A crossover clinical study to evaluate pain intensity from microneedle insertion in different parts of the oral cavity

Biodegradable polymeric insulin microneedles - a design and materials perspective review

Microneedle (MN) delivery devices are more accepted by people than regular traditional needle injections (e.g. vaccination) due to their simplicity and adaptability. Thus, patients of chronic diseases like diabetes look for alternative pain-free treatment regimens circumventing regular subcutaneous injections. Insulin microneedles (INS-MNs) are a thoughtfully researched topic (1) to overcome needle phobia in patients, (2) for controlled delivery of the peptide, (3) decreasing the frequency of drug administration, (4) to ease the drug administration procedure, and (5) thus increasing patient adherence to the treatment dosage regimes. MNs physically disrupt the hard outer skin layer to create minuscule pores for insulin (INS) to pass through the dermal capillaries into the systemic circulation. Biodegradable polymeric MNs are of greater significance for INS and vaccine delivery than silicon, metal, glass, or non-biodegradable polymeric MNs due to their ease of fabrication, mass production, cost-effectiveness, and bioerodability. In recent years, INS-MNs have been researched to deliver INS through the transdermal implants, buccal mucosa, stomach wall, intestinal mucosal layers, and colonic mucosa apart from the usual transdermal delivery. This review focuses on the design characteristics and the applications of biodegradable/dissolvable polymeric INS-MNs in transdermal, intra-oral, gastrointestinal (GI), and implantable delivery. The prospective approaches to formulate safe, controlled-release INS-MNs were highlighted. Biodegradable/dissolvable polymers, their significance, their impact on MN morphology, and INS release characteristics were outlined. The developments in biodegradable polymeric INS-MN technology were briefly discussed. Bio-erodible polymer selection, MN fabrication and evaluation factors, and other design aspects were elaborated.

Application of hydrogel microneedles in the oral cavity

Microneedles are a transdermal drug delivery system in which the needle punctures the epithelium to deliver the drug directly to deep tissues, thus avoiding the influence of the first-pass effect of the gastrointestinal tract and minimizing the likelihood of pain induction. Hydrogel microneedles are microneedles prepared from hydrogels that have good biocompatibility, controllable mechanical properties, and controllable drug release and can be modified to achieve environmental control of drug release in vivo. The large epithelial tissue in the oral cavity is an ideal site for drug delivery via microneedles. Hydrogel microneedles can overcome mucosal hindrances to delivering drugs to deep tissues; this prevents humidity and a highly dynamic environment in the oral cavity from influencing the efficacy of the drugs and enables them to obtain better therapeutic effects. This article analyzes the materials and advantages of common hydrogel microneedles and reviews the application of hydrogel microneedles in the oral cavity.

Safety tests and clinical research on buccal and nasal microneedle swabs for genomic analysis

Conventional swabs have been used as a non-invasive method to obtain samples for DNA analysis from the buccal and the nasal mucosa. However, swabs may not always collect pure enough genetic material. In this study, buccal and nasal microneedle swab is developed to improve the accuracy and reliability of genomic analysis. A cytotoxicity test, a skin sensitivity test, and a skin irritation test are conducted with microneedle swabs. Polymer microneedle swabs meet the safety requirements for clinical research and commercial use. When buccal and nasal microneedle swabs are used, the amount of genetic material obtained is greater than that from commercially available swabs, and DNA purity is also high. The comparatively short microneedle swab (250 μm long) cause almost no pain to all 25 participants. All participants also report that the microneedle swabs are very easy to use. When genotypes are compared at five SNP loci from blood of a participant and from that person's buccal or nasal microneedle swab, the buccal and nasal microneedle swabs show 100% concordance for all five SNP genotypes. Microneedle swabs can be effectively used for genomic analysis and prevention through genomic analysis, so the utilization of microneedle swabs is expected to be high.

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.

Fabrication of 3D Printed Hollow Microneedles by Digital Light Processing for the Buccal Delivery of Actives

In the present study, two different microneedle devices were produced using digital light processing (DLP). These devices hold promise as drug delivery systems to the buccal tissue as they increase the permeability of actives with molecular weights between 600 and 4000 Da. The attached reservoirs were designed and printed along with the arrays as a whole device. Light microscopy was used to quality control the printability of the designs, confirming that the actual dimensions are in agreement with the digital design. Non-destructive volume imaging by means of microfocus computed tomography was employed for dimensional and defect characterization of the DLP-printed devices, demonstrating the actual volumes of the reservoirs and the malformations that occurred during printing. The penetration test and finite element analysis showed that the maximum stress experienced by the needles during the insertion process (10 N) was below their ultimate compressive strength (240-310 N). Permeation studies showed the increased permeability of three model drugs when delivered with the MN devices. Size-exclusion chromatography validated the stability of all the actives throughout the permeability tests. The safety of these printed devices for buccal administration was confirmed by histological evaluation and cell viability studies using the TR146 cell line, which indicated no toxic effects.

