Treatment of Periodontal Infections, the Possible Role of Hydrogels as Antibiotic Drug-Delivery Systems

With the advancement of biomedical research into antimicrobial treatments for various diseases, the source and delivery of antibiotics have attracted attention. In periodontal diseases, antibiotics are integral in positive treatment outcomes; however, the use of antibiotics is with caution as the potential for the emergence of resistant strains is of concern. Over the years, conventional routes of drug administration have been proven to be effective for the treatment of PD, yet the problem of antibiotic resistance to conventional therapies continues to remain a setback in future treatments. Hydrogels fabricated from natural and synthetic polymers have been extensively applied in biomedical sciences for the delivery of potent biological compounds. These polymeric materials either have intrinsic antibacterial properties or serve as good carriers for the delivery of antibacterial agents. The biocompatibility, low toxicity and biodegradability of some hydrogels have favoured their consideration as prospective carriers for antibacterial drug delivery in PD. This article reviews PD and its antibiotic treatment options, the role of bacteria in PD and the potential of hydrogels as antibacterial agents and for antibiotic drug delivery in PD. Finally, potential challenges and future directions of hydrogels for use in PD treatment and diagnosis are also highlighted.

Drug loaded implantable devices to treat cardiovascular disease

INTRODUCTION

It is widely acknowledged that cardiovascular diseases (CVDs) continue to be the leading cause of death globally. Furthermore, CVDs are the leading cause of diminished quality of life for patients, frequently as a result of their progressive deterioration. Medical implants that release drugs into the body are active implants that do more than just provide mechanical support; they also have a therapeutic role. Primarily, this is achieved through the controlled release of active pharmaceutical ingredients (API) at the implementation site.

AREAS COVERED

In this review, the authors discuss drug-eluting stents, drug-eluting vascular grafts, and drug-eluting cardiac patches with the aim of providing a broad overview of the three most common types of cardiac implant.

EXPERT OPINION

Drug eluting implants are an ideal alternative to traditional drug delivery because they allow for accurate drug release, local drug delivery to the target tissue, and minimise the adverse side effects associated with systemic administration. Despite the fact that there are still challenges that need to be addressed, the ever-evolving new technologies are making the fabrication of drug eluting implants a rewarding therapeutic endeavour with the possibility for even greater advances.

Therapeutic Potential of Cannabinoids on Tumor Microenvironment: A Molecular Switch in Neoplasia Transformation

The efficacy of chemotherapy depends on the tumor microenvironment. This microenvironment consists of a complex cellular network that can exert both stimulatory and inhibitory effects on tumor genesis. Given the increasing interest in the effectiveness of cannabis, cannabinoids have gained much attention as a potential chemotherapy drug. Cannabinoids are a group of marker compounds found in Cannabis sativa L., more commonly known as marijuana, a psychoactive drug used since ancient times for pain management. Although the anticancer potential of C. sativa, has been recognized previously, increased attention was generated after discovering the endocannabinoid system and the successful production of cannabinoid receptors. In vitro and in vivo studies on various tumor models have shown therapeutic efficiency by modifying the tumor microenvironment. However, despite extensive attention regarding potential therapeutic implications of cannabinoids, considerable clinical and preclinical analysis is needed to adequately define the physiological, pharmacological, and medicinal aspects of this range of compounds in various disorders covered in this review. This review summarizes the key literature surrounding the role of cannabinoids in the tumor microenvironment and their future promise in cancer treatment.

