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Boonnada Pamornpathomkul,1 Adisak Wongkajornsilp,2 Wanida Laiwattanapaisal,3 Theerasak Rojanarata,1 Praneet Opanasopit,1 Tanasait Ngawhirunpat1 1Department of Pharmaceutical Technology, Faculty of Pharmacy, Pharmaceutical Development of Green Innovations Group, Silpakorn University, Nakhon Pathom, 2Department of Pharmacology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 3Department of Clinical Chemistry, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok, Thailand Abstract: The aim of this study was to investigate the use of different types of microneedles (MNs) and nanocarriers for in vitro skin permeation and in vivo immunization of plasmid DNA encoding ovalbumin (pOVA). In vitro skin permeation studies indicated that hollow MNs had a superior enhancing effect on skin permeation compared with solid MN patches, electroporation (EP) patches, the combination of MN and EP patches, and untreated skin. Upon using hollow MNs combined with nanocarriers for pOVA delivery, the skin permeation was higher than for the delivery of naked pOVA, as evidenced by the increased amount of pOVA in Franz diffusion cells and immunoglobulin G (IgG) antibody responses. When the hollow MNs were used for the delivery of nanocarrier:pOVA complexes into the skin of mice, they induced a stronger IgG immune response than conventional subcutaneous (SC) injections. In addition, immunization of mice with the hollow MNs did not induce signs of skin infection or pinpoint bleeding. Accordingly, the hollow MNs combined with a nanocarrier delivery system is a promising approach for delivering pOVA complexes to the skin for promoting successful immunization. Keywords: hollow microneedle, solid microneedle, electroporation, plasmid DNA encoding ovalbumin, skin immunization, nanocarrier

The purpose of this study was to evaluate the use of different formulations, including solution, gel, liposome and niosome for in vitro skin permeation and antioxidant activity of Centella asiatica (CA) extract. The liposomes and niosomes loaded with CA were characterized to observe the physicochemical properties i.e., particle size, zeta potential, percentage of entrapment efficiency (%EE) and percentage of loading efficiency (%LE). In vitro skin permeation studies revealed that liposome formulations had a superior enhancing effect on skin permeation compared to niosome, gel and solution formulation. Upon applied niosome formulations for the delivery of CA extract at 24 hours (h), the antioxidant activity was higher than liposome, gel and solution formulation, as evidenced by the increased in percent inhibition using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. However, there was no significant difference in antioxidant activity between niosome and liposome formulations. Accordingly, both the liposome and noisome formulations are promising approaches for transdermal delivery of CA extract for promoting successful antioxidant activity.

The current study focused on the development of crosslinked hydrogel microneedle patches (cHMNs) incorporating 5-FU-hydroxypropyl beta-cyclodextrin inclusion complex-loaded flexible PEGylated liposomes (5-FU-HPβCD-loaded FP-LPs) to enhance treatment efficacy and reduce drug toxicity. The research utilized artificial intelligence (AI) algorithms to design, optimize, and evaluate the cHMNs. Various AI models were assessed for accuracy, with metrics such as root mean square error and coefficient of determination guiding the selection of the most effective formulation. The physicochemical and mechanical properties, swelling behavior, in vitro skin permeation, and safety of the chosen cHMNs were tested. The results demonstrated that the 5-FU-HPβCD-loaded FP-LPs, stabilized with limonene, had an optimal particle size of 36.23 ± 2.42 nm, narrow size distribution, and zeta potential of -10.24 ± 0.37 mV, with high encapsulation efficiency. The cHMNs exhibited a conical needle shape with sufficient mechanical strength to penetrate the stratum corneum up to approximately 467.87 ± 65.12 μm. The system provided a high skin permeation rate of 41.78 ± 4.26 % and significant drug accumulation in the skin. Additionally, the formulation was proven safe in cell culture while effectively inhibiting cancer growth and promoting apoptosis. This study highlights the potential of AI-enhanced cHMNs for delivering 5-FU-HPβCD-loaded FP-LPs transdermally, offering a promising new treatment avenue for non-melanoma skin cancers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Untreated or poorly managed chronic wounds can progress to skin cancer. Topically applied 5-fluorouracil (5-FU), a nonspecific cytostatic agent, can cause various side effects. Its high polarity also results in low cell membrane affinity and bioavailability. Hydrogel, used for its occlusive effect, is one platform for treating chronic wounds combined with