Nasal drug delivery: Design of a novel mucoadhesive and in situ gelling polymer

Development of a nasal spray based on cyclodextrin/hydrophobically-modified hydroxypropyl-methyl cellulose for the prevention of viral respiratory infections

The work aims to develop mucoadhesive and thermo-responsive in situ gelling systems, using hydrophobically-modified hydroxypropyl-methyl cellulose (Sangelose, SG) and beta-cyclodextrin (β-CD) derivatives, for preventing viral respiratory infections. Eight SG/CD systems with varying CD concentrations were evaluated for rheological properties, mucoadhesiveness, spreadability and sprayability via nasal devices; cytotoxicity was in vitro investigated on reconstituted nasal epithelia. Additionally, droplet size distribution and spray deposition were assessed for the most promising systems. The addition of β-CD derivatives to SG solution was responsible for a rapid sol-gel transition within a physiological temperature range (29-34 °C). SG/CD systems were characterized by a prevalence of the elastic properties on the viscous ones at 37 °C, functional to the formation of a protective gel barrier on the mucosa. The most promising systems showed sprayability and spreadability suitable for nasal administration, while in vitro tests demonstrated their non-toxicity. All the sprays were characterized by droplets with size >100 μm, functional to avoid droplet exhalation or lung deposition; spray deposition studies confirmed uniform distribution across nasal turbinates, crucial for trapping inhaled particles. In conclusion, a mucoadhesive and thermo-responsive in situ gelling system consisting of SG and β-CD derivatives was successfully developed as promising nasal spray for the prevention of respiratory infections.

Development of thiolated xanthan gum-stearylamine conjugate based mucoadhesive system for the delivery of biochanin-A to melanoma cells

Recently, instead of creating new active compounds, scientists have been working to increase the bioavailability and residence time of existing drugs by modifying the characteristics of the delivery systems. In the present study, a novel mucoadhesive bioconjugate (SN-XG-SH) was synthesized by functionalizing a polysaccharide xanthan gum (XG) with cysteamine hydrochloride (CYS) and a lipid stearylamine (SN). FTIR, CHNS and 1H NMR studies confirmed the successful synthesis of SN-XG-SH. Mucoadhesion of the thiolated XG was enhanced and evaluated by different methods. Disulfide bond formation between thiolated XG and skin mucus enhances mucoadhesive behavior. The mucoadhesive bioconjugate was used to prepare nanoparticles for the delivery of hydrophobic biochanin-A (Bio-A) for the treatment of melanoma. The thiolated xanthan gum nanoparticles also demonstrated high drug entrapment efficiency, sustained drug release, and high storage stability. The drug loaded nanoparticles (Bio-A@TXNPs) significantly improved the cytotoxicity of Bio-A against human epidermoid cancer cells (A431 cells) by inducing apoptosis and changing mitochondrial membrane potential. In conclusion, thiolation of XG improves its mucoadhesive properties and prolongs the release of Bio-A. Thus, thiolated XG conjugate has a high potential for use as a bioadhesive agent in controlled and localised delivery of drugs in different skin diseases including melanoma.

Green synthesis of nano-based drug delivery systems developed for hepatocellular carcinoma treatment: a review

This review presents an overview of one of the effective strategies for improving the anticancer impact of many drugs including sorafenib using a drug delivery system by employing nanoparticles that is produced through a biological system. The biological process has a lot of benefits, including being inexpensive and safe for the environment. Sorafenib is one of a multi-kinase inhibitor that inhibits molecularly targeted kinases. Because of its poor pharmacokinetic characteristics, such as fast elimination and limited water solubility, the bioavailability of Sorafenib is extremely low. More intelligent nano formulations of sorafenib have been developed to boost both the drug's target ability and bioavailability. Researchers in a wide variety of sectors, including nanomedicine, have recently been interested in the topic of nanotechnology. It is possible for the body to develop resistance to widely used drugs available for treatment of liver cancer, including sorafenib. As a result, our goal of this research is to highlight the efficacy of nanomedicine-based drug delivery system to enhance drug's cancer-fighting properties. Because of their magnetic properties, certain nanoparticle materials can be employed as a carrier for the medicine to the exact place where the cancer is located. This can lower the amount of the drug that is administered with no impact on the normal cells.

