Drug administration via hollow microneedles (HMN) have the advantages of painlessness, avoidance of first-pass effect, capability of sustained infusion, and no need for professional personnel operation. In addition, HMN can also be applied in the fields of body fluid extraction and biosensors, showing broad application prospects. However, traditional manufacturing technologies cannot meet the demand for low-cost mass production of HMN, limiting its widespread application. This paper reviews the main manufacturing technologies used for HMN in recent years, which include photolithography and etching, laser etching, sputtering and electroplating, micro-molding, three-dimensional (3D) printing and drawing lithography. It further analyzes the characteristics and limitations of existing manufacturing technologies and points out that the combination of various manufacturing technologies can improve production efficiency to a certain extent. In addition, this paper looks forward to the future trends of HMN manufacturing technology and proposes possible directions for its development. In conclusion, it is expected that this review can provide new ideas and references for follow-up research.
Printing, Three-Dimensional ; Needles ; Humans ; Drug Delivery Systems/methods* ; Equipment Design ; Microinjections/methods*

Compared with conventional transdermal drug delivery systems, dissolving microneedles significantly enhance drug bioavailability by penetrating the stratum corneum barrier and achieving intradermal drug delivery. In order to improve the transdermal bioavailability of dexmedetomidine hydrochloride, in this study, a novel microneedle delivery system was developed for dexmedetomidine hydrochloride based on 3D printing combined with micro-molding. By systematically optimizing the microneedle geometrical parameters, array arrangement, and preparation process parameters, we determined the optimal ratio of drug-carrying matrix as 15% PVP (polyvinyl pyrrolidone) K90. The microneedles exhibited significant drug loading gradients, with mean content of (209.99±27.56) μg/patch, (405.31±30.31) μg/patch, and (621.61±34.43) μg/patch. They showed a regular pyramidal structure under SEM and handheld electron microscopy, and their mechanical strength allowed effective penetration into the stratum corneum. The surface contact angles were all < 90°, indicating excellent hydrophilicity. The microneedles dissolved completely within 10 min after skin insertion, achieving a cumulative release rate of 90% (Higuchi model, r=0.996) during 2 hours of in vitro transdermal permeation. The cytotoxicity test and hemolysis test verified good biocompatibility. Pharmacodynamic evaluation showed that the microneedle group demonstrated pain-relieving effect within 15 min, with the pain threshold at the time point of 60 min being 3 times that in the transdermal cream group. The microneedle system developed in this study not only offers an efficient drug delivery option for patients but also establishes an innovative platform for rapid percutaneous delivery of hydrophilic drugs, demonstrating significant potential in perioperative pain management.
Dexmedetomidine/pharmacokinetics* ; Printing, Three-Dimensional ; Needles ; Drug Delivery Systems/methods* ; Administration, Cutaneous ; Animals ; Microinjections/instrumentation* ; Skin Absorption ; Skin/metabolism*

Conventional administration methods have problems including low bioavailability, complex operation process, and discomfort of patients with fear of needles. Transdermal delivery can avoid these problems, whereas most drugs are difficult to directly penetrate the skin cuticle and reach the diseased site. Microneedling is an emerging method of local drug delivery, enabling the drug penetration through the stratum corneum of the skin in a minimally invasive manner and delivering the drug directly to the diseased site, thereby improving the treatment effect. Stimuli-responsive microneedles have attracted much attention because of the spatiotemporal controllability, high drug delivery efficiency, and mild potential side effects. This review introduced the commonly used materials and various types of stimuli-responsive microneedles and the drug release mechanisms. In addition, this paper expounded the biomedical applications of stimuli-responsive microneedles as drug delivery systems in response to different stimuli and discusses the challenges and potential solutions for stimuli-responsive microneedles.
Needles ; Drug Delivery Systems/instrumentation* ; Microinjections/instrumentation* ; Humans ; Administration, Cutaneous

