Lack of pain associated with microfabricated microneedles

Microneedle and Polymeric Films: Delivery of Proteins, Peptides and Nucleic Acids

In the last 20 years, protein, peptide and nucleic acid-based therapies have become the fastest growing sector in the pharmaceutical industry and play a vital role in disease therapy. However, the intrinsic sensitivity and large molecular sizes of biotherapeutics limit the available routes of administration. Currently, the main administration routes of biomacromolecules, such as parenteral, oral, pulmonary, nasal, rectal and buccal routes, each have their limitations. Several non-invasive strategies have been proposed to overcome these challenges. Researchers were particularly interested in microneedles (MNs) and polymeric films because of their less invasiveness, convenience and greater potential to preserve the bioactivity of biotherapeutics. By facilitating with MNs and polymeric films, biomacromolecules could provide significant benefits to patients suffering from various diseases such as cancer, diabetes, infectious and ocular diseases. However, before these devices can be used on patients, how to upscale MN manufacture in a cost-effective and timely manner, as well as the long-term safety of MN and polymeric film applications necessitates further investigation.

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.

Observation on the Efficacy of a Combined Treatment for Moderate and Severe Androgenetic Alopecia Incorporating Electric Microneedles

Objective

To evaluate the effectiveness and safety of a combined treatment for moderate and severe androgenetic alopecia (AGA) involving the use of electric microneedles.

Methods

A total of 83 patients with moderate to severe AGA in the Department of Dermatology at Beijing Jishuitan Hospital were included in this study. The male patients were administered finasteride orally and 5% minoxidil for external use, while the female patients were given spironolactone orally or Diane-35 and 2% minoxidil for external use. All the patients were then treated via electric microneedle therapy alongside the YUFA ®medical care package (Foshan, China) once a week for 1-28 weeks. The seven-point method and root hair measurement using a hair mirror were adopted to evaluate the efficacy and any adverse reactions of the combined treatment.

Results

Eleven patients were treated for 1-3 weeks, 60 for 4-12 weeks, and 12 for more than 12 weeks. The efficacy evaluation using the seven-point method for 12 weeks of treatment indicated a 100% response rate, specifically, a 42.1% mild improvement rate, a 38.6% moderate improvement rate, and a 19.3% marked improvement rate. Besides, the efficacy assessment was also completed with root hair count method and the number of hair roots measured at fixed points were 148.67±11.15, 158.13±5.11 and 169.75±2.06 after treatment time at 16, 20 and 24 weeks, respectively. Of note, a statistical difference in the number of hair roots could be observed during the period of week 20-week 24 (P < 0.01).

Conclusion

The combined treatment of moderate to severe AGA using the electric microneedle technique has a clear effect and can effectively increase the hair density. With a simple operation and mild side effects, the technique has wide application prospects.

Dissolvable Microneedle Patch Increases the Therapeutic Effect of Jawoongo on DNCB-Induced Atopic Dermatitis in Mice

BACKGROUND

Jawoongo (JW) is a topical herbal ointment that has been used as an alternative treatment option for atopic dermatitis. Topical ointments are known to have less bioavailability because the stratum corneum allows only lipophilic and low molecular weight drugs to pass across it. This study aimed to investigate whether applying microneedle patches (MNP) increases the therapeutic effect of 2,4-dinitrochlorobenzene (DNCB)+JW for atopic dermatitis by enhancing transdermal delivery.

METHODS

Atopic dermatitis was induced by DNCB in BALB/c mice. The combination treatment of JW and MNP was estimated to study the effect of MNP in improving transdermal delivery. Histological analysis, quantitative real-time PCR (qPCR), and immunofluorescence were performed to verify the effect of MNP in enhancing the therapeutic effects of DNCB+JW on atopic dermatitis in mice.

RESULTS

Both combination treatment and DNCB+JW treatment ameliorated histological alterations and reduced skin thickness and infiltration of CD4+ T cells in atopic dermatitis-like skin lesions in DNCB-exposed BALB/c mice. However, the improvement of histological alterations was better in the combination treatment, which was almost normal. Furthermore, the combination treatment exhibited a larger decrease in mRNA levels of IL-4, IL-6, IL-13, iNOS, and TNF-α, compared to DNCB+JW only. In addition, skin thickness and infiltration of CD4+ T cells in the sensitized skin were significantly lower using the combination treatment than using DNCB+JW only.

CONCLUSION

Combination treatment with JW and MNP further decreased skin thickness and several inflammatory cytokines in atopic dermatitis like skin lesions compared to treatment using JW alone. These findings suggest that applying a dissolvable MNP after JW application could be useful for treating atopic dermatitis.

Microneedles in Action: Microneedling and Microneedles-Assisted Transdermal Delivery

Human skin is a multilayered physiochemical barrier protecting the human body. The stratum corneum (SC) is the outermost keratinized layer of skin through which only molecules with less or equal to 500 Da (Dalton) in size can freely move through the skin. Unfortunately, the conventional use of a hypothermic needle for large therapeutic agents is susceptible to needle phobia and the risk of acquiring infectious diseases. As a new approach, a microneedle (MN) can deliver therapeutically significant molecules without apparent limitations associated with its molecular size. Microneedles can create microchannels through the skin’s SC without stimulating the proprioceptive pain nerves. With recent technological advancements in both fabrication and drug loading, MN has become a versatile platform that improves the efficacy of transdermally applied therapeutic agents (TAs) and associated treatments for various indications. This review summarizes advanced fabrication techniques for MN and addresses numerous TA coating and TA elution strategies from MN, offering a comprehensive perspective on the current microneedle technology. Lastly, we discuss how microneedling and microneedle technologies can improve the clinical efficacy of a variety of skin diseases.

Development and characterization of a dry reservoir-hydrogel-forming microneedles composite for minimally invasive delivery of cefazolin

Cefazolin (CFZ) is one of the most extensively used cephalosporins. This antibiotic exerts its bactericidal activity by interfering with bacterial cell wall formation, leading to bacteriolysis. CFZ is highly polar, resulting in the drug having poor oral bioavailability. Accordingly, the antibiotic is administered via intramuscular or intravenous injections, which are both painful and invasive. Due to these limitations, there is an impetus to explore alternative drug delivery platforms which offer a minimally invasive approach to delivery CFZ into and across the skin. The current work presents the development of a composite pharmaceutical system composed of hydrogel-forming microneedles (MNs) in tandem with CFZ dry reservoirs. The hydrogel system was fabricated from Gantrez® S-97 and Carbopol® 974P NF crosslinked with PEG 10,000. Swelling kinetic studies showed that the hydrogel system developed was capable of achieving 4000% swelling in PBS pH 7.4. In addition, results from a solute diffusion study showed that CFZ was able to achieve ≈100% cumulative permeation across the swollen hydrogel film. When formulated into MNs, the hydrogel system was capable of breaching the stratum corneum, resulting in intradermal insertion of the hydrogel forming MNs into ex vivo neonatal porcine skin, as evidenced from optical coherence tomography. In addition, two different CFZ loaded dry reservoirs consisting of directly compressed tablets (DCT) and lyophilised (LYO) wafers were formulated and characterised. These dry reservoir systems showed fast dissolution, dissolving in phosphate buffer saline pH 7.4 in less than one minute. In vitro permeation studies, using full thickness ex vivo neonatal porcine skin were conducted. HPLC analysis demonstrated the dry reservoir combination consisting of DCT with hydrogel-forming MNs was capable of achieving up to 80 µg CFZ delivery into the epidermis within 2 hours of application. In addition, DCT reservoir coupled with hydrogel-forming MNs were able to deliver CFZ up to 1.8 mg into and across the skin at 24 hours. Should this system be translated into clinical practice, it may provide a minimally invasive strategy to administer CFZ for the treatment of infections such as septic arthritis, osteomyelitis and cellulitis.