Nano-Enabled Antivirals for Overcoming Antibody Escaped Mutations Based SARS-CoV-2 Waves

This review discusses receptor-binding domain (RBD) mutations related to the emergence of various SARS-CoV-2 variants, which have been highlighted as a major cause of repetitive clinical waves of COVID-19. Our perusal of the literature reveals that most variants were able to escape neutralizing antibodies developed after immunization or natural exposure, pointing to the need for a sustainable technological solution to overcome this crisis. This review, therefore, focuses on nanotechnology and the development of antiviral nanomaterials with physical antagonistic features of viral replication checkpoints as such a solution. Our detailed discussion of SARS-CoV-2 replication and pathogenesis highlights four distinct checkpoints, the S protein (ACE2 receptor coupling), the RBD motif (ACE2 receptor coupling), ACE2 coupling, and the S protein cleavage site, as targets for the development of nano-enabled solutions that, for example, prevent viral attachment and fusion with the host cell by either blocking viral RBD/spike proteins or cellular ACE2 receptors. As proof of this concept, we highlight applications of several nanomaterials, such as metal and metal oxide nanoparticles, carbon-based nanoparticles, carbon nanotubes, fullerene, carbon dots, quantum dots, polymeric nanoparticles, lipid-based, polymer-based, lipid-polymer hybrid-based, surface-modified nanoparticles that have already been employed to control viral infections. These nanoparticles were developed to inhibit receptor-mediated host-virus attachments and cell fusion, the uncoating of the virus, viral gene expression, protein synthesis, the assembly of progeny viral particles, and the release of the virion. Moreover, nanomaterials have been used as antiviral drug carriers and vaccines, and nano-enabled sensors have already been shown to enable fast, sensitive, and label-free real-time diagnosis of viral infections. Nano-biosensors could, therefore, also be useful in the remote testing and tracking of patients, while nanocarriers probed with target tissue could facilitate the targeted delivery of antiviral drugs to infected cells, tissues, organs, or systems while avoiding unwanted exposure of non-target tissues. Antiviral nanoparticles can also be applied to sanitizers, clothing, facemasks, and other personal protective equipment to minimize horizontal spread. We believe that the nanotechnology-enabled solutions described in this review will enable us to control repeated SAR-CoV-2 waves caused by antibody escape mutations.

Evaluation of bioadhesive gels for local action in the esophagus

Direct drug administration to the esophagus faces several obstacles, including continuous salivary dilution and removal of the dosage form from the tissue surface due to esophageal peristalsis. These actions often result in short exposure times and reduced concentrations of drug at the esophageal surface, providing limited opportunities for drug absorption into or across the esophageal mucosa. A variety of bioadhesive polymers were investigated for their ability to resist removal by salivary washings using an ex vivo porcine esophageal tissue model. Hydroxypropylmethylcellulose and carboxymethylcellulose both have reported bioadhesive properties, but neither was able to withstand repeated exposure to saliva, and the gels formulated with these polymers were quickly removed from the esophageal surface. Two polyacrylic polymers, carbomer and polycarbophil, also showed limited esophageal surface retention when exposed to salivary washing, likely due to the ionic composition of saliva affecting the inter-polymer interactions necessary for these polymers to maintain their increased viscosities. In situ gel forming polysaccharide gels (ion-triggered), including xanthan gum, gellan gum, and sodium alginate, showed superior tissue surface retention, and formulations containing these bioadhesive polymers along with ciclesonide, an anti-inflammatory soft prodrug, were investigated as potential, locally-acting esophageal delivery systems. Exposure of a segment of esophagus to the ciclesonide-containing gels resulted in therapeutic concentrations of des-ciclesonide, the active drug metabolite, in the tissues within 30 min. Increasing des-CIC concentrations were also observed over a 3-hour exposure interval suggesting continued release and absorption of ciclesonide into the esophageal tissues. These results demonstrate the ability to achieve therapeutic drug concentrations in the esophageal tissues using in situ gel-forming bioadhesive polymer delivery systems, and these systems provide promising opportunities for the local treatment of esophageal disease.

Thermo-responsive and mucoadhesive gels for the treatment of cystinosis

Mucoadhesive thermogels were developed by crosslinking poly(n-isopropylacrylamide) based polymers with chitosan and incorporating disulfide bridges, capable of releasing cysteamine upon interaction with mucin, for the treatment of cystinosis. Through crosslinking with chitosan and incorporating varying concentrations of the disulfide monomer into the polymer backbone, the extent of how mucoadhesive the developed thermogels were could be controlled. Through disulfide bridging with mucin, the thermogels released 6 to 10 μg of the conjugate model 2-mercaptopyridine over five days. Utilizing chitosan as the crosslinker, the developed thermogels were shown to degrade to a statistically higher extent following incubation with lysozyme, the highest concentration tear enzyme, by gravimetric and rheologic analysis. The developed thermogels were extensively tested in vivo utilizing a rat model in which materials were applied directly to the corneal surface and a rabbit model in which thermogels were applied to the inferior fornix. With the developed models, there was no adverse reactions or visual discomfort incurred following application of the thermogels. It has been demonstrated that the thermogels produced can be applied to the inferior fornix and release the stable conjugated payload over several days. The developed thermogel was designed to improve upon the current clinical treatment options for ocular cystinosis which are acidic topical formulations that require reapplication multiple times a day.

