Physical methods to promote drug delivery on mucosal tissues of the oral cavity

Revisited and innovative perspectives of oral ulcer: from biological specificity to local treatment

Mouth ulcers, a highly prevalent ailment affecting the oral mucosa, leading to pain and discomfort, significantly impacting the patient's daily life. The development of innovative approaches for oral ulcer treatment is of great importance. Moreover, a deeper and more comprehensive understanding of mouth ulcers will facilitate the development of innovative therapeutic strategies. The oral environment possesses distinct traits as it serves as the gateway to the digestive and respiratory systems. The permeability of various epithelial layers can influence drug absorption. Moreover, oral mucosal injuries exhibit distinct healing patterns compared to cutaneous lesions, influenced by various inherent and extrinsic factors. Furthermore, the moist and dynamic oral environment, influenced by saliva and daily physiological functions like chewing and speaking, presents additional challenges in local therapy. Also, suitable mucosal adhesion materials are crucial to alleviate pain and promote healing process. To this end, the review comprehensively examines the anatomical and structural aspects of the oral cavity, elucidates the healing mechanisms of oral ulcers, explores the factors contributing to scar-free healing in the oral mucosa, and investigates the application of mucosal adhesive materials as drug delivery systems. This endeavor seeks to offer novel insights and perspectives for the treatment of oral ulcers.

Intraoral medical devices for sustained drug delivery

OBJECTIVES

The oral cavity constitutes an attractive organ for the local and systemic application of drug substances. Oromucosal tablets, gels, or sprays are examples of the formulations applied. Due to the elution through the saliva, the residence time of the formulation at the application site is relatively short. Medical devices placed in the oral cavity, with a reservoir for an active substance, play an important role in solving this problem.

MATERIALS AND METHODS

In this review, we discuss the devices described in the literature that are designed to be used in the oral cavity, highlighting the advantages, disadvantages, and clinical applications of each of them.

RESULTS

Among the intraoral medical devices, special types are personalized 3D-printed devices, iontophoretic devices, and microneedle patches.

CONCLUSION

We anticipate that with the development of 3D printing and new polymers, the technology of flexible and comfortable devices for prolonged drug delivery in the oral cavity will develop intensively.

CLINICAL RELEVANCE

The presented review is therefore a useful summary of the current technological state, when in fact none of the existing devices has been widely accepted clinically.

Beyond traditional therapy: Mucoadhesive polymers as a new frontier in oral cancer management

In recent times mucoadhesive drug delivery systems are gaining popularity in oral cancer. It is a malignancy with high global prevalence. Despite significant advances in cancer therapeutics, improving the prognosis of late-stage oral cancer remains challenging. Targeted therapy using mucoadhesive polymers can improve oral cancer patients' overall outcome by offering enhanced oral mucosa bioavailability, better drug distribution and tissue targeting, and minimizing systemic side effects. Mucoadhesive polymers can also be delivered via different formulations such as tablets, films, patches, gels, and nanoparticles. These polymers can deliver an array of medicines, making them an adaptable drug delivery approach. Drug delivery techniques based on these mucoadhesive polymers are gaining traction and have immense potential as a prospective treatment for late-stage oral cancer. This review examines leading research in mucoadhesive polymers and discusses their potential applications in treating oral cancer.

Structure induced laminar vortices control anomalous dispersion in porous media

Natural porous systems, such as soil, membranes, and biological tissues comprise disordered structures characterized by dead-end pores connected to a network of percolating channels. The release and dispersion of particles, solutes, and microorganisms from such features is key for a broad range of environmental and medical applications including soil remediation, filtration and drug delivery. Yet, owing to the stagnant and opaque nature of these disordered systems, the role of microscopic structure and flow on the dispersion of particles and solutes remains poorly understood. Here, we use a microfluidic model system that features a pore structure characterized by distributed dead-ends to determine how particles are transported, retained and dispersed. We observe strong tailing of arrival time distributions at the outlet of the medium characterized by power-law decay with an exponent of 2/3. Using numerical simulations and an analytical model, we link this behavior to particles initially located within dead-end pores, and explain the tailing exponent with a hopping across and rolling along the streamlines of vortices within dead-end pores. We quantify such anomalous dispersal by a stochastic model that predicts the full evolution of arrival times. Our results demonstrate how microscopic flow structures can impact macroscopic particle transport.

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.

