Intradermal Vaccination with PLGA Nanoparticles via Dissolving Microneedles and Classical Injection Needles.

PURPOSE: A dissolving microneedle array (dMNA) is a vaccine delivery device with several advantages over conventional needles. By incorporating particulate adjuvants in the form of poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) into the dMNA, the immune response against the antigen might be enhanced. This study aimed to prepare PLGA-NP-loaded dMNA and to compare T-cell responses induced by either intradermally injected aqueous-PLGA-NP formulation or PLGA-NP-loaded dMNA in mice. METHODS: PLGA NPs were prepared with microfluidics, and their physicochemical characteristics with regard to encapsulation efficiencies of ovalbumin (OVA) and CpG oligonucleotide (CpG), zeta potentials, polydispersity indexes, and sizes were analysed. PLGA NPs incorporated dMNA was produced with three different dMNA formulations by using the centrifugation method, and the integrity of PLGA NPs in dMNAs was evaluated. The immunogenicity was evaluated in mice by comparing the T-cell responses induced by dMNA and aqueous formulations containing ovalbumin and CpG (OVA/CpG) with and without PLGA NP. RESULTS: Prepared PLGA NPs had a size of around 100 nm. The dMNA formulations affected the particle integrity, and the dMNA with poly(vinyl alcohol) (PVA) showed almost no aggregation of PLGA NPs. The PLGA:PVA weight ratio of 1:9 resulted in 100% of penetration efficiency and the fastest dissolution in ex-vivo human skin (< 30 min). The aqueous formulation with soluble OVA/CpG and the aqueous-PLGA-NP formulation with OVA/CpG induced the highest CD4 + T-cell responses in blood and spleen cells. CONCLUSIONS: PLGA NPs incorporated dMNA was successfully fabricated and the aqueous formulation containing PLGA NPs induce superior CD4+ and CD8+ T-cell responses.

Visualizing Anatomy in Dental Morphology Education.

Tooth morphology is a foundation course for all dental healthcare students including dentists, dental hygiene, dental therapy, and dental nursing students. This chapter explores the conventional and innovative teaching methods to deliver tooth morphology educational modules. The teaching tools are explored with a 2D and 3D lens, with a particular focus on visualization, student understanding, and engagement. Traditional methods of teaching tooth morphology must be complemented with innovative pedagogical approaches in order to maintain student's attention and accommodate their diverse learning methods. Teaching 3D anatomy enables students to visualize and spatially comprehend the link between various anatomical components. Online tests and quizzes motivate students and are also beneficial in preparing students for exams. Online self-examinations offering visualization with 3D teeth enable students to evaluate their knowledge and offers immediate feedback, which aids in the long-term retention of information. These tools can be as efficient as other teaching methods, allowing the students to study at their own pace and with repetition. The authors conclude that blended and innovative teaching methods should supplement student learning and not replace, traditional face-to-face educational methods.

'Smart' wound dressings for advanced wound care: a review.

Hard-to-heal wounds are a common side-effect of diabetes, obesity, pressure ulcers and age-related vascular diseases, the incidences of which are growing worldwide. The increasing financial burden of hard-to-heal wounds on global health services has provoked technological research into improving wound diagnostics and therapeutics via 'smart' dressings, within which elements such as microelectronic sensors, microprocessors and wireless communication radios are embedded. This review highlights the progress being made by research groups worldwide in producing 'smart' wound device prototypes. Significant advances have been made, for example, flexible substrates have replaced rigid circuit boards, sensors have been printed on commercial wound dressing materials and wireless communication has been demonstrated. Challenges remain, however, in the areas of power supply, disposability, low-profile components, multiparametric sensing and seamless device integration in commercial wound dressings.

Bio-inspired microneedle design for efficient drug/vaccine coating.

Biomimetics is the interdisciplinary scientific field focused on the study and imitation of biological systems, with the aim of solving complex technological problems. In this paper, we present a new bio-inspired design for microneedles (MNs) and MN arrays, intended for rapidly coating the MNs with drug/vaccine. The biomimetic approach consists in ornamenting the lateral sides of pyramidal MNs with structures inspired by the external scent efferent systems of some European true bugs, which facilitate a directional liquid transport. To realize these MNs, two-photon polymerization (TPP) technique was used. Liquid coating capabilities of structured and non-structured MNs were compared. Moreover, both in-vivo and ex-vivo skin tests were performed to prove that MNs pierce the skin. We show that the arrays of MNs can be accurately replicated using a micro-moulding technique. We believe this design will be beneficial for the process of drug/vaccine loading onto the needles' surfaces, by making it more efficient and by reducing the drug/vaccine wastage during MN coating process.

Analysis of a Low-Cost EEG Monitoring System and Dry Electrodes toward Clinical Use in the Neonatal ICU.

Electroencephalography (EEG) is an important clinical tool for monitoring neurological health. However, the required equipment, expertise, and patient preparation inhibits its use outside of tertiary care. Non-experts struggle to obtain high-quality EEG due to its low amplitude and artefact susceptibility. Wet electrodes are currently used, which require abrasive/conductive gels to reduce skin-electrode impedance. Advances in dry electrodes, which do not require gels, have simplified this process. However, the assessment of dry electrodes on neonates is limited due to health and safety barriers. This study presents a simulation framework for assessing the quality of EEG systems using a neonatal EEG database, without the use of human participants. The framework is used to evaluate a low-cost EEG acquisition system and compare performance of wet and dry (Micro Transdermal Interface Platforms (MicroTIPs), g.tec-g.SAHARA) electrodes using accurately acquired impedance models. A separate experiment assessing the electrodes on adult participants was conducted to verify the simulation framework's efficacy. Dry electrodes have higher impedance than wet electrodes, causing a reduction in signal quality. However, MicroTIPs perform comparably to wet electrodes at the frontal region and g.tec-g.SAHARA performs well at the occipital region. Using the simulation framework, a 25dB signal-to-noise ratio (SNR) was obtained for the low-cost EEG system. The tests on adults closely matched the simulated results.

Structural characterization and in-vivo reliability evaluation of silicon microneedles.

This work presents an analysis of the failure mechanisms, structural properties and reliability of wet-etched silicon microneedles, which have wide-ranging applications in transdermal delivery, sensing and diagnostics. For the first time, in-vivo skin insertion forces are measured and the structural properties of individual silicon microneedles are assessed using both compression and shear tests. Compressive failure of this particular microneedle design does not occur because of buckling, but instead is predominantly due to progressive fracture along the relatively weak {111} crystal plane. Compressive and shear failure strengths are experimentally determined to be (2.9 +/- 0.3) GPa and (9.2 +/- 0.2) MPa, respectively. It is also shown that basic mechanical tests that are commonly used in the field of microneedle development may significantly underestimate safety factors for this type of needle due to the unrepresentative nature of the interaction of a rigid surface with the needle tips. Therefore, a new figure-of-merit for the reliability of such microneedles is proposed, which is based on the ratio of material failure strength to peak stress during skin insertion. The distribution of forces over the sharp, conical needle tip during skin penetration leads to a very large safety margin of over 700, and a correspondingly high degree of reliability when applied to in-vivo human tissue.

Machine learning based canine posture estimation using inertial data.

The aim of this study was to design a new canine posture estimation system specifically for working dogs. The system was composed of Inertial Measurement Units (IMUs) that are commercially available, and a supervised learning algorithm which was developed for different behaviours. Three IMUs, each containing a 3-axis accelerometer, gyroscope, and magnetometer, were attached to the dogs' chest, back, and neck. To build and test the model, data were collected during a video-recorded behaviour test where the trainee assistance dogs performed static postures (standing, sitting, lying down) and dynamic activities (walking, body shake). Advanced feature extraction techniques were employed for the first time in this field, including statistical, temporal, and spectral methods. The most important features for posture prediction were chosen using Select K Best with ANOVA F-value. The individual contributions of each IMU, sensor, and feature type were analysed using Select K Best scores and Random Forest feature importance. Results showed that the back and chest IMUs were more important than the neck IMU, and the accelerometers were more important than the gyroscopes. The addition of IMUs to the chest and back of dog harnesses is recommended to improve performance. Additionally, statistical and temporal feature domains were more important than spectral feature domains. Three novel cascade arrangements of Random Forest and Isolation Forest were fitted to the dataset. The best classifier achieved an f1-macro of 0.83 and an f1-weighted of 0.90 for the prediction of the five postures, demonstrating a better performance than previous studies. These results were attributed to the data collection methodology (number of subjects and observations, multiple IMUs, use of common working dog breeds) and novel machine learning techniques (advanced feature extraction, feature selection and modelling arrangements) employed. The dataset and code used are publicly available on Mendeley Data and GitHub, respectively.

