Mucoadhesive nanomedicines: characterization and modulation of mucoadhesion at the nanoscale

Chitosan and liposomal delivery systems for epicatechin or propyl gallate targeting localized treatment of vulvovaginal candidiasis

Natural polyphenols are promising alternatives to antifungals for novel treatments of vulvovaginal candidiasis (VVC) in an era of antimicrobial resistance. However, polyphenols are poorly soluble and prone to degradation. To overcome their limitations, we propose incorporation in liposomes. The study aimed to develop chitosan and liposome comprising delivery systems for epicatechin (EC) or propyl gallate (PG) as treatment of VVC. EC was selected for its antioxidative properties and PG as an ester of antifungal gallic acid. To improve formulation retention at vaginal site, mucoadhesive chitosan was introduced into formulation as liposomal surface coating or hydrogel due to intrinsic antifungal properties. These polyphenol-loaded liposomes exhibited an average size of 125 nm with a 64 % entrapment efficiency (for both polyphenols). A sustained in vitro polyphenol release was seen from liposomes, particularly in chitosan hydrogel (p < 0.01 or lower). Viscosity was evaluated since increased viscosity upon mucin contact indicated adhesive bond formation between chitosan and mucin confirming mucoadhesiveness of formulations. Antifungal activity was evaluated by the broth microdilution method on Candida albicans CRM-10231. Unlike PG, incorporation of EC in liposomes enabled antifungal activity. Fungicidal activity of chitosan was confirmed both when used as liposomal coating material and as hydrogel vehicle.

An antibacterial, multifunctional nanogel for efficient treatment of neutrophilic asthma

Asthma is a chronic and heterogeneous disease affecting the lungs and respiratory tract. In particular, the neutrophil subtype of asthma was described as persistent, more severe, and corticosteroid-resistant. Growing evidence suggested that nontypeable Haemophilus influenzae (NTHi) infection contributes to the development of neutrophilic asthma, exacerbating clinical symptoms and increasing the associated medical burden. In this work, arginine-grafted chitosan (CS-Arg) was ionically cross-linked with tris(2-carboxyethyl) phosphine (TCEP), and a highly-efficient antimicrobial agent, poly-ε-L-Lysine (ε-PLL), was incorporated to prepare ε-PLL/CS-Arg/TCEP (ECAT) composite nanogels. The results showed that ECAT nanogels exhibited highly effective inhibition against the proliferation of NTHi, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). In addition, ECAT nanogels could effectively inhibit the formation of mucins aggregates in vitro, suggesting that the nanogel might have the potential to destroy mucin in respiratory disease. Furthermore, in the ovalbumin (OVA)/NTHi-induced Balb/c mice model of neutrophilic asthma, the number of neutrophils in the alveolar lavage fluid and the percentage of inflammatory cells in the blood were effectively reduced by exposure to tower nebulized administration of ECAT nanogels, and reversing airway hyperresponsiveness (AHR) and reducing inflammation in neutrophilic asthma mice. In conclusion, the construction of ECAT nanogels was a feasible anti-infective and anti-inflammatory therapeutic strategy, which demonstrated strong potential in the clinical treatment of neutrophilic asthma.

Recent advances and strategies for nanocarrier-mediated topical therapy and theranostic for posterior eye disease

Posterior eye disorders, such as age-related macular degeneration, diabetic retinopathy, and glaucoma, have a significant impact on human quality of life and are the primary cause of age-related retinal diseases among adults. There is a pressing need for innovative topical approaches to treat posterior eye disorders, as current methods often rely on invasive procedures with inherent risks. Limited success was attained in the realm of topical ophthalmic delivery through non-invasive means. Additionally, there exists a dearth of literature that delves into the potential of this approach for drug delivery and theranostic purposes, or that offers comprehensive design strategies for nanocarrier developers to surmount the significant physiological ocular barriers. This review offers a thorough and up-to-date state-of-the-art overview of 40 studies on therapeutic loaded nanocarriers and theranostic devices that, to the best of our knowledge, represent all successful works that reached posterior eye segments through a topical non-invasive administration. Most importantly, based on the successful literature studies, this review provides a comprehensive summary of the potential design strategies that can be implemented during nanocarrier development to overcome each ocular barrier.

Experimental design approach for development of carboplatin loaded chitosan modified liposomal formulation with improved topical vaginal therapeutic potential

One of the most prevalent cancers affecting women globally is cervical cancer. Cervical cancer is thought to cause 570 000 new cases annually, and standard treatments can have serious side effects. In this work, the main aim is to design, fabrication, and evaluation of carboplatin loaded chitosan coated liposomal formulation (CCLF-I) for vaginal delivery in the treatment of cervical cancer. The particle size and polydispersity index of the CCLF-1 were observed at 269.33 ± 1.15 and 0.40 ± 0.002 nm, respectively. The in vitro mucin binding studies showed good adhesiveness of CCLF-I as compared to plain liposomes (CPLF-I), which was found at 23.49 and 10.80%, respectively. The ex-vivo percent drug permeation from plain liposomal formulation (CPLF-I) was found to be higher in comparison to chitosan coated liposomal formulation which was 56.33% while in CCLF-I it was observed 47.32% this is due to, higher retainability of delivery system (CCLF-I) on targeted site attained by coating of mucoadhesive polymer on liposomes. Ex vivo tissue retention studies exhibited 24.2% of CCLF-I in comparison to 10.34% from plain drug formulation (CPLF-I). The in vivo vaginal retention studies exhibited 14% of drug retention after 24 h from the novel formulation in comparison to 6% from the plain formulation. The developed CCLF-I formulation would open a new avenue in the cervical treatment.

