Cell Adhesion and Interactions with Biomaterials

The related phenomena of biocompatibility and biodegradation are of major concern in the selection of synthetic polymers for use as implantable biomedical devices. These properties are largely determined by the consequences of the cellular interactions that occur at the polymer/tissue interface during inflammation. Using an in vivo cage implant system, in conjunction with surface analysis techniques, we have investigated the variation in the cellular events that occurred on a polyetherure-thaneurea and a cytotoxic polyvinyl chloride). Quantitative and qualitative information that describe the cellular response to polymer implantation will be presented. From the results, a chronological sequence has been established which suggests that the important events follow cellular adhesion, and include cell spreading over a polymer surface accompanied by lysosomal degranulation of the adherent cells.     

Vision implants: An electrical device will bring light to the blind

Cochlear implant has been successfully applied in clinic. Recent research indicates vision implants may be the potential way to restore sight for the blind. Here, principle and common structure of vision implants are introduced. Main vision approaches of retinal, optic nerve, and cortical prosthesis are reviewed. In our progress, electrical response at visual cortex is recorded, when penetrating electrodes stimulate rabbit optic nerve, vision implants based on optic nerve stimulator chip （ONSC） and Chipcon radio frequency （RF） chip are under developing. Despite several obstacles to overcome, promising results in animal and human experiments give scientists confidence that artificial vision implants will bring light to the blind in the near future.     

Corrosion of bio implants

Chemical stability, mechanical behaviour and biocompatibility in body fluids and tissues are the basic requirements for successful application of implant materials in bone fractures and replacements. Corrosion is one of the major processes affecting the life and service of orthopaedic devices made of metals and alloys used as implants in the body. Among the metals and alloys known, stainless steels (SS), Co-Cr alloys and titanium and its alloys are the most widely used for the making of biodevices for extended life in human body. Incidences of failure of stainless steel implant devices reveal the occurrence of significant localised corroding viz., pitting and crevice corrosion. Titanium forms a stable TiO₂ film which can release titanium particles under wear into the body environment. To reduce corrosion and achieve better biocompatibility, bulk alloying of stainless steels with titanium and nitrogen, surface alloying by ion implantation of stainless steels and titanium and its alloys, and surface modification of stainless steel with bioceramic coatings are considered potential methods for improving the performance of orthopaedic devices. This review discusses these issues in depth and examines emerging directions.     

A Low-Power Wide-Dynamic-Range Analog VLSI Cochlea

Low-power wide-dynamic-range systems are extremely hard to build. The biological cochlea is one of the most awesome examples of such a system: It can sense sounds over 12 orders of magnitude in intensity, with an estimated power dissipation of only a few tens of microwatts. In this paper, we describe an analog electronic cochlea that processes sounds over 6 orders of magnitude in intensity, and that dissipates 0.5 mW. This 117-stage, 100 Hz to 10 KHz cochlea has the widest dynamic range of any artificial cochlea built to date. The wide dynamic range is attained through the use of a wide-linear-range transconductance amplifier, of a low-noise filter topology, of dynamic gain control (AGC) at each cochlear stage, and of an architecture that we refer to as overlapping cochlear cascades. The operation of the cochlea is made robust through the use of automatic offset-compensation circuitry. A BiCMOS circuit approach helps us to attain nearly scale-invariant behavior and good matching at all frequencies. The synthesis and analysis of our artificial cochlea yields insight into why the human cochlea uses an active traveling-wave mechanism to sense sounds, instead of using bandpass filters. The low power, wide dynamic range, and biological realism make our cochlea well suited as a front end for cochlear implants.