Microfluidic integration of substantially round glass capillaries for lateral patch clamping on chip.
High-throughput screening of drug candidates for channelopathies can greatly benefit from an automated patch-clamping assay. Automation of the patch clamping through microfluidics ideally requires on-chip integration of glass capillaries with substantially round cross section. Such round capillaries, if they can only be integrated to connect isolated reservoirs on a substrate surface, will lead to a "lateral" configuration which is simple yet powerful for the patch clamping. We demonstrate here "lateral" patch clamping through microfluidic integration of substantially round glass capillaries in a novel process. The process adopts two well-known phenomena from microelectronics: keyhole-void formation and thermal-reflow of phosphosilicate glass in silicon trenches. The process relies on the same physical principle as the preparation of conventional micropipette electrodes by heat-pulling and fire-polishing glass tubes. The optimized process forms capillaries with a diameter approximately 1.5 microm and variation <10%. Functionality of the integrated glass capillaries for the patch-clamp recording has been verified by statistical test results from a sample of one hundred capillaries on mammalian cells (RBL-1) in suspension: 61% formed gigaseals (>1 GOmega) and of those approximately 48% (29% of all) achieved whole-cell recordings. Pharmacological blockade of ion channel activity and longevity of a whole-cell mode on these capillaries have also been presented.
Ong
Wee-Liat
WL
Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore, 117685.
Tang
Kum-Cheong
KC
Agarwal
Ajay
A
Nagarajan
Ranganathan
R
Luo
Lian-Wee
LW
Yobas
Levent
L
D002197:Capillary Action; D018929:Cell Culture Techniques / Q000295:instrumentation* / Q000379:methods; D002469:Cell Separation / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation* / Q000379:methods; D005898:Glass; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D018408:Patch-Clamp Techniques / Q000295:instrumentation*; D018511:Systems Integration