α-Tocopherol-loaded multi-layer nanoemulsion using chitosan, and dextran sulfate: Cellular uptake, antioxidant activity, and in vitro bioaccessibility

The potential of multi-layer nanoemulsions (NEs) for improving the cellular uptake, antioxidant activity, and in vitro bioaccessibility of α-tocopherol (ToC) was examined. ToC-loaded multi-layer NEs were prepared using lecithin (primary-NEs, P-NEs), chitosan (secondary-NEs, S-NEs), and dextran sulfate (tertiary-NEs, T-NEs) as wall materials. The bioadhesion, cellular permeability, and uptake of the multi-layer NEs were significantly higher than that of the free coumarin 6 (C6). As a result of cellular uptake, the mean fluorescence intensity of T-NEs was the highest among the three types of multi-layer NEs and was 9.8-fold higher than that of free C6. The cellular antioxidant abilities of P-NEs, S-NEs, and T-NEs were 40, 45, and 50 %, respectively. Multi-layer nanoencapsulation sustains free fatty acid release after digestion. Moreover, the bioavailability of T-NEs exhibited a two-fold increase compared with that of the free ToC. These findings indicate that by multi-layer NEs using a layer-by-layer method, the cellular uptake, in vitro bioaccessibility, and antioxidant activity of ToC can be improved. Furthermore, T-NEs using chitosan and dextran sulfate can potentially enhance the cellular uptake, in vitro bioaccessibility, and antioxidant activity of ToC. These findings would facilitate the application of multi-layer NEs for lipophilic bioactive compounds using biopolymers.

Nanocarriers transport across the gastrointestinal barriers: The contribution to oral bioavailability via blood circulation and lymphatic pathway

Oral administration is the preferred route of drug delivery in clinical practice due to its noninvasiveness, safety, convenience, and high patient compliance. The gastrointestinal tract (GIT) plays a crucial role in facilitating the targeted delivery of oral drugs. However, the GIT presents multiple barriers that impede drug absorption, including the gastric barrier in the stomach and the mucus and epithelial barriers in the intestine. In recent decades, nanotechnology has emerged as a promising approach for overcoming these challenges by utilizing nanocarrier-based drug delivery systems such as liposomes, micelles, polymeric nanoparticles, solid lipid nanoparticles, and inorganic nanoparticles. Encapsulating drugs within nanocarriers not only protects them from degradation but also enhances their transport and absorption across the GIT, ultimately improving oral bioavailability. The aim of this review is to elucidate the mechanisms underlying nanocarrier-mediated transportation across the GIT into systemic circulation via both the blood circulation and lymphatic pathway.

Nanoparticle-Mediated Strategies for Enhanced Drug Penetration and Retention in the Airway Mucosa

Airway mucus is a complex viscoelastic gel composed mainly of water, glycoproteins, lipids, enzymes, minerals, etc. Among them, glycoproteins are the main factors determining mucus's gel-like rheology. Airway mucus forms a protective barrier by secreting mucin, which represents a barrier for absorption, especially for more lipophilic drugs. It rapidly removes drugs from the airway through the physiological mucus clearance mechanism so drugs cannot remain in the lungs or reach the airway epithelial tissue for a long time. Significant progress has been made in enhancing drug lung deposition recently, but strategies are still needed to help drugs break through the lung mucosal barrier. Based on the physiopathological mechanisms of airway mucus, this paper reviews and summarizes strategies to enhance drug penetration and retention in the airway mucosa mediated by nano-delivery systems, including mucosal permeation systems, mucosal adhesion systems, and enzyme-modified delivery systems. On this basis, the potential and challenges of nano-delivery systems for improving airway mucus clearance are revealed. New ideas and approaches are provided for designing novel nano-delivery systems that effectively improve drug retention and penetration in the airway mucus layer.

Impact of local drug delivery and natural agents as new target strategies against periodontitis: new challenges for personalized therapeutic approach

Periodontitis is a persistent inflammation of the soft tissue around the teeth that affects 60% of the population in the globe. The self-maintenance of the inflammatory process can cause periodontal damage from the alveolar bone resorption to tooth loss in order to contrast the effects of periodontitis, the main therapy used is scaling and root planing (SRP). At the same time, studying the physiopathology of periodontitis has shown the possibility of using a local drug delivery system as an adjunctive therapy. Using local drug delivery devices in conjunction with SRP therapy for periodontitis is a potential tool since it increases drug efficacy and minimizes negative effects by managing drug release. This review emphasized how the use of local drug delivery agents and natural agents could be promising adjuvants for the treatment of periodontitis patients affected or not by cardiovascular disease, diabetes, and other system problems. Moreover, the review evidences the current issues and new ideas that can inspire potential later study for both basic research and clinical practice for a tailored approach.

