Biomedical subjects

Wijaya Martanto

Publications and source records attributed to Wijaya Martanto.

4 recordsLinked to original sources

PubMed2006

Microinfusion using hollow microneedles.

PURPOSE: The aim of the study is to determine the effect of experimental parameters on microinfusion through hollow microneedles into skin to optimize drug delivery protocols and identify rate-limiting barriers to flow. METHODS: Glass microneedles were inserted to a depth of 720-1080 microm into human cadaver skin to microinfuse sulforhodamine solution at constant pressure. Flow rate was determined as a function of experimental parameters, such as microneedle insertion and retraction distance, infusion pressure, microneedle tip geometry, presence of hyaluronidase, and time. RESULTS: Single microneedles inserted into skin without retraction were able to infuse sulforhodamine solution into the skin at flow rates of 15-96 microl/h. Partial retraction of microneedles increased flow rate up to 11.6-fold. Infusion flow rate was also increased by greater insertion depth, larger infusion pressure, use of a beveled microneedle tip, and the presence of hyaluronidase such that flow rates ranging from 21 to 1130 microl/h were achieved. These effects can be explained by removing or overcoming the large flow resistance imposed by dense dermal tissue, compressed during microneedle insertion, which blocks flow from the needle tip. CONCLUSIONS: By partially retracting microneedles after insertion and other methods to overcome flow resistance of dense dermal tissue, protocols can be designed for hollow microneedles to microinfuse fluid at therapeutically relevant rates.

Drug Delivery Systems↗

PubMed2006

Mechanism of fluid infusion during microneedle insertion and retraction.

Previous work has shown that infusion flow rates can be increased by an order of magnitude by partially retracting microneedles after insertion into the skin. This study sought to determine the mechanism by which retraction increases fluid infusion by piercing human cadaver skin with single microneedles, fixing the skin after retracting microneedles to different distances, and examining skin microstructure by histology. We found that microneedle insertion to 1080 microm from the skin surface resulted primarily in skin indentation and only 100-300 microm penetration into the skin. This caused significant compaction of the skin, which probably pressed out most water and thereby dramatically lowered the flow conductivity of skin beneath the needle tip. Retraction of the microneedle allowed the skin to recoil back toward its original position, which relieved the skin compaction and increased local flow conductivity. Altogether, these results suggest that microneedle insertion to penetrate into the skin followed by microneedle retraction to relieve skin compaction is an effective approach to infuse fluid into the skin in a minimally invasive manner.

Humans↗

PubMed2005

Hollow metal microneedles for insulin delivery to diabetic rats.

The goal of this study was to design, fabricate, and test arrays of hollow microneedles for minimally invasive and continuous delivery of insulin in vivo. As a simple, robust fabrication method suitable for inexpensive mass production, we developed a modified-LIGA process to micromachine molds out of polyethylene terephthalate using an ultraviolet laser, coated those molds with nickel by electrodepostion onto a sputter-deposited seed layer, and released the resulting metal microneedle arrays by selectively etching the polymer mold. Mechanical testing showed that these microneedles were sufficiently strong to pierce living skin without breaking. Arrays containing 16 microneedles measuring 500 microm in length with a 75 microm tip diameter were then inserted into the skin of anesthetized, diabetic, hairless rats. Insulin delivery through microneedles caused blood glucose levels to drop steadily to 47% of pretreatment values over a 4-h insulin delivery period and were then approximately constant over a 4-h postdelivery monitoring period. Direct measurement of plasma insulin levels showed a peak value of 0.43 ng/ml. Together, these data suggest that microneedles can be fabricated and used for in vivo insulin delivery.

Animals↗

PubMed2004

Transdermal delivery of insulin using microneedles in vivo.

PURPOSE: The purpose of this study was to design and fabricate arrays of solid microneedles and insert them into the skin of diabetic hairless rats for transdermal delivery of insulin to lower blood glucose level. METHODS: Arrays containing 105 microneedles were laser-cut from stainless steel metal sheets and inserted into the skin of anesthetized hairless rats with streptozotocin-induced diabetes. During and after microneedle treatment, an insulin solution (100 or 500 U/ml) was placed in contact with the skin for 4 h. Microneedles were removed 10 s, 10 min, or 4 h after initiating transdermal insulin delivery. Blood glucose levels were measured electrochemically every 30 min. Plasma insulin concentration was determined by radioimmunoassay at the end of most experiments. RESULTS: Arrays of microneedles were fabricated and demonstrated to insert fully into hairless rat skin in vivo. Microneedles increased skin permeability to insulin, which rapidly and steadily reduced blood glucose levels to an extent similar to 0.05-0.5 U insulin injected subcutaneously. Plasma insulin concentrations were directly measured to be 0.5-7.4 ng/ml. Higher donor solution insulin concentration, shorter insertion time, and fewer repeated insertions resulted in larger drops in blood glucose level and larger plasma insulin concentrations. CONCLUSIONS: Solid metal microneedles are capable of increasing transdermal insulin delivery and lowering blood glucose levels by as much as 80% in diabetic hairless rats in vivo.

Administration, Cutaneous↗