In Situ-Based Gels for Nose to Brain Delivery for the Treatment of Neurological Diseases

Recent Advances in the Development of In Situ Gelling Drug Delivery Systems for Non-Parenteral Administration Routes

In situ gelling drug delivery systems have gained enormous attention over the last decade. They are in a sol-state before administration, and they are capable of forming gels in response to different endogenous stimuli, such as temperature increase, pH change and the presence of ions. Such systems can be administered through different routes, to achieve local or systemic drug delivery and can also be successfully used as vehicles for drug-loaded nano- and microparticles. Natural, synthetic and/or semi-synthetic polymers with in situ gelling behavior can be used alone, or in combination, for the preparation of such systems; the association with mucoadhesive polymers is highly desirable in order to further prolong the residence time at the site of action/absorption. In situ gelling systems include also solid polymeric formulations, generally obtained by freeze-drying, which, after contact with biological fluids, undergo a fast hydration with the formation of a gel able to release the drug loaded in a controlled manner. This review provides an overview of the in situ gelling drug delivery systems developed in the last 10 years for non-parenteral administration routes, such as ocular, nasal, buccal, gastrointestinal, vaginal and intravesical ones, with a special focus on formulation composition, polymer gelation mechanism and in vitro release studies.

New Opportunity to Formulate Intranasal Vaccines and Drug Delivery Systems Based on Chitosan

In an attempt to develop drug delivery systems that bypass the blood–brain barrier (BBB) and prevent liver and intestinal degradation, it was concluded that nasal medication meets these criteria and can be used for drugs that have these drawbacks. The aim of this review is to present the influence of the properties of chitosan and its derivatives (mucoadhesion, permeability enhancement, surface tension, and zeta potential) on the development of suitable nasal drug delivery systems and on the nasal bioavailability of various active pharmaceutical ingredients. Interactions between chitosan and proteins, lipids, antigens, and other molecules lead to complexes that have their own applications or to changing characteristics of the substances involved in the bond (conformational changes, increased stability or solubility, etc.). Chitosan and its derivatives have their own actions (antibacterial, antifungal, immunostimulant, antioxidant, etc.) and can be used as such or in combination with other molecules from the same class to achieve a synergistic effect. The applicability of the properties is set out in the second part of the paper, where nasal formulations based on chitosan are described (vaccines, hydrogels, nanoparticles, nanostructured lipid carriers (NLC), powders, emulsions, etc.).

Alginate Affects Bioactivity of Chimeric Collagen-Binding LL37 Antimicrobial Peptides Adsorbed to Collagen-Alginate Wound Dressings

Chronic infected wounds cause more than 23,000 deaths annually. Antibiotics and antiseptics are conventionally used to treat infected wounds; however, they can be toxic to mammalian cells, and their use can contribute to antimicrobial resistance. Antimicrobial peptides (AMPs) have been utilized to address the limitations of antiseptics and antibiotics. In previous work, we modified the human AMP LL37 with collagen-binding domains from collagenase (cCBD) or fibronectin (fCBD) to facilitate peptide tethering and delivery from collagen-based wound dressings. We found that cCBD-LL37 and fCBD-LL37 were retained and active when bound to 100% collagen scaffolds. Collagen wound dressings are commonly made as composites with other materials, such as alginate. The goal of this study was to investigate how the presence of alginate affects the tethering, release, and antimicrobial activity of LL37 and CBD-LL37 peptides adsorbed to commercially available collagen-alginate wound dressings (FIBRACOL Plus-a 90% collagen and 10% alginate wound dressing). We found that over 85% of the LL37, cCBD-LL37, and fCBD-LL37 was retained on FIBRACOL Plus over a 14-day release study (90.3, 85.8, and 98.6%, respectively). Additionally, FIBRACOL Plus samples loaded with peptides were bactericidal toward Pseudomonas aeruginosa, even after 14 days in release buffer but demonstrated no antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis. The presence of alginate in solution induced conformational changes in the cCBD-LL37 and LL37 peptides, resulting in increased peptide helicity, and reduced antimicrobial activity against P. aeruginosa. Peptide-loaded FIBRACOL Plus scaffolds were not cytotoxic to human dermal fibroblasts. This study demonstrates that CBD-mediated LL37 tethering is a viable strategy to reduce LL37 toxicity, and how substrate composition plays a crucial role in modulating the antimicrobial activity of tethered AMPs.