Medical Device Development for Children and Young People-Reviewing the Challenges and Opportunities

Development of specific medical devices (MDs) is required to meet the healthcare needs of children and young people (CYP). In this context, MD development should address changes in growth and psychosocial maturation, physiology, and pathophysiology, and avoid inappropriate repurposing of adult technologies. Underpinning the development of MD for CYP is the need to ensure MD safety and effectiveness through pediatric MD-specific regulations. Contrary to current perceptions of limited market potential, the global pediatric healthcare market is expected to generate around USD 15,984 million by 2025. There are 1.8 billion young people in the world today; 40% of the global population is under 24, creating significant future healthcare market opportunities. This review highlights a number of technology areas that have led to successful pediatric MD, including 3D printing, advanced materials, drug delivery, and diagnostic imaging. To ensure the targeted development of MD for CYP, collaboration across multiple professional disciplines is required, facilitated by a platform to foster collaboration and drive innovation. The European Pediatric Translational Research Infrastructure (EPTRI) will be established as the European platform to support collaboration, including the life sciences industrial sector, to identify unmet needs in child health and support the development, adoption, and commercialization of pediatric MDs.

Directly Compressed Tablets: A Novel Drug-Containing Reservoir Combined with Hydrogel-Forming Microneedle Arrays for Transdermal Drug Delivery

Microneedle (MN) patches consist of a hydrogel-forming MN array and a drug-containing reservoir. Drug-containing reservoirs documented in the literature include polymeric films and lyophilized wafers. While effective, both reservoir formulations are aqueous based, and so degradation can occur during formulation and drying for drugs inherently unstable in aqueous media. The preparation and characterization of novel, nonaqueous-based, directly compressed tablets (DCTs) for use in combination with hydrogel-forming MN arrays are described for the first time. In this work, a range of drug molecules are investigated. Precipitation of amoxicillin (AMX) and primaquine (PQ) in conventional hydrogel-forming MN arrays leads to use of poly(vinyl alcohol)-based MN arrays. Following in vitro permeation studies, in vivo pharmacokinetic studies are conducted in rats with MN patches containing AMX, levodopa/carbidopa (LD/CD), and levofloxacin (LVX). Therapeutically relevant concentrations of AMX (≥2 µg mL^-1 ), LD (≥0.5 µg mL^-1 ), and LVX (≥0.2 µg mL^-1 ) are successfully achieved at 1, 2, and 1 h, respectively. Thus, the use of DCTs offers promise to expand the range of drug molecules that can be delivered transdermally using MN patches.

Development, Evaluation, and Pharmacokinetic Assessment of Polymeric Microarray Patches for Transdermal Delivery of Vancomycin Hydrochloride

Methicillin-resistant Staphylococcus aureus (MRSA) can cause harmful and potentially deadly infections. Vancomycin remains the first-line antibiotic treatment for MRSA-derived infections. Nevertheless, as a peptide drug, it is poorly absorbed when administered orally because of its high molecular weight and low permeability in the gastrointestinal tract and is therefore administered intravenously for the treatment of systemic diseases. In order to circumvent some of the many drawbacks associated with intravenous injection, other routes of drug delivery should be investigated. One of the strategies which has been employed to enhance transdermal drug delivery is based on microarray patches (MAPs). This work, for the first time, describes successful transdermal delivery of vancomycin hydrochloride (VCL) using dissolving MAPs (DMAPs) and hydrogel-forming MAPs (HFMAPs). VCL was formulated into DMAPs and reservoirs [film dosage forms, lyophilized wafers, and compressed tablets (CSTs)] using excipients such as poly(vinyl pyrrolidone), poly(vinyl alcohol), sodium hyaluronate, d-sorbitol, and glycerol. In this study, HFMAPs were manufactured using aqueous blends containing poly(methylvinyl ether-co-maleic acid) cross-linked by esterification with poly(ethylene glycol). The VCL-loaded CSTs (60% w/w VCL) were the most promising reservoirs to be integrated with HFMAPs based on the physicochemical evaluations performed. Both HFMAPs and DMAPs successfully delivered VCL in ex vivo studies with the percentage of drug that permeated across the neonatal porcine skin recorded at 46.39 ± 8.04 and 7.99 ± 0.98%, respectively. In in vivo studies, the area under the plasma concentration time curve from time zero to infinity (AUC_0-∞) values of 162.04 ± 61.84 and 61.01 ± 28.50 μg h/mL were achieved following the application of HFMAPs and DMAPs, respectively. In comparison, the AUC_0-∞ of HFMAPs was significantly greater than that of the oral administration control group, which showed an AUC_0-∞ of 30.50 ± 9.18 μg h/mL (p < 0.05). This work demonstrates that transdermal delivery of VCL is feasible using DMAPs and HFMAPs and could prove effective in the treatment of infectious diseases caused by MRSA, such as skin and soft tissue infections, lymphatic-related infections, and neonatal sepsis.

