The tiny needles can be fabricated under normal temperature and pressure and from water, so they can be loaded with sensitive biochemical compounds and maintain their activity prior to use. They are also biodegradable and biocompatible.
The research paper "Fabrication of Silk Microneedles for Controlled-Release Drug Delivery" appeared in Advanced Functional Materials December 2 online in advance of print.
The Tufts researchers successfully demonstrated the ability of the silk microneedles to deliver a large-molecule, enzymatic model drug, horseradish peroxidase (HRP), at controlled rates while maintaining bioactivity. In addition, silk microneedles loaded with tetracycline were found to inhibit the growth of Staphylococcus aureus, demonstrating the potential of the microneedles to prevent local infections while also delivering therapeutics.
"By adjusting the post-processing conditions of the silk protein and varying the drying time of the silk protein, we were able to precisely control the drug release rates in laboratory experiments," said Fiorenzo Omenetto, Ph.D., senior author on the paper. "The new system addresses long-standing drug delivery challenges, and we believe that the technology could also be applied to other biological storage applications."
The Drug Delivery Dilemma
While some drugs can be swallowed, others can't survive the gastrointestinal tract. Hypodermic injections can be painful and don't allow a slow release of medication. Only a limited number of small-molecule drugs can be transmitted through transdermal patches. Microneedles—no more than a micron in size and able to penetrate the upper layer of the skin without reaching nerves—are emerging as a painless new drug delivery mechanism. But their development has been limited by constraints ranging from harsh manufacturing requirements that destroy sensitive biochemicals, to the inability to precisely control drug release or deliver sufficient drug volume, to problems with infections due to the small skin punctures.
The process developed by the Tufts bioengineers addresses all of these limitations. The process involves ambient pressure and temperature and aqueous processing. Aluminum microneedle molding masters were fabricated into needle arrays of about 500 µm needle height and tip radii of less than 10 µm. The elastomer polydimethylsiloxane (PDMS) was cast over the master to create a negative mold; a drug-loaded silk protein solution was then cast over the mold. When the silk was dry, the drug-impregnated silk microneedles were removed. Further processing through water vapor annealing and various temperature, mechanical and electronic exposures provided control over the diffusity of the silk microneedles and drug release kinetics.
"Changing the structure of the secondary silk protein enables us to 'pre-program' the properties of the microneedles with great precision," said David L. Kaplan, Ph.D., coauthor of the study, chair of biomedical engineering at Tufts and a leading researcher on silk and other novel biomaterials. "This is a very flexible technology that can be scaled up or down, shipped and stored without refrigeration and administered as easily as a patch or bandage. We believe the potential is enormous."
Other co-authors on the paper, all associated with the Department of Biomedical Engineering, are Konstantinos Tsioris, doctoral student; Waseem Raja, post-doctoral associate; Eleanor Pritchard, post-doctoral associate; and Bruce Panilaitis, research assistant professor.
The research was based on work supported in part by the U.S. Army Research Laboratory, the U.S. Army Research Office, the Defense Advanced Research Projects Agency-Defense Sciences Office and the Air Force Office of Scientific Research.
Tsioris, K., Raja, W. K., Pritchard, E. M., Panilaitis, B., Kaplan, D. L. and Omenetto, F. G. (2011), Fabrication of Silk Microneedles for Controlled-Release Drug Delivery. Advanced Functional Materials. doi: 10.1002/adfm.201102012
Located on Tufts' Medford/Somerville campus, the School of Engineering offers a rigorous engineering education in a unique environment that blends the intellectual and technological resources of a world-class research university with the strengths of a top-ranked liberal arts college. Close partnerships with Tufts' undergraduate, graduate and professional schools, coupled with a long tradition of collaboration, provide a strong platform for interdisciplinary education and scholarship. The School of Engineering's mission is to educate engineers committed to the innovative and ethical application of science and technology in addressing the most pressing societal needs, to develop and nurture twenty-first century leadership qualities in its students, faculty, and alumni, and to create and disseminate transformational new knowledge and technologies that further the well-being and sustainability of society in such cross-cutting areas as human health, environmental sustainability, alternative energy, and the human-technology interface.
Kim Thurler | EurekAlert!
Further reports about: > Advanced Functional Materials > Advanced Investigator Grant > Army > Drug Delivery > Functional Airspace Blocks > Panilaitis > Staphylococcus aureus > drug-loaded silk protein solution > enzymatic model drug > microneedles > sensitive biochemical compounds > silk protein > tetracycline
An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences