Solubilization of salicylamide and acetaminophen by antihistamines in aqueous solution

Nano Lipid Carriers as a Promising Drug Delivery Carrier for Neurodegenerative Disorders - An Overview of Recent Advances

The last few decades have seen a rise in the number of deaths caused by neurological disorders. The blood-brain barrier (BBB), which is very complex and has multiple mechanisms, makes drug delivery to the brain challenging for many scientists. Lipid nanoparticles (LNPs) such as nanoemulsions, solid-lipid nanoparticles, liposomes, and nano lipid carriers (NLCs) exhibit enhanced bioavailability and flexibility among these nanocarriers. NLCs are found to be very effective. In the last few decades, they have been a center of attraction for controlled drug delivery. According to the current global status of specific neurological disorders, out of all LNPs, NLC significantly reduces the cross-permeability of drugs through the BBB due to their peculiar properties. They offer a host of advantages over other carriers because of their biocompatibility, safety, non-toxicity, non-irritating behavior, stability, high encapsulation efficiency, high drug loading, high drug targeting, control of drug release, and ease in manufacturing. The biocompatible lipid matrix is ideally suited as a drug carrier system due to the nano-size range. For certain neurological conditions such as Parkinsonism, Alzheimer's, Epilepsy, Multiple sclerosis, and Brain cancer, we examined recent advances in NLCs to improve brain targeting of bioactive with special attention to formulation aspects and pharmacokinetic characteristics. This article also provides a brief overview of a critical approach for brain targeting, i.e., direct nose-to-brain drug delivery and some recent patents published on NLC".

Recent strategies and advances in the fabrication of nano lipid carriers and their application towards brain targeting

In last two decades, the lipid nanocarriers have been extensively investigated for their drug targeting efficiency towards the critical areas of the human body like CNS, cardiac region, tumor cells, etc. Owing to the flexibility and biocompatibility, the lipid-based nanocarriers, including nanoemulsion, liposomes, SLN, NLC etc. have gained much attention among various other nanocarrier systems for brain targeting of bioactives. Across different lipid nanocarriers, NLC remains to be the safest, stable, biocompatible and cost-effective drug carrier system with high encapsulation efficiency. Drug delivery to the brain always remains a challenging issue for scientists due to the complex structure and various barrier mechanisms surrounding the brain. The application of a suitable nanocarrier system and the use of any alternative route of drug administration like nose-to-brain drug delivery could overcome the hurdle and improves the therapeutic efficiency of CNS acting drugs thereof. NLC, a second-generation lipid nanocarrier, upsurges the drug permeation across the BBB due to its unique structural properties. The biocompatible lipid matrix and nano-size make it an ideal drug carrier for brain targeting. It offers many advantages over other drug carrier systems, including ease of manufacturing and scale-up to industrial level, higher drug targeting, high drug loading, control drug release, compatibility with a wide range of drug substances, non-toxic and non-irritant behavior. This review highlights recent progresses towards the development of NLC for brain targeting of bioactives with particular reference to its surface modifications, formulations aspects, pharmacokinetic behavior and efficacy towards the treatment of various neurological disorders like AD, PD, schizophrenia, epilepsy, brain cancer, CNS infection (viral and fungal), multiple sclerosis, cerebral ischemia, and cerebral malaria. This work describes in detail the role and application of NLC, along with its different fabrication techniques and associated limitations. Specific emphasis is given to compile a summary and graphical data on the area explored by scientists and researchers worldwide towards the treatment of neurological disorders with or without NLC. The article also highlights a brief insight into two prime approaches for brain targeting, including drug delivery across BBB and direct nose-to-brain drug delivery along with the current global status of specific neurological disorders.

Assessment of novel iloperidone- and idebenone-loaded nanostructured lipid carriers: brain targeting efficiency and neuroprotective potential

BACKGROUND

To evaluate the outcome of combining iloperidone with idebenone in the form of brain-targeted nanostructured lipid carrier (NLC) on the expression of endogenous antioxidant enzymes present in the brain, and hence establish the neuroprotective activity.