Parametric Drug Release Optimization of Anti-Inflammatory Drugs by Gold Nanoparticles for Topically Applied Ocular Therapy

Eye drops represent 90% of all currently used ophthalmic treatments. Only 0.02% of therapeutic molecules contained in eye drops reach the eye anterior chamber despite their high concentration. The tear film efficiently protects the cornea, reducing access to the target. Thereby, the increase in the drug bioavailability and efficiency must come from the mucoadhesion optimization of the drug delivery system. The gold nanoparticles, used as a drug delivery system in this study, already showcased ultrastable and mucoadhesive properties. The goal was to study the gold nanoparticles' ability to release two specific ophthalmic drugs, flurbiprofen and ketorolac. The parameters of interest were those involving the loading conditions, the gold nanoparticles properties, and the release experimental conditions. The drug release was measured using an in vitro model based on dialysis bags coupled with UV-visible spectroscopy. Gold nanoparticles showed an ability to release different molecules, whether hydrophobic or hydrophilic, in passive or active drug release environments. Based on these preliminary results, gold nanoparticles could represent a promising drug delivery system for ketorolac and flurbiprofen when topically applied through eye drops.

Construction of lipid-biomacromolecular compounds for loading and delivery of carotenoids: Preparation methods, structural properties, and absorption-enhancing mechanisms

Due to the unstable chemical properties and poor water solubility of carotenoids, their processing adaptation and oral bioavailability are poor, limiting their application in hydrophilic food systems. Lipid-biomacromolecular compounds can be excellent carriers for carotenoid delivery by taking full advantage of the solubilization of lipids to non-polar nutrients and the water dispersion and gastrointestinal controlled release properties of biomacromolecules. This paper reviewed the research progress of lipid-biomacromolecular compounds as encapsulation and delivery carriers of carotenoids and summarized the material selection and preparation methods for biomacromolecular compounds. By considering the interaction between the two, this paper briefly discussed the effect of these compounds on carotenoid water solubility, stability, and bioavailability, emphasizing their delivery effect on carotenoids. Finally, various challenges and future trends of lipid-biomacromolecular compounds as carotenoid delivery carriers were discussed, providing new insight into efficient loading and delivery of carotenoids.

The Mucoadhesive Nanoparticle-Based Delivery System in the Development of Mucosal Vaccines

Mucosal tissue constitutes the largest interface between the body and the external environment, regulating the entry of pathogens, particles, and molecules. Mucosal immunization is the most effective way to trigger a protective mucosal immune response. However, the majority of the currently licensed vaccines are recommended to be administered by intramuscular injection, which has obvious shortcomings, such as high production costs, low patient compliance, and lack of mucosal immune response. Strategies for eliciting mucosal and systemic immune responses are being developed, including appropriate vaccine adjuvant, delivery system, and bacterial or viral vectors. Biodegradable mucoadhesive nanoparticles (NPs) are the most promising candidate for vaccine delivery systems due to their inherent immune adjuvant property and the ability to protect the antigen from degradation, sustain the release of loaded antigen, and increase the residence time of antigen at the administration site. The current review outlined the complex structure of mucosa, the mechanism of interaction between NPs and mucosa, factors affecting the mucoadhesion of NPs, and the application of the delivery system based on mucoadhesive NPs in the field of vaccines. Moreover, this review demonstrated that the biodegradable and mucoadhesive NP-based delivery system has the potential for mucosal administration of vaccines.

Mucoadhesive, Antibacterial, and Reductive Nanogels as a Mucolytic Agent for Efficient Nebulized Therapy to Combat Allergic Asthma

Asthma is an intractable disease involving the infiltration of inflammatory cells and mucus plugging. Despite small molecular mucolytics having the ability to break the disulfide bonds of mucins, offering a potential way to overcome the airflow obstruction and airway infection, these mucolytics have limited therapeutic effects in vivo. Therefore, in this work, arginine-grafted chitosan (CS-Arg) is ionically cross-linked with tris(2-carboxyethyl)phosphine (TCEP) to obtain nanogels as a mucolytic agent. The positively charged nanogels effectively inhibit the formation of large aggregates of mucin in vitro, probably thanks to the formation of an ionic interaction between CS-Arg and mucin, as well as the breakage of disulfide bonds in mucin by the reductive TCEP. Moreover, the nanogels show good cytocompatibility at concentrations up to 5 mg mL^-1, exhibiting effective inhibitory effects against the proliferation of both Staphylococcus aureus and Escherichia coli at 5 mg mL^-1. After the administration of the nanogels by nebulization into a Balb/c mouse model with allergic asthma, they can efficiently reduce the mucus obstruction in bronchioles and alveoli and relieve airway inflammation. Therefore, these CS-Arg/TCEP nanogels potentially represent a promising mucolytic agent for the efficient treatment of allergic asthma and other muco-obstructive diseases.