Semi-interpenetrating chitosan/ionic liquid polymer networks as electro-responsive biomaterials for potential wound dressings and iontophoretic applications

In this work, electro-responsive chitosan/ionic liquid-based hydrogels were synthetized for the first time, envisaging the development of iontophoretic biomaterials for the controlled release/permeation of charged biomolecules. The main goal was to enhance and tune the physicochemical, mechanical, electro-responsive, and haemostatic properties of chitosan-based biomaterials to obtain multi-stimuli responsive (responsive to electrical current, ionic strength, and pH) and mechanically stable hydrogels. To accomplish this objective, polycationic semi-interpenetrating copolymer networks (semi-IPN) were prepared by combining chitosan (CS) and ionic liquid-based polymers and copolymers, namely poly(1-butyl-3-vinylimidazolium chloride) (poly(BVImCl)) and poly(2-hydroxymethyl methacrylate-co-1-butyl-3-vinylimidazolium chloride) (poly(HEMA-co-BVImCl)). Results show that prepared semi-IPNs presented high mechanical stability and were positively charged over a broad pH range, including basic pH. Semi-IPNs also presented faster permeation and release rates of lidocaine hydrochloride (LH), under external electrical stimulus (0.56 mA/cm²) in aqueous media at 32 °C. The kinetic release constants and the LH diffusion coefficients measured under electrical stimulus were ~1.5 and > 2.7 times higher for those measured for passive release. Finally, both semi-IPNs were non-haemolytic (haemolytic index ≤0.2%) and showed strong haemostatic activity (blood clotting index of ~12 ± 1%). Altogether, these results show that the prepared polycationic semi-IPN hydrogels presented advantageous mechanical, responsive and biological properties that enable them to be potentially employed for the design of new, safer, and advanced stimuli-responsive biomaterials for several biomedical applications such as haemostatic and wound healing dressings and iontophoretic patches.

In situ delivery of corticosteroids for treatment of oral diseases

In many mucocutaneous disorders, corticosteroids therapy is currently central. Systemic therapy is restricted to severe disorders whereas topical applications are considered as the first-line treatment. The oral cavity environment, the medication form and other factors related to the delivery method are key factors for the therapy efficiency and effectiveness. Current marketed medications are not able to avoid wrong drug exposure and scarce patients' compliance. Innovative in situ delivery systems are able to prolong the drug retention time on the mucosa and to avoid the drawbacks of conventional formulations. This review is intended to give a general overview of oral mucocutaneous pathologies and highlight the potential of new technologies in designing innovative delivery systems able to release corticosteroids in situ for the treatment of various oral cavity disorders.

Polymeric drug delivery systems for intraoral site-specific chemoprevention of oral cancer

Oral cancer is among the most prevalent cancers in the world. Moreover, it is one of the major health problems and causes of death in many regions of the world. The traditional treatment modalities include surgical removal, radiation therapy, systemic chemotherapy, or a combination of these methods. In recent decades, there has been significant interest in intraoral site-specific chemoprevention via local drug delivery using polymeric systems. Because of its easy accessibility and clear visibility, the oral mucosa is amenable for local drug delivery. A variety of polymeric systems-such as gels, tablets, films, patches, injectable systems (e.g., millicylindrical implants, microparticles, and in situ-forming depots), and nanosized carriers (e.g., polymeric nanoparticles, nanofibers, polymer-drug conjugates, polymeric micelles, nanoliposomes, nanoemulsions, and polymersomes)-have been developed and evaluated for the local delivery of natural and synthetic chemopreventive agents. The findings of in vitro, ex vivo, and in vivo studies and the positive outcome of clinical trials demonstrate that intraoral site-specific drug delivery is an attractive, highly effective and patient-friendly strategy for the management of oral cancer. Intraoral site-specific drug delivery provides unique therapeutic advantages when compared to systemic chemotherapy. Moreover, intraoral drug delivery systems are self-administrable and can be removed when needed, increasing patient compliance. This article covers important aspects and advances related to the design, development, and efficacy of polymeric systems for intraoral site-specific drug delivery. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1383-1413, 2018.

Preparation of the Multifunctional Liposome-Containing Microneedle Arrays as an Oral Cavity Mucosal Vaccine Adjuvant-Delivery System

Recently, the multifunctional liposome-constituted microneedle arrays (LiposoMAs) have been proven to be an interesting vaccine adjuvant-delivery system (VADS) that are stable and can be vaccinated via oral cavity mucosal route. When given to mice at oral mucosa, the LiposoMAs can effectively eliminate the ingredient loss caused by chewing, swallowing, and saliva flowing and can, thus, elicit robust systemic as well as mucosal immunoresponses against the loaded antigens. In addition, the LiposoMAs can induce a mixed Th1/Th2 immunoresponse and strong cellular/humoral immunity due to special adjuvanticity and targeting delivery functions of the nanoparticulate VADS. In this chapter, the preparation, characterization as well as mucosal vaccination of the LiposoMAs are introduced. In addition, the methods for sampling mouse organs, tissues, and cells and for evaluation of the immunization efficacy are mainly included.