Microneedle systems for delivering nucleic acid drugs

Background

Nucleic acid-based gene therapy is a promising technology that has been used in various applications such as novel vaccination platforms for infectious/cancer diseases and cellular reprogramming because of its fast, specific, and effective properties. Despite its potential, the parenteral nucleic acid drug formulation exhibits instability and low efficacy due to various barriers, such as stability concerns related to its liquid state formulation, skin barriers, and endogenous nuclease degradation. As promising alternatives, many attempts have been made to perform nucleic acid delivery using a microneedle system. With its minimal invasiveness, microneedle can deliver nucleic acid drugs with enhanced efficacy and improved stability.

Area covered

This review describes nucleic acid medicines' current state and features and their delivery systems utilizing non-viral vectors and physical delivery systems. In addition, different types of microneedle delivery systems and their properties are briefly reviewed. Furthermore, recent advances of microneedle-based nucleic acid drugs, including featured vaccination applications, are described.

Expert opinion

Nucleic acid drugs have shown significant potential beyond the limitation of conventional small molecules, and the current COVID-19 pandemic highlights the importance of nucleic acid therapies as a novel vaccination platform. Microneedle-mediated nucleic acid drug delivery is a potential platform for less invasive nucleic acid drug delivery. Microneedle system can show enhanced efficacy, stability, and improved patient convenience through self-administration with less pain.

Microneedle-based insulin transdermal delivery system: current status and translation challenges

Diabetes mellitus is a metabolic disease manifested by hyperglycemia. For patients with type 1 and advanced type 2 diabetes mellitus, insulin therapy is essential. Subcutaneous injection remains the most common administration method. Non-invasive insulin delivery technologies are pursued because of their benefits of decreasing patients' pain, anxiety, and stress. Transdermal delivery systems have gained extensive attention due to the ease of administration and absence of hepatic first-pass metabolism. Microneedle (MN) technology is one of the most promising tactics, which can effectively deliver insulin through skin stratum corneum in a minimally invasive and painless way. This article will review the research progress of MNs in insulin transdermal delivery, including hollow MNs, dissolving MNs, hydrogel MNs, and glucose-responsive MN patches, in which insulin dosage can be strictly controlled. The clinical studies about insulin delivery with MN devices have also been summarized and grouped based on the study phase. There are still several challenges to achieve successful translation of MNs-based insulin therapy. In this review, we also discussed these challenges including safety, efficacy, patient/prescriber acceptability, manufacturing and scale-up, and regulatory authority acceptability.

A Pilot Study to Compare Therapeutic Efficacy and Safety of Combined Treatment of Skin Microneedling and Depigmenting Cream versus Depigmenting Cream Alone in Facial Melasma at Tertiary Care Center

Background:

Melasma is a commonly acquired, chronic, and relapsing disorder that results in symmetrical, brownish facial pigmentation. It is more common in women than in men, which generally starts between 20 and 40 years of age, and it can lead to considerable embarrassment and distress. Managing melasma is a difficult challenge that requires long-term treatment with a number of topical agents. Microneedling has been described as a new technique to enhance the drug’s transdermal penetration, and has also been reported to result in sustained long-term improvement of recalcitrant melasma.

Aim:

The aim of this article was to compare the therapeutic efficacy and safety of combined treatment of skin microneedling and depigmenting cream versus depigmenting cream alone in the treatment of melasma.

Materials and Methods:

A prospective study was conducted with a sample size of 40 patients, with twenty in each of the treatment arms; 20 patients were treated with combined skin needling and depigmenting cream and 20 with depigmenting cream alone. The outcome was evaluated periodically for up to 2 months using the modified Melasma Area and Severity Index (MASI) score.

Results:

Significant reduction was observed in modified MASI score in the combined treatment, with P value <0.05.

Conclusion:

Combining microneedling with Kligman’s regimen gives better results in melasma treatment compared to topical treatment alone.

Microneedle-based devices for point-of-care infectious disease diagnostics

Recent infectious disease outbreaks, such as COVID-19 and Ebola, have highlighted the need for rapid and accurate diagnosis to initiate treatment and curb transmission. Successful diagnostic strategies critically depend on the efficiency of biological sampling and timely analysis. However, current diagnostic techniques are invasive/intrusive and present a severe bottleneck by requiring specialist equipment and trained personnel. Moreover, centralised test facilities are poorly accessible and the requirement to travel may increase disease transmission. Self-administrable, point-of-care (PoC) microneedle diagnostic devices could provide a viable solution to these problems. These miniature needle arrays can detect biomarkers in/from the skin in a minimally invasive manner to provide (near-) real-time diagnosis. Few microneedle devices have been developed specifically for infectious disease diagnosis, though similar technologies are well established in other fields and generally adaptable for infectious disease diagnosis. These include microneedles for biofluid extraction, microneedle sensors and analyte-capturing microneedles, or combinations thereof. Analyte sampling/detection from both blood and dermal interstitial fluid is possible. These technologies are in their early stages of development for infectious disease diagnostics, and there is a vast scope for further development. In this review, we discuss the utility and future outlook of these microneedle technologies in infectious disease diagnosis.

Ultrasonic actuation of a fine-needle improves biopsy yield

Despite the ubiquitous use over the past 150 years, the functions of the current medical needle are facilitated only by mechanical shear and cutting by the needle tip, i.e. the lancet. In this study, we demonstrate how nonlinear ultrasonics (NLU) extends the functionality of the medical needle far beyond its present capability. The NLU actions were found to be localized to the proximity of the needle tip, the SonoLancet, but the effects extend to several millimeters from the physical needle boundary. The observed nonlinear phenomena, transient cavitation, fluid streams, translation of micro- and nanoparticles and atomization, were quantitatively characterized. In the fine-needle biopsy application, the SonoLancet contributed to obtaining tissue cores with an increase in tissue yield by 3-6× in different tissue types compared to conventional needle biopsy technique using the same 21G needle. In conclusion, the SonoLancet could be of interest to several other medical applications, including drug or gene delivery, cell modulation, and minimally invasive surgical procedures.

