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Towards Stronger Microcapsules for Non-Autologous Somatic Gene Therapy

Contact Person: Jeremy M. Van Raamsdonk (vanraaj@mcmaster.ca)

Materials and Methods

Our lab primarily uses alginate-polylysine-alginate(APA) microcapsules. Alginate is a polysaccharide composed of mannuronic(M) and guluronic(G) acid units.

Microencapsulation Protocol:

Myoblasts are transfected with a plasmid vector to create universal cell lines that secrete a therapeutic protein(eg. factor IX). The myoblasts are harvested and mixed with a 1.5% or 2% alginate solution at concentrations of about 2 million cells per ml. of alginate. This cell-alginate mixture is extruded through a 27 gauge blunt ended needle into calcium chloride with concentric air flow to induce droplet formation. When the alginate droplet contacts the calcium chloride bath, the calcium ions cross-link the alginate molecules inducing gel bead formation. The resulting cell-alginate beads are washed with a series of solutions that provide for capsule strength while maintaining cell viability. The polylysine(PLL) wash coats the capsule with a layer of polylysine which gives strength to the microcapsule and determines the molecular weight cutoff of the capsules(ie. pore size).An outer layer of alginate is added after the polylysine coating for biocompatability. The inner core can be dissolved with sodium citrate to create hollow capsules. The microcapsules are generally between 200 and 500 um in size.

Figure 5. On the left from top to bottom: Structure of alginate composed of M and G units, the cross-linking of alginate with calcium ions, chelation of calcium by 2 G units. On the right is a diagrammatic overview of encapsulation process.

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Van Raamsdonk, J.; Chang, P.; (1998). Towards Stronger Microcapsules for Non-Autologous Somatic Gene Therapy. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/pharmtox/van_raamsdonk0239/index.html
© 1998 Author(s) Hold Copyright