Optical-fiber sensors can be used in situations where the use of conventional sensors is not practical. The sensors are usually compact and lightweight, minimally invasive, and can be multiplexed. They are immune to electromagnetic interference, and can survive in difficult environments. Multiple analytes can be measured simultaneously using optical sensor arrays. In this instance, multiple sensing chemistries are attached to the end of optical fibers in a fiber bundle and different sensing chemistries may be identified by either spatial or spectral resolution. Ink-jet technology was used to print multiple indicator chemistries on optically accessible surfaces like the tip of an optical fiber.
To minimize the effects of chemotherapy, localized sustained release of the bioactive components is preferred. One approach to drug localization and controlled pharmacokinetics is direct injection of drug-loaded-microspheres into tumor tissue. The release kinetics are determined by the microsphere size and structure. Ink-jet microdispensing was used to fabricate monosized microspheres of biodegradable polymers loaded with paclitaxel. In the drug eluting stents area, ink-jet was employed to coat the stents’ struts with bioactive material to prevent restenosis.
Dye Assisted Laser Ablation
Laser energy has been used in manufacturing to selectively remove material for cutting or drilling. Laser ablation can be used for removal of biological materials like bone and teeth tissues, in which case overheating becomes critical as the tissue should not reach temperatures that could cause permanent damage. By placing nanoliter scale volumes of energy adsorbing dye at the same rates as the pulsing laser, the ablation process becomes independent of the tissue energy absorption characteristics. The higher absorption and the increased pulsing rate (allowed by the cooling effect of the dye) lead to faster ablation rates.
Microarrays (In Situ)
Microarrays consist of spots of biological solutions on a rectangular grid. Microarrays can be fabricated by dispensing presynthesized biological materials (cDNA, PCR products, peptides/proteins, etc.) or by synthesizing (in situ) the biomaterial directly on the substrate. When arrays contain a large number of samples, in situ synthesis has the advantage of only requiring very small volumes of the different synthesis reagents regardless of the number of different end products within the microarray. Ink-jet dispensing the fluids involved in the synthesis permits the minimization of the features and avoids cross contamination as it is a non-contact technology.
Presynthesized microarrays are created by the microdeposition of presynthesized biological compounds (oligonucleotides, cDNA, enzymes, antibodies, various proteins, human serum, microspheres and even cells) onto a substrate (glass slides, nitrocellulose or PVDF membranes, acrylamide, polystyrene, cellulose). The ability of ink-jet to generate minute drops of liquid translates in a small spot on the substrate and has been vital in generating dense arrays.
Microdispensing refers to the generation of small drops of solutions. A wide range of reagents and solutions involving biomaterials, dissolved and suspended solids have been dispensed using MicroFab’s piezoelectrically actuated ink-jet dispensers. Non-contact microdispensing systems offer accurate and high-throughput deposition of bioactive fluids for many biological and life science applications.
Proteomics involves the systematic separation, identification and characterization of the proteins present in a tissue or other biological sample. A piezoelectric liquid microdispenser having an integrated liquid chromatography (LC) column was developed for the purpose of separating and dispensing proteolysed peptides onto MALDI-TOF MS target plates for subsequent mass spec analysis. Other proteomics activities include protein analysis on 2D-Page protein arrays that have been transferred to a PVDF membrane.
Control of microsphere size and size distribution are the ultimate goals of drug delivery, since a particular release rate and a desired route of administration require a particular sphere size. Using ink-jet technology and single emulsion-solvent evaporation techniques, MicroFab has obtained paclitaxel-loaded PLGA microspheres of narrow size distribution and controlled diameter (figure below).
The site of angioplasty or stent procedure of blood vessels can re-narrow (restenosis) after treatment. Coronary artery stents coated with a variety of pharmacologic agents are used to prevent restenosis. Drug-eluting stents allow controlled local release of a drug directly to the injured endothelium, avoiding systemic side effects. When used to coat the struts, ink-jet provides excellent process control. The solutions can be deposited very precisely (location and amount) onto the stent and, if desired, only on the outer strut surfaces. Multiple solutions can be employed in the coating process.
Structural Genomics (Protein Crystallization)
Obtaining homogenous and monodisperse protein and subsequently crystals large enough for diffraction experiments are two of the largest obstacles for crystallographers. Decreasing the amount of protein required for initial screening of crystallization conditions is desirable. Ink-jet technology provides the opportunity to perform initial protein crystallization screening experiments using small drops to conserve protein with high-throughput dispensing to increase the number of experiments in a given time. Because of the small scale, the crystals in the ink-jet screenings formed more rapidly.
Acute, chronic or congenital injuries often require treatment with replacement tissues and organs. Beyond whole organ replacement, the need for tissues to treat acute trauma is also vital. Creating artificial means to generate supplement tissue has many significant process barriers, due to the diverse materials and fine features to be created. Ink-jet printing technology can be used to dispense the scaffolding material and the growth factors and the cells that are required to create the replacement tissues.