One-Shot Fabrication of Polymeric Hollow Microneedles by Standard Photolithography

Microneedles (MNs) are an emerging technology in pharmaceutics and biomedicine, and are ready to be commercialized in the world market. However, solid microneedles only allow small doses and time-limited administration rates. Moreover, some well-known and already approved drugs need to be re-formulated when supplied by MNs. Instead, hollow microneedles (HMNs) allow for rapid, painless self-administrable microinjection of drugs in their standard formulation. Furthermore, body fluids can be easily extracted for analysis by a reverse use of HMNs, thus making them perfect for sensing issues and theranostics applications. The fabrication of HMNs usually requires several many-step processes, increasing the costs and consequently decreasing the commercial interest. Photolithography is a well-known fabrication technique in microelectronics and microfluidics that fabricates MNs. In this paper, authors show a proof of concept of a patented, easy and one-shot fabrication of two kinds of HMNs: (1) Symmetric HMNs with a “volcano” shape, made by using a photolithographic mask with an array of transparent symmetric rings; and (2) asymmetric HMNs with an oblique aperture, like standard hypodermic steel needles, made by using an array of transparent asymmetric rings, defined by two circles, which centers are slightly mismatched. Simulation of light propagation, fabrication process, and preliminary results on ink microinjection are presented.

Delivery of Insulin via Skin Route for the Management of Diabetes Mellitus: Approaches for Breaching the Obstacles

Insulin is used for the treatment of diabetes mellitus, which is characterized by hyperglycemia. Subcutaneous injections are the standard mode of delivery for insulin therapy; however, this procedure is very often invasive, which hinders patient compliance, particularly for individuals requiring insulin doses four times a day. Furthermore, cases have been reported of sudden hypoglycemia occurrences following multidose insulin injections. Such an invasive and intensive approach motivates the quest for alternative, more user-friendly insulin administration approaches. For example, transdermal delivery has numerous advantages, such as prolonged drug release, low variability in the drug plasma level, and improved patient compliance. In this paper, the authors summarize different approaches used in transdermal insulin delivery, including microneedles, chemical permeation enhancers, sonophoresis, patches, electroporation, iontophoresis, vesicular formulations, microemulsions, nanoparticles, and microdermabrasion. Transdermal systems for insulin delivery are still being widely researched. The conclusions presented in this paper are extracted from the literature, notably, that the transdermal route could effectively and reliably deliver insulin into the circulatory system. Consistent progress in this area will ensure that some of the aforementioned transdermal insulin delivery systems will be introduced in clinical practice and commercially available in the near future.

Microneedle arrays for the treatment of chronic wounds

INTRODUCTION

Chronic wounds are seen frequently in diabetic and bedbound patients. Such skin injuries, which do not heal in a timely fashion, can lead to life-threatening conditions. In an effort to resolve the burdens of chronic wounds, numerous investigations have explored the efficacy of various therapeutics on wound healing. Therapeutics can be topically delivered to cutaneous wounds to reduce the complications associated with systemic drug delivery because the compromised skin barrier is not expected to negatively affect drug distribution. However, researchers have recently demonstrated that the complex environment of chronic wounds could lower the localized availability of the applied therapeutics. Microneedle arrays (MNAs) can be exploited to enhance delivery efficiency and consequently improved healing.

AREAS COVERED

In this review, we briefly describe the pathophysiology of chronic wounds and current treatment strategies. We further introduce methods and materials commonly used for the fabrication of MNAs. Subsequently, the studies demonstrating the benefits of MNAs in wound care are highlighted.

EXPERT OPINION

Microneedles have great potential to treat the complicated pathophysiology of chronic wounds. Challenges that will need to be addressed include development of a robust chronic wound model and MNAs that combine complex functionality with simplicity of use.

Polyvinylpyrrolidone microneedles for localized delivery of sinomenine hydrochloride: preparation, release behavior of in vitro & in vivo, and penetration mechanism

Sinomenine (SIN) is an anti-inflammatory alkaloid derived from Sinomenium acutum, and the products sinomenine hydrochloride (SH) tablets and injections have been marketed in China to treat rheumatoid arthritis (RA). Oral administration of SH has shortcomings of gastrointestinal irritation and low bioavailability. The injection may require professional training and higher cost. It is of interest to develop an alternative form that is easier to administer and avoids the first-pass metabolism. In this study, SH-loaded dissolving microneedles (SH-MN) were fabricated using polyvinyl pyrrolidone and chondroitin sulfate with a casting method. In percutaneous permeation studies of In vitro, the cumulative permeation and permeation rate of SH-MN were 5.31 and 5.06 times higher than that of SH-gel (SH-G). In percutaneous pharmacokinetic studies, the values of the area under the curve after administration of SH-MN in the skin and blood were 1.43- and 1.63-fold higher than that of SH-G, respectively. In percutaneous absorption studies, SH-MN could absorb into tissue fluid; and dissolve after skin penetration. The drug was released along the channel and spread to surrounding skin tissue. After 4 h, the needle tip was almost completely dissolved, and the drug could penetrate to a depth of 200 μm under the skin. These results demonstrate that the SH-MN is an effective, safe, and simple strategy for transdermal SH delivery.

Microneedles Drug Delivery Systems for Treatment of Cancer: A Recent Update

Microneedles (MNs) are tiny needle like structures used in drug delivery through layers of the skin. They are non-invasive and are associated with significantly less or no pain at the site of administration to the skin. MNs are excellent in delivering both small and large molecules to the subjects in need thereof. There exist several strategies for drug delivery using MNs, wherein each strategy has its pros and cons. Research in this domain lead to product development and commercialization for clinical use. Additionally, several MN-based products are undergoing clinical trials to evaluate its safety, efficacy, and tolerability. The present review begins by providing bird's-eye view about the general characteristics of MNs followed by providing recent updates in the treatment of cancer using MNs. Particularly, we provide an overview of various aspects namely: anti-cancerous MNs that work based on sensor technology, MNs for treatment of breast cancer, skin carcinoma, prostate cancer, and MNs fabricated by additive manufacturing or 3 dimensional printing for treatment of cancer. Further, the review also provides limitations, safety concerns, and latest updates about the clinical trials on MNs for the treatment of cancer. Furthermore, we also provide a regulatory overview from the "United States Food and Drug Administration" about MNs.

Opportunities for biomaterials to address the challenges of COVID-19

The coronavirus disease 2019 (COVID‐19) pandemic has revealed major shortcomings in our ability to mitigate transmission of infectious viral disease and provide treatment to patients, resulting in a public health crisis. Within months of the first reported case in China, the virus has spread worldwide at an unprecedented rate. COVID‐19 illustrates that the biomaterials community was engaged in significant research efforts against bacteria and fungi with relatively little effort devoted to viruses. Accordingly, biomaterials scientists and engineers will have to participate in multidisciplinary antiviral research over the coming years. Although tissue engineering and regenerative medicine have historically dominated the field of biomaterials, current research holds promise for providing transformative solutions to viral outbreaks. To facilitate collaboration, it is imperative to establish a mutual language and adequate understanding between clinicians, industry partners, and research scientists. In this article, clinical perspectives are shared to clearly define emerging healthcare needs that can be met by biomaterials solutions. Strategies and opportunities for novel biomaterials intervention spanning diagnostics, treatment strategies, vaccines, and virus‐deactivating surface coatings are discussed. Ultimately this review serves as a call for the biomaterials community to become a leading contributor to the prevention and management of the current and future viral outbreaks.