Hydroxyethylcellulose-Based Hydrogels Containing Liposomes Functionalized with Cell-Penetrating Peptides for Nasal Delivery of Insulin in the Treatment of Diabetes

Liposomes functionalized with cell-penetrating peptides are a promising strategy to deliver insulin through the nasal route. A hydrogel based on hydroxyethylcellulose (HEC) aqueous solution was prepared, followed by a subsequent addition of liposomes containing insulin solution functionalized with trans-activator of transcription protein of HIV-1 (TAT) or Penetratin (PNT). The formulations were characterized for rheological behavior, mucoadhesion, syringeability, in vitro release and in vivo efficacy. Rheological tests revealed non-Newtonian fluids with pseudoplastic behavior, and the incorporation of liposomes (HLI, HLI_TAT and HLI_PNT) in hydrogels did not alter the behavior original pseudoplastic characteristic of the HEC hydrogel. Pseudoplastic flow behavior is a desirable property for formulations intended for the administration of drugs via the nasal route. The results of syringeability and mucoadhesive strength from HEC hydrogels suggest a viable vehicle for nasal delivery. Comparing the insulin release profile, it is observed that HI was the system that released the greatest amount while the liposomal gel promoted greater drug retention, since the liposomal system provides an extra barrier for the release through the hydrogel. Additionally, it is observed that both peptides tested had an impact on the insulin release profile, promoting a slower release, due to complexation with insulin. The in vitro release kinetics of insulin from all formulations followed Weibull's mathematical model, reaching approximately 90% of release in the formulation prepared with HEC-based hydrogels. Serum insulin levels and the antihyperglycemic effects suggested that formulations HI and HLI have potential as carriers for insulin delivery by the nasal pathway, a profile not observed when insulin was administered by subcutaneous injection or by the nasal route in saline. Furthermore, formulations functionalized with TAT and PNT can be considered promoters of late and early absorption, respectively.

Therapeutic Applications of Curcumin in Diabetes: A Review and Perspective

Diabetes is a metabolic disease with multifactorial causes which requires lifelong drug therapy as well as lifestyle changes. There is now growing scientific evidence to support the effectiveness of the use of herbal supplements in the prevention and control of diabetes. Curcumin is one of the most studied bioactive components of traditional medicine, but its physicochemical characteristics are represented by low solubility, poor absorption, and low efficacy. Nanotechnology-based pharmaceutical formulations can help overcome the problems of reduced bioavailability of curcumin and increase its antidiabetic effects. The objectives of this review were to review the effects of nanocurcumin on DM and to search for databases such as PubMed/MEDLINE and ScienceDirect. The results showed that the antidiabetic activity of nanocurcumin is due to complex pharmacological mechanisms by reducing the characteristic hyperglycemia of DM. In light of these results, nanocurcumin may be considered as potential agent in the pharmacotherapeutic management of patients with diabetes.

Using the Intranasal Route to Administer Drugs to Treat Neurological and Psychiatric Illnesses: Rationale, Successes, and Future Needs

While the intranasal administration of drugs to the brain has been gaining both research attention and regulatory success over the past several years, key fundamental and translational challenges remain to fully leveraging the promise of this drug delivery pathway for improving the treatment of various neurological and psychiatric illnesses. In response, this review highlights the current state of understanding of the nose-to-brain drug delivery pathway and how both biological and clinical barriers to drug transport using the pathway can been addressed, as illustrated by demonstrations of how currently approved intranasal sprays leverage these pathways to enable the design of successful therapies. Moving forward, aiming to better exploit the understanding of this fundamental pathway, we also outline the development of nanoparticle systems that show improvement in delivering approved drugs to the brain and how engineered nanoparticle formulations could aid in breakthroughs in terms of delivering emerging drugs and therapeutics while avoiding systemic adverse effects.