Stability of Monoclonal Antibodies as Solid Formulation for Auto-Injectors: A Pilot Study.

Drug adherence is a significant medical issue, often responsible for sub-optimal outcomes during the treatment of chronic diseases such as rheumatoid or psoriatic arthritis. Monoclonal antibodies (which are exclusively given parenterally) have been proven to be an effective treatment in these cases. The use of auto-injectors is an effective strategy to improve drug adherence in parenteral treatments since these pen-like devices offer less discomfort and increased user-friendliness over conventional syringe-based delivery. This study aims to investigate the feasibility of including a monoclonal antibody as a solid formulation inside an auto-injector pen. Specifically, the objective was to evaluate the drug stability after a concentration (to reduce the amount of solvent and space needed) and freeze-drying procedure. A preliminary screening of excipients to improve stability was also performed. The nano-DSC results showed that mannitol improved the stability of the concentrated, freeze-dried antibody in comparison to its counterpart without it. However, a small instability of the CH2 domain was still found for mannitol samples, which will warrant further investigation. The present results serve as a stepping stone towards advancing future drug delivery systems that will ultimately improve the patient experience and associated drug adherence.

Hollow silicon microneedles, fabricated using combined wet and dry etching techniques, for transdermal delivery and diagnostics.

Microneedle-based technologies are the subject of intense research and commercial interest for applications in transdermal delivery and diagnostics, primarily because of their minimally invasive and painless nature, which in turn could lead to increased patient compliance and self-administration. In this paper, a process for the fabrication of arrays of hollow silicon microneedles is described. This method uses just two bulk silicon etches - a front-side wet etch to define the 500 µm tall octagonal needle structure itself, and a rear-side dry etch to create a 50 µm diameter bore through the needle. This reduces the number of etches and process complexity over the approaches described elsewhere. Ex-vivo human skin and a customised applicator were used to demonstrate biomechanical reliability and the feasibility of using these microneedles for both transdermal delivery and diagnostics. Microneedle arrays show no damage even when applied to skin up to 40 times, are capable of delivering several mL of fluid at flowrates of 30 µL/min, and of withdrawing 1 µL of interstitial fluid using capillary action.

Efficient fabrication of thermo-stable dissolving microneedle arrays for intradermal delivery of influenza whole inactivated virus vaccine.

Dissolving microneedle arrays (dMNAs) can be used to deliver vaccines via the intradermal route. Fabrication of dMNAs using centrifugation is the most common preparation method of dMNAs, but it results in a substantial loss of antigens. In order to solve the issue of antigen waste, we engineered an automatic dispensing system for dMNA preparation. Here, we report on the fabrication of influenza whole inactivated virus (WIV) vaccine-loaded dMNAs (WIV dMNAs) by using the automatic dispensing system. Prior to the dispensing process, polydimethylsiloxane (PDMS) moulds were treated with oxygen plasma to increase surface hydrophilicity. WIV dMNAs were prepared with 1% (w/v) trehalose and pullulan (50 : 50 weight ratio). During the dispensing process, reduced pressure was applied to the PDMS mould via a vacuum chamber to make microneedle cavities airless. After producing dMNAs, WIV was quantified and 1.9 µg of WIV was loaded per dMNA, of which 1.3 µg was in the microneedle tips. Compared to the centrifugation method, this automatic dispensing system resulted in a 95% reduction of antigen waste. A hemagglutination assay confirmed that WIV dMNA maintained the stability of the antigen for at least four weeks of storage, even at room temperature or at 37 °C. The WIV dMNAs displayed 100% penetration efficiency in human skin, and 83% of the microneedle volume was dissolved in the skin within 10 minutes. In a vaccination study, mice immunised with WIV dMNAs showed similar IgG levels to those that received WIV intramuscularly. In conclusion, using the automatic dispensing system for dMNA production strongly reduced antigen waste and yielded dMNAs with excellent physical, mechanical, and immunological properties.

Smart Compression Therapy Devices for Treatment of Venous Leg Ulcers: A Review.

Venous leg ulcers can have significant social and economic impacts, and are generally treated by applying compression to the lower limb, which aids in promoting blood return to the heart. Compression therapies commonly involve the use of passive bandages that suffer from issues associated with incorrect application, and although automated solutions have begun to appear; these are often bulky and hinder mobility. Emerging microtechnologies and new materials enable the development of "smart" compression therapy devices, which are defined as systems that use miniaturized and lightweight actuators and electronics to control the applied pressure. This paper reviews the state of the art in smart compression therapy research. A total of seventeen different devices has been identified, categorized as using one of three actuation mechanisms: pneumatic compression, motor-driven mechanisms, and smart materials (including shape memory alloys, shape memory polymers, and electroactive polymers). The field is still in its relative infancy and further refinements are required to create mass manufacturable compression dressing systems that meet medical, ergonomic, and economic standards. The use of miniaturized actuators has immense potential for the development of smart compression dressings, which will ultimately lead to higher compliance, increased patient comfort, enhanced mobility, and better treatment outcomes.

Design, Fabrication and Performance Assessment of Flexible, Microneedle-Based Electrodes For ECG Signal Monitoring.

Microneedle-based electrodes have attracted significant attention for the monitoring of physiological signals, including ECG, EMG, and E OG, as they have the potential to eliminate the skin preparation and stability issues associated with conventional wet gel electrodes. This paper describes the development of a polymeric flexible microneedle electrode (FMNE) that does not require skin abrasion and can be used for long-term ECG monitoring. Fabricated using a combination of epoxy resin microneedles bonded to a flexible substrate, the performance of the FMNE was compared to that of a conventional wet-gel electrode by simultaneously capturing the ECG signal using both electrodes, and estimating the signal-to-noise ratio (SNR) of each. Results show that the flexible electrode can acquire ECG signals in which all the characteristic components of the wave are visible, and that are comparable in quality to those obtained using commercial wet electrodes. Bland-Altman plots were drawn to validate the performance of FMNE, and show that the mean difference ± standard deviation in SNR obtained using wet electrodes and FMNE was [Formula: see text]. Clinical Relevance- These microneedle-based 'dry electrodes' could be used in long-term monitoring of biopotential activity.

Exploration of Microneedle-assisted skin delivery of cyanocobalamin formulated in ultraflexible lipid vesicles.

Vitamin B12 (cyanocobalamin) deficiency is a widespread condition because of its different aetiologies, like malabsorption syndrome or lifestyles as strict veganism that is increasing its incidence and prevalence in developed countries. It has important haematological consequences that require pharmacological treatment. Current therapy consists of oral or parenteral supplements of cyanocobalamin; however, the oral route is discarded for malabsorption syndrome patients and the parenteral route is not well accepted generally. Topical treatments have been suggested as an alternative, but the molecular weight and hydrophilicity of cyanocobalamin limits its diffusion through the skin. Lipid vesicles can allow the transdermal absorption of molecules > 500 Da. The aim of this work was to use different ultraflexible lipid vesicles (transfersomes and ethosomes) to enhance cyanocobalamin transdermal delivery. Vesicles were characterized and lyophilised for long-term stability. The ability to deliver cyanocobalamin through the skin was assessed in vitro using full-thickness porcine skin in Franz diffusion cells. As expected, the best transdermal fluxes were provided by ultraflexible vesicles, in comparison to a drug solution. Moreover, the pre-treatment of the skin with a solid microneedle array boosts the amount of drug that could potentially reach the systemic circulation.

Towards Micropump- and Microneedle-based Drug Delivery using Micro Transdermal Interface Platforms (MicroTIPs).

Micro Transdermal Interface Platforms (MicroTIPs) will combine minimally invasive microneedle arrays with highly miniaturized sensors, actuators, control electronics, wireless communications and artificial intelligence. These patch-like devices will be capable of autonomous physiological monitoring and transdermal drug delivery, resulting in increased patient adherence and devolved healthcare. In this paper, we experimentally demonstrate the feasibility of controlled transdermal drug delivery using a combination of 500 µm tall silicon microneedles, a commercial micropump, pressure and flow sensors, and bespoke electronics. Using ex-vivo human skin samples and a customized application/retraction system, leak-free delivery of volumes ranging from 0.7-1.1 mL has been achieved in under one hour. Clinical Relevance - This work experimentally confirms the feasibility of combining micropumps with microneedle arrays for applications in transdermal drug delivery.

