Intranasal delivery system of bacterial antigen using thermosensitive hydrogels based on a Pluronic-Gantrez conjugate

Preparation, Properties and Therapeutic Effect of a TPL Nanoparticle Thermosensitive Gel for Intra-Articular Injection

Most injectable preparations for the articular cavity are solution-type preparations that are frequently administered because of rapid elimination. In this study, triptolide (TPL), an effective ingredient in the treatment of rheumatoid arthritis (RA), was prepared in the form of a nanoparticle thermosensitive gel (TPL-NS-Gel). The particle size distribution and gel structure were investigated by TEM, laser particle size analysis and laser capture microdissection. The effect of the nanoparticle carrier material PLGA on the phase transition temperature was investigated by ¹H variable temperature NMR and DSC. The tissue distribution, pharmacokinetic behavior, four inflammatory factors and therapeutic effect were determined in a rat RA model. The results suggested that PLGA increased the gel phase transition temperature. The drug concentration of the TPL-NS-Gel group in joint tissues was higher than that in other tissues at different time points, and the retention time was longer than that of the TPL-NS group. After 24 days of administration, TPL-NS-Gel significantly improved the joint swelling and stiffness of the rat models, and the improvement degree was better than that of the TPL-NS group. TPL-NS-Gel significantly decreased the levels of hs-CRP, IL-1, IL-6 and TNF-α in serum and joint fluid. There was a significant difference between the TPL-NS-Gel and TPL-NS groups on Day 24 (p < 0.05). Pathological section results showed that inflammatory cell infiltration was lower in the TPL-NS-Gel group, and no other obvious histological changes were observed. Upon articular injection, the TPL-NS-Gel prolonged drug release, reduced the drug concentration outside the articular tissue and improved the therapeutic effect in a rat RA model. The TPL-NS-Gel can be used as a new type of sustained-release preparation for articular injection.

Preparation, thermal response mechanisms and biomedical applications of thermosensitive hydrogels for drug delivery

INTRODUCTION

Drug treatment is one of the main ways of coping with disease today. For the disadvantages of drug management, thermosensitive hydrogel is used as a countermeasure, which can realize the simple sustained release of drugs and the controlled release of drugs in complex physiological environments.

AREAS COVERED

This paper talks about thermosensitive hydrogels that can be used as drug carriers. The common preparation materials, material forms, thermal response mechanisms, characteristics of thermosensitive hydrogels for drug release and main disease treatment applications are reviewed.

EXPERT OPINION

When thermosensitive hydrogels are used as drug loading and delivery platforms, desired drug release patterns and release profiles can be tailored by selecting raw materials, thermal response mechanisms, and material forms. The properties of hydrogels prepared from synthetic polymers will be more stable than natural polymers. Integrating multiple thermosensitive mechanisms or different kinds of thermosensitive mechanisms on the same hydrogel is expected to realize the spatiotemporal differential delivery of multiple drugs under temperature stimulation. The industrial transformation of thermosensitive hydrogels as drug delivery platforms needs to meet some important conditions.

Hydrogels for Mucosal Drug Delivery

Mucosal tissues are often a desirable site of drug action to treat disease and engage the immune system. However, systemically administered drugs suffer from limited bioavailability in mucosal tissues where technologies to enable direct, local delivery to these sites would prove useful. In this Spotlight on Applications article, we discuss hydrogels as an attractive means for local delivery of therapeutics to address a range of conditions affecting the eye, nose, oral cavity, gastrointestinal, urinary bladder, and vaginal tracts. Considering the barriers to effective mucosal delivery, we provide an overview of the key parameters in the use of hydrogels for these applications. Finally, we highlight recent work demonstrating their use for inflammatory and infectious diseases affecting these tissues.

The Role of Mucoadhesion and Mucopenetration in the Immune Response Induced by Polymer-Based Mucosal Adjuvants

Mucus is a viscoelastic gel that acts as a protective barrier for epithelial surfaces. The mucosal vehicles and adjuvants need to pass through the mucus layer to make drugs and vaccine delivery by mucosal routes possible. The mucoadhesion of polymer particle adjuvants significantly increases the contact time between vaccine formulations and the mucosa; then, the particles can penetrate the mucus layer and epithelium to reach mucosa-associated lymphoid tissues. This review presents the key findings that have aided in understanding mucoadhesion and mucopenetration while exploring the influence of physicochemical characteristics on mucus-polymer interactions. We describe polymer-based particles designed with mucoadhesive or mucopenetrating properties and discuss the impact of mucoadhesive polymers on local and systemic immune responses after mucosal immunization. In future research, more attention paid to the design and development of mucosal adjuvants could lead to more effective vaccines.