PEGylated liposomes (LPs), developed to increase drug-skin affinity. This research aimed to develop a novel hydrogel forming chitosan-based microneedles (HFM) chemowrap patch containing 5-FU PEGylated LPs, improving 5-FU efficiency for pre-carcinogenic and carcinogenic skin lesions. The results indicated that the 5-FU-PEGylated LPs-loaded HFM chemowrap patch exhibited desirable physical and mechanical characteristics with complete penetration ability. Furthermore, in vivo skin permeation studies demonstrated the highest percentage of 5-FU permeated the skin (42.06 ± 11.82 %) and skin deposition (75.90 ± 1.13 %) compared to the other treatments, with demonstrated superior percentages of complete wound healing in in vivo (47.00 ± 5.77 % wound healing at day 7) and in NHF cells (92.79 ± 7.15 % at 48 h). Furthermore, 5-FU-PEGylated LPs-loaded HFM chemowrap patches exhibit efficient anticancer activity while maintaining safety for normal cells. The results also show that the developed formulation of a 5-FU-PEGylated LPs-loaded HFM chemowrap patch could enhance apoptosis higher than that of the 5-FU solution. Consequently, 5-FU PEGylated LPs-loaded HFM chemowrap patch represented a promising drug delivery approach for treating pre-carcinogenic and carcinogenic skin lesions., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Currently, artificial intelligence (AI), machine learning (ML), and deep learning (DL) are gaining increased interest in many fields, particularly in pharmaceutical research and development, where they assist in decision-making in complex situations. Numerous research studies and advancements have demonstrated how these computational technologies are used in various pharmaceutical research and development aspects, including drug discovery, personalized medicine, drug formulation, optimization, predictions, drug interactions, pharmacokinetics/ pharmacodynamics, quality control/quality assurance, and manufacturing processes. Using advanced modeling techniques, these computational technologies can enhance efficiency and accuracy, handle complex data, and facilitate novel discoveries within minutes. Furthermore, these technologies offer several advantages over conventional statistics. They allow for pattern recognition from complex datasets, and the models, typically developed from data-driven algorithms, can predict a given outcome (model output) from a set of features (model inputs). Additionally, this review discusses emerging trends and provides perspectives on the application of AI with quality by design (QbD) and the future role of AI in this field. Ethical and regulatory considerations associated with integrating AI into pharmaceutical technology were also examined. This review aims to offer insights to researchers, professionals, and others on the current state of AI applications in pharmaceutical research and development and their potential role in the future of research and the era of pharmaceutical Industry 4.0 and 5.0., (© 2024. The Author(s), under exclusive licence to American Association of Pharmaceutical Scientists.)

Periodontitis is a common chronic inflammatory disease primarily caused by the prevalence of bacterial overgrowth resulting in the development of an inflammatory condition that destroys the tooth's supporting tissues and eventual tooth loss. Comparatively, to other treatment methods, it is difficult for topical antibacterial drugs to effectively permeate the biofilm's physical barrier, making conventional therapy for periodontitis more challenging. This novel study combines thermosensitive in situ hydrogel with microparticles (MPs) to enhance the targeted delivery of metronidazole (MET) to the periodontal pocket. Polycaprolactone (PCL) polymer was utilized to produce bacteria-sensitive MPs. Additionally, the study assessed the attributes of MPs and demonstrated an enhancement in the in vitro antibacterial efficacy of MPs towards Staphylococcus aureus (SA) and Escherichia coli (EC). Subsequently, we incorporated MET-MPs into thermosensitive in situ hydrogel formulations using chitosan. The optimized formulations exhibited stability, appropriate gelation temperature, mucoadhesive strength, and viscosity. In vitro permeation tests showed selective and prolonged drug release against SA and EC. Ex vivo experiments demonstrated no significant differences between in situ hydrogel containing pure MET and MET-MPs in biofilm quantity, bacterial counts, and metabolic activity in biofilms. According to in vitro tests and the effectiveness of the antibacterial activity, this study has exhibited a novel methodology for more efficacious therapies for periodontitis. This study aims to utilize MET in MPs to improve its effectiveness, enhance its antibacterial activity, and improve patient treatment outcomes. In further research, the efficacy of the treatment should be investigated in vivo using an appropriate animal model.

Red fruit (Pandanus conoideus Lam.) boasts high β-carotene (BC) content, often consumed orally. However, absorption issues and low bioavailability due to food matrix interaction have led to transdermal delivery exploration. Nevertheless, BC has a short skin retention time. To address these limitations, this study formulates a β-carotene solid dispersion (SD-BC) loaded thermoresponsive gel combined with polymeric solid microneedles (PSM) to enhance in vivo skin bioavailability. Characterization of SD-BC includes saturation solubility, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and in vitro release. Characterization of SD-BC thermoresponsive gel includes gelation temperature, viscosity, rheological behaviour, pH, bio-adhesiveness, spreadability, and extrudability. PSM's mechanical properties and insertion capability were assessed. Ex vivo and in vivo dermato-pharmacokinetic studies, drug content, hemolysis, and skin irritation assessments were conducted to evaluate overall performance. Results confirm amorphous SD-BC formation, enhancing solubility. Both SD-BC thermoresponsive gel and PSM exhibit favourable characteristics, including rheological properties and mechanical strength. In vitro release studies showed a seven-fold increase in BC release compared to plain hydrogel. SD-BC thermoresponsive gel combined with PSM achieves superior ex vivo permeation (C max  = 305.43 ± 32.07 µg.mL -1 ) and enhances in vivo dermato-pharmacokinetic parameters by 200-400 %. Drug content, hemolysis, and skin irritation studies confirmed its safety and non-toxicity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Fluconazole (FNL) is one of the first-line treatments for fungal keratitis as it is an effective broad-spectrum antimicrobial commonly administered orally or topically. However, FNL has a very low water solubility, limiting its drug formulation, therapeutic application, and bioavailability through tissues. To overcome these limitations, this study aimed to develop FNL inclusion complexes (FNL-IC) with cyclodextrin (α-cyclodextrin, sulfobutylether-β-cyclodextrin, and hydroxypropyl-γ cyclodextrin) and incorporate it into a dissolvable microneedle (DMN) system to improve solubility and drug penetration. FNL-IC was evaluated for saturation solubility, Fourier transform infrared spectroscopy, differential scanning calorimetry, in vitro release, minimum inhibitory concentration, minimum fungicidal concentration, and time-killing assay. DMN-FNL-IC was evaluated for mechanical and insertion properties, surface pH, moisture absorption ability, water vapor transmission, and drug content recovery. Moreover, ocular kinetic, ex vivo antimicrobial, in vivo antifungal, and chorioallantoic membrane (HET-CAM) assays were conducted to assess the overall performance of the formulation. Mechanical strength and insertion properties revealed that DMN-FNL-IC has great mechanical and insertion properties. The in vitro release of FNL-IC was significantly improved, exhibiting a 9-fold increase compared to pure FNL. The ex vivo antifungal activity showed significant inhibition of Candida albicans from 6.54 to 0.73 log cfu/mL or 100-0.94%. In vivo numbers of colonies of 0.87 ± 0.13 log cfu/mL (F2), 4.76 ± 0.26 log cfu/mL (FNL eye drops), 3.89 ± 0.24 log cfu/mL (FNL ointments), and 8.04 ± 0.58 log cfu/mL (control) showed the effectiveness of DMN preparations against other standard commercial preparations. The HET-CAM assay showed that DMN-FNL-IC (F2) did not show any vascular damage. Finally, a combination of FNL-IC and DMN was developed appropriately for ocular delivery of FNL, which was safe and increased the effectiveness of treatments for fungal keratitis.