Nanotechnology in Chronic Pain Relief

Increasing awareness of chronic pain due to both injury and disease have encouraged drug companies and pharmaceutical researchers alike to design and fabricate better, more specific drugs for pain relief. However, overuse of clinically available pain medication has caused a multitude of negative repercussions, including drug tolerance, addiction, and other severe side effects, which can prolong suffering and reduce pain mediation. Applications of nanotechnology to the field of drug delivery has sought to enhance the treatment efficiency, lower side effects, and mitigate the formation of tolerance. The use of nanomaterials has several advantages for chronic pain relief, such as controlled release, prolonged circulation time, and limited side effects. With the development of nanotechnology, strategies for chronic pain relief have also bourgeoned utilizing a variety of nanomaterials and targeting surface modifications. In addition to using these materials as carriers for drug delivery, nanomaterials can also be designed to have inherent properties that relieve chronic pain. This minireview covers the current status of designed nanomaterials for pain relief and provides a discussion of future considerations for nanotechnology designed for relieving chronic pain.

Batch Fabrication of Silicon Nanometer Tip Using Isotropic Inductively Coupled Plasma Etching

This work reports a batch fabrication process for silicon nanometer tip based on isotropic inductively coupled plasma (ICP) etching technology. The silicon tips with nanometer apex and small surface roughness are produced at wafer-level with good etching homogeneity and repeatability. An ICP etching routine is developed to make silicon tips with apex radius less than 5 nm, aspect ratio greater than 5 at a tip height of 200 nm, and tip height more than 10 μm, and high fabrication yield is achieved by mask compensation and precisely controlling lateral etch depth, which is significant for large-scale manufacturing.

Characterization of Hepatitis B Surface Antigen Loaded Polylactic Acid-Based Microneedle and Its Dermal Safety Profile

A surge of interest in microneedle (MN) vaccines as a novel vaccination system has emerged. Before the clinical application of MN vaccine, an assessment of potential biological risks to skin and quality control of MN must be performed. Therefore, the present study aims to evaluate the physicochemical properties of MN and to evaluate the histological changes and inflammatory cell infiltrations after the application of MN with hepatitis B surface antigen (HBsAg). During in vitro and in vivo release testing, HBsAg MN released over 70% of HBsAg at 30 min. During the pyrogen test of HBsAg MN in rabbit, no rabbit showed an individual rise in temperature of 0.5 °C or more. MN with HBsAg produced the moderate immunization in mice. MN application did not alter the thickness of dermal and epidermal layers in mice. In addition, the topical applications of MN and MN for hepatitis B vaccine did not acutely induce the inflammation, allergic reaction, dermal toxicity and skin irritation. Thus, the MN system for the delivery of HBsAg could be the promising technology in the hepatitis B vaccination.

Srivastava S. Wearable Skin Sensors and Their Challenges: A Review of Transdermal, Optical, and Mechanical Sensors

Wearable technology and mobile healthcare systems are both increasingly popular solutions to traditional healthcare due to their ease of implementation and cost-effectiveness for remote health monitoring. Recent advances in research, especially the miniaturization of sensors, have significantly contributed to commercializing the wearable technology. Most of the traditional commercially available sensors are either mechanical or optical, but nowadays transdermal microneedles are also being used for micro-sensing such as continuous glucose monitoring. However, there remain certain challenges that need to be addressed before the possibility of large-scale deployment. The biggest challenge faced by all these wearable sensors is our skin, which has an inherent property to resist and protect the body from the outside world. On the other hand, biosensing is not possible without overcoming this resistance. Consequently, understanding the skin structure and its response to different types of sensing is necessary to remove the scientific barriers that are hindering our ability to design more efficient and robust skin sensors. In this article, we review research reports related to three different biosensing modalities that are commonly used along with the challenges faced in their implementation for detection. We believe this review will be of significant use to researchers looking to solve existing problems within the ongoing research in wearable sensors.

Advanced trends in protein and peptide drug delivery: a special emphasis on aquasomes and microneedles techniques

Proteins and peptides have a great potential as therapeutic agents; they have higher efficiency and lower toxicity, compared to chemical drugs. However, their oral bioavailability is very low; also, the transdermal peptide delivery faces absorption limitations. Accordingly, most of proteins and peptides are administered by parenteral route, but there are many problems associated with this route such as patient discomfort, especially for pediatric use. Thus, it is a great challenge to develop drug delivery systems for administration of proteins and peptides by routes other than parenteral one. This review provides an overview on recent advances adopted for protein and peptide drug delivery, focusing on oral and transdermal routes. This is followed by an emphasis on two recent approaches adopted as delivery systems for protein and peptide drugs, namely aquasomes and microneedles. Aquasomes are nanoparticles fabricated from ceramics developed to enhance proteins and peptides stability, providing an adequate residence time in circulation. It consists of ceramic core coated with poly hydroxyl oligomer, on which protein and peptide drug can be adsorbed. Aquasomes preparation, characterization, and application in protein and peptide drug delivery are discussed. Microneedles are promising transdermal approach; it involves creation of micron-sized pores in the skin for enhancing the drug delivery across the skin, as their length ranged between 150 and 1500 μm. Types of microneedles with different drug delivery mechanisms, characterization, and application in protein and peptide drug delivery are discussed. Graphical abstract.

Microneedle - Future prospect for efficient drug delivery in diabetes management

This review aims at focusing on the use of microneedles (MNs) as an emerging novel drug delivery carrier for an effective treatment in diabetic patients. There are many limitations in various modes of delivery such as oral, subcutaneous, nasal, and other modes which cause pain and have many other side effects. Hence, this drug delivery research has found to have tremendous potential in combining both the diagnostic and therapeutic elements, thus treating diabetes in a better way. Most glucose-sensing techniques and conventional insulin therapies are engaged in the transfer of physical entities through the skin. MN- based drug delivery system can accomplish in an noninvasive or minimally invasive manner which can be an add on advantage towards pain-free administration, easy handling, discrete, continuous as well as providing a controlled release system. Hence, the review addresses on the current advancement of this bioengineered system like MNs, constituting a “smart” system specifically for autonomous diabetes therapy.

