Ceramic Hybrid Microneedles Alleviate IV Drug Delivery

New polymerization technology is being used to create hollow needles so fine patients cannot feel them piercing the skin, reports a new study.

Researchers at the University of North Carolina (UNC, Chapel Hill, USA) and Laser Zentrum Hannover (Germany) used the two-photon-polymerization (2PP) technique of organically modified ceramic hybrid materials (ormocers) to create microneedles resistant to breakage. When the liquid materials are used, the polymerization results in localized solidification of the material, forming the needles. Clustered together on a patch, these microneedles can deliver drugs or draw blood efficiently as standard hypodermic needles. Another benefit of the hybrid needles is that they can be made in a wider range of sizes than those made with conventional microfabrication techniques.

The 2PP process involves both temporal and spatial overlap of photons, leading to nonlinear absorption in a highly localized volume. Absorbed photons induce chemical reactions between starter molecules and monomers within a transparent medium, causing polymers to form. Since the light and matter interaction region is confined within the focal volume, moving the laser focus within the photosensitive material (in this case ormocer) causes a trace of polymerized material to be produced. In principle, any computer-generated three-dimensional (3D) structure can be formed; the quadratic intensity dependence of the two-photon-absorption probability and the well-defined polymerization threshold allow resolutions of less than 100 nanometers in the polymerized structures. The study was published in the December 2007 issue of the International Journal of Applied Ceramic Technology.

"Microneedles may be integrated with micropumps and biosensors to provide autonomous sampling of blood, analysis, and drug-delivery capabilities for treatment of chronic disease,” said lead author Roger Narayan, M.D., Ph.D, of UNC. "For example, one needle, pump, and sensor unit would assay the glucose level in interstitial fluid of patients with diabetes mellitus. Another needle, pump and drug-delivery unit would deliver insulin in a continuous or programmed manner.”

Ormocers contain strong covalent bonds between the inorganic and organic components. During synthesis, the inorganic components (alkoxysilane precursors) cross-link and form an inorganic network through the condensation of organically-modified silicon alkoxide groups. Light, thermal, or reduction-oxidation (redox) processes can cross-link the organic components (methacrylate groups). Cross-linking between the inorganic groups and the organic groups provides the ormocers with exceptional chemical and thermal stability.


Related Links:
University of North Carolina
Laser Zentrum Hannover