Advances and future perspectives in epithelial drug delivery

Epithelial surfaces protect exposed tissues in the body against intrusion of foreign materials, including xenobiotics, pollen and microbiota. The relative permeability of the various epithelia reflects their extent of exposure to the external environment and is in the ranking: intestinal≈ nasal ≥ bronchial ≥ tracheal > vaginal ≥ rectal > blood-perilymph barrier (otic), corneal > buccal > skin. Each epithelium also varies in their morphology, biochemistry, physiology, immunology and external fluid in line with their function. Each epithelium is also used as drug delivery sites to treat local conditions and, in some cases, for systemic delivery. The associated delivery systems have had to evolve to enable the delivery of larger drugs and biologicals, such as peptides, proteins, antibodies and biologicals and now include a range of physical, chemical, electrical, light, sound and other enhancement technologies. In addition, the quality-by-design approach to product regulation and the growth of generic products have also fostered advancement in epithelial drug delivery systems.

Therapeutic nanoparticles in the brain: A review of types, physicochemical properties and challenges

One of the main obstacles in the treatment of neurological diseases, perhaps the biggest one, is the delivery of therapeutic compounds to the central nervous system, and nanoparticles are promising tools to overcome this challenge. Different types of nanoparticles may be used as delivery systems, including liposomes, carbon nanotubes, and dendrimers. Nevertheless, these nanoparticles must display characteristics to be useful in brain drug delivery, such as stability, permeability to blood vessels, biocompatibility, and specificity. All of these aspects are intrinsically related to the physicochemical properties of nanoformulations: size, composition, electric charge, hydrophobicity, mucoadherence, permeability to the blood-brain barrier, and many others. Furthermore, there are challenging hindrances involved in the development and application of nanoparticles - hence the importance of studying and understanding these pharmaceutical tools.

Combination and nanotechnology based pharmaceutical strategies for combating respiratory bacterial biofilm infections

Respiratory infections are one of the major global health problems. Among them, chronic respiratory infections caused by biofilm formation are difficult to treat because of both drug tolerance and poor drug penetration into the complex biofilm structure. A major part of the current research on combating respiratory biofilm infections have been focused on destroying the matrix of extracellular polymeric substance and eDNA of the biofilm or promoting the penetration of antibiotics through the extracellular polymeric substance via delivery technologies in order to kill the bacteria inside. There are also experimental data showing that certain inhaled antibiotics with simple formulations can effectively penetrate EPS to kill surficially located bacteria and centrally located dormant bacteria or persisters. This article aims to review recent advances in the pharmaceutical strategies for combating respiratory biofilm infections with a focus on nanotechnology-based drug delivery approaches. The formation and characteristics of bacterial biofilm infections in the airway mucus are presented, which is followed by a brief review on the current clinical approaches to treat respiratory biofilm infections by surgical removal and antimicrobial therapy, and also the emerging clinical treatment approaches. The current combination of antibiotics and non-antibiotic adjuvants to combat respiratory biofilm infections are also discussed.

Enhanced Mucosal Transport of Polysaccharide-Calcium Phosphate Nanocomposites for Oral Vaccination

Oral vaccine has attracted much interest, as it can stimulate both mucosal and systemic immunity with noninvasive and good patient compliance. However, the oral vaccine efficiency is strongly constrained by the low absorption of antigens in the small intestine due to the mucosal barriers. Physicochemical characteristics of nanoparticles (NPs) have strong effects on antigen mucosal penetration, helping to improve immune response. However, surface functions of NPs on mucosal transportation have not been clearly understood. In this work, we elaborately investigated how the surface characteristics of mucoadhesive chitosan and its derivant act on oral antigen absorption and immune response. Core-shell chitosan- and o-carboxymethyl chitosan-coated calcium phosphate (CaP) nanocomposites have been fabricated to investigate the surface property effect on protein antigen delivery using the oral route. The interaction between polymer-coated CaP NPs and the intestinal mucosal layer was studied using mucin absorption, NP diffusion through the mucus layer, NP permeability across the epithelium monolayer, and their cellular uptake by antigen presenting cells in detail. Ex vivo mucosa distribution and in vivo oral immunization of polymer-coated CaP nanocomposites were further examined to demonstrate that the surface property of NPs affects CaP diffusion and penetration through the mucosal layer. As expected, OVA orally delivered by polymer-coated CaP nanocomposites improved the response of mucosal immunity compared to antigen OVA itself in vivo.

Improved Bioavailability of Poorly Soluble Drugs through Gastrointestinal Muco-Adhesion of Lipid Nanoparticles

Gastrointestinal absorption remains indispensable in the systemic delivery of most drugs, even though it presents several challenges that, paradoxically, may also provide opportunities that can be exploited to achieve maximal bioavailability. Drug delivery systems made from nanoparticle carriers and especially, lipid carriers, have the potential to traverse gastrointestinal barriers and deploy in the lymphatic pathway, which aptly, is free from first pass via the liver. Several poorly soluble drugs have presented improved systemic bioavailability when couriered in lipid nanoparticle carriers. In this review, we propose an additional frontier to enhancing the bioavailability of poorly soluble drugs when encapsulated in lipid nano-carriers by imparting muco-adhesion to the particles through application of appropriate polymeric coating to the lipid carrier. The combined effect of gastrointestinal muco-adhesion followed by lymphatic absorption is a promising approach to improving systemic bioavailability of poorly soluble drugs following oral administration. Evidence to the potential of this approach is backed-up by recent studies within the review.