RESULTS

The combination NLC demonstrated good targeting potential (>85%) as compared with pure iloperidone (22.21%). The levels of various endogenous antioxidant enzymes present in the brain were reduced significantly (p < 0.001) in case of 28 days repeated administration of pure iloperidone, while administration of the combination NLC helped to restore the levels of these enzymes.

CONCLUSION

Combining iloperidone with idebenone and converting into NLC has contributed in effectively reducing oxidative stress in the brain and helped in reversing the catalepsy induced by repeated iloperidone administration.

Hydrotropic Solubilization by Urea Derivatives: A Molecular Dynamics Simulation Study

Hydrotropy is a phenomenon where the presence of a large quantity of one solute enhances the solubility of another solute. The mechanism of this phenomenon remains a topic of debate. This study employed molecular dynamics simulation to investigate the hydrotropic mechanism of a series of urea derivatives, that is, urea (UR), methylurea (MU), ethylurea (EU), and butylurea (BU). A poorly water-soluble compound, nifedipine (NF), was used as the model solute that was solubilized. Structural, dynamic, and energetic changes upon equilibration were analyzed to supply insights to the solubilization mechanism. The study demonstrated that NF and urea derivatives underwent significant nonstoichiometric molecular aggregation in the aqueous solution, a result consistent with the self-aggregation of urea derivatives under the same conditions. The analysis of hydrogen bonding and energy changes revealed that the aggregation was driven by the partial restoration of normal water structure. The energetic data also suggested that the promoted solubilization of NF is favored in the presence of urea derivatives. While the solutes aggregated to a varying degree, the systems were still in single-phase liquid state as attested by their active dynamics.

New spectrophotometric estimation of indomethacin capsules with niacinamide as hydrotropic solubilizing agent

BACKGROUND

Hydrotropic solubilization process involves cooperative intermolecular interaction with several balancing molecular forces, rather than either a specific complexation event or a process dominated by a medium effect, such as co-solvency or salting-in.

MATERIALS AND METHODS

In the present investigation, hydrotropic solution of 2 M niacinamide was employed as the solubilizing agent to solubilize the poorly water-soluble drug, indomethacin, from the capsule dosage form for spectrophotometric determination in ultraviolet region.

RESULTS

Hydrotropic agent used did not interfere in the spectrophotometric analysis. In preliminary solubility studies, it was found that there was more than fivefold enhancement in the aqueous solubility of indomethacin (poorly water-soluble drug) in 2 M niacinamide solution as compared to its aqueous solubility at 28 ± 1°C.

CONCLUSION

The proposed method is new, simple, safe, environmentally friendly, economic, accurate and cost-effective and can be successfully employed in routine analysis.

Parallel stacking of caffeine with riboflavin in aqueous solutions: the potential mechanism for hydrotropic solubilization of riboflavin

Hydrotropy is a phenomenon where the presence of a large quantity of one solute enhances the solubility of another solute. The mechanism of this phenomenon remains elusive and a topic of debate. This study employed molecular dynamics simulation to investigate solute interactions of a model system consisting of a hydrotropic agent, caffeine (CAF), a poorly water-soluble solute, riboflavin (RBF), and water. The study demonstrates that CAF and RBF undergo molecular parallel stacking in the aqueous solution, a result correlating closely to the self-stacking of CAF under the same conditions. The correlations are found both structurally and dynamically, suggesting that the self-stacking of CAF is the primary effect, and incorporation of RBF is the secondary effect. The solute stacking gives rise to the partitioning of solutes and water, which helps restoring the normal water structure and drives down the system energy. The interactions between the solutes are found insignificant to the solute clustering. The dynamic data confirm that the solute stacks are dynamically active. These results suggest that hydrotropic effect of CAF may be attributed to solute parallel stacking.

