Growth kinetics of genetically engineered E. coli DH 5 cells in artificial cell APA membrane microcapsules: preliminary report

Use of whey protein beads as a new carrier system for recombinant yeasts in human digestive tract

A new immobilizing protocol using whey protein isolates was developed to entrap recombinant Saccharomyces cerevisiae. The model yeast strain expresses the heterologous P45073A1 that converts trans-cinnamic acid into p-coumaric acid. Beads resulted from a cold-induced gelation of a whey protein solution (10%) containing yeasts (7.5 x 10(7)cells ml(-1)) into 0.1M CaCl(2). The viability and growth capability of yeasts were not altered by our entrapment process. The release and activity of immobilized yeasts were studied in simulated human gastric conditions. During the first 60 min of digestion, 2.2+/-0.9% (n=3) of initial entrapped yeasts were recovered in the gastric medium suggesting that beads should cross the gastric barrier in human. The P45073A1 activity of entrapped yeasts remained significantly higher (p<0.05) than that of free ones throughout digestion (trans-cinnamic acid conversion rate of 63.4+/-1.6% versus 51.5+/-1.8% (n=3) at 120 min). The protein matrix seemed to create a microenvironment favoring the activity of yeasts in the stringent gastric conditions. These results open up new opportunities for the development of drug delivery system using recombinant yeasts entrapped in whey protein beads. The main potential medical applications include biodetoxication or the correction of digestive enzyme deficiencies.

Artificial Cell Therapy: New Strategies for the Therapeutic Delivery of Live Bacteria

There has been rapid growth in research regarding the use of live bacterial cells for therapeutic purposes. The recognition that these cells can be genetically engineered to synthesize products that have therapeutic potential has generated considerable interest and excitement among clinicians and health professionals. It is expected that a wide range of disease modifying substrates such as enzymes, hormones, antibodies, vaccines, and other genetic products will be used successfully and will impact upon health care substantially. However, a major limitation in the use of these bacterial cells is the complexity of delivering them to the correct target tissues. Oral delivery of live cells, lyophilized cells, and immobilized cells has been attempted but with limited success. Primarily, this is because bacterial cells are incapable of surviving passage through the gastrointestinal tract. In many occasions, when given orally, these cells have been found to provoke immunogenic responses that are undesirable. Recent studies show that these problems can be overcome by delivering live bacterial cells, such as genetically engineered cells, using artificial cell microcapsules. This review summarizes recent advances in the therapeutic use of live bacterial cells for therapy, discusses the principles of using artificial cells for the oral delivery of bacterial cells, outlines methods for preparing suitable artificial cells for this purpose, addresses potentials and limitations for their application in therapy, and provides insight for the future direction of this emergent and highly prospective technology.

Microencapsulated Genetically Engineered Lactobacillus plantarum 80 (pCBH1) for Bile Acid Deconjugation and Its Implication in Lowering Cholesterol

Cholesterol is known to be a major risk factor for coronary heart disease (CHD). Current treatments for elevated blood cholesterol include dietary management, regular exercise, and drug therapy with fibrates, bile acid sequestrants, and statins. Such therapies, however, are often suboptimal and carry a risk for serious side effects. This study shows that microencapsulated Lactobacillus plantarum 80 (pCBH1) cells can efficiently break down and remove bile acids, and establishes a basis for their use in lowering blood serum cholesterol. Results show that microencapsulated LP80 (pCBH1) is able to effectively break down the conjugated bile acids glycodeoxycholic acid (GDCA) and taurodeoxycholic acid (TDCA) with bile salt hydrolase (BSH) activities of 0.19 and 0.08 μmol DCA/mg CDW/h respectively. This article also summarizes the physiological interrelationship between bile acids and cholesterol and predicts the oral doses of microencapsulated Lactobacillus plantarum 80 (pCBH1) cells required for lowering cholesterol.

Artificial cells for replacement of metabolic organ functions

Artificial cells are being actively investigated for use in the replacement of cell and organ functions, especially related to metabolic functions. The earliest routine clinical use of artificial cells is in the form of coated activated charcoal for hemoperfusion. Implantation of encapsulated cells are being studied for the treatment of diabetes, liver failure, kidney failure and the use of encapsulated genetically engineered cells for gene therapy. Blood substitutes based on modified hemoglobin are already in Phase III clinical trials in patients with as much as 20 units infused into each patient during trauma surgery. Artificial cells containing enzymes are being developed for clinical trial in hereditary enzyme deficiency diseases and other diseases. Artificial cell is also being investigated for drug delivery and for other uses in biotechnology, chemical engineering and medicine.