Mucoadhesive properties of nanogels based on stimuli-sensitive glycosaminoglycan-graft-pNIPAAm copolymers

Mucoadhesive formulations capable of situ gelation are promising for improving ocular drug delivery. Here we investigated two types of nanogels based on anionic glycosaminoglycans with grafted thermo-responsive poly(N-isopropylacrylamide) chains. One type of nanogels were formed by thermo-induced gelling of heparin-graft-poly(N-isopropylacrylamide) and chondroitin sulfate-graft-poly(N-isopropylacrylamide) copolymers. Another type of nanogels was based on the same copolymers, but terminal groups of thermosensitive macromolecular chains were modified to form covalent disulfide cross-links. All types of nanogels were studied towards their ability to encapsulate and release model drug - dexamethasone. Mucoadhesivity of both thermo-gelled and covalently cross-linked polymeric systems, as well as their ability to interact with dexamethasone, was assessed by microscale thermophoresis (MST). Mucoadhesion properties were also evaluated by isothermal titration calorimetry (ITC), which were in good correlation with MST data. The presence of disulfide linkages and thiol groups were shown to favor improved binding of cross-linked nanogels to mucin. Moreover, in vivo intraocular pressure studies showed that presence of polymers in solution can alter the ocular absorption of carbonic anhydrase inhibitor from eyedrops. The pharmacological effect was in line with mucoadhesive properties of these copolymers.

Ocular drug delivery to the anterior segment using nanocarriers: A mucoadhesive/mucopenetrative perspective

There is a growing demand for effective treatments for ocular conditions that improve patient compliance and reduce side-effects. While methods such as implants and injections have proven effective, topical administration remains the method of choice for the delivery of therapeutics to the anterior segment of the eye. However, topical administration suffers from multiple drawbacks including low bioavailability of the target therapeutic, systemic toxicity, and the requirement for high therapeutic doses due to the effective clearance mechanisms that exist in the eye. Nanoparticles that have tunable mucoadhesion and/or mucopenetration offer outstanding potential to overcome the anatomical and physiological barriers present to improve ocular bioavailability, reduce toxicity, and increase ocular retention, among other benefits. The current review highlights recent advances in the field of developing nanocarriers with tunable mucoadhesion and mucopenetration for drug delivery to the eye.

Polycaprolactone/polyethylene-glycol capsules made by injection molding: A drug release modeling

Polycaprolactone (PCL)/Polyethylene-glycol (PEG) capsules are prepared by injection molding with the aim of producing Colon-specific Drug Delivery Systems (CDDS). PCL, being a gastroresistant polymer, is suitable for this kind of delivery; however, the release from PCL devices is too slow. For this reason, in this paper, different percentages of PEG (10, 20 and 30 w/w %) have been added to obtain blends able to modulate the release from PCL-based capsules. The drug release rate from PCL/PEG capsules increases with the PEG percentage; using PCL/PEG 70/30 w/w capsules, the drug release is suitable for CDDS. The experimental data have been modelled, accounting for three steps: the penetration of the release medium into the capsule, the drug dissolution in the release medium, and the drug migration from the capsule to the medium. The model accurately describes the data, showing a mass transfer coefficient strongly dependent on the PEG percentage.

Current approaches in lipid-based nanocarriers for oral drug delivery

Lipid-based nanocarriers have gained much interest as carriers of drugs with poor oral bioavailability because of their remarkable advantages like low toxicity, affordable scale-up manufacture, strong biocompatibility or high drug loading efficiency. The potential of these nanocarriers lies in their ability to improve the gastrointestinal stability, solubility and permeability of their cargo drugs. However, achieving efficient oral drug delivery through lipid-based nanocarriers is a challenging task, since they encounter multiple physicochemical barriers along the gastrointestinal tract, e.g. the gastric acidic content, the intestinal mucus layer or the enzymatic degradation, that they must surmount to reach their target. These limitations may be turned into opportunities through a rational design of lipid-based nanocarriers. For that purpose, this review focuses on the main challenges of the oral route indicating the strategies undertaken for lipid-based nanocarriers in order to overcome them. Understanding their shortcomings and identifying their strengths will determine the future clinical success of lipid-based nanocarriers.

Local drug delivery systems as therapeutic strategies against periodontitis: A systematic review

Periodontitis is a chronic inflammation of the soft tissue surrounding and supporting the teeth, which causes periodontal structural damage, alveolar bone resorption, and even tooth loss. Its prevalence is very high, with nearly 60% of the global population affected. Hence, periodontitis is an important public health concern, and the development of effective healing treatments for oral diseases is a major target of the health sciences. Currently, the application of local drug delivery systems (LDDS) as an adjunctive therapy to scaling and root planning (SRP) in periodontitis is a promising strategy, giving higher efficacy and fewer side effects by controlling drug release. The cornerstone of successful periodontitis therapy is to select an appropriate bioactive agent and route of administration. In this context, this review highlights applications of LDDS with different properties in the treatment of periodontitis with or without systemic diseases, in order to reveal existing challenges and future research directions.