Stimuli-Responsive Polymers for Transdermal, Transmucosal and Ocular Drug Delivery

Despite their conventional and widespread use, oral and intravenous routes of drug administration face several limitations. In particular, orally administered drugs undergo enzymatic degradation in the gastrointestinal tract and first-pass metabolism in the liver, which tend to decrease their bioavailability. Intravenous infusions of medications are invasive, painful and stressful for patients and carry the risk of infections, tissue damage and other adverse reactions. In order to account for these disadvantages, alternative routes of drug delivery, such as transdermal, nasal, oromucosal, ocular and others, have been considered. Moreover, drug formulations have been modified in order to improve their storage stability, solubility, absorption and safety. Recently, stimuli-responsive polymers have been shown to achieve controlled release and enhance the bioavailability of multiple drugs. In this review, we discuss the most up-to-date use of stimuli-responsive materials in order to optimize the delivery of medications that are unstable to pH or undergo primary metabolism via transdermal, nasal, oromucosal and ocular routes. Release kinetics, diffusion parameters and permeation rate of the drug via the mucosa or skin are discussed as well.

Compatibility of a Thermoresponsive and Controlled Release System for Promoting Sinonasal Cilia Regeneration

The current clinical goal for managing chronic rhinosinusitis (CRS), a heterogenous disease of the paranasal sinuses, is to control inflammation, yet adjunct therapies that promote mucosal regeneration can improve the long-term health of the upper airways. The small natural openings to the sinuses, however, limit the efficacy of traditional drug delivery methods (i.e., nasal sprays and irrigation). Accordingly, a conformable thermoresponsive and controlled release system ("TEMPS", Thermogel, Extended-release Microsphere-based delivery to the Paranasal Sinuses) is developed. The poly(lactic-co-glycolic acid) microsphere component enables the encapsulation of numerous therapeutics, such as retinoic acid (RA), an analog of vitamin A (VA). Studies in CRS patients and preclinical models have shown that aqueous RA or VA gels promoted the differentiation of ciliated cells and improved mucosal healing following repeat applications. In the present study, TEMPS is designed for the controlled release of RA such that a single dose of RA-TEMPS delivers bioactive drug for at least 30 days. Furthermore, as TEMPS will be in direct contact with sinonasal tissue, its compatibility with ciliated human nasal epithelium is explored. After ex vivo incubation in thermogel for 24 h, cilia motility is maintained, providing evidence that TEMPS can be compatible for application along the sinonasal epithelium.

Thiol- and Disulfide-Based Stimulus-Responsive Soft Materials and Self-Assembling Systems

Properties and applications of synthetic thiol- and disulfide-based materials, principally polymers, are reviewed. Emphasis is placed on soft and self-assembling materials in which interconversion of the thiol and disulfide groups initiates stimulus-responses and/or self-healing for biomedical and non-biomedical applications.

Tragacanth Gum/Chitosan Polyelectrolyte Complexes-Based Hydrogels Enriched with Xanthan Gum as Promising Materials for Buccal Application

Polyelectrolyte complexes based on the electrostatic interactions between the polymers mixed are of increasing importance, therefore, the aim of this study was to develop hydrogels composed of anionic tragacanth gum and cationic chitosan with or without the addition of anionic xanthan gum as carriers for buccal drug delivery. Besides the routine quality tests evaluating the hydrogel’s applicability on the buccal mucosa, different methods directed toward the assessment of the interpolymer complexation process (e.g., turbidity or zeta potential analysis, scanning electron microscopy and Fourier-transform infrared spectroscopy) were employed. The addition of xanthan gum resulted in stronger complexation of chitosan that affected the hydrogel’s characteristics. The formation of a more viscous PEC hydrogel with improved mucoadhesiveness and mechanical strength points out the potential of such polymer combination in the development of buccal drug dosage forms.

Thiolated PVP-Amphotericin B Complexes: An Innovative Approach toward Highly Mucoadhesive Gels for Mucosal Leishmaniasis Treatment