Scalp Micro-Pigmentation via Transcutaneous Implantation of Flexible Tissue Interlocking Biodegradable Microneedles

Alopecia, characterized by hair follicle blockage and hair loss, disrupts the normal cycle of hair growth. Although not a life-threatening condition, a growing body of evidence suggests that the psychological state of individuals experiencing alopecia can be highly influenced. Despite considerable research on hair loss treatment, interest in micro-pigmentation has increased in recent decades. Micro-pigmentation is an effective method to camouflage the visual contrast between the scalp and hair strands. However, the localization, intensity and dimension of microdots depend highly upon the physician performing the implantation. Incorrectly localized microdots within the skin may lead to patchy or faded micro-pigmentation. To overcome the limitations of conventional micro-pigmentation, we aimed to develop micro-pigment-encapsulated biodegradable microneedles (PBMs), capable of accurately implanting pigments below the epithelial-dermal junction of the scalp in a minimally invasive manner. A tissue interlocking microneedle technique was utilized to fabricate double-layered PBMs over a biodegradable flexible sheet, which could be washed off post-implantation. We confirmed that the intensity, dimension and insertion depth of 1000 μm-long PBMs was maintained on pig cadaver skin over time. This study suggested that the developed PBMs would serve as an attractive platform for scalp micro-pigmentation in the future.

Development of a thermostable microneedle patch for polio vaccination

The aim of this study was to develop a dissolving microneedle (MN) patch for administration of inactivated polio vaccine (IPV) with improved thermal stability when compared with conventional liquid IPV. Excipient screening showed that a combination of maltodextrin and D-sorbitol in histidine buffer best preserved IPV activity during MN patch fabrication and storage. As determined by D-antigen ELISA, all three IPV serotypes maintained > 70% activity after 2 months and > 50% activity after 1-year storage at 5 °C or 25 °C with desiccant. Storage at 40 °C yielded > 40% activity after 2 months and > 20% activity after 1 year. In contrast, commercial liquid IPV types 1 and 2 lost essentially all activity within 1 month at 40 °C and IPV type 3 had < 40% activity. Residual moisture content in MN patches measured by thermogravimetric analysis was 1.2–6.5%, depending on storage conditions. Glass transition temperature measured by differential scanning calorimetry, structural changes measured by X-ray diffraction, and molecular interactions measured by Fourier transform infrared spectroscopy showed changes in MN matrix properties, but they did not correlate with IPV activity changes during storage. We conclude that appropriately formulated MN patches can exhibit thermostability that could enable distribution of IPV with less reliance on cold chain storage.

A novel scalable fabrication process for the production of dissolving microneedle arrays

Microneedle arrays have emerged as an alternative method for transdermal drug delivery. Although micromolding using a centrifugation method is widely used to prepare microneedles in laboratory, few researchers were focused on manufacturing processes capable of facile scale-up. A novel female mold was initially designed in this study, namely double-penetration female mold (DPFM) with the pinpoints covered by waterproof breather membrane which was beneficial to reduce the influence of gas resistance and solution viscosity. In addition, DPFM-based positive-pressure microperfusion technique (PPPT) was proposed for the scale-up fabrication of dissolving microneedle arrays (DMNA). In this method, polymer solution and base solution were poured into the DPFM by pressure difference, followed by drying and demolding. The results of optimal microscopy and SEM revealed that the obtained microneedles were uniformly distributed conical-shaped needles. The skin penetration test showed that DMNA prepared using PPPT were able to penetrate the rat skin with a high penetration rate. To realize the transition of microneedles fabrication from laboratory to industry, an automatic equipment was further designed in this study. Different from micromolding method using centrifugation, the equipment based on PPPT and DPFM has superiorities in the scale-up fabrication of microneedles in a highly effective, controllable, and scalable way.

Tissue Interlocking Dissolving Microneedles for Accurate and Efficient Transdermal Delivery of Biomolecules

The interest in safe and efficient transdermal drug delivery systems has been increasing in recent decades. In light of that, polymeric dissolving microneedles (DMNs) were developed as an ideal platform capable of delivering micro- and macro-biomolecules across the skin in a minimally invasive manner. A vast majority of studies, however, suggest that the shape of DMNs, as well as the elastic properties of skin, affects the delivery efficiency of materials encapsulated within DMNs. Likewise, in dynamic tissues, DMNs would easily distend from the skin, leading to inefficient delivery of encapsulated agents. Thus, herein, to improve delivery efficiency of DMN encapsulated agents, a novel hyaluronic acid backbone-based tissue interlocking DMN (TI-DMN) is developed. TI-DMN is simple to fabricate and significantly improves the transdermal delivery efficiency of encapsulated materials compared with traditional DMNs. The enhanced tissue interlocking feature of TI-DMN is achieved through its sharp tip, wide body, and narrow neck geometry. This paper demonstrates that TI-DMN would serve as an attractive transdermal delivery platform to enhance penetration and delivery efficiency of a wide range of biomolecules into the body.

Insulin-Loaded Silk Fibroin Microneedles as Sustained Release System

Silk fibroin has widely been used in biomedical applications for its excellent biocompatibility, degradability, and mechanical properties. Microneedles are a suitable method for transdermal drug delivery. In this work, we have prepared microneedles using silk fibroin as the main material and have added proline to change its crystal structure. The fabricated microneedles are nontoxic and degradable and show relatively slow drug release. Our results indicate that the fibroin/proline microneedles can act as carriers of insulin. Fourier transform infrared (FTIR) observations show that the structure of proline-treated fibroin is transformed from random coils to β-sheets. A more regular arrangement is formed between the molecular segments. X-ray diffraction patterns show that proline has good compatibility with fibroin and induces the secondary conformation of the microneedles to a Silk I type structure. The needles have enough strength to pierce the stratum corneum of the skin. In vitro release experiments with insulin indicate that the release time from the microneedles is maintained up to 60 h. This system of delivery may provide a painless and effective route of insulin intake for the treatment of diabetic patients.

Three-Step Thermal Drawing for Rapid Prototyping of Highly Customizable Microneedles for Vascular Tissue Insertion

Microneedles (MNs) have been extensively developed over the last two decades, and highly efficient drug delivery was demonstrated with their minimal invasiveness via a transdermal route. Recently, MNs have not only been applied to the skin but also to other tissues such as blood vessels, scleral tissue, and corneal tissue. In addition, the objective of the MN application has been diversified, ranging from drug delivery to wound closure and biosensing. However, since most MN fabrication methods are expensive and time-consuming, they are inappropriate to prototype MNs for various tissues that have different and complex anatomies. Although several drawing-based techniques have been introduced for rapid MN production, they fabricated MNs with limited shapes, such as thin MNs with wide bases. In this study, we propose a three-step thermal drawing for rapid, prototyping MNs that can have a variety of shapes and can be fabricated on curved surfaces. Based on the temperature control of polymer bridge formation during thermal drawing, the body profile and aspect ratios of MNs were conveniently controlled, and the effect of temperature control on the body profile of MNs was explained. Thermally drawn MNs with different shapes were fabricated both on flat and curved surfaces, and they were characterized in terms of their mechanical properties and insertion into vascular tissue to find an optimal shape for vascular tissue insertion.