Nanoparticle-mediated pulmonary drug delivery: state of the art towards efficient treatment of recalcitrant respiratory tract bacterial infections

Recalcitrant respiratory tract infections caused by bacteria have emerged as one of the greatest health challenges worldwide. Aerosolized antimicrobial therapy is becoming increasingly attractive to combat such infections, as it allows targeted delivery of high drug concentrations to the infected organ while limiting systemic exposure. However, successful aerosolized antimicrobial therapy is still challenged by the diverse biological barriers in infected lungs. Nanoparticle-mediated pulmonary drug delivery is gaining increasing attention as a means to overcome the biological barriers and accomplish site-specific drug delivery by controlling release of the loaded drug(s) at the target site. With the aim to summarize emerging efforts in combating respiratory tract infections by using nanoparticle-mediated pulmonary delivery strategies, this review provides a brief introduction to the bacterial infection-related pulmonary diseases and the biological barriers for effective treatment of recalcitrant respiratory tract infections. This is followed by a summary of recent advances in design of inhalable nanoparticle-based drug delivery systems that overcome the biological barriers and increase drug bioavailability. Finally, challenges for the translation from exploratory laboratory research to clinical application are also discussed and potential solutions proposed.

N-(2-hydroxy)-propyl-3-trimethylammonium, O-palmitoyl chitosan: Synthesis, physicochemical and biological properties

Two samples of N-(2-hydroxy)-propyl-3-trimethylammonium, O-palmitoyl chitosan (DPCat) with different average degrees of quaternization named as DPCat35 (DQ¯ = 35%) and DPCat80 (DQ¯ = 80%), were successfully synthesized by reacting glycidyltrimethylammonium chloride (GTMAC) with O-palmitoyl chitosan (DPCh) derivative (DS¯ = 12%). Such amphiphilic derivatives of chitosan were fully water-soluble at 1.0 < pH < 12.0 and showed significant electrostatic stability enhancement of a self-assembly micellar nanostructure (100-320 nm) due to its positively-charged out-layer. In vitro mucoadhesive and cytotoxicity essays toward healthy fibroblast cells (Balb/C 3T3 clone A31 cell), human prostate cancer (DU145) and liver cancer (HepG2/C3A) cell lines revealed that the biological properties of DPCat derivatives were strongly dependent on DQ¯. Additionally, DPCat35 had better interactions with the biological tissue and with mucin glycoproteins at pH 7.4 as well as exhibited potential to be used on the development of drug delivery systems for prostate and liver cancer treatment.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

Design, Optimization, and Characterization of Lactoferrin-Loaded Chitosan/TPP and Chitosan/Sulfobutylether-β-cyclodextrin Nanoparticles as a Pharmacological Alternative for Keratoconus Treatment

This research study describes the design, optimization, and characterization of two different types of chitosan-based nanoparticles as novel drug delivery systems of a protein drug, lactoferrin. A preclinical consistent base was obtained for both nanosystems, being considered as the first pharmacological treatment for keratoconus as an alternative to current invasive clinical methods. Both types of nanoparticles were obtained via the ionotropic gelation technique. The size and morphology of the nanoparticles were studied as a function of the preparation conditions. A mean size of 180.73 ± 40.67 nm, a size distribution [polydispersity index (PDI)] of 0.170 ± 0.067, and positive ζ-potential values, ranging from 17.13 to 19.89 mV, were achieved. Lactoferrin was successfully incorporated into both types of nanocarriers. In vitro release profiles showed a lactoferrin enhanced, prolonged, and controlled delivery from the polymeric matrix. These formulations also demonstrated no stability or cytotoxicity problems, as well as appropriate mucoadhesive properties, with a high permanence time in the ocular surface. Thus, both types of nanoparticles may be considered as nanocarriers for the controlled release of lactoferrin as novel topical ophthalmic drug delivery systems.

Lactobacillus crispatus BC1 Biosurfactant Delivered by Hyalurosomes: An Advanced Strategy to Counteract Candida Biofilm

The emergence of resistance to antifungal drugs has made the treatment of vulvovaginal candidiasis (VVC) very challenging. Among natural substances, biosurfactants (BS) produced by Lactobacillus have gained increasing interest in counteracting Candida infections for their proven anti-adhesive properties and safety profile. In the present study, liposomes (LP-BS) or liposomes coated with hyaluronic acid (HY-LP-BS) were prepared in the presence of the BS isolated from the vaginal strain Lactobacillus crispatus BC1 and characterized in terms of size, ζ potential, stability and mucoadhesion. The anti-biofilm activity of free BS, LP-BS and HY-LP-BS was investigated against different Candida albicans and non-albicans strains (C. glabrata, C. lusitaniae, C. tropicalis, C. krusei and C. parapsilosis), clinically isolated from patients affected by VVC. The inhibition of biofilm formation and the dispersal of pre-formed biofilm were evaluated. The obtained phospholipid vesicles showed suitable size for vaginal application and good stability over the storage period. HY-LP-BS exhibited good mucoadhesive properties and the best anti-biofilm profile, both in preventing or limiting the surface colonization by a broad spectrum of Candida species. In conclusion, the formulation of a novel antifungal agent derived from the vaginal microbiota into mucoadhesive nanocarriers appears to be a promising biotherapeutic strategy to counteract vulvovaginal candidiasis.