Progesterone (PG) has been approved for hormone replacement therapy to mitigate the risk of endometrial carcinoma. However, there has been a lack of success in oral PG due to its rapid degradation. Transdermal PG has advantages but lacks efficacy due to its poor solubility (Log p  = 3.9). Therefore, this study aimed to evaluate how combining self-microemulsifying drug delivery systems (SMEDDS) and polymeric microneedles (MNs) could improve the transdermal delivery of PG in a controlled-release manner. Among PG-SMEDDS, PG-SME5 was selected for its desirable properties and stability. The two-layer polymeric MNs formulation incorporating PG-SME5 (PG-SMEDDS-tMNs) was formulated from aqueous blends of polymers as a first layer and 20% PCL as a second layer. It successfully penetrated neonatal porcine skin with the dissolution of the first layer observed within 15 min after application. In vitro skin permeation revealed that the percentage of PG which permeated the skin over 82 h using PG-SMEDDS-tMNs was higher than a PG-suspension and PG-SMEDDS. The Higuchi kinetic showed controlled release over 15 days of PG from PG-SMEDDS-tMNs. These studies suggested that incorporating PG-SMEDDS into controlled-release two-layer polymeric MNs could be a promising approach for improving the transdermal delivery of PG.

Fungal keratitis (FK) is a fungal infection of the cornea, which is part of the eye and causes corneal ulcers and an increased risk of permanent blindness, which is often found in Candida albicans species. Amphotericin B (AMB), which is a group of polyenes as the first-line treatment of FK, is effective in annihilating C. albicans . However, AMB preparations such as eye drops and ointments have major drawbacks, for instance, requiring more frequent administrations, loss of the drug by the drainage process, and rapid elimination in the precornea, which result in low bioavailability of the drug. An ocular dissolving microneedle containing the solid dispersion amphotericin B (DMN-SD-AMB) had been developed using a mixture of poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) polymers, while the solid dispersion AMB (SD-AMB) was contained in the needle as a drug. This study aims to determine the most optimal and safest DMN-SD-AMB formula for the treatment of FK in the eye as well as a solution to overcome the low bioavailability of AMB eye drops and ointment preparations. SD-AMB had been successfully developed, which was characterized by increased antifungal activity and drug release in vitro compared to other treatments. Furthermore, DMN-SD-AMB studies had also been successfully performed with the best formulation, which exhibited the best ex vivo corneal permeation profile and antifungal activity as well as being safe from eye irritation. In addition, an in vivo antifungal activity using a rabbit infection model shows that the number of fungal colonies was 0.98 ± 0.11 log 10 CFU/mL (F3), 5.76 ± 0.32 log 10 CFU/mL (AMB eye drops), 4.01 ± 0.28 log 10 CFU/mL (AMB ointments), and 9.09 ± 0.65 log 10 CFU/mL (control), which differed significantly ( p < 0.05). All of these results evidence that DMN-SD-AMB is a new approach to developing intraocular preparations for the treatment of FK.

Alpha-arbutin (AA) and resveratrol (Res) are widely used in skin-lightening products. However, current topical formulations have minimal skin-lightening effects due to the low absorption and poor solubility of these active compounds. This study investigated the efficacy and safety of using dissolving microneedle (DMN) patches to improve the delivery of AA and Res for skin depigmentation. The DMN patches (F0-F3) fabricated from polyvinyl pyrrolidone-K90 (PVP-K90)/Eudragit RL100 blends successfully penetrated excised porcine skin and showed sufficient mechanical strength to resist compression forces. Loading DMNs with 10% AA and 2% Res at a ratio of 5 : 1 (F3) resulted in a synergistic interaction between the drugs with desirable dissolving ability, drug loading, and stability. Furthermore, both in vitro and in vivo studies revealed that the use of F3 DMN patches successfully enhanced the intradermal delivery of AA and Res over a 24 h period, with the delivered amount being higher (∼2.6 times) than that provided by a cream formulation ( P < 0.05). After removing the DMN patches, the mice's skin was spontaneously and completely resealed within 12 h. In clinical studies, F3 DMN patches slightly decreased the melanin index of the participants without causing skin irritation or erythema at any time during the 24 h period when the patches were applied ( P < 0.05). Moreover, application of the patches for 24 h was not found to affect skin hydration, transepidermal water loss, or skin elasticity. Therefore, AA/Res-loaded DMN patches could offer a promising approach for the effective local delivery of cosmetic agents for skin depigmentation.

