Sustained epidermal powder drug delivery via skin microchannels

Laser-assisted topical delivery of vismodegib reduces hedgehog gene expression in human basal cell carcinomas in vivo

BACKGROUND

Systemically delivered hedgehog inhibitors including vismodegib and sonidegib are widely used to treat basal cell carcinomas (BCCs). Ablative fractional laser (AFL)-assisted topical delivery of vismodegib has been demonstrated in preclinical studies. The aim of this explorative clinical study was to evaluate intratumoral vismodegib concentrations and effect on hedgehog pathway gene expression following AFL-assisted topical vismodegib delivery to BCCs.

METHODS

In an open-label clinical trial, 16 nodular BCCs (in n = 9 patients) received one application of CO2 -AFL (40 mJ/microbeam, 10% density) followed by topical vismodegib emulsion. After 3-4 days, vismodegib concentrations in tumor biopsies (n = 15) and plasma were analyzed and compared with samples from patients receiving oral treatment (n = 3). GLI1, GLI2, PTCH1, and PTCH2 expression was determined by quantitative polymerase chain reaction (n = 7) and GLI1 additionally by in situ hybridization (n = 3).

RESULTS

Following AFL-assisted topical administration, vismodegib was detected in 14/15 BCCs and reached a median concentration of 6.2 µmol/L, which compared to concentrations in BCC tissue from patients receiving oral vismodegib (9.5 µmol/L, n = 3, p = 0.8588). Topical vismodegib reduced intratumoral GLI1 expression by 51%, GLI2 by 55%, PTCH1 and PTCH2 each by 73% (p ≤ 0.0304) regardless of vismodegib concentrations (p ≥ 0.3164). In situ hybridization demonstrated that GLI1 expression was restricted to tumor tissue and downregulated in response to vismodegib exposure.

CONCLUSION

A single AFL-assisted topical application of vismodegib resulted in clinically relevant intratumoral drug concentrations and significant reductions in hedgehog pathway gene expressions.

Laser microporation facilitates topical drug delivery: a comprehensive review about preclinical development and clinical application

INTRODUCTION

Topical drug delivery is highly attractive and yet faces tissue barrier challenges. Different physical and chemical methods have been explored to facilitate topical drug delivery.

AREAS COVERED

Ablative fractional laser (AFL) has been widely explored by the scientific community and dermatologists to facilitate topical drug delivery since its advent less than two decades ago. This review introduces the major efforts in exploration of AFL to facilitate transdermal, transungual, and transocular drug delivery in preclinical and clinical settings.

EXPERT OPINION

Most of the preclinical and clinical studies find AFL to be safe and highly effective to facilitate topical drug delivery with little restriction on physicochemical properties of drugs. Clinical studies support AFL to enhance drug efficacy, shorten treatment time, reduce pain, improve cosmetic outcomes, reduce systemic drug exposure, and improve safety. Considering most of the clinical trials so far involved a small sample size and were in early phase, future trials will benefit from enrolling a large group of patients for thorough evaluation of the safety and efficacy of AFL-assisted topical drug delivery. The manufacturing of small and less costly AFL devices will also facilitate the translation of AFL-assisted topical drug delivery.

Optical Imaging Visualizes a Homogeneous and Horizontal Band-Like Biodistribution of Large- and Small-Size Hydrophilic Compounds Delivered by Ablative Fractional Laser

The skin barrier generally limits the topical delivery of hydrophilic molecules. Ablative fractional laser (AFL) facilitates cutaneous drug uptake of smaller hydrophilic compounds in several studies. In this imaging-based study, we aim to investigate the cutaneous biodistribution of two different-sized hydrophilic compounds delivered by an ablative fractional CO₂ laser at minimally invasive settings. Intact or CO₂ AFL-pretreated (2.5 mJ/mb and 5% density) ex vivo porcine skin was topically applied with a large or small hydrophilic compound (fluorescence labeled antibody nivolumab (150,000 g/mol, n = 4) or ATTO 647N (746 g/mol, n = 3)). Samples were incubated for 20 h in a Franz cell setup, whereafter optical coherence tomography (OCT) was used to assess laser channel depth, and ex vivo confocal microscopy (EVCM) was used to assess epidermal thickness and cutaneous biodistribution of nivolumab and ATTO 647N. With an EVCM-assessed median epidermal thickness of 70.3 µm and OCT-assessed ablation depth of 31.9 µm, minimally invasive settings enabled shallow penetration into the mid-epidermis. The AFL-assisted uptake of the antibody nivolumab and the smaller compound ATTO 647N showed a similar homogenous and horizontal band-like biodistribution pattern that reached mid-dermis. No uptake of nivolumab or ATTO 647N was observed in intact skin. In conclusion, AFL-induced mid-epidermal laser channels facilitates the cutaneous delivery of two hydrophilic compounds that are distributed in a similar homogeneous and horizontal band-like pattern, irrespective of their molecular size.

