An overview on the advantages and limitations of 3D printing of microneedles.

The use of 3D printing (3DP) technology, which has been continuously evolving since the 1980s, has recently become common in healthcare services. The introduction of 3DP into the pharmaceutical industry particularly aims at the development of patient-centered dosage forms based on structure design. It is still a new research direction with potential to create the targeted release of drug delivery systems in freeform geometries. Although the use of 3DP technology for solid oral dosage forms is more preferable, studies on transdermal applications of the technology are also increasing. Microneedle sequences are one of the transdermal drug delivery (TDD) methods which are used to bypass the minimally invasive stratum corneum with novel delivery methods for small molecule drugs and vaccines. Microneedle arrays have advantages over many traditional methods. It is attractive with features such as ease of application, controlled release of active substances and patient compliance. Recently, 3D printers have been used for the production of microneedle patches. After giving a brief overview of 3DP technology, this article includes the materials necessary for the preparation of microneedles and microneedle patches specifically for penetration enhancement, preparation methods, quality parameters, and their application to TDD. In addition, the applicability of 3D microneedles in the pharmaceutical industry has been evaluated.

Electrospinning/electrospraying coatings for metal microneedles: A design of experiments (DOE) and quality by design (QbD) approach.

The research presented here shows QbD implementation for the optimisation of the key process parameters in electrohydrodynamic atomisation (EHDA). Here, the electrosprayed nanoparticles and electrospun fibers consisting of a polymeric matrix and dye. Eight formulations were assessed consisting of 5% w/v of polycaprolactone (PCL) in dichloromethane (DCM) and 5% w/v polyvinylpyrrolidone (PVP) in ethanol. A full factorial DOE was used to assess the various parameters (applied voltage, deposition distance, flow rate). Further particle and fiber analysis using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), particle/fiber size distribution. In addition to this in vitro release studied were carried out using fluorescein and Rhodamine B as model dyes and in vitro permeation studies were applied. The results show a significant difference in the morphology of resultant structures as well as a more rapid release profile for the PVP particles and fibers in comparison to the sustained release profiles found with PCL. In vitro drug release studies showed 100% drug release after 7 days for PCL particles and showed 100% drug release within 120 min for PVP particles. The release kinetics and the permeation study showed that the MN successfully pierced the membrane and the electrospun MN coating released a large amount of the loaded drug within 6 h. This study has demonstrated the capability of these robust MNs to encapsulate a diverse range drugs within a polymeric matrix giving rise to the potential of developed personalised medical devices.

Fabrication, Physicochemical Characterization, and Performance Evaluation of Biodegradable Polymeric Microneedle Patch System for Enhanced Transcutaneous Flux of High Molecular Weight Therapeutics.

A revolutionary paradigm shift is being observed currently, towards the use of therapeutic biologics for disease management. The present research was focused on designing an efficient dosage form for transdermal delivery of α-choriogonadotropin (high molecular weight biologic), through biodegradable polymeric microneedles. Polyvinylpyrrolidone-based biodegradable microneedle arrays loaded with high molecular weight polypeptide, α-choriogonadotropin, were fabricated for its systemic delivery via transdermal route. Varied process and formulation parameters were optimized for fabricating microneedle array, which in turn was expected to temporally rupture the stratum corneum layer of the skin, acting as a major barrier to drug delivery through transdermal route. The developed polymeric microneedles were optimized on the basis of quality attributes like mechanical strength, axial strength, insertion ratio, and insertion force analysis. The optimized polymeric microneedle arrays were characterized for in vitro drug release studies, ex vivo drug permeation studies, skin resealing studies, and in vivo pharmacokinetic studies. Results depicted that fabricated polymeric microneedle arrays with mechanical strength of above 5 N and good insertion ratio exhibited similar systemic bioavailability of α-choriogonadotropin in comparison to marketed subcutaneous injection formulation of α-choriogonadotropin. Thus, it was ultimately concluded that the designed drug delivery system can serve as an efficient tool for systemic delivery of therapeutic biologics, with an added benefit of overcoming the limitations of parenteral delivery, achieving better patient acceptability and compliance.

Microneedle patches for vaccination in developing countries.

Millions of people die of infectious diseases each year, mostly in developing countries, which could largely be prevented by the use of vaccines. While immunization rates have risen since the introduction of the Expanded Program on Immunization (EPI), there remain major challenges to more effective vaccination in developing countries. As a possible solution, microneedle patches containing an array of micron-sized needles on an adhesive backing have been developed to be used for vaccine delivery to the skin. These microneedle patches can be easily and painlessly applied by pressing against the skin and, in some designs, do not leave behind sharps waste. The patches are single-dose, do not require reconstitution, are easy to administer, have reduced size to simplify storage, transportation and waste disposal, and offer the possibility of improved vaccine immunogenicity, dose sparing and thermostability. This review summarizes vaccination challenges in developing countries and discusses advantages that microneedle patches offer for vaccination to address these challenges. We conclude that microneedle patches offer a powerful new technology that can enable more effective vaccination in developing countries.

Visualization of virus-infected brain regions using a GFP-illuminating flashlight enables accurate and rapid dissection for biochemical analysis.

Engineered viral vectors tagged with a fluorescent protein such as enhanced green fluorescent protein (EGFP) have been widely used to study neuronal function after intracranial injection into specific brain regions. A rapid dissection of the virus-expressing region is required for certain biochemical analyses. To improve the accuracy of the rapid dissection, we developed a method that employs a Bluestar flashlight in combination with barrier filter glasses to visualize the expression of EGFP lentivirus that has been microinjected into the nucleus accumbens. Processing of dissected tissue for EGFP immunoblotting further validated the approach.

Increased efficacy of the 6-hydroxydopamine lesion of the median forebrain bundle in small rats, by modification of the stereotaxic coordinates.

The 6-hydroxydopamine (6-OHDA) lesion is the most widely used rat model of Parkinson's disease. A single unilateral injection of 6-OHDA into the median forebrain bundle (MFB) selectively destroys dopamine neurons in the ipsilateral substantia nigra pars compacta (SNc) and ventral tegmental area (VTA), removing more than 95% of the dopamine innervation from target areas. The stereotaxic coordinates used to deliver 6-OHDA to the MFB have been used in our laboratory successfully for more than 25 years. However, in recent years we have observed a decline in the success rate of this lesion. Previously regular success rates of >80% of rats lesioned, have become progressively more variable, with rates as low as 20% recorded in some experiments. Having excluded variability of the neurotoxin and operator errors, we hypothesized that the change seen might be due to the use of smaller rats at the time of first surgery. An attempt to proportionally adjust the lesion coordinates base on head size did not increase lesion efficacy. However, in support of the small rat hypothesis it was observed that, using the standard coordinates, rat's heads had a "nose-up" position in the stereotaxic fame. Adjustment of the nose bar to obtain a flat head position during surgery improved lesion success, and subsequent adjustments of the lesion coordinates to account for smaller head size led to a greatly increased lesion efficacy (>90%) as assessed by amphetamine induced rotation.

Microneedles in clinical practice--an exploratory study into the opinions of healthcare professionals and the public.

PURPOSE: Microneedles are being developed to administer vaccines and therapeutics to and through skin. To date there has been no qualitative or quantitative research into public and health professionals' views on this new delivery technique. METHODS: Focus groups (n=7) comprising public and healthcare professionals were convened to capture the perceived advantages for, and concerns with, microneedles. Discussions were audio-recorded and transcribed. Transcript analysis identified themes that were explored using a questionnaire identifying consensus or otherwise. RESULTS: Participants identified many potential benefits of the microneedle delivery system, including reduced pain, tissue damage and risk of transmitting infections compared with conventional injections, as well as potential for self-administration (subject to safeguards such as an indicator to confirm dose delivery). Delayed onset, cost, accurate and reliable dosing and the potential for misuse were raised as concerns. A range of potential clinical applications was suggested. The public (100%) and professional (74%) participants were positive overall about microneedle technology. CONCLUSIONS: This exploratory research study captured the views of the eventual end-users of microneedle technology. Microneedle researchers should now reflect on their research and development activities in the context of stakeholder engagement in order to facilitate the transfer of this new technology 'from bench to bedside.'

A pressure system for the microinjection of substances into the brain of awake monkeys.

We describe a method for placing pressure microinjections of drugs or anatomical tracers in physiologically defined sites in the brain of awake monkeys. This method provides a means to record neuronal activity from the tip of an injection cannula so that an injection can be made at a physiologically defined location. It uses pressure in a closed system to precisely control the amount of fluid injected and provides a visible means for monitoring injection volume. The injection cannula is easy to make with readily available components and can be used repeatedly for multiple recording sessions and injections.

Successful intracytoplasmic sperm injection without performing cytoplasmic aspiration.

OBJECTIVE: To compare the effect of cytoplasmic aspiration versus no aspiration before intracytoplasmic sperm injection (ICSI) on the rate of oocyte damage, fertilization rate, and embryo quality. DESIGN: A randomized prospective study on sibling oocytes. SETTING: The Egyptian IVF-ET Center, Cairo, Egypt. PARTICIPANTS: Fifty-eight patients who were infertile due to male factor who underwent 60 ICSI cycles. INTERVENTION: Intracytoplasmic sperm injection was performed on randomly allocated metaphase II oocytes with cytoplasmic aspiration in group I and without cytoplasmic aspiration in group II before sperm injection. MAIN OUTCOME MEASURE: Fertilization rate, oocyte damage rate, and embryo quality. RESULTS: Normal fertilization rate per injected oocyte was 61.4% in group I compared with 62.5% in group II. The damage rate per injected oocyte was 16.8% in group I compared with 4.6% in group II. Grade I embryos were 24.5% in group I compared with 48.5% in group II. CONCLUSION: Cytoplasmic aspiration before sperm injection in ICSI is not essential for oocyte activation. It did not improve the rate of normal fertilization. On the other hand, it increased the damaged oocyte rate and the rate of cytoplasmic fragments.

Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte.

Intracytoplasmic sperm injection (ICSI) is a promising assisted-fertilisation technique that may benefit women who have not become pregnant by in-vitro fertilisation (IVF) or subzonal insemination (SUZI) of oocytes. We have used ICSI to treat couples with infertility because of severely impaired sperm characteristics, and in whom IVF and SUZI had failed. Direct injection of a single spermatozoon into the ooplasm was done in 47 metaphase-II oocytes: 38 oocytes remained intact after injection, 31 became fertilised, and 15 embryos were replaced in utero. Four pregnancies occurred after eight treatment cycles--two singleton and one twin pregnancy, and a preclinical abortion. Two healthy boys have been delivered from the singleton pregnancies and a healthy boy and girl from the twin pregnancy.