Hydrogel-forming microneedle arrays as a therapeutic option for transdermal esketamine delivery

Treatment resistant depression is, by definition, difficult to treat using standard therapeutic interventions. Recently, esketamine has been shown as a viable rescue treatment option in patients in depressive crisis states. However, IV administration is associated with a number of drawbacks and advanced delivery platforms could provide an alternative parenteral route of esketamine dosing in patients. Hydrogel-forming microneedle arrays facilitate transdermal delivery of drugs by penetrating the outer layer of the skins surface, absorbing interstitial skin fluid and swelling. This subsequently facilitates permeation of medicines into the dermal microcirculation. This paper outlines the in vitro formulation development for hydrogel-forming microneedle arrays containing esketamine. Analytical methods for the detection and quantitation of esketamine were developed and validated according to International Conference on Harmonisation standards. Hydrogel-forming microneedle arrays were fully characterised for their mechanical strength and skin insertion properties. Furthermore, a series of esketamine containing polymeric films and lyophilised reservoirs were assessed as drug reservoir candidates. Dissolution testing and content drug recovery was carried out, followed by permeation studies using 350 μm thick neonatal porcine skin in modified Franz cell apparatus. Lead reservoir candidates were selected based on measured physicochemical properties and brought forward for testing in female Sprague-Dawley rats. Plasma samples were analysed using reverse phase high performance liquid chromatography for esketamine. Both polymeric film and lyophilised reservoirs candidate patches achieved esketamine plasma concentrations higher than the target concentration of 0.15-0.3 μg/ml over 24 h. Mean plasma concentrations in rats, 24 h post-application of microneedle patches with drug reservoir F3 and LW3, were 0.260 μg/ml and 0.498 μg/ml, respectively. This developmental study highlights the potential success of hydrogel-forming microneedle arrays as a transdermal drug delivery platform for ESK and supports moving to in vivo tests in a larger animal model.

Evaluation of the clinical impact of repeat application of hydrogel-forming microneedle array patches

Hydrogel-forming microneedle array patches (MAPs) have been proposed as viable clinical tools for patient monitoring purposes, providing an alternative to traditional methods of sample acquisition, such as venepuncture and intradermal sampling. They are also undergoing investigation in the management of non-melanoma skin cancers. In contrast to drug or vaccine delivery, when only a small number of MAP applications would be required, hydrogel MAPs utilised for sampling purposes or for tumour eradication would necessitate regular, repeat applications. Therefore, the current study was designed to address one of the key translational aspects of MAP development, namely patient safety. We demonstrate, for the first time in human volunteers, that repeat MAP application and wear does not lead to prolonged skin reactions or prolonged disruption of skin barrier function. Importantly, concentrations of specific systemic biomarkers of inflammation (C-reactive protein (CRP); tumour necrosis factor-α (TNF-α)); infection (interleukin-1β (IL-1β); allergy (immunoglobulin E (IgE)) and immunity (immunoglobulin G (IgG)) were all recorded over the course of this fixed study period. No biomarker concentrations above the normal, documented adult ranges were recorded over the course of the study, indicating that no systemic reactions had been initiated in volunteers. Building upon the results of this study, which serve to highlight the safety of our hydrogel MAP, we are actively working towards CE marking of our MAP technology as a medical device.