Carrier mediated transport of chlorpheniramine and chlorcyclizine across bovine olfactory mucosa: Implications on nose‐to‐brain transport

Delivery to the CNS via the nasal cavity has been pursued as a means to circumvent the blood-brain barrier (BBB), yet the mechanism of drug transport across this novel route is not well understood. Hydroxyzine and triprolidine have been reported to readily reach the CNS following nasal administration, whereas no measurable amounts of chlorcyclizine or chlorpheniramine, structurally similar antihistamines, were observed in the CSF. The permeation of chlorpheniramine and chlorcyclizine in vitro across the bovine olfactory mucosa was studied to investigate the biological and physicochemical characteristics that contribute to the limited CNS disposition of these compounds following nasal administration. The submucosal to mucosal fluxes (J(s-m)) of chlorcyclizine and chlorpheniramine across the olfactory mucosa were significantly greater than the mucosal to submucosal fluxes (J(m-s)). Moreover, the submucosal-mucosal permeability of both compounds was temperature dependent and saturable. In the presence of metabolic inhibitors (ouabain and 2,4-dinitrophenol) and P-glycoprotein (P-gp)/multidrug resistance protein 1 (MRP1) inhibitors (quinidine and verapamil), the J(m-s) increased and J(s-m) decreased significantly. These results indicate that chlorpheniramine and chlorcyclizine are effluxed from the olfactory mucosa by efflux transporters such as P-gp and MRP1. Transport studies across inert polymeric membranes demonstrated that the permeability of chlorpheniramine and chlorcyclizine decreased at donor concentrations higher than 3 mM suggesting that physicochemical properties such as self-aggregation also play a role in the reduced olfactory mucosal permeability of these compounds at higher concentrations.

Hydrotropic solubilization--mechanistic studies

PURPOSE

This study examines the mechanism of hydrotropic solubilization using the riboflavin-nicotinamide system. The most commonly proposed mechanism for hydrotropic solubilization is complexation, and therefore, is investigated. Additionally, since nicotinamide and several other hydrotropic agents self-associate in aqueous solution, the possibility that self-association of the hydrotropic agent is important mechanistically is examined by studying the effect of temperature on hydrotropic ability. Researchers have shown that the degree of self association decreases with increasing temperature. Therefore, if temperature affects the solubilizing capacity of nicotinamide, self-association must be mechanistically significant.

METHODS

The complexation hypothesis is tested by looking at nicotinamide's ability to quench riboflavin fluorescence and by examining changes in the UV/Vis spectrum of riboflavin upon addition of nicotinamide. The solubility of riboflavin in nicotinamide solutions as a function of temperature is determined to assess the impact of self-association on hydrotropicity.

RESULTS

Nicotinamide does not alter the intrinsic fluorescence of riboflavin nor are changes indicative of complexation observed in the UV/Vis spectrum Temperature does have an effect on the hydrotropic ability of nicotinamide. Specifically, as temperature increases, the solubilizing capacity of nicotinamide decreases.

CONCLUSIONS

Because nicotinamide is unable to quench riboflavin fluorescence, and does not produce significant spectral changes, complexation of hicotinamide and riboflavin does not occur. However, since increasing temperature causes a decrease in the hydrotropic ability of nicotinamide and in its degree of self-association, it is proposed here that the self-association of nicotinamide impacts the hydrotropic mechanism.

Solubility enhancement of nucleosides and structurally related compounds by complex formation

Water-soluble vitamins, amino acids, and nontoxic pharmaceutical excipients were studied as solubilizing agents for poorly water-soluble adenine (nucleic acid base), guanosine (nucleoside), and structurally related drugs (acyclovir and triamterene). The apparent solubility of the substrates (adenine, guanosine, acyclovir, or triamterene) was appreciably increased by forming complexes with the ligands (vitamins, amino acids, or other ligand). Apparent association constants (Ka) values were measured at 25 degrees C in pH 7 phosphate buffer using phase solubility analysis. The effect of combination ligands on substrate solubility was also studied. Additive solubility enhancement was obtained for several ligand pairs.