective applications of nanocarriers for biopharmaceuticals delivery via invasive and noninvasive routes (oral, pulmonary, nasal, and skin) are presented here. The presented data undoubtedly demonstrate the great potential of combining nanocarriers with biopharmaceuticals to improve healthcare products in the future clinical landscape. In conclusion, nanocarriers are promising delivery tool for the hormones, cytokines, nucleic acids, vaccines, antibodies, enzymes, and gene- and cell-based therapeutics for the treatment of multiple pathological conditions.