The aim of this study was to synthesize polymeric excipients that can form mucoadhesive hydrogels containing amphotericin B (AmB) for the treatment of mucosal leishmaniasis. 2-(2-Acryloylaminoethyldisulfanyl)-nicotinic acid (ACENA) was copolymerized with N-vinyl pyrrolidone to obtain thiolated polyvinylpyrrolidone (PVP) that was then complexed with AmB to improve its solubility. The resulting structure of thiolated PVP was evaluated by ¹H nuclear magnetic resonance to confirm S-protected thiol groups, and the average molecular mass was determined by size exclusion chromatography. Moreover, variants of thiolated PVP-AmB were studied for the thiol content, amount of complexed AmB, cytotoxicity, mucoadhesive properties, and antileishmaniasis activity. The highest achieved degree of thiolation was 772 ± 24.64 μmol/g, and the amount of complexed AmB was 27.05 ± 0.31 μmol per g of polymer. Thiolated PVP and thiolated PVP-AmB variants (0.5% m/v) showed no cytotoxicity, whereas the equivalent concentration of free AmB reduced Caco-2 cell viability to 70% within 24 h. Thiol-functionalized PVP and PVP-AmB complexes displayed 7.66- and 7.20-fold higher adhesion to the mucosal surface in comparison to unmodified PVP and PVP-AmB, respectively. In addition, variants of thiolated PVP-AmB complexes displayed 100% antileishmaniasis activity in comparison to the 80% killing efficiency of Fungizone, which has been applied in the equivalent AmB concentration of 0.2 μg/mL. Thiol-functionalized PVP proved to be a promising novel excipient for the delivery of AmB providing enhanced solubility and improved mucoadhesive properties which are beneficial for the treatment of mucosal leishmaniasis.

Thiolated sodium alginate conjugates for mucoadhesive and controlled release behavior of metformin microspheres

The absorption of BCS III drugs can be improved by inhibiting the P-glycoprotein (P-gp) efflux and by increasing the mucoadhesion of natural polymers. In the present study, an esterification of sodium alginate (SA) with thioglycolic acid (TGA) was applied for the preparation of thiolated sodium alginate (TSA). The Ellman's test was applied to quantify the thiol group and a di-sulphide bond test was performed to confirm any SS linkages. The FTIR, DSC, XRD, ¹H NMR and charring point determinations were confirmed the thiol group of TSA. The gel like rheological properties with porcine mucous was confirmed by viscoelasticity properties and the mucoadhesion with the rabbit intestine was carried out after compression of 30 mg tablets of TSA. The content of thiol group was in the range of 320-730 μmoL/g of the polymer. The FTIR spectrum showed a characteristic peak of sulfhydryl group at 2557 cm^-1 in TSA and the reduction of the charring point from 220 °C to 178 °C was confirmed the thiolation of TSA. A direct relationship of mucoadhesion and swelling was observed with the concentration of TGA and SA, respectively. The prepared microspheres were 2-7 μm in size, excellent rheological properties and non-fickian drug release behavior was observed.

A gellan gum derivative as in-situ gelling cationic polymer for nasal drug delivery

The aim of the present study was the development of a novel gellan gum derivative exhibiting mucoadhesive properties for nasal application. Accomplishing this, amino groups have been introduced to the polymeric backbone. The resulting synthesis products were characterized in terms of the amount of attached amino groups, regarding hydration, zeta potential and gel characteristics. Mucoadhesiveness was assessed studying rheological synergism, by rotating cylinder and regarding tensile studies. Next to erythrocyte-/cytotoxicity evaluation, the impact on ciliary beat frequency of nasal epithelial cells was investigated. Results revealed coupling rates up to 1259.50 ± 75.98 μmol/g polymer as well as accelerated hydration of the derivatives. Comparing aminated with unmodified gellan, enhanced mucoadhesion was verified by a 32-fold increase in viscosity of polymer/mucus mixtures and by a 14-fold extended mucosal adhesion time. Tensile studies demonstrated a 9-fold higher total work of adhesion and a 3.75-fold elevated maximum detachment force. Cellular membrane was not seriously impaired. CBF studies proved a reversible inhibition due to the application of the novel derivative. According to the outlined findings, aminated gellan gum can be considered as a promising excipient for nasal dosage forms improving drug bioavailability by superior adhesive features.

In vitro evaluation of a self-emulsifying drug delivery system (SEDDS) for nasal administration of dimenhydrinate

The objective of the study was the development and in vitro characterization of a self-emulsifying drug delivery system (SEDDS) for the nasal application of dimenhydrinate. Final composition of SEDDS was established based on drug solubility and stability studies. Dimenhydrinate was loaded into the SEDDS pre-concentrates to 7.5% (m/v). The droplet size of the final SEDDS formulations was in a range between 60 and 220 nm. Permeability, as well as tissue toxicity, of the formulations was investigated using bovine nasal mucosa. Enhancement in permeation up to 2.8-fold compared to pure dimenhydrinate was confirmed. Furthermore, toxicity studies did not reveal any serious tissue damages related to the SEDDS. Additionally, irritation potential of SEDDS was evaluated in ciliary beat frequency measurements. Incorporation of dimenhydrinate into SEDDS might therefore be considered as a promising approach within the field of nasal delivery of antiemetics by utilizing permeation enhancement strategy.