PEGylation and folate conjugation effects on the stability of chitosan-tripolyphosphate nanoparticles

Chitosan-based nanoparticles (Ch-NPs) prepared via ionotropic gelation of Ch with sodium tripolyphosphate (TPP) have been widely examined as potential drug carriers. Yet, recent studies have shown these particles to be unstable in model (pH 7.2-7.4) physiological media. To this end, here we explored the possibility of improving TPP-crosslinked Ch-NP stability through chemical Ch modification. Specifically, Ch samples with either 76% or 92% degrees of deacetylation (DD) were grafted with either polyethylene glycol (PEG), a hydrophilic molecule, or folic acid (F), a hydrophobic molecule. Limited variation in dispersion light scattering intensity, particle size and apparent ζ-potential, and lack of macroscopic precipitation were chosen as analytical evidence of dispersion stability. TPP titrations were performed to determine the optimal TPP:glucosamine molar ratio for preparing particles with near 200-nm diameters, which are desirable for systemic administration of drugs, cellular uptake, and enhancing NP blood circulation. Both DD and Ch modification influenced the particle formation process and the evolution in NP size and ζ-potential upon 30-day storage in virtually salt-free water at 25 °C and 37 °C, where the NPs underwent partial aggregation (along with possible dissolution and swelling) but remained colloidally dispersed. Under model physiological (pH 7.2; 163 mM ionic strength) conditions, however (where the chitosan amine groups were largely deprotonated), the particles quickly became destabilized, evidently due to particle dissolution followed by Ch precipitation. Overall, within the degrees of substitution used for this work (~1% for PEG, and 3 and 6% for F), neither PEG nor F qualitatively improved Ch-NP stability at physiological pH 7.2 conditions. Thus, application of TPP-crosslinked Ch-NPs in drug delivery (even when Ch is derivatized with PEG or F) should likely be limited to administration routes with acidic pH (at which these NPs remain stable).

Pharmacotechnical Development of a Nasal Drug Delivery Composite Nanosystem Intended for Alzheimer's Disease Treatment

Direct nose-to-brain delivery has been raised as a non-invasive powerful strategy to deliver drugs to the brain bypassing the blood-brain barrier (BBB). This study aimed at preparing and characterizing an innovative composite formulation, associating the liposome and hydrogel approaches, suitable for intranasal administration. Thermosensitive gel formulations were obtained based on a mixture of two hydrophilic polymers (Poloxamer 407, P407 and Poloxamer 188, P188) for a controlled delivery through nasal route via liposomes of an active pharmaceutical ingredient (API) of potential interest for Alzheimer’s disease. The osmolarity and the gelation temperature (T° sol-gel) of formulations, defined in a ternary diagram, were investigated by rheometry and visual determination. Regarding the issue of assays, a mixture composed of P407/P188 (15/1%, w/w) was selected for intranasal administration in terms of T° sol-gel and for the compatibility with the olfactory mucosal (280 ± 20 mOsmol, pH 6). Liposomes of API were prepared by the thin film hydration method. Mucoadhesion studies were performed by using mucin disc, and they showed the good natural mucoadhesive characteristics of in situ gel formulations, which increased when liposomes were added. The study demonstrated successful pharmacotechnical development of a promising API-loaded liposomes in a thermosensitive hydrogel intended for nasal Alzheimer’s disease treatment.

Nose-to-Brain Delivery

Nose-to-brain delivery represents a big challenge. In fact there is a large number of neurological diseases that require therapies in which the drug must reach the brain, avoiding the difficulties due to the blood-brain barrier (BBB) and the problems connected with systemic administration, such as drug bioavailability and side-effects. For these reasons the development of nasal formulations able to deliver the drug directly into the brain is of increasing importance. This Editorial regards the contributions present in the Special Issue "Nose-to-Brain Delivery".

Design and Development of Lomustine Loaded Chitosan Nanoparticles for Efficient Brain Targeting

AIMS

The present research work discussed the preparation of lomustine loaded with chitosan nanoparticles (LNCp) by ionic gelation method with homogenization using the design on experiments by Box-Behnken design.

METHODS

The nanoparticles are evaluated by particle size, zeta potential, surface morphology, drug content, entrapment efficiency and in-vitro drug release.

RESULTS

The FT-IR results support that drug have no interaction with excipients, which are used in the preparation of nanoparticle. The particle size, drug content and encapsulation efficiency of the developed nanoparticles ranged from 190 to 255 nm, 80.88% to 94.02%, and 77.12 to 88.74%, respectively. The drug release rate is diffusion-controlled over 8 hours. The F-value for all of the responses shows that the models are significant. The p-value, less than 0.05 for all the responses reveals the significance of the models. Graphical optimisation is done by desirability plot and overlay plot, which contains optimal values of independent variables with the desirability of 1.

CONCLUSION

In conclusion, the results suggested that the optimised lomustine loaded chitosan nanoparticles are useful for brain targeting hence hold the potential for further research and clinical application.

Chitosan-Based Nanocarriers for Nose to Brain Delivery

In the treatment of brain diseases, most potent drugs that have been developed exhibit poor therapeutic outcomes resulting from the inability of a therapeutic amount of the drug to reach the brain. These drugs do not exhibit targeted drug delivery mechanisms, resulting in a high concentration of the drugs in vital organs leading to drug toxicity. Chitosan (CS) is a natural-based polymer. It has unique properties such as good biodegradability, biocompatibility, mucoadhesive properties, and it has been approved for biomedical applications. It has been used to develop nanocarriers for brain targeting via intranasal administration. Nanocarriers such as nanoparticles, in situ gels, nanoemulsions, and liposomes have been developed. In vitro and in vivo studies revealed that these nanocarriers exhibited enhanced drug uptake to the brain with reduced side effects resulting from the prolonged contact time of the nanocarriers with the nasal mucosa, the surface charge of the nanocarriers, the nano size of the nanocarriers, and their capability to stretch the tight junctions within the nasal mucosa. The aforementioned unique properties make chitosan a potential material for the development of nanocarriers for targeted drug delivery to the brain. This review will focus on chitosan-based carriers for brain targeting.