Objective: To explore the effects of pulsed dye laser (PDL) and ultra-pulsed fractional carbon dioxide laser (UFCL) combined with multipoint microinjection of triamcinolone acetonide in the treatment of red hypertrophic scar at early stage in burn children. Methods: A retrospective cohort before-after control study in the same patients was conducted. From February 2019 to December 2020, a total of 67 burn children who met the inclusion criteria (32 males and 35 females, aged 1 to 12 years) with red hyperplastic scar at early stage, were treated in Hunan Provincial People's Hospital (1^st Affiliated Hospital of Hunan Normal University). All the children were treated with composite laser technique (PDL and UFCL) combined with triamcinolone acetonide (hereinafter referred to as combined treatment). After 2 months, they received the second combined treatment. Before the first combined treatment and 6 months after the last combined treatment, the scar of children was evaluated with the patient and observer scar assessment scale (POSAS) by physicians and family members. Six months after the last combined treatment, the satisfaction of the patients' family members with the efficacy was recorded and the overall satisfaction rate was calculated. Adverse reactions were recorded throughout the treatment process. Data were statistically analyzed with paired sample t test. Results: Six months after the last combined treatment, the POSAS scores of children on the thickness, blood vessels distribution, color, surface roughness, texture, scope, and overall evaluation of scar evaluated by the physicians, and the POSAS scores of children on the color, degree of pain, degree of itching, hardness, thickness, shape and size, and overall evaluation of scar evaluated by the family members were significantly lower than those before the first combined treatment (with t values of 17.32, 16.73, 15.00, 14.91, 19.62, 28.74, 29.83, 17.43, 20.52, 29.01, 28.82, 24.91, 20.30, and 42.13, respectively, P<0.01). Six months after the last combined treatment, 62 (93%), 3 (4%), and 2 (3%) children's family members were very satisfied, satisfied, and relatively satisfied with the treatment effect, respectively, and the overall satisfaction rate was 97% (65/67). Six months after the last combined treatment, no scar thickening or infection occurred in all the wounds of children. Conclusions: Composite laser technique combined with multipoint microinjection of triamcinolone acetonide in the treatment of red hypertrophic scar at early stage in burn children can improve the appearance and texture of scar, reduce scar pain and pruritus, with high satisfaction of children's family members to the treatment effect and less adverse reactions.
Burns/therapy* ; Child ; Cicatrix, Hypertrophic/pathology* ; Female ; Humans ; Lasers, Gas ; Male ; Microinjections ; Pain ; Pruritus ; Retrospective Studies ; Treatment Outcome ; Triamcinolone Acetonide/therapeutic use*

The transposon vector containing enhanced green fluorescent protein (EGFP) was injected into early housefly (Musca domestica L.) eggs by microinjection method to realize stable gene expression in vivo for verification, and to study housefly gene function. A borosilicate glass micro injection needle suitable for microinjection of housefly eggs was made, the softening treatment conditions of housefly egg shells were explored, and a microinjection technology platform suitable for housefly was constructed with a high-precision microsyringe Nanoject Ⅲ as the main body. The recombinant plasmid PiggyBac-[3×P3]-EGFP containing the eye-specific 3×P3 promoter and EGFP and the stable genetic expression helper plasmid pHA3pig helper were microinjected into the treated housefly eggs. After emergence, the eye luminescence was observed, and the expression and transcription level of EGFP were detected. The results showed that the normal hatching rate of housefly eggs was 55% when rinsed in bleaching water for 35 s. The hardness of the egg shell treated for 35 s was suitable for injection and the injection needle was not easy to break. About 3% of the emerged housefly eyes had green fluorescence. Through further molecular detection, EGFP specific fragments with a size of 750 bp were amplified from DNA and RNA of housefly. Through the technical platform, the stable expression of reporter genes in housefly can be conveniently and effectively realized, and a bioreactor with housefly as the main body can be established, which provides certain reference value for subsequent research on housefly gene function.
Animals ; Animals, Genetically Modified ; Gene Expression ; Genes, Reporter ; Green Fluorescent Proteins/genetics* ; Houseflies/genetics* ; Microinjections

Microneedles have been developed rapidly in the field of transdermal administration in the past few decades. In recent years, the development of microelectronics technology has expanded the applications of microneedles by combining with microelectronic systems, especially in biological diagnosis and treatment. Different types of microneedles have been designed to extract blood and tissue fluids for detection, or as electrodes to directly detect blood sugar, melanoma and pH in real-time in vivo, both show good prospects for real-time detection applications. In this paper, we review the design of materials and structure of microelectronic-based microneedles, and discuss their advances in biological diagnosis.
Administration, Cutaneous ; Drug Delivery Systems ; Electrodes ; Microinjections ; Needles

The ezrin-radixin-moesin (ERM) proteins are a family of membrane-associated proteins known to play roles in cell-shape determination as well as in signaling pathways. We have previously shown that amphetamine decreases phosphorylation levels of these proteins in the nucleus accumbens (NAcc), an important neuronal substrate mediating rewarding effects of drugs of abuse. In the present study, we further examined what molecular pathways may be involved in this process. By direct microinjection of LY294002, a PI3 kinase inhibitor, or of S9 peptide, a proposed GSK3β activator, into the NAcc core, we found that phosphorylation levels of ERM as well as of GSK3β in this site are simultaneously decreased. These results indicate that ERM proteins are under the regulation of Akt-GSK3β signaling pathway in the NAcc core. The present findings have a significant implication to a novel signal pathway possibly leading to structural plasticity in relation with drug addiction.
Amphetamine ; Animals ; Glycogen Synthase Kinases ; Humans ; Membrane Proteins ; Microinjections ; Negotiating ; Neurons ; Nucleus Accumbens ; Phosphorylation ; Phosphotransferases ; Plastics ; Proto-Oncogene Proteins c-akt ; Rats ; Reward ; Signal Transduction ; Street Drugs ; Substance-Related Disorders