Xanthan gum derivatives: review of synthesis, properties and diverse applications

Natural polysaccharides are well known for their biocompatibility, non-toxicity and biodegradability. These properties are also inherent to xanthan gum (XG), a microbial polysaccharide. This biomaterial has been extensively investigated as matrices for tablets, nanoparticles, microparticles, hydrogels, buccal/transdermal patches, tissue engineering scaffolds with different degrees of success. However, the native XG has its own limitations with regards to its susceptibility to microbial contamination, unusable viscosity, poor thermal and mechanical stability, and inadequate water solubility. Chemical modification can circumvent these limitations and tailor the properties of virgin XG to fulfill the unmet needs of drug delivery, tissue engineering, oil drilling and other applications. This review illustrates the process of chemical modification and/crosslinking of XG via etherification, esterification, acetalation, amidation, and oxidation. This review further describes the tailor-made properties of novel XG derivatives and their potential application in diverse fields. The physicomechanical modification and its impact on the properties of XG are also discussed. Overall, the recent developments on XG derivatives are very promising to progress further with polysaccharide research.

Due to presence of hydroxy and carboxy functional groups, xanthan gum is amenable to various chemical modification for producing derivatives such as carboxymethyl xanthan and carboxymethyl hydroxypropyl xanthan with desirable properties for end use.

Intranasal Nanoparticulate Systems as Alternative Route of Drug Delivery

There is always a need for alternative and efficient methods of drug delivery. The nasal cavity can be considered as a non-invasive and efficient route of administration. It has been used for local, systemic, brain targeting, and vaccination delivery. Although many intranasal products are currently available on the market, the majority is used for local delivery with fewer products available for the other targets. As nanotechnology utilization in drug delivery has rapidly spread out, the nasal delivery has become attractive as a promising approach. Nanoparticulate systems facilitate drug transportation across the mucosal barrier, protect the drug from nasal enzyme degradation, enhance the delivery of vaccines to the lymphoid tissue of the nasal cavity with an adjuvant activity, and offer a way for peptide delivery into the brain and the systemic circulation, in addition to their potential for brain tumor treatment. This review article aims at discussing the potential benefit of the intranasal nanoparticulate systems, including nanosuspensions, lipid and surfactant, and polymer-based nanoparticles as regards productive intranasal delivery. The aim of this review is to focus on the topicalities of nanotechnology applications for intranasal delivery of local, systemic, brain, and vaccination purposes during the last decade, referring to the factors affecting delivery, regulatory aspects, and patient expectations. This review further identifies the benefits of applying the Quality by Design approaches (QbD) in product development. According to the reported studies on nanotechnology-based intranasal delivery, potential attention has been focused on brain targeting and vaccine delivery with promising outcomes. Despite the significant research effort in this field, nanoparticle-based products for intranasal delivery are not available. Thus, further efforts are required to promote the introduction of intranasal nanoparticulate products that can meet the requirements of regulatory affairs with high patient acceptance.

Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature

Thiolated polymers designated "thiomers" are obtained by covalent attachment of thiol functionalities on the polymeric backbone of polymers. In 1998 these polymers were first described as mucoadhesive and in situ gelling compounds forming disulfide bonds with cysteine-rich substructures of mucus glycoproteins and crosslinking through inter- and intrachain disulfide bond formation. In the following, it was shown that thiomers are able to form disulfides with keratins and membrane-associated proteins exhibiting also cysteine-rich substructures. Furthermore, permeation enhancing, enzyme inhibiting and efflux pump inhibiting properties were demonstrated. Because of these capabilities thiomers are promising tools for drug delivery guaranteeing a strongly prolonged residence time as well as sustained release on mucosal membranes. Apart from that, thiomers are used as drugs per se. In particular, for treatment of dry eye syndrome various thiolated polymers are in development and a first product has already reached the market. Within this review an overview about the thiomer-technology and its potential for different applications is provided discussing especially the outcome of studies in non-rodent animal models and that of numerous clinical trials. Moreover, an overview on product developments is given.