Intranasal (IN) administration, a non-invasive route, is explored to overcome the limitations of conventional subcutaneous (SC) injection for Japanese encephalitis (JE) immunisation. Mucoadhesive nanoparticles (NPs) are recognised for the benefits they offer via IN delivery, such as extended retention time of the vaccine on the mucosa. The purpose of this study was to evaluate immunisation effect of live attenuated Japanese encephalitis-chimeric virus vaccine (JE-CV)-loaded mucoadhesive NPs based on chitosan (CS) or chitosan maleimide (CM), a novel mucoadhesive polymer, via the IN route to improve the mucosal immunisation against JE. The results revealed that IN immunisation stimulated seroprotection following PRNT 50 evaluation. Moreover, compared with SC immunisation, IN immunisation in mice provided a higher sIgA level, leading to improved mucosal immune response. In addition, chitosan-based NPs showed an adjuvant effect on the IN vaccine due to their mucoadhesive and antigen-uptaken properties. CM NPs successfully induced sIgA. In contrast, SC JE-CV immunisation induced negligible mucosal immunity. These immunological advantages revealed that JE-CV-loaded mucoadhesive NPs are a promising approach for IN vaccination as an alternative route for JE protection due to the stimulatory effects on both mucosal and systemic immune responses., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this study, polyacrylic acid-co-maleic acid (PAMA) and polyvinyl alcohol (PVA) (1:4) were used to fabricate dissolving microneedles (DMNs) and hydrogel forming microneedles (HMNs) which incorporated α-arbutin. Αlpha-arbutin is commonly used as a skin lightening agent. However, it has poor penetration ability due to its hydrophilic properties. The purpose of this study was to compare the permeation of α-arbutin into the skin using DMNs and HMNs. Both types of microneedles (MNs) were sharp, strong with elegant appearance and approximately 100% penetrated the neonatal porcine skin. All needles of α-arbutin loaded DMNs were completely dissolved within 45 min, whereas maximum swelling of HMNs was observed at 4 h. In vitro permeation studies showed that α-arbutin loaded DMNs and HMNs provided significantly about 4.5 and 2.8 times, respectively, greater α-arbutin permeability than gel and commercial cream (P < 0.05). In vivo study also showed high intradermal delivery of α-arbutin levels using DMNs (5.33 µg/mL) and HMNs (1.47 µg/mL) when compared to that of commercial cream 0.15 µg/mL. Moreover, the micro-holes caused by applying MNs can reseal within 1 h. MNs were also stable at 25 °C for 3 months. The results suggested that DMNs and HMNs developed have a promising platform for transdermal delivery., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Alpha-arbutin is one of the most efficient skin lightener agents, which shows the effect on reducing the pigmentation by competitively inhibiting human tyrosinase. However, alpha-arbutin has difficulty in skin permeability due to its hydrophilic property. The objective of this study was, therefore, to develop alpha-arbutin-loaded dissolving microneedles (DMNs) for improving the delivery of alpha-arbutin into the skin. The DMN patch was prepared using Gantrez™ S-97, hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone K-90 (PVP), chitosan, and their combinations. The optimal 8% alpha-arbutin-loaded DMNs, aside from Gantrez™ S-97, was successfully formulated with combination of 8% w/w HPMC and 40% w/w PVP K-90 (HPMC/PVP) at the weight ratio of 1:1. Both DMNs had 100% of penetration into porcine skin. Over 12 h of skin permeation, the flux of Gantrez™ S-97 DMNs and the HPMC/PVP DMNs were 66.21 μg/cm 2 /h and 74.24 μg/cm 2 /h, respectively. The accumulation amount of alpha-arbutin in the skin from Gantrez™ S-97 DMNs and HPMC/PVP DMNs was 107.76 μg and 312.23 μg, respectively. In comparison to the gel formulations, Gantrez™ S-97 DMNs and HPMC/PVP DMNs increase the delivery of alpha-arbutin across the skin approximately 2 and 4.7 times, respectively. In vivo studies found that alpha-arbutin-loaded HPMC/PVP DMNs delivered more alpha-arbutin into the skin than commercial cream. Moreover, the skin can reseal naturally after removal of DMNs patch without any signs of infection and remain stable in accelerated conditions for 4 weeks. Accordingly, alpha-arbutin-loaded HPMC/PVP DMNs could be a promising delivery platform for promoting trans-epidermal delivery of alpha-arbutin for skin lightening.

