@article { ISI:000299775500022, title = {Controlled release of nutrients to mammalian cells cultured in shake flasks}, journal = {Biotechnology Progress}, volume = {28}, number = {1}, year = {2012}, month = {JAN}, pages = {188-195}, publisher = {WILEY-BLACKWELL}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

Though cell culture-based protein production processes are rarely carried out under batch mode of operation, cell line and initial process development operations are usually carried out in batch mode due to simplicity of operation in widely used scale down platforms like shake flasks. Nutrient feeding, if performed, is achieved by bolus addition of concentrated feed solution at different intervals, which leads to large transient increases in nutrient concentrations. One negative consequence is increased waste metabolite production. We have developed a hydrogel-based nutrient delivery system for continuous feeding of nutrients in scale down models like shake flasks without the need for manual feed additions or any additional infrastructure. Continuous delivery also enables maintaining nutrient concentrations at low levels, if desired. The authors demonstrate the use of these systems for continuous feeding of glucose and protein hydrolysate to a suspension Chinese Hamster Ovary (CHO) culture in a shake flask. Glucose feeding achieved using the glucose-loaded hydrogel resulted in a 23\% higher integral viable cell density and an 89\% lower lactate concentration at the end of the culture when compared with a bolus-feed of glucose. (c) 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2012

}, issn = {8756-7938}, doi = {10.1002/btpr.729}, author = {Hegde, Swati and Pant, Tejal and Pradhan, Ketaki and Badiger, Manohar V. and Gadgil, Mugdha} } @article { ISI:000310642900002, title = {Effect of addition of {\textquoteleft}carrier{\textquoteright} DNA during transient protein expression in suspension CHO culture}, journal = {Cytotechnology}, volume = {64}, number = {6}, year = {2012}, month = {DEC}, pages = {613-622}, publisher = {SPRINGER}, address = {VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}, abstract = {

Transient protein expression using polyethyleneimine as a transfection agent is useful for the rapid production of small amounts of recombinant proteins. It is known that an increase in extracellular DNA concentration during transfection can lead to a nonlinear increase in intracellular DNA concentration. We present an approach that hypothesizes that this nonlinearity can be used to decrease the amount of plasmid required for productive transfections. Through addition of non coding {\textquoteleft}carrier{\textquoteright} DNA to increase total DNA concentration during transfection, we report a statistically significant increase in protein (IgG) expression per unit plasmid used for transfection. This approach could be useful to increase protein yields for large scale transfections under conditions where plasmid availability is limited.

}, keywords = {Carrier DNA, Cell age, DNA: polyethyleneimine particle size, Medium equilibration with CO2, pH excursion, Salmon sperm DNA, Transient protein expression}, issn = {0920-9069}, doi = {10.1007/s10616-012-9435-4}, author = {Pradhan, Ketaki and Gadgil, Mugdha} } @article { ISI:000312157100027, title = {In situ pH maintenance for mammalian cell cultures in shake flasks and tissue culture flasks}, journal = {Biotechnology Progress}, volume = {28}, number = {6}, year = {2012}, month = {NOV}, pages = {1605-1610}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

pH in animal cell cultures decreases due to production of metabolites like lactate. pH control via measurement and base addition is not easily possible in small-scale culture formats like tissue-culture flasks and shake flasks. A hydrogel-based system is reported for in situ pH maintenance without pH measurement in such formats, and is demonstrated to maintain pH between 6.8 and 7.2 for a suspension CHO cell line in CD CHO medium and between 7.3 and 7.5 for adherent A549 cells in DMEM:F12 containing 10\% FBS. This system for pH maintenance, along with our previous report of hydrogels for controlled nutrient delivery in shake flasks can allow shake flasks to better mimic bioreactor-based fed batch operation for initial screening during cell line and process development for recombinant protein production in mammalian cells. (C) 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012

}, keywords = {high throughput screening, pH control for cell culture, pH control in shake flask, pH control in tissue culture flasks, small scale platforms for cell culture}, issn = {8756-7938}, doi = {10.1002/btpr.1614}, author = {Pradhan, Ketaki and Pant, Tejal and Gadgil, Mugdha} }