Nanosized Transferosome-Based Intranasal In Situ Gel for Brain Targeting of Resveratrol: Formulation, Optimization, In Vitro Evaluation, and In Vivo Pharmacokinetic Study

Resveratrol (RES) is a potent antioxidant used for the management of several central nervous system diseases. RES bioavailability is less than 1 owing to its low solubility and extensive intestinal and hepatic metabolism. The aim of the study was to enhance RES bioavailability through developing intranasal transferosomal mucoadhesive gel. Reverse evaporation-vortexing sonication method was employed to prepare RES-loaded transferosomes. Transferosomes were developed via 3⁴ definitive screening design, using soya lecithin, permeation enhancers, and surfactants. The optimized formula displayed spherical shape with vesicle size of 83.79 ± 2.54 nm and entrapment efficiency (EE%) of 72.58 ± 4.51%. Mucoadhesive gels were prepared and evaluated, then optimized RES transferosomes were incorporated into the selected gel and characterized using FTIR spectroscopy, in vitro release, and ex vivo permeation study. Histopathological examination of nasal mucosa and in vivo pharmacokinetic study were conducted. In vitro drug release from transferosomal gel was 65.87 ± 2.12% and ex vivo permeation was 75.95 ± 3.19%. Histopathological study confirmed the safety of the optimized formula. The C_max of RES in the optimized RES trans-gel was 2.15 times higher than the oral RES suspension and AUC_(0-∞) increased by 22.5 times. The optimized RES trans-gel developed intranasal safety and bioavailability enhancement through passing hepatic and intestinal metabolism.

How to characterize a nasal product. The state of the art of in vitro and ex vivo specific methods

Nasal delivery offers many benefits over other conventional routes of delivery (e.g. oral or intravenous administration). Benefits include, among others, a fast onset of action, non-invasiveness and direct access to the central nervous system. The nasal cavity is not only limited to local application (e.g. rhinosinusitis) but can also provide direct access to other sites in the body (e.g. the central nervous system or systemic circulation). However, both the anatomy and the physiology of the nose impose their own limitations, such as a small volume for delivery or rapid mucociliary clearance. To meet nasal-specific criteria, the formulator has to complete a plethora of tests, in vitro and ex vivo, to assess the efficacy and tolerance of a new drug-delivery system. Moreover, depending on the desired therapeutic effect, the delivery of the drug should target a specific pathway that could potentially be achieved through a modified release of this drug. Therefore, this review focuses on specific techniques that should be performed when a nasal formulation is developed. The review covers both the tests recommended by regulatory agencies (e.g. the Food and Drug Administration) and other complementary experiments frequently performed in the field.

S-protected gellan gum: Decisive approach towards mucoadhesive antimicrobial vaginal films

The aim of this study was to synthesize novel polymeric excipients forming mucoadhesive films for treatment of vaginal microbial infections. 2-(2-Amino ethyldisulfanyl) nicotinic acid was conjugated with gellan gum via amide bond formation. The structure of the resulting S-protected gellan gum was confirmed by ¹H NMR. S-protected gellan gum variants were characterized for thiol content, cytotoxicity, rheological behaviour and film forming capability. Depending on the added amount of AMENA degree of thiolation was 81 ± 13 (S-GG 81) and 174 ± 16 (S-GG 174) μmol/g, respectively. Vaginal films were casted from S-protected gellan gum variants and studied for adherence to vaginal mucosa, drug release and antimicrobial activity. S-protected gellan gum remained biocompatible showing >87% cell viability. S-GG 81 and S-GG 174 exhibited 1.84- and 4.3-fold increased dynamic viscosity in porcine mucus in comparison to unmodified gellan gum, respectively. Compared to gellan gum films, thiol functionalized gellan gum films showed 3-fold improved adhesion on mucosal surface over a period of 3 h along with significant antimicrobial activity. Moreover, S-protected gellan gum provided a sustained release of metronidazole. According to these results, S-protected gellan gum proved to be a promising novel excipient for casting vaginal films, exhibiting strongly improved mucoadhesive and antimicrobial properties.

Advanced formulations for intranasal delivery of biologics

INTRODUCTION

The global biologics market has been ever increasing over the last decades and is predicted to top Euro 350 by 2020. Facing this scenario, the parenteral route of biologics administration as hitherto standard route is inconvenient for the future. Among the alternatives, the intranasal delivery of therapeutic biologicals seems to be most promising but researchers are still facing challenges as indicated by the scarce number of successfully marketed peptide drugs.

AREAS COVERED

This review article is a compilation of current research focusing on achievements in the field of auxiliary agents for biologics delivery. First, the key benefits of the nose as most promising alternative route of drug administration are highlighted. Then, the potential of the different auxiliary agents in preclinical research is in detail discussed. Moreover, the most used permeation enhancing agents, mucolytic agents, mucoadhesive agents, in situ gelling agents and enzyme inhibiting agents in the formulation of nasal drug delivery systems are described. Thus, the overall purpose of this review is to highlight recent achievements in nasal delivery of biologics and to encourage researchers to work in the direction of needle-free nasal administration of biologics.