Formulation Strategies to Improve Nose-to-Brain Delivery of Donepezil

Donepezil (DPZ) is widely used in the treatment of Alzheimer's disease in tablet form for oral administration. The pharmacological efficacy of this drug can be enhanced by the use of intranasal administration because this route makes bypassing the blood⁻brain barrier (BBB) possible. The aim of this study was to develop a nanoemulsion (NE) as well as a nanoemulsion with a combination of bioadhesion and penetration enhancing properties (PNE) in order to facilitate the transport of DPZ from nose-to-brain. Composition of NE was established using three pseudo-ternary diagrams and PNE was developed by incorporating Pluronic F-127 to the aqueous phase. Parameters such as physical properties, stability, in vitro release profile, and ex vivo permeation were determined for both formulations. The tolerability was evaluated by in vitro and in vivo models. DPZ-NE and DPZ-PNE were transparent, monophasic, homogeneous, and physically stable with droplets of nanometric size and spherical shape. DPZ-NE showed Newtonian behavior whereas a shear thinning (pseudoplastic) behavior was observed for DPZ-PNE. The release profile of both formulations followed a hyperbolic kinetic. The permeation and prediction parameters were significantly higher for DPZ-PNE, suggesting the use of polymers to be an effective strategy to improve the bioadhesion and penetration of the drug through nasal mucosa, which consequently increase its bioavailability.

Intranasal Delivery of Genistein-Loaded Nanoparticles as a Potential Preventive System against Neurodegenerative Disorders

Genistein has been reported to have antioxidant and neuroprotective activity. Despite encouraging in vitro and in vivo results, several disadvantages such as poor water solubility, rapid metabolism, and low oral bioavailability limit the clinical application of genistein. The aim of this study was to design and characterize genistein-loaded chitosan nanoparticles for intranasal drug delivery, prepared by the ionic gelation technique by using sodium hexametaphosphate. Nanoparticles were characterized in vitro and their cytotoxicity was tested on PC12 cells. Genistein-loaded nanoparticles were prepared, and sodium hexametaphosphate was used as a valid alternative to well-known cross-linkers. Nanoparticle characteristics as well as their physical stability were affected by formulation composition and manufacturing. Small (mean diameters of 200–300 nm) and homogeneous nanoparticles were obtained and were able to improve genistein penetration through the nasal mucosa as compared to pure genistein. Nanoparticle dispersions showed a pH consistent with the nasal fluid and preserved PC12 cell vitality.

Mucosal Applications of Poloxamer 407-Based Hydrogels: An Overview

Poloxamer 407, also known by the trademark Pluronic^® F127, is a water-soluble, non-ionic triblock copolymer that is made up of a hydrophobic residue of polyoxypropylene (POP) between the two hydrophilic units of polyoxyethylene (POE). Poloxamer 407-based hydrogels exhibit an interesting reversible thermal characteristic. That is, they are liquid at room temperature, but they assume a gel form when administered at body temperature, which makes them attractive candidates as pharmaceutical drug carriers. These systems have been widely investigated in the development of mucoadhesive formulations because they do not irritate the mucosal membranes. Based on these mucoadhesive properties, a simple administration into a specific compartment should maintain the required drug concentration in situ for a prolonged period of time, decreasing the necessary dosages and side effects. Their main limitations are their modest mechanical strength and, notwithstanding their bioadhesive properties, their tendency to succumb to rapid elimination in physiological media. Various technological approaches have been investigated in the attempt to modulate these properties. This review focuses on the application of poloxamer 407-based hydrogels for mucosal drug delivery with particular attention being paid to the latest published works.

Design and Efficacy of Nanogels Formulations for Intranasal Administration

Nanogels are drug delivery systems that can bypass the blood-brain barrier and deliver drugs to the desired site when administered intranasally. They have been used as a drug delivery platform for the management of brain diseases such as Alzheimer disease, migraine, schizophrenia and depression. nanogels have also been developed as vaccine carriers for the protection of bacterial infections such as influenza, meningitis, pneumonia and as veterinary vaccine carriers for the protection of animals from encephalomyelitis and mouth to foot disease. It has been developed as vaccine carriers for the prevention of lifestyle disease such as obesity. Intranasal administration of therapeutics using nanogels for the management of brain diseases revealed that the drug transportation was via the olfactory nerve pathway resulting in rapid drug delivery to the brain with excellent neuroprotective effect. The application of nanogels as vaccine carriers also induced significant responses associated with protective immunity against selected bacterial and viral infections. This review provides a detailed information on the enhanced therapeutic effects, mechanisms and biological efficacy of nanogels for intranasal administration.