Evaluation of a Particulate Breast Cancer Vaccine Delivered via Skin

Breast cancer impacts female population globally and is the second most common cancer for females. With various limitations and adverse effects of current therapies, several immunotherapies are being explored. Development of an effective breast cancer vaccine can be a groundbreaking immunotherapeutic approach. Such approaches are being evaluated by several clinical trials currently. On similar lines, our research study aims to evaluate a particulate breast cancer vaccine delivered via skin. This particulate breast cancer vaccine was prepared by spray drying technique and utilized murine breast cancer whole cell lysate as a source of tumor-associated antigens. The average size of the particulate vaccine was 1.5 μm, which resembled the pathogenic species, thereby assisting in phagocytosis and antigen presentation leading to further activation of the immune response. The particulate vaccine was delivered via skin using commercially available metal microneedles. Methylene blue staining and confocal microscopy were used to visualize the microchannels. The results showed that microneedles created aqueous conduits of 50 ± 10 μm to deliver the microparticulate vaccine to the skin layers. Further, an in vivo comparison of immune response depicted significantly higher concentration of serum IgG, IgG2a, and B and T cell (CD4+ and CD8+) populations in the vaccinated animals than the control animals (p < 0.001). Upon challenge with live murine breast cancer cells, the vaccinated animals showed five times more tumor suppression than the control animals confirming the immune response activation and protection (p < 0.001). This research paves a way for individualized immunotherapy following surgical tumor removal to prolong relapse episodes.

Effect of dosing regimen and microneedle pretreatment on in vitro skin retention of topically applied beta-blockers

Topical beta-blocker formulations are commonly used to treat infantile hemangiomas (IHs); however, the skin concentrations and drug permeation through the skin have not been quantified. Microneedles (MNs) may increase local skin concentrations, which could further enhance lesion clearance and improve dosing regimens. The objective of this study was to quantify skin concentrations and drug permeation of two beta-blockers, propranolol and timolol, in vitro after application to intact skin and skin pretreated with solid MNs of two lengths. Propranolol skin concentrations and drug permeation were significantly higher than timolol skin concentrations for all study conditions, which is likely due to the lipophilic nature of propranolol compared to the hydrophilicity of timolol. Propranolol skin concentrations were significantly influenced by dosing regimen, as skin concentrations increased with increasing drug application. Pretreatment of the skin with solid 250 μm and 500 μm length MNs increased local skin concentrations of timolol; propranolol skin concentrations did not significantly increase after MN pretreatment. Propranolol and timolol permeation through the skin increased after MN pretreatment with both MN lengths for both compounds. Taken together, solid MN pretreatment prior to application of topical timolol may be beneficial for deep or mixed IHs upon further optimization of the MN treatment paradigm.

Enhanced Cancer Vaccination by In Situ Nanomicelle-Generating Dissolving Microneedles

Efficient delivery of tumor antigens and immunostimulatory adjuvants into lymph nodes is crucial for the maturation and activation of antigen-presenting cells (APCs), which subsequently induce adaptive antitumor immunity. A dissolving microneedle (MN) has been considered as an attractive method for transcutaneous immunization due to its superior ability to deliver vaccines through the stratum corneum in a minimally invasive manner. However, because dissolving MNs are mostly prepared using water-soluble sugars or polymers for their rapid dissolution in intradermal fluid after administration, they are often difficult to formulate with poorly water-soluble vaccine components. Here, we develop amphiphilic triblock copolymer-based dissolving MNs in situ that generate nanomicelles (NMCs) upon their dissolution after cutaneous application, which facilitate the efficient encapsulation of poorly water-soluble Toll-like receptor 7/8 agonist (R848) and the delivery of hydrophilic antigens. The sizes of NMCs range from 30 to 40 nm, which is suitable for the efficient delivery of R848 and antigens to lymph nodes and promotion of cellular uptake by APCs, minimizing systemic exposure of the R848. Application of MNs containing tumor model antigen (OVA) and R848 to the skin of EG7-OVA tumor-bearing mice induced a significant level of antigen-specific humoral and cellular immunity, resulting in significant antitumor activity.

Novel nanosuspension-based dissolving microneedle arrays for transdermal delivery of a hydrophobic drug

A nanosuspension (NS) was formulated from the lipophilic molecule cholecalciferol (CL) for enhanced transdermal delivery by embedding this NS into hydrophilic polymer-based dissolving microneedles (DMNs). First, the NS was prepared by sonoprecpitation with different molecular weights of poly (vinyl alcohol) and poly (vinyl pyrrolidone) as stabilizers and using two different solvents for particle size and zeta potential optimization. DMN arrays were then prepared by centrifugation-assisted micromoulding and subsequently dried. Poly (vinyl alcohol) (10 kDa) produced a NS with the lowest particle size ( ~ 300 nm). These particles yielded DMN with good mechanical properties when combined with aqueous blends of high molecular weight poly (vinyl pyrrolidone) (360 kDa). The particle size remained similar before and after MN preparation, as confirmed by scanning electron microscope. The CL was in the amorphous state in the free particles as well as in the DMN and, hence, no characteristic CL peak was observed in differential scanning calorimetry or X-ray diffraction. DMN arrays were found to be strong enough to bear a 32 N force, showed efficient skin insertion, and penetrated down to the third layer (depth ≈ 375 μm) of the validated skin model Parafilm M®. An ex vivo porcine skin permeation study using Franz diffusion cells compared the permeation of CL from CL-NS-loaded DMN arrays and MN-free CL-NS patches. It was observed that CL-NS-loaded DMN arrays showed significantly higher (498.19 μg ± 89.3 μg) ex vivo skin permeation compared with MN-free CL-NS patches (73.2 μg ± 26.5 μg) over 24 h. This is the first time a NS of a hydrophobic drug has been successfully incorporated into dissolving MN and suggest that NS-containing DMN systems could be a promising strategy for transdermal delivery of hydrophobic drugs.

Polymeric microneedles for transdermal protein delivery

The intrinsic properties of therapeutic proteins generally present a major impediment for transdermal delivery, including their relatively large molecule size and susceptibility to degradation. One solution is to utilize microneedles (MNs), which are capable of painlessly traversing the stratum corneum and directly translocating protein drugs into the systematic circulation. MNs can be designed to incorporate appropriate structural materials as well as therapeutics or formulations with tailored physicochemical properties. This platform technique has been applied to deliver drugs both locally and systemically in applications ranging from vaccination to diabetes and cancer therapy. This review surveys the current design and use of polymeric MNs for transdermal protein delivery. The clinical potential and future translation of MNs are also discussed.

Transdermal delivery of vitamin K using dissolving microneedles for the prevention of vitamin K deficiency bleeding

Vitamin K deficiency within neonates can result in vitamin K deficiency bleeding. Ensuring that newborns receive vitamin K is particularly critical in places where access to health care and blood products and transfusions is limited. The World Health Organization recommends that newborns receive a 1 mg intramuscular injection of vitamin K at birth. Evidence from multiple surveillance studies shows that the introduction of vitamin K prophylaxis reduces the incidence of vitamin K deficiency bleeding. Despite these recommendations, coverage of vitamin K prophylactic treatment in low-resource settings is limited.