Effect of α-tocopherol on the physicochemical, antioxidant and antibacterial properties of levofloxacin loaded hybrid lipid nanocarriers

Non-toxic hybrid lipidic nanoparticles become a promising tool for enhanced lung delivery of levofloxacin in combination with antioxidant properties.

Nanoparticle-Mediated Drug Delivery: Blood-Brain Barrier as the Main Obstacle to Treating Infectious Diseases in CNS

BACKGROUND

Parasitic infections affecting the central nervous system (CNS) present high morbidity and mortality rates and affect millions of people worldwide. The most important parasites affecting the CNS are protozoans (Plasmodium sp., Toxoplasma gondii, Trypanosoma brucei), cestodes (Taenia solium) and free-living amoebae (Acantamoeba spp., Balamuthia mandrillaris and Naegleria fowleri). Current therapeutic regimens include the use of traditional chemicals or natural compounds that have very limited access to the CNS, despite their elevated toxicity to the host. Improvements are needed in drug administration and formulations to treat these infections and to allow the drug to cross the blood-brain barrier (BBB).

METHODS

This work aims to elucidate the recent advancements in the use of nanoparticles as nanoscaled drug delivery systems (NDDS) for treating and controlling the parasitic infections that affect the CNS, addressing not only the nature and composition of the polymer chosen, but also the mechanisms by which these nanoparticles may cross the BBB and reach the infected tissue.

RESULTS

There is a strong evidence in the literature demonstrating the potential usefulness of polymeric nanoparticles as functional carriers of drugs to the CNS. Some of them demonstrated the mechanisms by which drugloaded nanoparticles access the CNS and control the infection by using in vivo models, while others only describe the pharmacological ability of these particles to be utilized in in vitro environments.

CONCLUSION

The scarcity of the studies trying to elucidate the compatibility as well as the exact mechanisms by which NDDS might be entering the CNS infected by parasites reveals new possibilities for further exploratory projects. There is an urgent need for new investments and motivations for applying nanotechnology to control parasitic infectious diseases worldwide.

The Antimicrobial Properties of Chitosan Can be Tailored by Formulation

Topical administration of drugs into the vagina can provide local therapy of vaginal infections, preventing the possible systemic side effects of the drugs. The natural polysaccharide chitosan is known for its excellent mucoadhesive properties, safety profile, and antibacterial effects, and thus it can be utilized in improving localized vaginal therapy by prolonging the residence time of a drug at the vaginal site while acting as an antimicrobial in synergy. Therefore, we aimed to explore the potential of chitosan, namely chitosan-coated liposomes and chitosan hydrogel, as an excipient with intrinsic antimicrobial properties. Liposomes were prepared by the thin-film hydration method followed by vesicle size reduction by sonication to the desired size, approximately 200 nm, and coated with chitosan (0.01, 0.03, 0.1, and 0.3%, w/v, respectively). The mucoadhesive properties of chitosan-coated liposomes were determined through their binding efficiency to mucin compared to non-coated liposomes. Non-coated liposomal suspensions were incorporated in chitosan hydrogels forming the liposomes-in-hydrogel formulations, which were further assessed for their texture properties in the presence of biological fluid simulants. The antibacterial effect of chitosan-coated liposomes (0.03%, 0.1% and 0.3%, w/v) and chitosan hydrogels (0.1% and 0.3%, w/w) on Staphylococcus epidermidis and Staphylococcus aureus was successfully confirmed.

Nanoparticles for the regulation of intestinal inflammation: opportunities and challenges

Prevalence of chronic inflammation of the gastrointestinal tract is increasing, emerging as a public health challenge. Conventional drug delivery systems targeting the colon have improved the treatment of inflammatory bowel disease. However, therapy frequently results in inconsistent efficacy and toxicity problems. Novel approaches based on nanoparticles offer several advantages over conventional dosage forms due to their ability to selectively target inflamed tissues. Several formulation efforts have been made in order to obtain increasingly selective nanosized systems, some with promising results in animal models of colitis. Despite all advances, no nanomedicines are yet approved for clinical use in inflammatory bowel disease. This review discusses the most recent efforts made toward the development of nanoparticles for regulating chronic intestinal inflammation.

Rational Development of Liposomal Hydrogels: A Strategy for Topical Vaginal Antiretroviral Drug Delivery in the Context of HIV Prevention

HIV/AIDS stands as a global burden, and vaginal microbicides constitute a promising strategy for topical pre-exposure prophylaxis. Preceding the development of a microbicide containing tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC), in silico and in vitro studies were performed to evaluate the physicochemical characteristics of both drugs, and to study their biophysical impact in lipid model systems. Results from these pre-formulation studies defined hydrogels as adequate vehicles to incorporate TDF-loaded liposomes and FTC. After studying interactions with mucin, zwitterionic liposomes with a mean diameter of 134 ± 13 nm, an encapsulation TDF efficiency of approximately 84%, and a transition temperature of 41 °C were selected. The chosen liposomal formulation was non-cytotoxic to HEC-1-A and CaSki cells, and was able to favor TDF permeation across polysulfone membranes (J_ss = 9.9 μg·cm^-2·h^-1). After the incorporation of TDF-loaded liposomes and FTC in carbomer hydrogels, the drug release profile was sustained over time, reaching around 60% for both drugs within 3-6 h, and best fitting the Weibull model. Moreover, liposomal hydrogels featured pseudoplastic profiles that were deemed suitable for topical application. Overall, the proposed liposomal hydrogels may constitute a promising formulation for the vaginal co-delivery of TDF/FTC.