Research progress of microneedles in the treatment of melanoma

Melanoma is an aggressive malignancy deriving from melanocytes, which is characterized by high tendency of metastases and mortality rate. Current therapies for melanoma, like chemotherapy, immunotherapy and targeted therapy, have the problem of systemic exposure of drugs, which will lead to many side effects and premature degradation of drugs. The resulting low drug accumulation at the lesion limits the therapeutic effect on melanoma and makes the cure rate low. As an emerging drug delivery system, microneedles (MNs) can efficiently deliver drugs through the skin, increase the drug distribution in deeper tumor sites and minimize the leakage of therapeutic drugs into adjacent tissues, thus improving the therapeutic effect. In addition, compared with traditional drug delivery methods, MN-based drug delivery system has the advantages of simplicity, safety and little pain. So MNs can be developed for the treatment of melanoma, which can relieve the pain of patients and improve the survival rate. This review aims to introduce an update on the progress of MNs as an innovative strategy for melanoma, especially when MNs combining with different therapies against melanoma, such as chemotherapy, targeted therapy, immunotherapy, photothermal therapy (PTT), photodynamic therapy (PDT) and synergic therapy.

Cutaneous Delivery of Cosmeceutical Peptides Enhanced by Picosecond- and Nanosecond-Domain Nd:YAG Lasers with Quick Recovery of the Skin Barrier Function: Comparison with Microsecond-Domain Ablative Lasers

Picosecond or nanosecond-domain non-ablative lasers generate faster photothermal effects and cause less injury than microsecond lasers. In this study, we investigated the enhancing effect of 1064 nm picosecond- and nanosecond-domain neodymium (Nd):yttrium–aluminum–garnet (YAG) lasers on the cutaneous delivery of cosmeceutical peptides. Microsecond-domain fractional ablative CO2 and fully ablative erbium (Er):YAG lasers were also used for comparison. In the Franz diffusion cell study, pig or mouse skin was treated with a laser before exposure to palmitoyl tripeptide (PT)-1, PT-38, and copper tripeptide (CT)-1 at a concentration of 150 μM. Psoriasiform, atopic dermatitis (AD)-like, and photoaged skins were also developed as permeation barriers. The non-ablative laser elicited the ultrastructural disruption of the stratum corneum and epidermal vacuolation. All laser modalities significantly increased the skin permeation of peptides in vitro. The non-ablative laser chiefly enhanced peptide delivery to the receptor compartment, whereas the ablative laser mainly increased the intracutaneous peptide deposition. The picosecond- and nanosecond-domain Nd:YAG lasers elevated the amount of PT-1 in the receptor up to 40- and 22-fold compared with untreated skin, respectively. Laser treatment promoted peptide delivery in barrier-deficient and inflamed skins, although this enhancement effect was less than that observed in healthy skin. Fluorescence microscopy indicated the capability of the non-ablative laser to deliver peptides to deeper skin strata. The ablative laser confined the peptide distribution in the epidermis. Confocal microscopy showed that peptides penetrated the skin along the microdots created by the fractional Nd:YAG and CO2 lasers. The skin barrier function determined by transepidermal water loss suggested quick recovery when using a nanosecond-domain laser (within 4 h). A longer period was needed for the skin treated with the fully ablative Er:YAG laser (76–84 h). Nanosecond non-ablative laser-facilitated peptide delivery may become an efficient and safe approach for cosmeceutical applications.