A Novel Transdermal Protein Delivery Strategy via Electrohydrodynamic Coating of PLGA Microparticles onto Microneedles

Transdermal delivery of biological therapeutics is emerging as a potent alternative to intravenous or subcutaneous injections. The latter possess major challenges including patient discomfort, the necessity for trained personnel, specialized sharps disposal, and risk of infection. The microneedle (MN) technology circumvents many of the abovementioned challenges, delivering biological materials directly into the skin and allowing sustained release of the active ingredient both in animal models and in humans. This study describes the use of electrohydrodynamic atomization (EHDA) to coat ovalbumin (OVA)-loaded PLGA nanoparticles onto hydrogel-forming MN arrays. The particles showed extended release of OVA over ca. 28 days. Microscopic analysis demonstrated that EHDA could generate a uniform particle coating on the MNs, with 30% coating efficiency. Furthermore, the coated MN array manifested similar mechanical characteristics and insertion properties to the uncoated system, suggesting that the coating should have no detrimental effects on the application of the MNs. The coated MNs resulted in no significant increase in anti-OVA-specific IgG titres in C57BL/6 mice in vivo as compared to the untreated mice (paired t-test, p > 0.05), indicating that the formulations are nonimmunogenic. The approach of using EHDA to coat an MN array thus appears to have potential as a novel noninvasive protein delivery strategy.

Pullulan-based dissolving microneedle arrays for enhanced transdermal delivery of small and large biomolecules

One specific technological advance in transdermal drug delivery is the development of dissolving microneedles (DMNs), which efficiently deliver therapeutics through a rapid dissolution of polymers after penetration into the skin. However, there is a limited range of water soluble, biodegradable polymers that can be used to manufacture DMN. Here, we report for the first time, the preparation and characterisation of a DMN system from the carbohydrate biopolymer, pullulan (PL). PL gels, of varying concentration, were studied for viscosity, film formation properties, and subsequently, microneedle formation. Model molecules and protein/peptide were loaded into PL DMN and characterised. The stability of model biomolecules, such as FITC-BSA and insulin, following DMN manufacture were assessed using circular dichroism. Ex-vivo porcine skin permeation studies using Franz diffusion cell apparatus for Flu-Na and FITC-BSA loaded PL-DMN were conducted. This study demonstrates that PL DMNs may serve as a promising tool for efficient transdermal drug delivery.

Control of Klebsiella pneumoniae Infection in Mice by Using Dissolving Microarray Patches Containing Gentamicin

Using a murine model of Klebsiella pneumoniae bacterial infection, we demonstrate that gentamicin dissolving microarray patches, applied to murine ears, could control K. pneumoniae infection. Mice treated with microarray patches had reduced bacterial burden in the nasal-associated lymphoid tissue and lungs compared with their untreated counterparts. This proof of concept study represents the first published data on the in vivo delivery of the antibiotic gentamicin via dissolving microarray patches, resulting in the control of bacterial infection.

Novel Hydrogel-Forming Microneedle Array for Intradermal Vaccination in Mice Using Ovalbumin as a Model Protein Antigen

Global vaccination strategies have traditionally relied on the hypodermic needle and syringe model. However, to facilitate increased immunization coverage and reduce costs, novel methods of vaccine delivery are warranted. Dissolving microneedle arrays (MNs) have been proposed as an alternative approach to the hypodermic needle, offering the prospect for self-vaccination and increased immunogenicity via direct targeting of skin dendritic cells. This study, for the first time, compares the use of novel hydrogel-forming MNs and dissolving MNs for the delivery of a model protein antigen ovalbumin (OVA). We provide comparative data on both MN types in terms of in vitro characteristics and in vivo immunogenicity. Herein, both MN platforms were tested and characterized in terms of mechanical integrity and insertion properties using a validated skin insertion model. A comparative in vivo vaccination study in BALB/c mice was conducted, whereby anti-OVA specific IgG was used as a measure of delivery efficacy and subsequent immune response. While vaccination of mice with both MN platforms resulted in IgG responses, those vaccinated with dissolving MNs had significantly higher IgG titers ( p < 0.0149), despite the quantity of OVA delivered being significantly less. This study highlights the importance of MN design and the potential impact of dissolving MN polymers on the immune response to vaccine antigens. Furthermore, detailed studies are therefore required to elucidate the effects of polymer-vaccine interactions and their subsequent effect on immune responses.

Hydrogel-forming microneedles enhance transdermal delivery of metformin hydrochloride

We investigated, for the first time, the potential for a hydrogel-forming microneedle (MN) patch to deliver the high-dose drug metformin HCl transdermally in a sustained manner. This may minimize some gastrointestinal side effects and small intestine absorption variations associated with oral delivery. Patches (two layers) were assembled from a lyophilised drug reservoir layer, with the MN layer made from aqueous blend of 20% w/w poly (methylvinylether-co-maleic acid) crosslinked by esterification with 7.5% w/w poly (ethylene glycol) 10,000 Da. >90% of metformin was recovered from homogeneous drug reservoirs. Drug reservoir dissolution time in PBS (pH 7.4) was <10 min. MN penetrated a validated skin model Parafilm® M consistently. Permeation of metformin HCl across dermatomed neonatal porcine skin in vitro was enhanced by using MN. The combined MN and metformin HCl reservoir patch (containing 75 mg or 50 mg metformin HCl, respectively) delivered 9.71 ± 2.22 mg and 10.04 ± 1.92 mg at 6 h, respectively, and 28.15 ± 2.37 mg and 23.25 ± 3.58 mg at 24 h, respectively.In comparison, 0.34 ± 0.39 mg and 0.85 ± 0.68 mg was delivered at 6 h, respectively, and 0.39 ± 0.39 mg and 1.01 ± 0.84 mg was delivered at 24 h, respectively, from a control set-up employing only the drug reservoirs. In vivo, metformin HCl was detected in rat plasma at 1 h post MN application at a concentration of 0.62 ± 0.51 μg/mL, increasing to 3.76 ± 2.58 μg/ml at 3 h. A maximal concentration of 3.77 ± 2.09 μg/ml was achieved at 24 h. Css was 3.2 μg/mL. Metformin transdermal bioavailability using MNs was estimated as 30%.Hydrogel-forming MN are a promising technology that has demonstrated successful transdermal delivery of metformin HCl. Potential clearly exists for administration of other high-dose drugs using this system.

Future of the transdermal drug delivery market--have we barely touched the surface?

INTRODUCTION

Transdermal drug delivery is the movement of drugs across the skin for absorption into the systemic circulation. Transfer of the drug can occur via passive or active means; passive transdermal products do not disrupt the stratum corneum to facilitate delivery whereas active technologies do. Due to the very specific physicochemical properties necessary for successful passive transdermal drug delivery, this sector of the pharmaceutical industry is relatively small. There are many well-documented benefits of this delivery route however, and as a result there is great interest in increasing the number of therapeutic substances that can be delivered transdermally.

AREAS COVERED

This review discusses the various transdermal products that are currently/have been marketed, and the paths that led to their success, or lack of. Both passive and active transdermal technologies are considered with the advantages and limitations of each highlighted. In addition to marketed products, technologies that are in the investigative stages by various pharmaceutical companies are reviewed.

EXPERT OPINION

Passive transdermal drug delivery has made limited progress in recent years, however with the ongoing intense research into active technologies, there is great potential for growth within the transdermal delivery market. A number of active technologies have already been translated into marketed products, with other platforms including microneedles, rapidly progressing towards commercialisation.

Microneedle applications in improving skin appearance

Microneedles (MNs) are micron-sized, minimally invasive devices that breach the outermost layer of the skin, the stratum corneum (SC), creating transient, aqueous pores in the skin and facilitating the transport of therapeutic molecules into the epidermis. Following many years of extensive research in the area of MN-mediated trans- and intra-dermal drug delivery, MNs are now being exploited in the cosmeceutical industry as a means of disrupting skin cell architecture, inducing elastin and collagen expression and deposition. They are also being used as vehicles to deliver cosmeceutic molecules across the skin, in addition to their use in combinatorial treatments with topical agents or light sources. This review explores the chronology of microneedling methodologies, which has led to the emergence of MN devices, now extensively used in cosmeceutical applications. Recent developments in therapeutic molecule and peptide delivery to the skin via MN platforms are addressed and some commercially available MN devices are described. Important safety and regulatory considerations relating to MN usage are addressed, as are studies relating to public perception of MN, as these will undoubtedly influence the acceptance of MN products as they progress towards commercialisation.