An intramuscular injection is the most common method of vitamin K administration in neonates. In low- and middle-income countries, needle sharing may occur, which may result in the spread of bloodborne diseases. The objective of our study was to investigate the manufacture of microneedles for the delivery of vitamin K. Following microneedle fabrication, we performed insertion studies to assess the microneedle’s mechanical properties. Results indicate that vitamin K in a microneedle array was successfully delivered in vitro across neonatal porcine skin with 1.80 ± 0.08 mg delivered over 24 h. Therefore, this initial study shows that microneedles do have the potential to prevent vitamin K deficiency bleeding. Future work will assess delivery of vitamin K in microneedle array in vivo.

Assessment of solid microneedle rollers to enhance transmembrane delivery of doxycycline and inhibition of MMP activity

Many chronic wounds exhibit high matrix metalloproteinase (MMP) activity that impedes the normal wound healing process. Intradermal delivery (IDD) of sub-antimicrobial concentrations of doxycycline, as an MMP inhibitor, could target early stages of chronic wound development and inhibit further wound progression. To deliver doxycycline intradermally, the skin barrier must be disrupted. Microneedle rollers offer a minimally invasive technique to penetrate the skin by creating multiple microchannels that act as temporary conduits for drugs to diffuse through. In this study, an innovative and facile approach for delivery of doxycycline across Strat-M^TM membrane was investigated using microneedle rollers. The quantity and rate of doxycycline diffusing through the micropores directly correlated with increasing microneedle lengths (250, 500 and 750 μm). Treatment of Strat-M^TM with microneedle rollers resulted in a reduction in fibroblast-mediated collagen gel contraction and MMP activity compared with untreated Strat-M^TM. Our results show that treatment of an epidermal mimetic with microneedle rollers provides sufficient permeabilization for doxycycline diffusion and inhibition of MMP activity. We conclude that microneedle rollers are a promising, clinically ready tool suitable for delivery of doxycycline intradermally to treat chronic wounds.

Skin Delivery of Hydrophilic Biomacromolecules Using Marine Sponge Spicules

We report the development of sponge Haliclona sp. spicules, referred to as SHS, and its topical application in skin delivery of hydrophilic biomacromolecules, a series of fluorescein isothiocyanate-dextrans (FDs). SHS are silicious oxeas which are sharp-edged and rod-shaped (∼120 μm in length and ∼7 μm in diameter). SHS can physically disrupt skin in a dose-dependent manner and retain within the skin over at least 72 h, which allows sustained skin penetration of hydrophilic biomacromolecules. The magnitude of enhancement of FD delivery into skin induced by SHS treatment was dependent on its molecular weight. Specifically, SHS topical application enhanced FD-10 (MW: 10 kDa) penetration into porcine skin in vitro by 33.09 ± 7.16-fold compared to control group (p < 0.01). SHS dramatically increased the accumulation of FD-10 into and across the dermis by 62.32 ± 13.48-fold compared to the control group (p < 0.01). In vivo experiments performed using BALB/c mice also confirmed the effectiveness of SHS topical application; the skin absorption of FD-10 with SHS topical application was 72.14 ± 48.75-fold (p < 0.05) and 15.39 ± 9.91-fold (p < 0.05) higher than those from the PBS and Dermaroller microneedling, respectively. Further, skin irritation study and transepidermal water loss (TEWL) measurement using guinea pig skin in vivo indicated that skin disruption induced by SHS treatment is self-limited and can be recovered with time and efficiently. SHS can offer a safe, effective, and sustained skin delivery of hydrophilic biomacromolecules and presents a promising platform technology for a wide range of cosmetic and medical applications.

Polymers for 3D Printing and Customized Additive Manufacturing

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting. The range of polymers used in AM encompasses thermoplastics, thermosets, elastomers, hydrogels, functional polymers, polymer blends, composites, and biological systems. Aspects of polymer design, additives, and processing parameters as they relate to enhancing build speed and improving accuracy, functionality, surface finish, stability, mechanical properties, and porosity are addressed. Selected applications demonstrate how polymer-based AM is being exploited in lightweight engineering, architecture, food processing, optics, energy technology, dentistry, drug delivery, and personalized medicine. Unparalleled by metals and ceramics, polymer-based AM plays a key role in the emerging AM of advanced multifunctional and multimaterial systems including living biological systems as well as life-like synthetic systems.

Flexible and Stretchable Microneedle Patches with Integrated Rigid Stainless Steel Microneedles for Transdermal Biointerfacing

This paper demonstrates flexible and stretchable microneedle patches that combine soft and flexible base substrates with hard and sharp stainless steel microneedles. An elastomeric polymer base enables conformal contact between the microneedle patch and the complex topography and texture of the underlying skin, while robust and sharp stainless steel microneedles reliably pierce the outer layers of the skin. The flexible microneedle patches have been realized by magnetically assembling short stainless steel microneedles into a flexible polymer supporting base. In our experimental investigation, the microneedle patches were applied to human skin and an excellent adaptation of the patch to the wrinkles and deformations of the skin was verified, while at the same time the microneedles reliably penetrate the surface of the skin. The unobtrusive flexible and stretchable microneedle patches have great potential for transdermal biointerfacing in a variety of emerging applications such as transdermal drug delivery, bioelectric treatments and wearable bio-electronics for health and fitness monitoring.

Microneedles with Controlled Bubble Sizes and Drug Distributions for Efficient Transdermal Drug Delivery

Drug loaded dissolving microneedles (DMNs) fabricated with water soluble polymers have received increasing attentions as a safe and efficient transdermal drug delivery system. Usually, to reach a high drug delivery efficiency, an ideal drug distribution is gathering more drugs in the tip or the top part of DMNs. In this work, we introduce an easy and new method to introduce a bubble with controlled size into the body of DMNs. The introduction of bubbles can prevent the drug diffusion into the whole body of the MNs. The heights of the bubbles are well controlled from 75 μm to 400 μm just by changing the mass concentrations of polymer casting solution from 30 wt% to 10 wt%. The drug-loaded bubble MNs show reliable mechanical properties and successful insertion into the skins. For the MNs prepared from 15 wt% PVA solution, bubble MNs achieve over 80% of drug delivery efficiency in 20 seconds, which is only 10% for the traditional solid MNs. Additionally, the bubble microstructures in the MNs are also demonstrated to be consistent and identical regardless the extension of MN arrays. These scalable bubble MNs may be a promising carrier for the transdermal delivery of various pharmaceuticals.