Talaromyces marneffei is the only dimorphic species in its genus and causes a fatal systemic mycosis named talaromycosis. Our previous study indicated that knockdown of AcuD gene (encodes isocitrate lyase of glyoxylate bypass) of T. marneffei by RNA interference approach attenuated the virulence of T. marneffei, while the virulence of the AcuD knockout strains was not studied. In this study, T. marneffei-zebrafish infection model was successfully established through hindbrain microinjection with different amounts of T. marneffei yeast cells. After co-incubated at 28°C, the increasing T. marneffei inoculum doses result in greater larval mortality; and hyphae generation might be one virulence factor involved in T. marneffei-zebrafish infection. Moreover, the results demonstrated that the virulence of the ΔAcuD was significantly attenuated in this Zebrafish infection model.
Gene Knockout Techniques ; Hyphae ; Isocitrate Lyase ; Microinjections ; Mortality ; Rhombencephalon ; RNA Interference ; Talaromyces ; Virulence ; Yeasts ; Zebrafish

OBJECTIVE: This study was performed to explore the possibility that each oocyte and its surrounding cumulus cells might have different genetic expression patterns that could affect human reproduction. METHODS: Differential gene expression analysis was performed for 10 clusters of cumulus cells obtained from 10 cumulus-oocyte complexes from 10 patients. Same procedures related to oocyte maturation, microinjection, and microarray analyses were performed for each group of cumulus cells. Two differential gene expression analyses were performed: one for the outcome of clinical pregnancy and one for the outcome of live birth. RESULTS: Significant genes resulting from these analyses were selected and the top 20 affected pathways in each group were analyzed. Circadian entrainment is determined to be the most affected pathway for clinical pregnancy, and proteoglycans in cancer pathway is the most affected pathway for live birth. Circadian entrainment is also amongst the 12 pathways that are found to be in top 20 affected pathways for both outcomes, and has both lowest p-value and highest number of times found count. CONCLUSION: Although further confirmatory studies are necessary, findings of this study suggest that these pathways, especially circadian entrainment in cumulus cells, may be essential for embryo development and pregnancy.
Circadian Clocks ; Cumulus Cells ; Embryonic Development ; Female ; Gene Expression ; Granulosa Cells ; Humans ; Infertility ; Live Birth ; Microarray Analysis ; Microinjections ; Oocytes ; Ovarian Follicle ; Pregnancy ; Proteoglycans ; Reproduction ; Reproductive Techniques, Assisted

BACKGROUND: The trigeminal nucleus caudalis (Vc) is a primary central site for trigeminal transmitting. Noxious stimulation of the trigeminal nociceptors alters the central synaptic releases and neural expression of some inflammatory and trophic agents. Orexin-A and the orexin 1 receptor (OX1R) are expressed in pain pathways including trigeminal pain transmission. However, the the mechanism(s) underling orexin-A effects on trigeminal pain modulation have not been fully clarified. METHODS: Trigeminal pain was induced by subcutaneous injection of capsaicin in the upper lip in rats. The effect of trigeminal pain on cyclooxygenase-2 (COX-2) and brain-derived neurotrophic factor (BDNF) expression in the Vc of animals was determined by immunofluorescence. Subsequently, OX1R agonist (orexin-A) and antagonist (SB-334867-A) was administrated in the Vc to investigate the possible roles of the Vc OX1R on changes in COX-2 and BDNF levels following pain induction. RESULTS: The data indicated an increase in COX-2 and decrease in BDNF immuno-reactivity in the Vc of capsaicin, and capsaicin- pretreated with SB-334867-A (80 nM), groups of rat. However, the effect of capsaicin on COX-2 and BDNF expressions was reversed by a Vc microinjection of orexin-A (100 pM). CONCLUSIONS: Overall, the present data reveals that orexin-A can attenuate capsaicin-induced trigeminal pain through the modulation of pain effects on COX-2 and BDNF expressions in the Vc of rats.
Animals ; Brain-Derived Neurotrophic Factor ; Capsaicin ; Cyclooxygenase 2 ; Facial Pain ; Fluorescent Antibody Technique ; Injections, Subcutaneous ; Lip ; Microinjections ; Nociceptors ; Orexin Receptor Antagonists ; Orexins ; Pain Measurement ; Pain Perception ; Rats ; Trigeminal Caudal Nucleus ; Trigeminal Neuralgia ; Trigeminal Nuclei