Hydrogel-forming microneedles prepared from "super swelling" polymers combined with lyophilised wafers for transdermal drug delivery

We describe, for the first time, hydrogel-forming microneedle arrays prepared from "super swelling" polymeric compositions. We produced a microneedle formulation with enhanced swelling capabilities from aqueous blends containing 20% w/w Gantrez S-97, 7.5% w/w PEG 10,000 and 3% w/w Na2CO3 and utilised a drug reservoir of a lyophilised wafer-like design. These microneedle-lyophilised wafer compositions were robust and effectively penetrated skin, swelling extensively, but being removed intact. In in vitro delivery experiments across excised neonatal porcine skin, approximately 44 mg of the model high dose small molecule drug ibuprofen sodium was delivered in 24 h, equating to 37% of the loading in the lyophilised reservoir. The super swelling microneedles delivered approximately 1.24 mg of the model protein ovalbumin over 24 h, equivalent to a delivery efficiency of approximately 49%. The integrated microneedle-lyophilised wafer delivery system produced a progressive increase in plasma concentrations of ibuprofen sodium in rats over 6 h, with a maximal concentration of approximately 179 µg/ml achieved in this time. The plasma concentration had fallen to 71±6.7 µg/ml by 24 h. Ovalbumin levels peaked in rat plasma after only 1 hour at 42.36±17.01 ng/ml. Ovalbumin plasma levels then remained almost constant up to 6 h, dropping somewhat at 24 h, when 23.61±4.84 ng/ml was detected. This work represents a significant advancement on conventional microneedle systems, which are presently only suitable for bolus delivery of very potent drugs and vaccines. Once fully developed, such technology may greatly expand the range of drugs that can be delivered transdermally, to the benefit of patients and industry. Accordingly, we are currently progressing towards clinical evaluations with a range of candidate molecules.

The role of microneedles for drug and vaccine delivery

INTRODUCTION

Transdermal drug delivery offers a number of advantages for the patient, not only due to its non-invasive and convenient nature, but also due to factors such as avoidance of first-pass metabolism and prevention of gastrointestinal degradation. It has been demonstrated that microneedles (MNs) can increase the number of compounds amenable to transdermal delivery by penetrating the skin's protective barrier, the stratum corneum, and creating a pathway for drug permeation to the dermal tissue below.

AREAS COVERED

MNs have been extensively investigated for drug and vaccine delivery. The different types of MN arrays and their delivery capabilities are discussed in terms of drugs, including biopharmaceutics and vaccines. Patient usage and effects on the skin are also considered.

EXPERT OPINION

MN research and development is now at the stage where commercialisation is a viable possibility. There are a number of long-term safety questions relating to patient usage which will need to be addressed moving forward. Regulatory guidance is awaited to direct the scale-up of the manufacturing process alongside provision of clearer patient instruction for safe and effective use of MN devices.

Design of an electrical impedance tomography phantom using active elements

The architecture of a novel phantom for electrical impedance tomography (EIT) is proposed. The design employs active elements, which include multiplying digital to analogue converters (MDAC), so that the impedance distribution in the phantom may be varied dynamically using computer control. The phantom is designed to assist in the validation of an EIT system under test. A number of published layouts for passive phantoms are analysed, and the requirements for an active element are specified for the most applicable of these. The use of active elements throughout a phantom imposes significant costs because of the need for each active element to operate independently. This proposal limits the cost and complexity by employing active elements in a restricted region of the phantom. Currently available technology, principally due to the limited analogue bandwidth of the MDAC, precludes the construction of a fully capable phantom from active elements. However, a design is specified that would enable its future development to cover the frequency range from 10 kHz to 1 MHz.