Topical delivery of PD-1 inhibitors with laser-assisted passive diffusion and active intradermal injection: Investigation of cutaneous pharmacokinetics and biodistribution patterns

BACKGROUND AND OBJECTIVES

Current cancer immunotherapeutic treatment with PD-1 inhibitors is administered systemically. However, a local treatment strategy may be advantageous as it could provide targeted drug delivery as well as attenuate side effects seen with systemic treatments. For keratinocyte cancers, where surgical excision is not always applicable, an alternate local treatment approach would be beneficial. This study aims to examine cutaneous pharmacokinetics and biodistribution of the PD-1 inhibitor nivolumab, locally delivered either by ablative fractional laser (AFL)-assisted passive diffusion or active intradermal injection, in vivo.

MATERIALS AND METHODS

In vivo pig skin was either exposed to CO₂ AFL (80 mJ/mb by two stacked pulses of 40 mJ/mb) at 5% or 15% density followed by topical application of nivolumab (1 mg/ml, 100 µl/10 × 10 mm) or intradermally injected with nivolumab (1 mg/ml, 100 µl). Cutaneous nivolumab delivery was evaluated at different timepoints (0, 1, 2, 4 hours and 2 days) at two tissue depths (100-800 and 900-1600 µm) by ELISA. Visualization of cutaneous biodistribution was shown in vertical tissue sections using HiLyte Fluor^TM 488 SE labeled nivolumab for fluorescence microscopy whereas nivolumab was DOTA-tagged with Dysprosium before the laser ablation-inductively coupled plasma-mass spectrometry analysis (LA-ICP-MS).

RESULTS

Our in vivo study revealed different pharmacokinetic and biodistribution patterns for the AFL- and injection techniques. A superficial horizontal band-like uptake of nivolumab was provided with AFL-assisted passive diffusion whereas a deep focal deposition was seen with active intradermal injection, compared with controls showing remnant deposition on the skin surface. AFL-assisted nivolumab uptake in upper dermis peaked after 4 hours (p < 0.01). The cutaneous concentration of nivolumab achieved by intradermal injection was markedly higher than with AFL, the highest deposition with intradermal injection was detected at time 0 hours in both upper and deep dermis (p < 0.01) and decreased throughout the study period, although the concentration remained higher compared with saline control injections at all time points (0 hours -2 d) (p < 0.01).

CONCLUSION

Local cutaneous delivery of nivolumab with either AFL or intradermal injection revealed two different pharmacokinetic and biodistribution patterns. Passive AFL-assisted diffusion of nivolumab resulted in enhanced uptake after 4 hours, while intradermal actively injected nivolumab showed immediate enhanced cutaneous deposition with retention up to 2 days after injection. The two local delivery techniques show potential for development of individualized treatment strategies depending on the clinical tumor appearance.

Vaccine delivery alerts innate immune systems for more immunogenic vaccination

Vaccine delivery technologies are mainly designed to minimally invasively deliver vaccines to target tissues with little or no adjuvant effects. This study presents a prototype laser-based powder delivery (LPD) with inherent adjuvant effects for more immunogenic vaccination without incorporation of external adjuvants. LPD takes advantage of aesthetic ablative fractional laser to generate skin microchannels to support high-efficient vaccine delivery and at the same time creates photothermal stress in microchannel-surrounding tissues to boost vaccination. LPD could significantly enhance pandemic influenza 2009 H1N1 vaccine immunogenicity and protective efficacy as compared with needle-based intradermal delivery in murine models. The ablative fractional laser was found to induce host DNA release, activate NLR family pyrin domain containing 3 inflammasome, and stimulate IL-1β release despite their dispensability for laser adjuvant effects. Instead, the ablative fractional laser activated MyD88 to mediate its adjuvant effects by potentiation of antigen uptake, maturation, and migration of dendritic cells. LPD also induced minimal local or systemic adverse reactions due to the microfractional and sustained vaccine delivery. Our data support the development of self-adjuvanted vaccine delivery technologies by intentional induction of well-controlled tissue stress to alert innate immune systems for more immunogenic vaccination.