Design as strategy for evaluation of the mechanical properties of binary mixtures composed of poly(methyl vinyl ether-alt-maleic anhydride) and Pluronic F127 for biomedical applications

The synergism between thermoresponsive and bioadhesive polymers can lead to the optimization of materials with enhanced mechanical and bioadhesive properties. Quality by Design can assure the understanding and control of formulation variables. In this approach, Design of Experiment has been widely utilized as an important strategy. Poly(methyl vinyl ether-alt-maleic anhydride) (PVMMA) is a bioadhesive polymer and Pluronic F127 (PF127) shows thermoresponsiveness. The association of these two polymers has been poorly investigated. The aim of this work was to study the mechanical, bioadhesive and rheological properties of polymer mixtures composed of PVMMA and PF127, in order to select the best conditions and formulations for biomedical applications. Textural properties (hardness, compressibility, adhesiveness, cohesiveness and elasticity), softness index, bioadhesion and rheological characteristics (flow and viscoelasticity) showed that 17.5-20% (w/w) PF127-polymer mixtures displayed improved values of the parameters. However, the rheological interaction parameter showed low synergism, due to the polymers' characteristics and system organization. The formulations displayed gelation temperatures suitable for administration, with improved bioadhesive properties mainly at 34 °C and suggests the formulations can be used for biomedical applications. DoE constituted an important tool to investigate these systems showing the main effects that significantly influence the binary mixtures.

Hydrogels as promising platforms for engineered living bacteria-mediated therapeutic systems

The idea of using engineered bacteria as prospective living therapeutic agents for the treatment of different diseases has been raised. Nevertheless, the development of safe and effective treatment strategies remains essential to the success of living bacteria-mediated therapy. Hydrogels have presented great promise for the delivery of living bacterial therapeutics due to their tunable physicochemical properties, good bioactivities, and excellent protection of labile payloads. In this review, we summarize the hydrogel design strategies for living bacteria-mediated therapy and review the recent advances in hydrogel-based living bacterial agent delivery for the treatment of typical diseases, including those for digestive health, skin fungal infections, wound healing, vaccines, and cancer, and discuss the current challenges and future perspectives of these strategies in the field. It is believed that the importance of hydrogel-based living bacteria-mediated therapy is expected to further increase with the development of both synthetic biology and biomaterials science in the future.

Long-Term Vaccine Delivery and Immunological Responses Using Biodegradable Polymer-Based Carriers

Biodegradable polymers are largely employed in the biomedical field, ranging from tissue regeneration to drug/vaccine delivery. The biodegradable polymers are highly biocompatible and possess negligible toxicity. In addition, biomaterial-based vaccines possess adjuvant properties, thereby enhancing immune responses. This Review introduces the use of different biodegradable polymers and their degradation mechanism. Different kinds of vaccines, as well as the interaction between the carriers with the immune system, then are highlighted. Natural and synthetic biodegradable micro-/nanoplatforms, hydrogels, and scaffolds for local or targeted and controlled vaccine release are subsequently discussed.

Development of Nasal Vaccines and the Associated Challenges

Viruses, bacteria, fungi, and several other pathogenic microorganisms usually infect the host via the surface cells of respiratory mucosa. Nasal vaccination could provide a strong mucosal and systemic immunity to combat these infections. The intranasal route of vaccination offers the advantage of easy accessibility over the injection administration. Therefore, nasal immunization is considered a promising strategy for disease prevention, particularly in the case of infectious diseases of the respiratory system. The development of a nasal vaccine, particularly the strategies of adjuvant and antigens design and optimization, enabling rapid induction of protective mucosal and systemic responses against the disease. In recent times, the development of efficacious nasal vaccines with an adequate safety profile has progressed rapidly, with effective handling and overcoming of the challenges encountered during the process. In this context, the present report summarizes the most recent findings regarding the strategies used for developing nasal vaccines as an efficient alternative to conventional vaccines.

Mucosal vaccine delivery: A focus on the breakthrough of specific barriers

Mucosal vaccines can effectively induce an immune response at the mucosal site and form the first line of defense against microbial invasion. The induced mucosal immunity includes the proliferation of effector T cells and the production of IgG and IgA antibodies, thereby effectively blocking microbial infection and transmission. However, after a long period of development, the transformation of mucosal vaccines into clinical use is still relatively slow. To date, fewer than ten mucosal vaccines have been approved. Only seven mucosal vaccines against coronavirus disease 2019 (COVID-19) are under investigation in clinical trials. A representative vaccine is the adenovirus type-5 vectored COVID-19 vaccine (Ad5-nCoV) developed by Chen and coworkers, which is currently in phase III clinical trials. The reason for the limited progress of mucosal vaccines may be the complicated mucosal barriers. Therefore, this review summarizes the characteristics of mucosal barriers and highlights strategies to overcome these barriers for effective mucosal vaccine delivery.

Thermosensitive Hydrogels and Advances in Their Application in Disease Therapy

Thermosensitive hydrogels, having unique sol–gel transition properties, have recently received special research attention. These hydrogels exhibit a phase transition near body temperature. This feature is the key to their applications in human medicine. In addition, hydrogels can quickly gel at the application site with simple temperature stimulation and without additional organic solvents, cross-linking agents, or external equipment, and the loaded drugs can be retained locally to improve the local drug concentration and avoid unexpected toxicity or side effects caused by systemic administration. All of these features have led to thermosensitive hydrogels being some of the most promising and practical drug delivery systems. In this paper, we review thermosensitive hydrogel materials with biomedical application potential, including natural and synthetic materials. We describe their structural characteristics and gelation mechanism and briefly summarize the mechanism of drug release from thermosensitive hydrogels. Our focus in this review was to summarize the application of thermosensitive hydrogels in disease treatment, including the postoperative recurrence of tumors, the delivery of vaccines, the prevention of postoperative adhesions, the treatment of nervous system diseases via nasal brain targeting, wound healing, and osteoarthritis treatment.