Microneedles for oral mucosal delivery - Current trends and perspective on future directions

INTRODUCTION

Oral cavity drug and vaccine delivery has the potential for local targeting, dose reduction, minimization of systemic side effects, and generation of mucosal immunity. To overcome current limitations of delivery into the oral cavity mucosa, microneedles (MNs) have emerged as a promising technology.

AREAS COVERED

We reviewed the literature on MN application in the oral cavity, including in vitro studies, in vivo animal studies, and human clinical trials.

EXPERT OPINION

MNs are sufficiently robust to cross the oral cavity epithelium and nearly painless when applied to different parts of the human oral mucosa including the lip, cheek, tongue, and palate. In recent years, MNs have been evaluated for different applications, including vaccination, topical anesthetic delivery, and treatment of local oral pathologies such as oral lesions or carcinomas. MNs are attractive because they have the potential to produce a better treatment outcome with reduced side effects. Over the coming years, we project a significant increase in research related to the development of MNs for use in dentistry and other medical conditions of the mouth.

Betamethasone-loaded dissolvable microneedle patch for oral ulcer treatment

Oral inflammatory disease (OID) is among the most common oral lesions, affecting people's quality of life and even leading to oral cancer. Oral ulcers are the most common OID. However, the pain and fear caused by the localized injection of hormones hinder the clinical treatment of oral ulcers. To address this problem, soluble hyaluronic acid (HA) microneedle patches (BSP-BDP@HAMN) containing betamethasone 21-phosphate sodium (BSP) and betamethasone 17,21-dipropionate (BDP) were fabricated for potential application in oral ulcers. BSP-BDP@HAMNs had the sufficient mechanical strength to penetrate the rat tongue abdomen mucosa with an insertion depth of approximately 207 ± 3 µm. The rapidly solubilized HA microneedle carrier released BSP and BDP into the ulcer base within 3 min of entering the mucosa. Cellular assays have shown that BDP@HAMNs have wound healing-promoting and anti-inflammatory effects. Compared with topical injections and creams, BSP-BDP@HAMNs not only penetrated the ulcer surface painlessly but also worked deep in the ulcer for a long time. In conclusion, the proposed BSP-BDP@HAMN patch can improve the comfort and efficacy of oral ulcer treatment, thus providing a new prospect for oral ulcer treatment.

Polymeric Biomaterials for Topical Drug Delivery in the Oral Cavity: Advances on Devices and Manufacturing Technologies

There are several routes of drug administration, and each one has advantages and limitations. In the case of the topical application in the oral cavity, comprising the buccal, sublingual, palatal, and gingival regions, the advantage is that it is painless, non-invasive, allows easy application of the formulation, and it is capable of avoiding the need of drug swallowing by the patient, a matter of relevance for children and the elderly. Another advantage is the high permeability of the oral mucosa, which may deliver very high amounts of medication rapidly to the bloodstream without significant damage to the stomach. This route also allows the local treatment of lesions that affect the oral cavity, as an alternative to systemic approaches involving injection-based methods and oral medications that require drug swallowing. Thus, this drug delivery route has been arousing great interest in the pharmaceutical industry. This review aims to condense information on the types of biomaterials and polymers used for this functionality, as well as on production methods and market perspectives of this topical drug delivery route.

Composite dissolvable microneedle patch for therapy of oral mucosal diseases

A composite microneedle patch (MN patch) is developed for oral transmucosal administration. To improve the oral transmucosal drug delivery efficiency, the composite MN patch is designed to consist of an array of 100 dissolvable microneedles (MNs) with drug-loaded tips and a backing layer. The MNs are composed of two parts, the hyaluronic acid (HA) tip part and the polyvinylpyrrolidone (PVP) base part. Due to the small size and sufficient mechanical strength, the HA-PVP MNs can painlessly penetrate the oral mucosa barrier and deliver drugs directly to the basal layer or submucosa. Betamethasone sodium phosphate (BSP), as the model drug, is concentrated in the HA tip parts to avoid the drug waste caused by mucosa elasticity. Considering the special moist environment and saliva flow in the mouth, a double-layer backing layer composed of a poly(vinyl alcohol) (PVA) adhesive layer and an ethyl cellulose (EC) waterproof layer is designed and constructed, which could reduce the saliva flow effects. The in vitro and in vivo results demonstrate that the MN patch could achieve rapid and efficient BSP release in oral mucosa due to the rapid dissolution of HA. The proposed MN patch provides a novel strategy for the therapy of oral mucosal diseases.

Lidocaine-Loaded Hyaluronic Acid Adhesive Microneedle Patch for Oral Mucosal Topical Anesthesia

The pain and fear caused by direct local injection of anesthetic or the poor experience with surface anesthetic cream increase the difficulty of clinical treatment for oral diseases. To address this problem, a hyaluronic acid microneedle patch (Li-HAMNs) that consists of fast-dissolving lidocaine hydrochloride (LDC)-loaded tips and a wet-adhesive backing layer made of polyvinyl alcohol (PVA)/carboxymethylcellulose sodium (CMC-Na) was fabricated to explore its potential use in dental topical anesthesia. Li-HAMNs could puncture the stratum corneum with an insertion depth of about 279 μm in the isolated porcine oral mucosal. The fast-dissolving tips could release LDC to improve the patients’ convenience and compliance. Importantly, the backing layer, which has good adhesion ability and water-absorbing properties, could surmount the contraction and extension of oral masticatory muscles and the saliva scour. In the tail flick test, the topical anesthesia efficacy of the Li-HAMNs group was much better than clinical lidocaine cream (EMLA cream, LDC, 1.2 mg) in spite of a relatively lower LDC dose with Li-HAMNs (LDC, 0.5 mg). It is believed that the proposed adhesive microneedle patch could enhance transmucosal delivery of anesthetics and thus open a new chapter in the painless treatment of oral diseases.

Needle-free anesthesia: clinical efficacy of a mucoadhesive patch for atraumatic anesthesia in dental procedures

This study showcases the clinical efficacy of mucoadhesive patches designed for the buccal delivery of lidocaine and prilocaine hydrochlorides (1:1, 30 mg/patch). Such patches were developed for needle-free pre-operative local anesthesia in dentistry, aiming at mitigating the use of infiltrative anesthesia for medium-complexity clinical procedures. The patches were manufactured encompassing drug-release, mucoadhesive and backing layers, all prepared through film casting using biocompatible materials. Fifty-eight (n = 58) adult patients (65% women and 35% men) were randomly selected and included in a one-arm open clinical prospective cohort study. The average age of the subjects was of 50 years. The majority (59%) of the subjects, mostly women (82%), reported needle-phobia or anxiety due to dental procedures, which was assessed through a questionnaire approved by the ethical council for human use in research. The patches were positioned in the gingival region of the teeth involved in the procedure (86% on the maxillary and 14% on the mandibular bone). Two anesthetic patches were applied on each patient: one in the vestibular region and another in the palate/lingual portion, and these patches remained attached to the placement sites throughout the procedures. Concerning the dental procedures performed, 40% were cavity preparations and dental restorations of medium cavities; 29% staple facilities; 10% gingival retractions; 9% subgingival scrapings; 3% gingivalplasties; 3% supragingival preparations; 3% occlusal adjustments; and 2% subgingival preparations. In 90% of the cases, it was not necessary to complement with conventional infiltrative local anesthesia during the procedures. Patients did not report any discomfort or side effect during or after the administration of the patches. Among the cases in which there was the need for complementation, 50% were cavity preparations and dental restorations; 33% supragingival preparations; and 17% gingivoplasties. The complementary anesthesia volume was of 0.63 ± 0.23 mL and women corresponded to 83% of the participants who needed such intervention. Furthermore, in most cases, the patch was capable of initiating the anesthesia within a short time frame (5 minutes) and reaching the maximum anesthetic effect within 15 and 25 min, lasting at least 50 min. Undesirable side effects were not reported either 2 h after the administration or within the 6-month follow-up. Therefore, the anesthetic patches developed provide needle-free, painless, safe, and patient/dentist-friendly advances in performing routine medium-complexity dental procedures.

Advances of microneedles in hormone delivery

The skin is recognized as a potential target for local and systemic drug delivery and hormone. However, the transdermal route of drug administration seems to be limited by substantial barrier properties of the skin. Recently, delivering hormone via the skin by transdermal patches is a big challenge because of the presence of the stratum corneum that prevents the application of hormone via this route. In order to overcome the limitations, microneedle (MN), consisting of micro-sized needles, are a promising approach to drill the stratum corneum and release hormone into the dermis via a minimal-invasive route. This review aimed to highlight advances in research on the development of MNs-based therapeutics for their implications in hormone delivery. The challenges during clinical translation of MNs from bench to bedside are also discussed.