Innovative Systems to Deliver Allergen Powder for Epicutaneous Immunotherapy

Allergy is a disorder owing to hyperimmune responses to a particular kind of substance like food and the disease remains a serious healthcare burden worldwide. This unpleasant and sometimes fatal allergic disease has been tackled vigorously by allergen-specific immunotherapy over a century, but the progress made so far is far from satisfactory for some allergies. Herein, we introduce innovative, allergen powder-based epicutaneous immunotherapies (EPIT), which could potentially serve to generate a new stream of technological possibilities that embrace the features of super safety and efficacious immunotherapy by manipulating the plasticity of the skin immune system via sufficient delivery of not only allergens but also tolerogenic adjuvants. We attempt to lay a framework to help understand immune physiology of the skin, epicutaneous delivery of powdered allergy, and potentials for tolerogenic adjuvants. Preclinical and clinical data are reviewed showing that deposition of allergen powder into an array of micropores in the epidermis can confer significant advantages over intradermal or subcutaneous injection of aqueous allergens or other epicutaneous delivery systems to induce immunological responses toward tolerance at little risk of anaphylaxis. Finally, the safety, cost-effectiveness, and acceptability of these novel EPITs are discussed, which offers the perspective of future immunotherapies with all desirable features.

Hollow microneedles: A perspective in biomedical applications

Microneedles (MN) have the potential to become a highly progressive device for both drug delivery and monitoring purposes as they penetrate the skin and pierce the stratum corneum barrier, allowing the delivery of drugs in the viable skin layers and the extraction of body fluids. Despite the many years of research and the different types of MN developed, only hollow MN have reached the pharmaceutical market under the path of medical devices. Therefore, this review focuses on hollow MN, materials and methods for their fabrication as well as their application in drug delivery, vaccine delivery and monitoring purposes. Furthermore, novel approaches for the fabrication of hollow MN are included as well as prospects of microneedle-based products on the market.

Topical Delivery of Nivolumab, a Therapeutic Antibody, by Fractional Laser and Pneumatic Injection

BACKGROUND AND OBJECTIVES

PD-L1 is a tumor ligand that binds to the PD-1 receptor on immune cells, thereby inhibiting the antitumor immune response. The antibody nivolumab is a PD-1 inhibitor, Food and Drug Administration approved for systemic treatment of several aggressive cancer types. Topically applied nivolumab may hold potential as a future strategy to treat keratinocyte cancer, but its molecular properties preclude unassisted topical uptake. The aim of this study was to investigate uptake and biodistribution of topically delivered nivolumab, assisted by two physical enhancement techniques with different delivery kinetics; ablative fractional laser (AFL) and electronically controlled pneumatic injection (EPI).

STUDY DESIGN/MATERIALS AND METHODS

In vitro porcine skin was exposed to CO₂ AFL (20 mJ/mb, 5% density), followed by passive diffusion of nivolumab in a Franz cell (1 mg/ml, 18 hours, n = 6) or treated with EPI (4 bar) for immediate delivery of nivolumab (1 mg/ml, 10 minutes, n = 6). The resulting nivolumab skin concentrations were quantified by enzyme-linked immunosorbent assay (ELISA) at three skin depths (100, 500, and 1500 µm), comparing the uptake from assisted delivery with intact skin. Biodistribution of nivolumab in the skin for all interventions was visualized by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and fluorescence microscopy.

RESULTS

Delivery of nivolumab by AFL-assisted passive diffusion and immediate EPI both resulted in significantly enhanced uptake of nivolumab in all skin depths compared with intact skin (P < 0.05). With AFL, nivolumab concentrations reached 86.3 µg/cm³ (100 µm), 105.8 µg/cm³ (500 µm), and 19.3 µg/cm³ (1500 µm), corresponding to 2-10% of the applied concentration, with the highest deposition in the mid dermis. Immediate EPI delivered 429.4 µg/cm³ (100 µm), 584.9 µg/cm³ (500 µm), and 295.9 µg/cm³ (1500 µm) into the skin, corresponding to 29-58% of the applied nivolumab concentration. From qualitative visualization of the biodistribution, it appeared that nivolumab distributed in a horizontal and continuous homogenous band in the upper and mid dermis through AFL-exposed skin, whereas EPI-delivery showed a deep focal deposition extending into the deep dermis.

CONCLUSIONS

AFL-assisted passive diffusion and immediate EPI-assisted delivery show the potential to deliver therapeutic antibodies locally. Future in vivo and pharmacokinetic studies would reveal the full potential for topical antibody delivery by energy-based devices. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Local drug delivery from surgical thread for area-specific anesthesia

The application of surgical suture-thread and the systemic analgesics regimens for pain control in the postoperative surgery remain the criterion standard. However, these medications have daunting adverse effects on the body's innate pain management system. To address this issue, we have developed a local analgesic-loaded suture system which could be efficiently used for surgical repair with localized sedation effect. The drug-loaded conventional suture has modified by adhesive poly-dopamine coating with the local anesthetic lidocaine. The surface modifications have been ascertained by FE-SEM imaging. The tensile strength of suture ensures required elasticity to use in surgical skin closure. In vitro drug release and the in vivo local analgesia was achieved one day after surgery and persisted approximately for one week in 80% of treated animals. Our pre-clinical results suggest that drug-loaded surgical thread may be an effective strategy for improving the overall outcome.

Laser facilitates week-long sustained transdermal drug delivery at high doses

Traditional patches are most successful in transdermal delivery of low-dose hydrophobic drugs. Week-long transdermal delivery of high-dose hydrophilic drugs remains a big challenge. This study explored ablative fractional laser (AFL) to assist 3-day to week-long sustained transdermal delivery of powder hydrophilic drugs in murine models. Bulk drug powder was coated into reservoir patches followed by topical application onto AFL-treated skin. Water evaporated from AFL-generated skin microchannels (MCs) gradually dissolve topical drug powder to elicit multi-day sustained drug delivery. Using sulforhodamine b, zidovudine, and bovine serum albumin as model hydrophilic drugs, we found tapped coating could coat 10-20 mg drug per 0.5 cm² reservoir patch to elicit 3-day sustained delivery, while compression coating could coat ~35-70 mg drug per 0.5 cm² reservoir patch to elicit week-long sustained delivery. Besides sustained drug delivery, AFL-assisted powder reservoir patch delivery showed a good safety. AFL-generated skin MCs resealed in 1-2 days and completely recovered in 3 days after the week-long sustained delivery. AFL-assisted powder reservoir patch delivery involves no complex powder formulation and only requires incorporation of highly water-soluble mannitol or a similar excipient to elicit the high-efficient delivery. Enlarging reservoir patch size to 10 cm² can conveniently expand the delivery capacity to gram scale. To our knowledge, this is the first time that high-dose week-long sustained transdermal delivery of hydrophilic drugs was achieved via a simple laser-based powder delivery platform.

Fundamentals of fractional laser-assisted drug delivery: An in-depth guide to experimental methodology and data interpretation

In the decade since their advent, ablative fractional lasers have emerged as powerful tools to enhance drug delivery to and through the skin. Effective and highly customizable, laser-assisted drug delivery (LADD) has led to improved therapeutic outcomes for several medical indications. However, for LADD to reach maturity as a standard treatment technique, a greater appreciation of its underlying science is needed. This work aims to provide an in-depth guide to the technology's fundamental principles, experimental methodology and unique aspects of LADD data interpretation. We show that drug's physicochemical properties including solubility, molecular weight and tissue binding behavior, are crucial determinants of how laser channel morphology influences topical delivery. Furthermore, we identify strengths and limitations of experimental models and drug detection techniques, interrogating the usefulness of in vitro data in predicting LADD in vivo. By compiling insights from over 75 studies, we ultimately devise an approach for intelligent application of LADD, supporting its implementation in the clinical setting.

Delivery of allergen powder for safe and effective epicutaneous immunotherapy

BACKGROUND

More effective and safer immunotherapies to manage peanut allergy are in great demand despite extensive investigation of sublingual/oral immunotherapy and epicutaneous immunotherapy (EPIT) currently in the clinics.

OBJECTIVE

We sought to develop a powder-laden, dissolvable microneedle array (PLD-MNA) for epidermal delivery of powdered allergens and to evaluate the efficacy of this novel EPIT in peanut-sensitized mice.

METHODS

PLD-MNA was packaged with a mixture of powdered peanut allergen (PNA), 1,25-dihydroxyvitamin D₃ (VD3), and CpG. Its epidermal delivery and therapeutic efficacy were evaluated alongside PNA-specific forkhead box P3-positive regulatory T cells and IL-10⁺ and TGF-β1⁺ skin-resident macrophages.

RESULTS

PLD-MNA was successfully laden with PNA/VD3/CpG powder and capable of epidermal delivery of most of its content 1 hour after application onto intact mouse skin concomitant with no significant leakage into the circulation or skin irritation. PLD-MNA-mediated EPIT substantially reduced clinical allergy scores to 1 from 3.5 in sham control mice (P < .001) after 6 treatments accompanied by lower levels of PNA-specific IgE and intestinal mucosal mast cells and eosinophils over sham treatments. Moreover, in comparison with allergens administered intradermally, powdered allergens delivered by means of PLD-MNA preferentially attracted immunoregulatory macrophages and stimulated the cells to produce IL-10, TGF-β, or both at the immunization site, which might account for increased numbers of regulatory T-like cells in lymph tissues in association with systemic tolerance. PNA/VD3/CpG-laden PLD-MNA was safe and required only 6 treatments and one fifth of the PNA adjuvant dose, with improved outcomes when compared with 12 conventional intradermal immunotherapies.

CONCLUSIONS

PLD-MNA holds great promise as a novel, safe, effective, and self-applicable modality to manage IgE-mediated allergies.

Fractional laser ablation for the targeted cutaneous delivery of an anti-CD29 monoclonal antibody - OS2966

Monoclonal antibodies targeting cytokines are administered parenterally for the systemic treatment of severe psoriasis. However, systemic exposure to the biologic increases the risk of side-effects including immunosuppression, whereas only a small fraction of the active molecules actually reaches the target organ, the skin. This preclinical study examines the feasibility of delivering a humanized anti-CD29 monoclonal antibody (OS2966) topically to skin using minimally-invasive fractional laser ablation. This approach would enable the targeted use of a biologic for the treatment of recalcitrant psoriatic plaques in patients with less widespread disease while minimizing the risk of systemic exposure. First, the effect of a wide range of laser poration conditions on skin permeation and deposition of OS2966 was tested in vitro to determine optimal microporation parameters. Subsequently, confocal laser scanning microscopy was employed to visualize the distribution of fluorescently-labelled OS2966 in skin. The results demonstrated that delivery of OS2966 into and across skin was feasible. Above fluences of 35.1 J/cm², skin deposition and permeation were statistically superior to passive delivery reaching values up to 3.7 ± 1.2 µg/cm² at the most aggressive condition. Selective targeting of the skin was also possible since ≥70% of the OS2966 was delivered locally to the skin. Although nanogramme quantities were able to permeate across skin, these amounts were orders of magnitude lower than levels seen following subcutaneous or intravenous injection and would result in minimal systemic exposure in vivo. The diffusion of fluorescently-labelled OS2966 into the skin surrounding the pores was clearly higher than in intact skin and demonstrated the feasibility of delivering the antibody at least as deep as the dermo-epithelial junction, a critical border region where inflammatory cells cross to promote disease progression. These preliminary results confirm that fractional laser ablation can be used for the cutaneous delivery of OS2966 and now preclinical/clinical studies are required to demonstrate therapeutic efficacy.

Enhanced in vitro efficacy for inhibiting hypertrophic scar by bleomycin-loaded dissolving hyaluronic acid microneedles

Hypertrophic scarring is a widespread skin disorder that affects a patient's confidence and quality of life.

BCG vaccine powder-laden and dissolvable microneedle arrays for lesion-free vaccination

Live attenuated Bacille Calmette-Guerin (BCG) bacillus is the only licensed vaccine for tuberculosis prevention worldwide to date. It must be delivered intradermally to be effective, which causes severe skin inflammation and sometimes, permanent scars. To minimize the side effects, we developed a novel microneedle array (MNA) that could deliver live attenuated freeze-dried BCG powder into the epidermis in a painless, lesion-free, and self-applicable fashion. The MNA was fabricated with biocompatible and dissolvable hyaluronic acid with a deep cave formed in the basal portion of each microneedle, into which BCG powder could be packaged directly. Viability of BCG vaccine packaged in the caves and the mechanical strength of the powder-laden MNA did not alter significantly before and after more than two months of storage at room temperature. Following insertion of the MNA into the skin, individual microneedle shafts melted away by interstitial fluid from the epidermis and upper dermis, exposing the powder to epidermal tissues. The powder sucked interstitial fluid, dissolved slowly, and diffused into the epidermis in a day against the interstitial fluid influx. Vaccination with BCG-MNA caused no overt skin irritation, in marked contrast to intradermal vaccination that provoked severe inflammation and bruise. While causing little skin irritation, vaccination efficacy of BCG-MNAs was comparable to that of intradermal immunization whether it was evaluated by humoral or cellular immunity. This powder-laden and dissolvable MNA represents a novel technology to sufficiently deliver live attenuated vaccine powders into the skin.