title: pH-responsive layer-by-layer nanoshells for direct regulation of cell activity.
abstract: Saccharomyces cerevisiae yeast cells encapsulated with pH-responsive synthetic nanoshells from lightly cross-linked polymethacrylic acid showed a high viability rate of around 90%, an indication of high biocompatibility of synthetic pH-responsive shells. We demonstrated that increasing pH above the isoelectric point of the polymer shell leads to a delay in growth rate; however, it does not affect the expression of enhanced green fluorescent protein. We suggest that progressive ionization and charge accumulation within the synthetic shells evoke a structural change in the outer shells which affect the membrane transport. This change facilitates the ability to manipulate growth kinetics and functionality of the cells with the surrounding environment. We observed that hollow layer-by layer nanoshells showed a remarkable degree of reversible swelling/deswelling over a narrow pH range (pH 5.0-6.0), but their assembly directly on the cell surface resulted in the suppression of large dimensional changes. We suggest that the variation in surface charges caused by deprotonation/protonation of carboxylic groups in the nanoshells controlled cell growth and cell function, which can be utilized for external chemical control of cell-based biosensors.
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Irina
authors.initials: I
authors.lastname: Drachuk
authors.forename: Olga
authors.initials: O
authors.lastname: Shchepelina
authors.forename: Milana
authors.initials: M
authors.lastname: Lisunova
authors.forename: Svetlana
authors.initials: S
authors.lastname: Harbaugh
authors.forename: Nancy
authors.initials: N
authors.lastname: Kelley-Loughnane
authors.forename: Morley
authors.initials: M
authors.lastname: Stone
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Tsukruk
mesh_terms: D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures