Understanding and developing capabilities for large area and continuous micro contact printing

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 141-143).Micro contact printing is a high spatial resolution-patterning tool that can be used for printing on large and non-planar surfaces because of which it has begun to find important applications in printed organic electronics and fiber optics. However, problems like achieving precise alignment and registration, air bubble trapping and low production rate still remain unresolved. The goal of this thesis is to conceptualize and implement a low cost solution to these problems to be used by a nano-technology based company in Cambridge, Massachusetts. In this dissertation, we first present an extensive literature review of soft lithography techniques, focusing more on micro-contact printing and critical factors for taking this technology from laboratory to commercial production. We then introduce another printing technique called flexography and discuss how this method when combined with micro contact printing can help in overcoming the above stated limitations and at the same time achieve high throughput rate at low cost. We propose a Flexography style micro contact printing mechanism with rotating cylindrical stamps enabling reel to reel processing. Finally, results from the experiments conducted to study the effect of parameters like ink concentration, speed and pressure on the print quality are documented.by Ambika Goel, Sowmya Laxminarayanan and Yun Xia.M.Eng

Charge based intra-cartilage delivery of single dose dexamethasone using Avidin nano-carriers suppresses cytokine-induced catabolism long term

Objective: Avidin exhibits ideal characteristics for targeted intra-cartilage drug delivery: its small size and optimal positive charge enable rapid penetration through full-thickness cartilage and electrostatic binding interactions that give long half-lives in vivo. Here we conjugated Avidin with dexamethasone (DEX) and tested the hypothesis that single-dose Avidin-delivered DEX can ameliorate catabolic effects in cytokine-challenged cartilage relevant to post-traumatic OA. Methods: Avidin was covalently conjugated with DEX using fast (ester) and slow, pH-sensitive release (hydrazone) linkers. DEX release kinetics from these conjugates was characterized using 3H-DEX-Avidin (scintillation counting). Cartilage explants treated with IL-1α were cultured with or without Avidin-DEX conjugates and compared to soluble DEX. Sulfated-glycosaminoglycan (sGAG) loss and biosynthesis rates were measured using DMMB assay and 35S-incorporation, respectively. Chondrocyte viability was measured using fluorescence staining. Results: Ester linker released DEX from Avidin significantly faster than hydrazone under physiological buffer conditions. Single dose Avidin-DEX suppressed cytokine-induced sGAG loss over 3-weeks, rescued IL-1α-induced cell death, and restored sGAG synthesis levels without causing cytotoxicity. The two Avidin-DEX conjugates in 1:1 combination (fast:slow) had the most prominent bioactivity compared to single dose soluble-DEX, which had a shorter-lived effect and thus needed continuous replenishment throughout the culture period to ameliorate catabolic effects. Conclusion: Intra-cartilage drug delivery remains inadequate as drugs rapidly clear from the joint, requiring multiple injections or sustained release of high doses in synovial fluid. A single dose of Avidin-conjugated drug enables rapid uptake and sustained delivery inside cartilage at low intratissue doses, and potentially can minimize unwanted drug exposure to other joint tissues.Deshpande Center for Technological InnovationNational Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (Award DMR-1419807

Charge-based transport and drug delivery into cartilage for localized treatment of degenerative joint diseases

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, February 2015.Cataloged from PDF version of thesis. "February 2015."Includes bibliographical references.Traumatic joint injuries significantly increase synovial fluid levels of pro-inflammatory cytokines that can initiate cartilage degeneration leading to osteoarthritis (OA). Articular cartilage is a highly negatively charged, avascular tissue, which relies on synovial fluid convection and electro-diffusion to transport proteins and therapeutics to tissue chondrocytes. No OA drug has yet passed the safety criteria of clinical trials due to ineffective intra-articular (i.a.) delivery methods, which require very high drug doses that cause systemic toxicity. There is a need to design local delivery mechanisms that can enable drugs or drug carriers to rapidly diffuse into the cartilage extracellular matrix to achieve intratissue therapeutic levels before these drugs are cleared from the joint space via lymphatics and synovium vasculature. This dissertation investigates the effects of size and charge of solutes on their penetration, binding and retention within negatively charged tissues such as cartilage. Based on this understanding we selected Avidin, a globular protein, as a drug carrier owing to its optimal size and high positive charge (66,000 Da, pI 10.5). Avidin resulted in a six-fold upward Donnan partitioning factor at the synovial fluid-cartilage interface, had a 400-fold higher uptake than its electrically neutral counterpart (Neutravidin), and remained bound within cartilage for at least 15 days. Competitive binding experiments revealed that despite Avidin's weak and reversible ionic binding (dissociation constant, KD ~150 [mu]M) to the negatively charged glycosaminoglycans, its long term retention was facilitated by large intratissue binding site density (NT ~ 2,920 [mu]M). Thus, structures like Avidin are ideal candidates for local i.a. drug delivery into cartilage. In vivo animal studies revealed that Avidin retained inside the joint space for extended time periods resulting half-life of 154h in rabbit cartilage which was 5-6 times longer than that in the thinner rat cartilage. This was confirmed to be consistent with the concept that diffusion-binding kinetics scale as the square of tissue thickness, emphasizing the necessity of using larger animal models for studying joint space transport and pharmacokinetics. Avidin's neutral counterpart (Neutravidin) was completely cleared from the joint space of both rats and rabbits within 24h. We then conjugated Avidin with the glucocorticoid, dexamethasone, using chemical linkers to enable its sustained release. Avidin delivered dexamethasone into cartilage deep zones where majority of chondrocytes reside thereby successfully inhibiting cytokine-induced catabolic activity in cartilage explants in-vitro. A single i.a. injection of Avidin-conjugated drug can thereby enable sustained drug delivery in low doses and therefore has the potential to replace the current clinical practice of using multiple injections of high dose glucocorticoids in patients. The biological efficacy of this system in rescuing degenerative mechanisms of OA is currently being validated in a well-accepted rabbit model of post-traumatic OA as part of a preclinical study.by Ambika Goel Bajpayee.Ph. D