Multifunctional liposomes constituting microneedles induced robust systemic and mucosal immunoresponses against the loaded antigens via oral mucosal vaccination

To develop effective, convenient and stable mucosal vaccines, mannose-PEG-cholesterol (MPC)/lipid A-liposomes (MLLs) entrapping model antigen bovine serum albumin (BSA) were prepared by the procedure of emulsification-lyophilization and used to constitute microneedles, forming the proMLL-filled microneedle arrays (proMMAs). The proMMAs were rather stable and hard enough to pierce porcine skin and, upon rehydration, dissolved rapidly recovering the MLLs without size and entrapment change. The proMMAs given to mice via oral mucosal (o.m.) route, rather than routine intradermal administration, elicited robust systemic and mucosal immunoresponses against the loaded antigens as evidenced by high levels of BSA-specific IgG in the sera and IgA in the salivary, intestinal and vaginal secretions of mice. Enhanced levels of IgG2a and IFN-γ in treated mice revealed that proMMAs induced a mixed Th1/Th2 immunoresponse. Moreover, a significant increase in CD8(+) T cells confirmed that strong cellular immunity had also been established by the immunization of the proMMAs. Thus, the proMMAs can be immunized via o.m. route to set up an effective multiple defense against pathogen invasion and may be an effective vaccine adjuvant-delivery system (VADS) applicable in the controlled temperature chain.

Mannosylated and lipid A-incorporating cationic liposomes constituting microneedle arrays as an effective oral mucosal HBV vaccine applicable in the controlled temperature chain

To develop an effective, convenient and stable mucosal vaccine against hepatitis B virus (HBV), the mannose-PEG-cholesterol/lipid A-liposomes (MLLs) loaded with HBsAg were prepared by the procedure of emulsification-lyophilization and, subsequently, filled into the microholes of microneedle array reverse molds and dried to form the proHBsAg-MLLs microneedle arrays (proHMAs). The proHMAs were stable even at 40 °C for up to 3 days and hard enough to pierce porcine skin but, upon rehydration, rapidly dissolved recovering the HBsAg-MLLs without obvious changes in size and antigen association efficiency. Notably, immunization of mice only once with the proHMAs at oral mucosa induced robust systemic and widespread mucosal immunoresponses, as evidenced by the high levels of HBsAg-specific IgG in the sera and IgA in the salivary, intestinal and vaginal secretions. In addition, a strong cellular immunity against HBV had been established through a mixed Th1/Th2 response, as confirmed by a significant increase in CD8(+) T cells as well as the enhanced levels of IgG2a and IFN-γ in the treated mice. Thus, the proHMAs can be conveniently vaccinated via oral mucosal route to set up a multiple immune defense against HBV invasion and, in addition, may be a stable HBV vaccine applicable in the controlled temperature chain for wide distribution.

Mannose derivative and lipid A dually decorated cationic liposomes as an effective cold chain free oral mucosal vaccine adjuvant-delivery system

To develop convenient, effective cold chain-free subunit vaccines, a mannose-PEG-cholesterol conjugate (MPC) was synthesized as a lectin binding molecule and anchored onto liposomes which entrapped lipid A and model antigen to form a vaccine adjuvant-delivery system targeting antigen presenting cells. With MPC, soy phosphatidylcholine, stearylamine and monophosphoryl lipid A as emulsifiers dissolved in oil phase (O), and sucrose and BSA in water phase (W), the O/W emulsions were prepared and subsequently lyophilized. The lyophilized product was stable enough to be stored at room temperature and, upon rehydration, formed MPC-/lipid A-liposomes (MLLs) with a size under 300 nm and antigen association rates of around 36%. The MLLs given to mice via oral mucosal (o.m.) administration showed no side effects but induced potent immune responses as evidenced by the high levels of IgG in the sera and IgA in the salivary, intestinal and vaginal secretions of mice. High levels of IgG2a and IFN-γ in treated mice revealed that MLLs via o.m. vaccination induced a mixed Th1/Th2 response against antigens, establishing both humoral and cellular immunity. Thus, the MLLs may be a potent cold chain-free oral mucosal vaccine adjuvant-delivery system.

Using procedure of emulsification-lyophilization to form lipid A-incorporating cochleates as an effective oral mucosal vaccine adjuvant-delivery system (VADS)

Using a procedure of emulsification-lyophilization (PEL), adjuvant lipid A-cochleates (LACs) were prepared as a carrier for model antigen bovine serum albumin (BSA). With phosphatidylserine and lipid A as emulsifiers dissolved in oil phase (O), sucrose and CaCl2 in the inner water phase (W1), and BSA, sucrose and PEG2000 in the outer water phase (W2), the W1/O/W2 emulsions were prepared and subsequently lyophilized to form a dry product which was stable enough to be stored at room temperature. Upon rehydration of the dry products, cochleates formed with a size of 800 nm and antigen association rates of 38%. After vaccination of mice through oral mucosal (o.m.) administration, LACs showed no side effects but induced potent immune responses as evidenced by high levels of IgG in the sera and IgA in the salivary, intestinal and vaginal secretions of mice. In addition, high levels of IgG2a and IFN-γ in the sera or culture supernatants of splenocytes of the immunized mice were also detected. These results revealed that LACs induced a mixed Th1/Th2 response against the loaded antigens. Thus, the LACs prepared by PEL were able to induce both systemic and mucosal immune responses and may act as a potent cold-chain-free oral mucosal vaccine adjuvant delivery system (VADS).