Biological Nanoparticles in Vaccine Development

Vaccines represent one of the most successful public health initiatives worldwide. However, despite the vast number of highly effective vaccines, some infectious diseases still do not have vaccines available. New technologies are needed to fully realize the potential of vaccine development for both emerging infectious diseases and diseases for which there are currently no vaccines available. As can be seen by the success of the COVID-19 mRNA vaccines, nanoscale platforms are promising delivery vectors for effective and safe vaccines. Synthetic nanoscale platforms, including liposomes and inorganic nanoparticles and microparticles, have many advantages in the vaccine market, but often require multiple doses and addition of artificial adjuvants, such as aluminum hydroxide. Biologically derived nanoparticles, on the other hand, contain native pathogen-associated molecular patterns (PAMPs), which can reduce the need for artificial adjuvants. Biological nanoparticles can be engineered to have many additional useful properties, including biodegradability, biocompatibility, and are often able to self-assemble, thereby allowing simple scale-up from benchtop to large-scale manufacturing. This review summarizes the state of the art in biologically derived nanoparticles and their capabilities as novel vaccine platforms.

Bioadhesive poly(methyl vinyl ether-co-maleic anhydride)-TPGS copolymer modified PLGA/lipid hybrid nanoparticles for improving intestinal absorption of cabazitaxel

A bioadhesive nanocarrier, PTNP, was constructed by utilizing a novel poly(methyl vinyl ether-co-maleic anhydride)- D-α-Tocopheryl polyethylene glycol succinate (PVMMA-TPGS) copolymer in the PLGA/lipid hybrid nanoparticles (PLGA NPs) for improving oral delivery of cabazitaxel (CTX). The PVMMA-TPGS was synthesized by the ring-opening polymerization of the anhydride groups with the hydroxyl groups, combining the bioadhesive property of PVMMA with P-glycoprotein (P-gp) inhibitory effect of TPGS. The CTX-loaded PTNPs (CTX-PTNPs) were prepared by an emulsification-solvent evaporation method and performed a spherical appearance with a uniform particle size of 192.2 nm. The CTX-PTNPs were surface negatively charged, and exhibited good drug loading (10.2%) and encapsulation efficiency (92.1%). A sustained drug release and high stability in simulated gastrointestinal environment were confirmed in in vitro studies. The in vitro mucin adhesion and in vivo intestinal retention experiments indicated that the PTNPs had a stronger bioadhesive effect and a notably longer intestinal retention than the control PLGA NPs, due to the interaction of PVMMA on the PTNP surface with the intestinal mucosa. Moreover, an enhanced intestinal permeability of the PTNPs was also verified in in vivo and ex vivo intestinal permeation studies, which was probably attributed to the extended retention of PTNPs in intestinal mucosa and the P-gp inhibitory effect of TPGS. As respected, in in vivo pharmacokinetic study, the T_max and oral bioavailability of CTX were dramatically improved to 1.08 h and 28.84% by the PTNPs, respectively, obviously superior to the CTX solution and the PLGA NPs, further demonstrating the high-efficiency in oral delivery of CTX. Hence, this bioadhesive carrier is proposed to be a potential and promising strategy for increasing oral absorption of small molecule insoluble drugs.

Use of Pluronic Surfactants in Gel Formulations of Photosensitive 1,4-Dihydropyridine Derivatives: A Potential Approach in the Treatment of Neuropathic Pain

1,4-Dihydropyridines (DHPs) are the most important class of L-type calcium channel blockers that are employed for the treatment of cardiovascular diseases, particularly hypertension. Various modifications on this scaffold lead to the discovery of new DHPs blocking different types of calcium channels. Among them, the T-type calcium channel has recently attracted great interest due to its role in chronic pain conditions. In this study, we selected three newly synthesized DHPs (HM8, HM10 and MD20) with different selectivity profiles to the T-type calcium channel and formulated them in micellar solutions and micellar-in-gel matrices to be tested for potential topical use in the treatment of neuropathic pain. To prevent the well-known sensitivity to light of the DHPs, the studied compounds were entrapped in colloidal aggregates obtained by using edible Pluronic^® surfactants and adding α-tocopherol as an antioxidant. All the prepared formulations were exposed to stressing light, according to international rules. Along with the degradation experiments, the concentrations of the parent compounds and by-products were calculated by multivariate curve resolution—alternating least squares (MCR-ALS) applied to the spectral data. The defined formulations proved suitable as light-stable matrices for the DHP compounds, showing an increase in stability for HM8 and MD20 and an almost complete photoprotection for HM10, compared to ethanol solutions and standard gel formulations.