A Comparison of Flow- and Pressure-Controlled Infusion Strategies for Microneedle-based Transdermal Drug Delivery.

Microneedle-based transdermal drug delivery is considered an attractive alternative to conventional injections using hypodermic needles due to its minimally invasive and painless nature; this has the potential to improve patient adherence to medication regimens. Hollow microneedles (MNs) are sharp, sub-millimeter protrusions with a channel that serves as a fluidic interface with the skin. This technology could be coupled with micro-pumps, embedded sensors, actuators and electronics to create Micro Transdermal Interface Platforms - smart, wearable infusion systems capable of delivering precise microdoses over a prolonged period. Using 500 µm tall hollow microneedles, ex-vivo human skin and a customized application/retraction device, this work focuses on comparing two infusion control strategies, namely 'set pressure' (SP) and 'set flow' (SF) infusion. It was found that flow-controlled infusion was capable of delivering higher volumes than pressure-driven delivery, and a mean volume of 3.8 mL was delivered using a set flowrate of 50 µL/minute. This suggests that flow driven delivery is a better control strategy and confirms that MN array retraction is beneficial for transdermal MN infusion.

Development and Characterization of Passivation Methods for Microneedle-based Biosensors.

Microneedles (MN) are short, sharp structures that have the ability to painlessly pierce the stratum corneum, the outermost layer of the skin, and interface with the dermal interstitial fluid that lies beneath. Because the interstitial fluid is rich in biomarkers, microneedle-based biosensors have the potential to be used in a wide range of diagnostic applications. To act as an electrochemical sensor, the tip or the body of the MN must be functionalized, while the substrate areas are generally passivated to block any unwanted background interference that may occur outside of the skin. This work presents four different passivation techniques, based on the application of SiO2, polymethyl methacrylate (PMMA), an adhesive film, and varnish to the substrate areas. Optical, SEM and electrochemical measurements were performed to quantitatively assess the performance of each film. The data shows that whilst manual application of varnish provided the highest level of electrical isolation, the spin-coating of a 5 µm thick layer of PMMA is likely to provide the best combination of performance and manufacturability. Clinical Relevance- Substrate passivation techniques will improve the performance of microneedle-based non-invasive continuous monitoring systems.

In vivo, in situ imaging of microneedle insertion into the skin of human volunteers using optical coherence tomography.

PURPOSE: To gather sub-surface in situ images of microneedle-treated human skin, in vivo, using optical coherence tomography (OCT). This is the first study to utilise OCT to investigate the architectural changes that are induced in skin following microneedle application. METHODS: Steel, silicon and polymer microneedle devices, with different microneedle arrangements and morphologies, were applied to two anatomical sites in human volunteers following appropriate ethical approval. A state-of-the-art ultrahigh resolution OCT imaging system operating at 800 nm wavelength and <3 µm effective axial resolution was used to visualise the microneedle-treated area during insertion and/or following removal of the device, without any tissue processing. RESULTS: Transverse images of a microneedle device, in situ, were captured by the OCT system and suggest that the stratified skin tissue is compressed during microneedle application. Following removal of the device, the created microchannels collapse within the in vivo environment and, therefore, for all studied devices, microconduit dimensions are markedly smaller than the microneedle dimensions. CONCLUSIONS: Microchannels created in the upper skin layers by microneedles are less invasive than previous histology predicts. OCT has the potential to play a highly influential role in the future development of microneedle devices and other transdermal delivery systems.

Engineering of an automated nano-droplet dispensing system for fabrication of antigen-loaded dissolving microneedle arrays.