Microfabrication for Drug Delivery

This review is devoted to discussing the application of microfabrication technologies to target challenges encountered in life processes by the development of drug delivery systems. Recently, microfabrication has been largely applied to solve health and pharmaceutical science issues. In particular, fabrication methods along with compatible materials have been successfully designed to produce multifunctional, highly effective drug delivery systems. Microfabrication offers unique tools that can tackle problems in this field, such as ease of mass production with high quality control and low cost, complexity of architecture design and a broad range of materials. Presented is an overview of silicon- and polymer-based fabrication methods that are key in the production of microfabricated drug delivery systems. Moreover, the efforts focused on studying the biocompatibility of materials used in microfabrication are analyzed. Finally, this review discusses representative ways microfabrication has been employed to develop systems delivering drugs through the transdermal and oral route, and to improve drug eluting implants. Additionally, microfabricated vaccine delivery systems are presented due to the great impact they can have in obtaining a cold chain-free vaccine, with long-term stability. Microfabrication will continue to offer new, alternative solutions for the development of smart, advanced drug delivery systems.

Microneedles: an innovative platform for gene delivery

The advent of microneedle (MN) technology has provided a revolutionary platform for the delivery of therapeutic agents, particularly in the field of gene therapy. For over 20 years, the area of gene therapy has undergone intense innovation and progression which has seen advancement of the technology from an experimental concept to a widely acknowledged strategy for the treatment and prevention of numerous disease states. However, the true potential of gene therapy has yet to be achieved due to limitations in formulation and delivery technologies beyond parenteral injection of the DNA. Microneedle-mediated delivery provides a unique platform for the delivery of DNA therapeutics clinically. It provides a means to overcome the skin barriers to gene delivery and deposit the DNA directly into the dermal layers, a key site for delivery of therapeutics to treat a wide range of skin and cutaneous diseases. Additionally, the skin is a tissue rich in immune sentinels, an ideal target for the delivery of a DNA vaccine directly to the desired target cell populations. This review details the advancement of MN-mediated DNA delivery from proof-of-concept to the delivery of DNA encoding clinically relevant proteins and antigens and examines the key considerations for the improvement of the technology and progress into a clinically applicable delivery system.

Paediatricians' opinions of microneedle-mediated monitoring: a key stage in the translation of microneedle technology from laboratory into clinical practice

Microneedle (MN) arrays could offer an alternative method to traditional drug delivery and blood sampling methods. However, acceptance among key end-users is critical for new technologies to succeed. MNs have been advocated for use in children and so, paediatricians are key potential end-users. However, the opinions of paediatricians on MN use have been previously unexplored. The aim of this study was to investigate the views of UK paediatricians on the use of MN technology within neonatal and paediatric care. An online survey was developed and distributed among UK paediatricians to gain their opinions of MN technology and its use in the neonatal and paediatric care settings, particularly for MN-mediated monitoring. A total of 145 responses were obtained, with a completion response rate of 13.7 %. Respondents believed an alternative monitoring technique to blood sampling in children was required. Furthermore, 83 % of paediatricians believed there was a particular need in premature neonates. Overall, this potential end-user group approved of the MN technology and a MN-mediated monitoring approach. Minimal pain and the perceived ease of use were important elements in gaining favour. Concerns included the need for confirmation of correct application and the potential for skin irritation. The findings of this study provide an initial indication of MN acceptability among a key potential end-user group. Furthermore, the concerns identified present a challenge to those working within the MN field to provide solutions to further improve this technology. The work strengthens the rationale behind MN technology and facilitates the translation of MN technology from lab bench into the clinical setting.

Microneedle-based drug and vaccine delivery via nanoporous microneedle arrays

In the literature, several types of microneedles have been extensively described. However, porous microneedle arrays only received minimal attention. Hence, only little is known about drug delivery via these microneedles. However, porous microneedle arrays may have potential for future microneedle-based drug and vaccine delivery and could be a valuable addition to the other microneedle-based drug delivery approaches. To gain more insight into porous microneedle technologies, the scientific and patent literature is reviewed, and we focus on the possibilities and constraints of porous microneedle technologies for dermal drug delivery. Furthermore, we show preliminary data with commercially available porous microneedles and describe future directions in this field of research.

Microneedling dilates the follicular infundibulum and increases transfollicular absorption of liposomal sepia melanin

Encapsulation of chemicals in liposomes and microneedling are currently used techniques to enhance the penetration of several substances through skin and hair. In this study, we apply a liposomal melanin–fluorescein compound to an ex vivo model of human skin, using a new electrical microneedling device (Nanopore turbo roller). The product was applied by hand massage (A) or with the assistance of the electrical roller for 2 minutes (B). An additional test was performed free of product and with only the E-roller (C). Histological changes and product absorption were evaluated by optical and fluorescent microscopy 60 and 90 minutes after the treatment. Site B showed larger deposits of melanin–fluorescein at superficial and deep levels of hair structures in comparison to site A. Light, epidermal deposits of the melanin–fluorescein complex were also observed. Sites B and C showed a significant widening (47%) of the follicular infundibulum which could explain the increased penetration of the formulation. Microneedling also removed the scales and sebum residues in the neighborhood of the infundibulum. Targeting hair follicles with melanin may be useful to dye poorly pigmented hairs, improving laser hair removal. The procedure accelerates the delivery of melanin into hair structures allowing an even absorption, larger pigment deposits, and deeper penetration of the formulation into the hair.

A patchless dissolving microneedle delivery system enabling rapid and efficient transdermal drug delivery

Dissolving microneedles (DMNs) are polymeric, microscopic needles that deliver encapsulated drugs in a minimally invasive manner. Currently, DMN arrays are superimposed onto patches that facilitate their insertion into skin. However, due to wide variations in skin elasticity and the amount of hair on the skin, the arrays fabricated on the patch are often not completely inserted and large amount of loaded materials are not delivered. Here, we report “Microlancer”, a novel micropillar based system by which patients can self-administer DMNs and which would also be capable of achieving 97 ± 2% delivery efficiency of the loaded drugs regardless of skin type or the amount of hair on the skin in less than a second.

Treating cutaneous squamous cell carcinoma using 5-aminolevulinic acid polylactic-co-glycolic acid nanoparticle-mediated photodynamic therapy in a mouse model

Background

Squamous cell carcinoma (SCC) is a common skin cancer, and its treatment is still difficult. The aim of this study was to evaluate the effectiveness of nanoparticle (NP)-assisted 5-aminolevulinic acid (ALA) delivery for topical photodynamic therapy (PDT) of cutaneous SCC.

Materials and methods

Ultraviolet-induced cutaneous SCCs were established in hairless mice. ALA-loaded polylactic-co-glycolic acid (PLGA) NPs were prepared and characterized. The kinetics of ALA PLGA NP-induced protoporphyrin IX fluorescence in SCCs, therapeutic efficacy of ALA NP-mediated PDT, and immune responses were examined.

Results

PLGA NPs enhanced protoporphyrin IX production in SCC. ALA PLGA NP-mediated topical PDT was more effective than free ALA of the same concentration in treating cutaneous SCC.

Conclusion

PLGA NPs provide a promising strategy for delivering ALA in topical PDT of cutaneous SCC.