Preparation of poly(glycolic acid) bonded fiber structures for cell attachment and transplantation

Tissue engineering

The loss or failure of an organ or tissue is one of the most frequent, devastating, and costly problems in human health care. A new field, tissue engineering, applies the principles of biology and engineering to the development of functional substitutes for damaged tissue. This article discusses the foundations and challenges of this interdisciplinary field and its attempts to provide solutions to tissue creation and repair.

Laminated three-dimensional biodegradable foams for use in tissue engineering

A novel processing technique is reported to construct three-dimensional biodegradable polymer foams with precise anatomical shapes. The technique involved the lamination of highly-porous membranes of porosities up to 90%. Implants with specific shapes were prepared made of poly(L-lactic acid) and copolymers of poly(DL-lactic-co-glycolic acid) to evaluate feasibility. The biomaterials produced have pore morphologies similar to those of the constituent membranes. The pores of adjacent layers of laminated devices are interconnected, resulting in continuous pore structures. The compressive creep behaviour of multilayered devices is also similar to that of the individual layers. Recent discoveries from our group and others that organs and tissues can be regenerated and reconstructed, using cells cultured on synthetic biodegradable polymers, renders this method useful in creating polymer-cell graft for use in cell transplantation.

The predicted and observed decline in onchocerciasis infection during 14 years of successful control of Simulium spp. in west Africa

In 55 villages from the well-protected central area of the Onchocerciasis Control Programme in West Africa (OCP), skin snip surveys have been carried out at regular intervals since the programme started, and the latest round of surveys was undertaken after 12-14 years of successful vector control. The observed trends in the prevalence and intensity of onchocerciasis infection in cohorts of adults were compared with the trends predicted using a host-parasite model. After 12-14 years of control the community microfilarial load (CMFL) was close to zero in all villages. During the last few years of control, the prevalence of infection declined at an accelerated rate, and this was predicted by the model. There was generally good agreement between observed and predicted trends. The predictions were based on an estimated average duration of infection of 10.4 years, which corresponds to a mean reproductive lifespan for Onchocerca volvulus of 9-9.5 years, and an upper limit of 15 years for 95% of the infections. Differences between the observed and predicted data included the trend in CMFL between the first and second surveys, which in 18 villages did not show the predicted decline. Furthermore, the observed final decline in prevalence was faster than predicted in the north-eastern part of the central OCP area. After 14 years of vector control, the level of onchocerciasis has fallen to such a low level that consideration is being given to ending larviciding.

Problems in the differential diagnosis of choroidal nevi and malignant melanomas. The XXXIII Edward Jackson Memorial Lecture

This article describes a novel method for preparing several spherical multicellular aggregates (spheroids) that have almost the same diameter on a microfabricated chip. The chip, fabricated by a simple method that uses a micromilling system, consisted of several thousand cavities, 100-500 microm in diameter, in a triangular arrangement on a polystyrene plate. Although no spheroid was formed on any chip when cultured under stationary conditions, hepatocytes formed spheroids in the cavities when turning force was applied with a rotary shaker. Especially on the chip with cavities 300 microm in diameter, one spheroid formed in each cavity; an orderly array of spheroids (1100 spheroids/cm(2)) of almost the same diameter was constructed. Ammonia removal and albumin secretion by the spheroids on the chip continued to occur at initial levels for at least 14 days of culture. Enzyme P-450 activity of the spheroids was also maintained and detected on this transparent chip by fluorescence of resorufin converted from ethoxyresorufin. The spheroid microarray chip seems to be a promising cellular platform for various biomedical applications such as in cell-based biosensors for toxicological and pharmacological examinations, and in bioartificial livers.