Microactuators toward microvalves for responsive controlled drug delivery (original) (raw)
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Review 32-37533473c0-7f26-460d-859c-afbd5d16dd0a.pdf
Micro-electro-mechanical system (MEMS) are tiny chips that can be produced by semiconductor processes to combine mechanical sensing, motion and control to solid state electronics to deliver extraordinary functionality and versatility. MEMS can sense pressure, detect motion, measure forces, identify bio-agents, pump and control fluids and perform other actions that have great value to the medical and biological fields. BioMEMS is the term used to describe the chips designed specifically for these applications. These MEMS devices can be used as in-vivo devices as well as transdermal devices. Some marketed MEMS drug delivery systems are also available. The review highlights the various fields in the drug delivery where this approach has been utilized and the various materials which are used for its manufacturing.
Conjugated-Polymer Micro- and Milliactuators for Biological Applications
MRS Bulletin, 2002
The development of new conjugated-polymer tools for the study of the biological realm, and for use in a clinical setting, is reviewed in this article. Conjugated-polymer actuators, based on the changes of volume of the active conjugated polymer during redox transformation, can be used in electrolytes employed in cell-culture media and in biological fluids such as blood, plasma, and urine. Actuators ranging in size from 10 m to 100 m suitable for building structures to manipulate single cells are produced with photolithographic techniques. Larger actuators may be used for the manipulation of blood vessels and biological tissue.
Incorporation of bioactive materials into integrated systems
Nanofabrication Technologies, 2003
Sandia is exploring two classes of integrated systems involving bioactive materials: 1) microfluidic systems that can be used to manipulate biomolecules for applications ranging from counter-terrorism to drug delivery systems, and 2) fluidic systems in which active biomolecules such as motor proteins provide specific functions such as active transport. An example of the first class involves the development of a reversible protein trap based on the integration of the thermally-switchable polymer poly(N-isopropylacrylamide)(PNIPAM) into a micro-hotplate device. To exemplify the second class, we describe the technical challenges associated with integrating microtubules and motor proteins into microfluidic systems for: 1) the active transport of nanoparticle cargo, or 2) templated growth of high-aspect ratio nanowires. These examples illustrate the functions of bioactive materials, synthesis and fabrication issues, mechanisms for switching surface chemistry and active transport, and new techniques such as the interfacial force microscope (IFM) that can be used to characterize bioactive surfaces.
Polymer actuator valves toward controlled drug delivery application
Biosensors and Bioelectronics, 2006
A novel controlled drug delivery system in which drug release is achieved by electrochemically actuating an array of polymeric valves on a set of drug reservoirs has been developed. The valves are bilayer structures, made in shape of a flap hinged on one side to a valve seat, consisting of thin films of evaporated gold and electrochemically deposited polypyrrole (PPy). Drugs (dry or wet) were pre-stored in an array of these reservoirs and their release is accomplished by bending the bilayer flaps away from the substrate with a small applied bias. In vitro color dye release experiment has been conducted. Seventy-five percent less energy consumption was achieved with this bilayer polymer valve design to open a same size reservoir compared to metal-corrosion based valves. Complex release patterns such as multiple drug pulsatile release and continuous linear release have been successfully implemented through flexible control of valve actuation sequence. These valves can be actuated under closed-loop-control of sensors responding to a specific biological or environmental stimulus, leading to potential applications in advanced responsive drug delivery systems.
Langmuir, 2010
A route toward mechanically robust, rapidly actuating, and biologically functionalized polymeric actuators using macroporous soft materials is described. The materials were prepared by combining silk protein and a synthetic polymer (poly(N-isopropylacrylamide) (PNIAPPm)) to form interpenetrating network materials and macroporous structures by freeze-drying, with hundreds of micrometer diameter pores and exploiting the features of both polymers related to dynamic materials and structures. The chemically cross-linked PNIPAAm networks provided stimuli-responsive features, while the silk interpenetrating network formed by inducing protein β-sheet crystallinity in situ for physical cross-links provided material robustness, improved expansion force, and enzymatic degradability. The macroporous hybrid hydrogels showed enhanced thermal-responsive properties in comparison to pure PNIPAAm hydrogels, nonporous silk/PNIPAAm hybrid hydrogels, and previously reported macroporous PNIPAAm hydrogels. These new systems reach near equilibrium sizes in shrunken/swollen states in less than 1 min, with the structural features providing improved actuation rates and stable oscillatory properties due to the macroporous transport and the mechanically robust silk network. Confocal images of the hydrated hydrogels around the lower critical solution temperature (LCST) revealed macropores that could be used to track changes in the real time morphology upon thermal stimulus. The material system transformed from a macroporous to a nonporous structure upon enzymatic degradation. To extend the utility of the system, an affinity platform for a switchable or tunable system was developed by immobilizing biotin and avidin on the macropore surfaces.