Acyclovir is widely indicated for the treatment of herpes labialis (cold sores), typically caused by the herpes simplex virus type 1 (HSV-1). However, topical acyclovir has poor efficacy, due to its low skin permeability. The purpose of this study was, therefore, to evaluate the ability of dissolving polymeric microneedle (MN) arrays to improve the local delivery of acyclovir. Acyclovir-loaded dissolving MN arrays (0.49 cm 2 ) were formulated from aqueous blends of Gantrez ® S-97 with 361 needles per array (589 ± 9.29 μm height). MN penetrated excised neonatal porcine skin, showing sufficient mechanical strength to resist compression and maintained their appearance after application of a 0.089 N per needle force for 30 s. Dissolution of the needles was observed within 15 min after application to skin and the needles had completely dissolved at 2 h in vitro. In vitro skin permeation studies revealed that the percentage of total acyclovir loading which permeated the skin over a 24 h period using MNs was approximately 45 times higher than that of a commercial cream formulation (Lipsore®). The accumulation of acyclovir at the basal epidermis, the target site of the herpes simplex virus, using MNs was a total of 21.5 μg/cm 3 in vitro, which is approximately 5 times greater than the 99% inhibition of viral cytopathic effect (ID 99 ) required for HSV infections. This level was also 16 times higher than that obtained using the cream formulation. An in vivo study showed that the use of acyclovir-loaded dissolving MN arrays successfully provided intradermal delivery of acyclovir over a 48 h period and the drug levels in the skin delivered using MN arrays (45.09 ± 13.28 μg/cm 3 ) were superior to those generated by the cream formulation (4.55 ± 1.37 μg/cm 3 ). Accordingly, acyclovir-loaded dissolving MN arrays could be a promising approach for effective local delivery of acyclovir., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The purpose of the present study was to evaluate the use of cationic niosomes composed of Span20:cholesterol:cationic lipid (N 1 ,N 1 -dimyristeroyloxyethyl-spermine) at the molar ratio of 2.5:2.5:0.5 mM combined with hollow microneedle (MN) devices for in vivo skin immunization of plasmid DNA-encoding ovalbumin (pOVA). The results revealed that using hollow MNs with cationic niosomes for pOVA penetration successfully induced both humoral and cell-mediated immune responses including immunoglobulin G (IgG) antibody responses, interleukin-4 (IL-4), and interferon gamma (IFN-γ) cytokine secretion. When using hollow MNs with cationic niosome/pOVA complexes, the immune response was superior to naked pOVA, which testifies the increased amount of IgG antibody responses and cytokine secretion. In comparison with conventional subcutaneous (SC) injections, using hollow MNs with cationic niosome/pOVA complexes induced a higher level of both IgG immune response and cytokine release. Moreover, a group of mice immunized with hollow MNs did not show infection or bleeding on the skin. Consequently, targeted delivery of pOVA using cationic niosomes combined with hollow MNs might prove a promising vaccination method for skin vaccination.

The purpose of this study was to evaluate the use of different types of microneedles and doses of ovalbumin antigen for in vitro skin permeation and in vivo immunization. In vitro skin permeation experiments and confocal laser scanning microscopy revealed that hollow microneedles had a superior enhancing effect on skin permeation compared with a solid microneedle patch and untreated skin by efficiently delivering ovalbumin-fluorescein conjugate into the deep skin layers. The flux and cumulative amount of ovalbumin-fluorescein conjugate at 8 h after administering with various conditions could be ranked as follows: hollow MN; high dose > medium dose > low dose > MN patch; high dose > medium dose > low dose > untreated skin; high dose > medium dose > low dose > without ovalbumin-fluorescein conjugate. As the dose of ovalbumin-fluorescein conjugate was increased to 500 μg, the antigen accumulated in the skin to a greater extent, as evidenced by the increasing green fluorescence intensity. When the hollow microneedle was used for the delivery of ovalbumin into the skin of mice, it was capable of inducing a stronger immunoglobulin G immune response than conventional subcutaneous injection at the same antigen dose. Immunoglobulin G levels in the hollow MN group were 5.7, 11.6, and 13.3 times higher than those of the subcutaneous injection group for low, medium, and high doses, respectively. Furthermore, the mice immunized using the hollow microneedle showed no signs of skin infection or pinpoint bleeding. The results suggest that the hollow MN is an efficient device for delivering the optimal dose of antigen via the skin for successful immunization.