Challenges and strategies in drug delivery systems for treatment of pulmonary infections

Inhalation therapy has been reported as the most effective treatment for respiratory bacterial infections due to the increasing relevance of drug bioavailability. Drug delivery systems (DDS) have the capacity to overcome pulmonary biological barriers limiting the bioavailability of inhaled anti-infectives. This is important to eradicate bacterial infections and to prevent the development of bacterial resistance. Despite substantial efforts in the field, the current state-of-the-art often fails to achieve those goals, and we still observe increasing bacterial resistance. We give a brief insight on benefits and challenges in pulmonary delivery of anti-infectives. In the context of drug delivery development for pulmonary infections, particularly focusing on Pseudomonas aeruginosa (PA) infections, this mini review will critically discuss the main requirements, as well as the recent strategies of drug delivery system synthesis and preparation. Finally, interaction of DDS with crucial pulmonary biological barriers will be of great importance for the success of future applications of the developed DDS.

Localized Therapy of Vaginal Infections and Inflammation: Liposomes-In-Hydrogel Delivery System for Polyphenols

Natural polyphenols, such as resveratrol (RES) or epicatechin (EPI), are attractive for treatments of various diseases, including vaginal infections and inflammation, because of their strong anti-oxidative and anti-inflammatory properties. However, their low solubility and consequent poor bioavailability limit their therapeutic uses. To overcome these limitations, a vaginal delivery system comprising either RES or EPI liposomes-in-hydrogel was developed. This system permits therapeutic action of both liposomal polyphenol (RES or EPI) and chitosan-based hydrogel. Liposomes of around 200 nm and entrapment efficiency of 81% and 77% for RES and EPI, respectively, were incorporated into chitosan hydrogel, respectively. Medium molecular weight chitosan (2.5%, w/w) was found to have optimal texture properties and mucoadhesiveness in ex vivo conditions. The in vitro release studies confirmed the sustained release of polyphenols from the system. Both liposomal polyphenols and polyphenols-in-liposomes-in-hydrogel exhibited only minor effects on cell toxicity. EPI showed superior radical scavenging activity at lower concentrations compared to antioxidants vitamin C and E. Anti-inflammatory activity expressed as the inhibitory activity of formulations on the NO production in the LPS-induced macrophages (RAW 264.7) confirmed the superiority of EPI liposomes-in-hydrogel. The plain liposomes-in-hydrogel also exhibited potent anti-inflammatory activity, suggesting that chitosan hydrogel acts in synergy regarding anti-inflammatory effect of formulation.

Intestinal uptake of barley protein-based nanoparticles for β-carotene delivery

Our previous study introduced a barley protein microparticle for encapsulation of hydrophobic drug/nutraceutical, which could release nanoparticles upon gastric digestion and deliver encapsulated compound to a simulated intestinal environment intact. This work focused on evaluating the potential of liberated nanoparticles to improve the absorption of encapsulated compounds (e.g., β-carotene) using in vitro Caco-2 cell and ex vivo small intestine models. Nanoparticles obtained from gastric digestion of barley protein microparticles had a spherical shape and an average size of 351 nm. Nanoparticles showed low cytotoxicity in Caco-2 cells and their cellular uptake was dependent on time, concentration and temperature. In a Caco-2 cell monolayer model, significantly greater uptake and transport of β-carotene were observed when it was delivered by nanoparticles (15%), compared to free β-carotene suspension (2.6%). In an ex vivo rat jejunum model, nanoparticles showed the capacity to retain in small intestinal tissue. Approximately 2.24 and 6.04 μg nanoparticle were able to permeate through each cm² intestinal tissue and translocate to the serosal side after 60 and 90 min, respectively. Results from this study demonstrated the absorption improving effect of the barley protein nanoparticles and suggested their potential as vehicles for hydrophobic compounds.

Insights into gold nanoparticles as a mucoadhesive system

A large number of drugs are administered on different mucosal surfaces. However, due to the poor mucoadhesion of the current formulations, their bioavailability is often very low. The development of efficient mucoadhesive drug delivery systems is thus crucial for improving the performance of these drugs. The mucoadhesive properties of gold nanoparticles were investigated. First, two types of gold nanoparticles were synthesized: AuNP1 and AuNP2. AuNP1 only contain internal thiol groups on their metallic core, and AuNP2 contain both internal and peripheral thiol groups. Different protocols based on an adapted quantitative colorimetric method, UV-visible and fluorescence spectroscopies were then developed to gather information on their mucoadhesive properties. Moreover, a global correction factor for the inner filter effect in spectrofluorimetry was proposed, and the data obtained were compared to those commonly used in the literature. Mucins deeply interact with AuNP1, perturbing their core, whereas they remain at the periphery of AuNP2. The quantitative method suggests that a larger number of mucins interact with AuNP2. The establishment of this protocol could be applied to assess the mucoadhesive properties of other stable molecules. This mucoadhesive property of gold nanoparticles could be combined with their drug delivery ability in order to improve the medication administered on mucosa.