EXPERT OPINION

The nasal epithelium is a promising route for biologics administration, which is reflected in a number of well-established products on the market treating chronic diseases as well as a large number of clinical trials currently in progress. The nasal route of drug administration might be a chance to improve therapy of biologics however break-through advances, especially for very complex molecules, such as antibodies, are still needed.

Nano based drug delivery systems: recent developments and future prospects

Nanomedicine and nano delivery systems are a relatively new but rapidly developing science where materials in the nanoscale range are employed to serve as means of diagnostic tools or to deliver therapeutic agents to specific targeted sites in a controlled manner. Nanotechnology offers multiple benefits in treating chronic human diseases by site-specific, and target-oriented delivery of precise medicines. Recently, there are a number of outstanding applications of the nanomedicine (chemotherapeutic agents, biological agents, immunotherapeutic agents etc.) in the treatment of various diseases. The current review, presents an updated summary of recent advances in the field of nanomedicines and nano based drug delivery systems through comprehensive scrutiny of the discovery and application of nanomaterials in improving both the efficacy of novel and old drugs (e.g., natural products) and selective diagnosis through disease marker molecules. The opportunities and challenges of nanomedicines in drug delivery from synthetic/natural sources to their clinical applications are also discussed. In addition, we have included information regarding the trends and perspectives in nanomedicine area.

In situ gelling and mucoadhesive polymers: why do they need each other?

INTRODUCTION

Mucosal drug delivery is an attractive route of administration, particularly in overcoming deficits of conventional dosage forms including high first-pass metabolism and poor bioavailability. Fast drainage from the target mucosa, however, represents a major limitation as it prevents sufficient drug absorption. In order to address these problems, mucoadhesive in situ gelling drug delivery systems have been investigated as they facilitate easy application in combination with a longer residence time at the administration site resulting in more desirable therapeutic effects.

AREAS COVERED

The present review evaluates the importance of the combination of mucoadhesive and in situ gelling polymers along with mechanisms of in situ gelation and mucoadhesion. In addition, an overview about recent applications in mucosal drug delivery is provided.

EXPERT OPINION

In situ gelling and mucoadhesive polymers proved to be essential excipients in order to prolong the mucosal residence time of drug delivery systems. Due to this prolonged residence time both local and systemic therapeutic efficacy of numerous drugs can be substantially improved. Depending on the site of administration and the incorporated drug, combinations of different polymers with in situ gelling and mucoadhesive properties are needed to keep the delivery system as long as feasible at the target site.

Rheological analysis and mucoadhesion: A 30 year-old and still active combination

At the end of 80s and in the early 90s, an increasing interest in the development of mucoadhesive formulations occurred in the pharmaceutical field. Such formulations, prolonging the drug permanence on the mucosa of action/absorption, improve drug availability/bioavailability and therefore its therapeutic effectiveness. Among the various methods reported in the literature for the evaluation of the mucoadhesive properties of polymers, in the early 1990s, the study of the rheological variation of the polymer solutions after mixing with a mucin solution/dispersion has been proposed as an approach to measure the strength of the mucoadhesive joint. Even today, both viscosity and viscoelastic measurements are used to evaluate the ability of polymers and formulations to adhere to the mucosa of application/action. This review aims at providing an overview of the rheological approaches employed in the development and characterization of mucoadhesive formulation, highlighting their advantages and disadvantages. To do this the scientific path that, since the beginning of the 90s, has led to the affirmation of the rheological analysis as a useful tool for the evaluation of the strength of the mucoadhesive bond is retraced.

Thiolated Chitosan Masked Polymeric Microspheres with Incorporated Mesocellular Silica Foam (MCF) for Intranasal Delivery of Paliperidone

In this study, mesocellular silica foam (MCF) was used to encapsulate paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. MCF with the drug adsorbed was further encapsulated into poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) 75/25 w/w microspheres and these have been coated with thiolated chitosan. As found by TEM analysis, thiolated chitosan formed a thin layer on the polymeric microspheres' surface and was used in order to enhance their mucoadhesiveness. These microspheres aimed at the intranasal delivery of paliperidone. The DSC and XRD studies showed that paliperidone was encapsulated in amorphous form inside the MCF silica and for this reason its dissolution profile was enhanced compared to the neat drug. In coated microspheres, thiolated chitosan reduced the initial burst effect of the paliperidone dissolution profile and in all cases sustained release formulations have been prepared. The release mechanism was also theoretically studied and three kinetic models were proposed and successfully fitted for a dissolution profile of prepared formulations to be found.