Dissolving microneedle arrays (dMNAs) are promising devices for intradermal vaccine delivery. The aim of this study was to develop a reproducible fabrication method for dMNAs based on an automated nano-droplet dispensing system that minimizes antigen waste. First, a polymer formulation was selected to dispense sufficiently small droplets (<18 nL) that can enter the microneedle cavities (base diameter 330 µm). Besides, three linear stages were assembled to align the dispenser with the cavities, and a vacuum chamber was designed to fill the cavities with dispensed droplets without entrapped air. Lastly, the dispenser and stages were incorporated to build a fully automated system. To examine the function of dMNAs as a vaccine carrier, ovalbumin was loaded in dMNAs by dispensing a mixture of ovalbumin and polymer formulation, followed by determining the ovalbumin loading and release into the skin. The results demonstrate that functional dMNAs which can deliver antigen into the skin were successfully fabricated via the automatic fabrication system, and hardly any antigen waste was encountered. Compared to the method that centrifuges the mould, it resulted in a 98.5% volume reduction of antigen/polymer solution and a day shorter production time. This system has potential for scale-up of manufacturing to an industrial scale.

Comparative efficacy evaluation of different penetration enhancement strategies for dermal delivery of poorly soluble drugs - A case with sertaconazole nitrate.

The aim of this study was to compare the efficacy of different approaches for enhancement of dermal availability of the highly lipophilic antifungal model drug - sertaconazole nitrate (SN). For this purpose, a physical penetration enhancer - dissolving microneedles (MNs) was fabricated by filling moulds with liquid formulation based on polyvinylpyrrolidone and loaded with SN. Dissolving MNs were characterised regarding their morphological and mechanical characteristics. A penetration enhancement efficacy of MNs was evaluated in vitro using porcine ear skin in parallel with the efficacy of formerly developed chemical penetration enhancer - biocompatible microemulsion (ME) formulation. Moreover, an ability of solid silicon MNs to significantly improve delivery of SN from ME into the skin has also been investigated. The obtained results showed that dissolving MNs had satisfying morphological properties and mechanical strength. This type of MNs provided comparable drug deposition in the skin as ME formulation, but also revealed an indication of percutaneous absorption of a portion of the administered drug dose. However, the penetration/permeation study results were largely influenced by experimental setup and dosing regimen. Although solid silicon MNs assisted SN dermal delivery led to increase of drug cutaneous retention (1.9-fold) under infinite dosing regimen, the synergistic action of solid MNs and ME applied under finite dosing was more pronounced in comparison with the application either of physical (dissolving MNs) or chemical enhancer (ME) alone. Namely, SN amount accumulated into the skin increased up to 4.67 and 4.37 folds in comparison with ME and dissolving MNs alone, respectively, while reaching a significant decrease in drug permeation through the skin compared to the use of dissolving MNs. Application of ME per se was the only approach that provided selective in vitro dermal drug delivery without SN permeation across the skin. However, despite both types of the used MNs lead to SN permeation in vitro, the ratio between the drug amount deposited in the skin and SN content permeated was significantly higher for the combined approach (12.05) than for dissolving MNs (2.10). Therefore, a combination of solid silicon MNs and biocompatible ME favoured more pronouncedly SN skin accumulation, which is preferable in the treatment of skin fungal infections.

Hyaluronan molecular weight: Effects on dissolution time of dissolving microneedles in the skin and on immunogenicity of antigen.

Biomaterials used as matrix for dissolving micro needles (dMNs) may affect the manufacturing process as well as the potency of the active pharmaceutical ingredient, e.g. the immunogenicity of incorporated vaccine antigens. The aim of this study was to investigate the effect of the molecular weight of hyaluronan, a polymer widely used in the fabrication of dMNs, ranging in molecular weight from 4.8 kDa to 1.8 MDa, on the dissolution of microneedles in the skin in time as well as the antibody response in mice and T-cell activation in vitro. Hyaluronan molecular weight (HA-MWs) did not affect antibody responses (when lower than 150 kDa) nor CD4+ T-cell responses against model antigen ovalbumin. However, the HA-MWs had an effect on the fabrication of dMNs. The 1.8 MDa HA was not suitable for the fabrication of dMNs. Similarly, the 4.8 kDa HA generated dMN arrays less robust compared to the other HA-MWs requiring optimization of the drying conditions. Finally, higher HA-MWs led to longer application time of dMN arrays for a complete dissolution of microneedles into the skin. Specifically, we identified 20 kDa HA as the optimal HA-MW for the fabrication of dMNs as with this MW the dMNs are robust and dissolve fast in the skin without affecting immunogenicity.