Sustained intra-cartilage delivery of low dose dexamethasone using a cationic carrier for treatment of post traumatic osteoarthritis

Disease-modifying osteoarthritis drugs (DMOADs) should reach their intra-tissue target sites at optimal doses for clinical efficacy. The dense, negatively charged matrix of cartilage poses a major hindrance to the transport of potential therapeutics. In this work, electrostatic interactions were utilised to overcome this challenge and enable higher uptake, full-thickness penetration and enhanced retention of dexamethasone (Dex) inside rabbit cartilage. This was accomplished by using the positively charged glycoprotein avidin as nanocarrier, conjugated to Dex by releasable linkers. Therapeutic effects of a single intra-articular injection of low dose avidin-Dex (0.5 mg Dex) were evaluated in rabbits 3 weeks after anterior cruciate ligament transection (ACLT). Immunostaining confirmed that avidin penetrated the full cartilage thickness and was retained for at least 3 weeks. Avidin-Dex suppressed injury-induced joint swelling and catabolic gene expression to a greater extent than free Dex. It also significantly improved the histological score of cell infiltration and morphogenesis within the periarticular synovium. Micro-computed tomography confirmed the reduced incidence and volume of osteophytes following avidin-Dex treatment. However, neither treatment restored the loss of cartilage stiffness following ACLT, suggesting the need for a combinational therapy with a pro-anabolic factor for enhancing matrix biosynthesis. The avidin dose used caused significant glycosaminoglycan (GAG) loss, suggesting the use of higher Dex : avidin ratios in future formulations, such that the delivered avidin dose could be much less than that shown to affect GAGs. This charge-based delivery system converted cartilage into a drug depot that could also be employed for delivery to nearby synovium, menisci and ligaments, enabling clinical translation of a variety of DMOADs.National Science Foundation (U.S.) (Grant DMR1419807)National Institutes of Health (U.S.) (Grant EB017755)National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant EB017755)National Institutes of Health (U.S.) (Grant AR057105)National Institutes of Health (U.S.) (Grant AR060331)National Institute of Arthritis and Musculoskeletal and Skin Diseases (U.S.) (Grant AR057105)National Institute of Arthritis and Musculoskeletal and Skin Diseases (U.S.) (Grant (Grant AR060331

Scalable Gastric Resident Systems for Veterinary Application

Gastric resident dosage forms have been used successfully in farm animals for the delivery of a variety of drugs helping address the challenge of extended dosing. Despite these advances, there remains a significant challenge across the range of species with large variation in body size. To address this, we investigate a scalable gastric resident platform capable of prolonged retention. We investigate prototypes in dimensions consistent with administration and retention in the stomachs of two species (rabbit and pig). We investigate sustained gastric retention of our scalable dosage form platform, and in pigs show the capacity to modulate drug release kinetics of a model drug in veterinary practice, meloxicam, with our dosage form. The ability to achieve gastric residence and thereby enable sustained drug levels across different species may have a significant impact in the welfare of animals in both research, agricultural, zoological, and clinical practice settings.Bill & Melinda Gates Foundation (Grant No. OPP1096734)Bill & Melinda Gates Foundation (Grant No. OPP1148627)National Institutes of Health (U.S.) (Grant# EB-000244)Max Planck Society (Research Award, Award Ltr Dtd. 2/11/08)Alexander von Humboldt FoundationBrigham and Women's Hospital. Division of GastroenterologyMassachusetts Institute of Technology. Division of Comparative Medicin