Academic literature on the topic 'Intradermal'

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 65-67).<br>This thesis presents a new method for needle-free powdered drug injection. The design, construction, and testing of a bench-top helium-powered device capable of delivering powder to controllable depths within the dermis is presented. This device uses a jet of gas undergoing choked flow to entrain powder and subsequently penetrates through the skin for delivery of the powder. Different nozzle designs and orifice geometries are also explored. In vitro injection of polymer beads (1-5 [mu]im in diameter) into porcine tissue demonstrate the device's capability of drug delivery to depths of 260 to 5000 [mu]m. The jet parameters of nozzle orifice diameter and applied pressure are shown to affect injection depth, shape, and success rate. The presented device has the potential to be implemented with stabilized formulations of vaccines to address the cold chain problem-the cost and risk of transporting temperature sensitive vaccines to developing countries.<br>by John Liu.<br>S.M.

Microneedles (MNs) have gained significant attention over the past decade in drug delivery and biosensing due to their minimally-invasive and less painful nature of use compared to intramuscular/subcutaneous injections, and significant biological benefits. Several fundamental processes enabling MN functionality have not been completely understood, including mechanical interaction between MNs and skin for targeted depth penetration; and precise quantification of fluid delivery in the skin. This thesis presents novel materials, and methodologies for evaluating MN interactions with skin, and investigates the performance of hollow MNs in both intradermal fluid drug delivery and biosensing. A micromechanical comparison between human skin and porcine skin was performed using to determine their mechanical behavior affecting MN insertions. Stratum corneum (SC) of human skin was significantly stiffer (117 ± 42 MPa) than porcine skin (81 ± 32 MPa), requiring higher force of MN insertion to rupture the SC in human skin (107 ± 17 mN) than porcine skin (96 ± 23 mN). An artificial mechanical skin model was developed layer-by-layer to simulate tough human skin (MN insertion force 162 ± 11 mN) and to study the dynamics of MN insertion. Key factors that affected MN insertions into skin, including velocity of impact and total energy delivered to the skin, were identified. ID fluid delivery by hollow MNs was assessed using a novel method involving the low-activity radiotracer technetium-99m pertechnetate (⁹⁹mTcO₄₋). Its delivery allowed accurate quantification of fluid delivered into the skin, back-flowed to the skin surface, and total fluid ejected from the syringes via ID devices with sub-nanoliter resolution. Hollow MNs performed more accurate ID injections than conventional needles (93% vs. 69-87% of fluid per 0.1 mL injection volume). A MN-optofluidic biosensing platform capable of eliminating blood sampling was developed with MNs that can access dermal interstitial fluid that contains numerous drugs at concentrations comparable to blood. The MN lumen was functionalized to collect, trap and detect drugs in 0.6 nL of sample. The optofluidic components provided specific high-sensitivity absorbance measurements for drug binding using enzyme-linked assays. Streptavidin-horseradish peroxidase (LoD = 60.2 nM) and vancomycin (LoD = 84 nM) binding validated this point of care system.<br>Applied Science, Faculty of<br>Electrical and Computer Engineering, Department of<br>Graduate

Epidermal Langerhans cells (LCs) and multiple subsets of dermal dendritic cells (dDCs) make skin a valuable route for vaccination, offering the potential for antigen-sparing immunisation. The interconnected immunological functions of dDC subsets and LCs are not fully understood however. This Thesis therefore aimed to explore the interactions of skin immune cells with viral pathogens and vaccines to inform the development of future therapeutics and intradermal vaccines. LCs and dDCs were isolated from ex vivo human skin tissue using a walkout protocol which allowed the enrichment of the migratory cells from the tissue. LCs and dDCs were infected with a lentiviral vector encoding GFP, allowing study of post-entry HIV viral restriction. The study uncovered the existence of a SAMHD-1-independent antiviral factor unique to LCs. LCs and dDCs from ex vivo skin were used to examine the cross-presentation of an inactivated influenza virus-derived matrix peptide to CD8+ T-cells. Two CD11c+ subsets of dDCs were found to potently cross present the antigen. Delivery of VLPs, which lack genetic material, markedly reduced cross-presentation, suggesting that viral genetic material is vital for dDCs to activate cross-presentation pathways. Future work is required to determine if this is true of other influenza peptides or pathogens. Vaccine delivery studies performed using murine and human models found that dDCs were responsible for the greatest uptake of ovalbumin peptide antigen and LCs did not migrate out of the epidermis in the first 4 hours after inactivated influenza virus vaccine delivery respectively. Collectively, this work highlighted the importance of dDCs in antigen uptake and cross-presentation to prime cytotoxic T-cell responses. Innovative delivery methods such as microneedles offer a means of accessing the dermal compartment in a pain-free manner, though further work is required to determine the optimal combination of vaccine formulation and delivery method to harness the immunostimulatory abilities of dDCs.

Current progress in the development of vaccines has decreased the incidence of fatal and non-fatal infections and increased longevity. However, new technologies need to be developed to combat an emerging generation of infectious diseases. DNA vaccination has been demonstrated to have great potential for use against a wide variety of diseases. Alone, this vaccine technology does not generate a significant immune response for vaccination, but combined with delivery by electroporation (EP), can enhance plasmid expression and immunity against the expressed antigen. Most EP systems, while effective, can be invasive and painful making them less desirable for use in vaccination. Our lab recently developed a non-invasive electrode known as the multi-electrode array (MEA), which lies flat on the surface of the skin without penetrating the tissue. This study evaluated the use of the MEA for the development of DNA vaccines. We assessed the appropriate delivery conditions for gene expression and the development of humoral immunity. We used both B. anthracis and HBV as infectious models for our experiments. Our results indicated that the MEA can enhance gene expression in a mouse model with minimal to no tissue damage. Optimal delivery conditions, based on generation of antibodies, were determined to be 125-175V/cm and 150ms with 200ug and a prime boost protocol administered on Day 0 and 14. Under these conditions, end-point titers of 20,000-25,000 were generated. Neutralizing antibodies were noted in 40-60% of animals. Additionally, we utilized a guinea pig model to assess the translation potential of this electrode. The plasmid encoding HBsAg, pHBsAg, was delivered intradermally with the MEA to guinea pig skin. The results show increased protein expression resulting from plasmid delivery using the MEA as compared to injection alone. Within 48 hours of treatment, there was an influx of cellular infiltrate in the experimental groups. Humoral responses were also increased significantly in both duration and intensity as compared to the injection only groups. Results from both experimental models demonstrate that protective levels of humoral immunity can be generated and that this electrode should translate well to the clinic.

Background: Pressure ulcers, a form of chronic wound, represent a significant health and resource burden in elderly and immobilised patient populations. Pressure ulcers have been shown to exhibit high matrix metalloproteinase (MMP) activity which prevents normal wound healing and doxycycline, as an MMP inhibitor, offers a potential novel treatment. Intradermal delivery of doxycycline could help treat the earliest stages of wound development and prevent further wound progression. The skin, however, has a natural barrier function which prevents the diffusion of large exogenous molecules. Microneedle rollers offer a minimally invasive technique to transiently permeabilise the skin, creating microscopic pores that act as conduits for doxycycline diffusion. / Methods: The research described in this thesis focusses on the repurposing of existing microneedle rollers for the intradermal delivery of doxycycline as a pressure ulcer treatment. Firstly, the effect of microneedle length and application method on micropore formation and rate of drug permeation was investigated using the recently-launched artificial membrane Strat-MTM and compared with excised biological tissue. Next, the biological effects of doxycycline and its transmembrane delivery were modelled in a dermal tissue equivalent (DTE) model, formed from collagen and dermal fibroblasts, by assessing changes DTE contractile behaviour and matrix metalloproteinase (MMP) activity. This simplified in vitro model was further developed to better emulate the pressure ulcer microenvironment by introducing: (i) mechanical loading using a bespoke metal weight, (ii) glucose deprivation through the use of glucose-free media, and (iii) inflammatory cells, specifically macrophages, through co-culture. Investigations progressed to a preliminary in vivo surgical wound model using compression by magnets to determine the biological effects of pressure in a whole organism. This pre-existing model was established in our lab for future investigations of microneedle-mediated doxycycline delivery. Finally, the repurposing of the existing non-invasive imaging technology optical coherence tomography (OCT) for pressure ulcer evaluation was explored in an observational clinical audit. / Results: The results demonstrate that microneedle rollers significantly enhance the transmembrane delivery of doxycycline with significant effect on tissue-equivalent contraction and MMP activity. Results from the pressure ulcer models corroborate previous findings that the pressure ulcer microenvironment augments MMP activity. Lastly, OCT is shown to detect subsurface biomarkers of skin in the earliest stages of pressure ulcer development, most suitable for treatment with doxycycline.

Microneedles (MNs) are minimally invasive drug delivery devices that can be used for transdermal drug delivery (TDD). They have the potential to enhance drug delivery for therapeutic agents which are currently difficult to deliver, costly, or cause a wide range of side effects. The therapeutic agent must normally overcome the highly hydrophobic barrier of the skin’s outermost layer, the stratum corneum (s.c.), in order to be delivered transdermally. MNs have a height of 50 m to 1500 m and overcome the barrier by penetrating the s.c. and creating aqueous pores. They can be fabricated from different materials, such as silicon, metal, glass, sugars, and polymers. Dissolving polymeric MNs are used to penetrate the s.c. and release the drug incorporated in the polymeric matrix into the epidermis when they dissolve by taking up skin interstitial fluid (ISF). This means that when nanoparticles (NPs) are delivered using dissolving MNs, the amount delivered is dependent upon the amount localized in the needle portion of the array. The present study developed and characterized dissolving MNs using a novel two-step process which improves the loading distribution of the therapeutic agent in the needle portion of the array. The two-step process fabricates the needles and the baseplate individually, allowing both to be fabricated from different for- mulations and optimized separately. The MNs were loaded with a model protein, ovalbumin (OVA), and poly(lactic-co-glycolide acid) (PLGA) NPs. When the loading distribution was measured for the NPs, it was found that about 80% of the NPs were localized in the needles. This is almost double the localization compared to arrays using the standard fabrication method. The MNs loaded with NPs were used in an in vivo mouse model. The NPs were successfully delivered into the skin of the mice and were detected in the draining lymph nodes. This showed that the developed TDD device can be used for targeted delivery of the lymphatic system. This study was overall successful in engineering a MN-mediated intradermal NP delivery device that can be used to target the lymphatic system.