A silicone-based microfluidic chip grafted with carboxyl functionalized hyperbranched polyglycerols for selective protein capture

Abstract

A poly(dimethylsiloxane) (PDMS)-based functional microfluidic device containing a charged matrix of PDMS pillar arrays grafted with hyperbranched polyglycerols (HPGs) was developed. Samples of PDMS were modified with allylamine plasma to form amine groups on the surface prior to the covalent grafting of succinimdyl ester-functionalized HPGs. The anionic functionality of the PDMS channel matrices was developed by altering the number of carboxyl groups present on the HPGs. The grafting of HPGs onto PDMS plates was investigated via contact angle measurement and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), while the grafting of the inside channel was investigated by electroosmotic flow (EOF) measurements. The charge density on grafted HPG was optimized to minimize the nonspecific protein adsorption and increase the selective capture of positively charged proteins. A proof-of-concept device was fabricated on PDMS and demonstrated that the device selectively captures positively charged protein (avidin) from a mixture of bovine serum albumin (BSA)-avidin at pH 7.4 in phosphate buffered saline (PBS). In order to increase the capture efficiency of the proteins in this PDMS-based device, pillar arrays have been fabricated within the channel. As a demonstration, the new device separated two proteins with an avidin capture efficiency of 100 ± 2.95% per 3 min from a 0.02 mg/ml protein solution (avidin:BSA wt ratio: 1:1). This new microfluidic-based device shows a great deal of promise as a tool for protein capture and analysis.

Surface modification for PDMS‐based microfluidic devices

“…The lack of functionality can be addressed by using hyperbranched polyglycerols (HPGs). HPGs with multiple peripheral succinimidyl ester groups have been grafted onto an Ar and then allylamine plasma‐treated PDMS surface 47. The resulting HPG‐modified PDMS showed a lower WCA of 73° compared to native PDMS at 100°.…”

“…Capture‐to and release‐of proteins from PDMS surfaces have also been pursued 17, 39, 47 to allow purification and enrichment from complex biological fluids, especially for diagnostic measurements in clinical applications.…”

“…HPG‐modified PDMS microchannels with pillar arrays (prepared by a “grafting‐to” polymer coating technique) were shown to reduce non‐specific adsorption of BSA and selectively capture positively charged avidin by electrostatic interaction at neutral pH 47. The captured avidin could then be released by using a higher ionic strength buffer.…”

Developing an ultra non-fouling SU-8 and PDMS hybrid microfluidic device by poly(amidoamine) engraftment

“…Poly(dimethylsiloxane) (PDMS) is a commonly used material to fabricate microfluidic channels because it has many desirable properties, such as optical transparency [5], chemical inertness [6], moldability [7], high elasticity [8], as well as excellent gas permeability to O 2 and CO 2 [9]. As another important material in microfabrication, SU-8 (negative photoresist) was initially used mainly as the material to prepare masters in PDMS device fabrications [10]; however, it has become increasingly popular as the material of choice to directly fabricate microfluidic devices in recent years [11]. For example, SU-8 has been used in waveguide applications, especially for optofluidic integrated devices [12].…”

Structure-induced spreading of liquid in micropillar arrays

“…For selected applications, structured channel walls are crucial to the function of the device. Recently, micropillar arrays have been incorporated into microfluidic channels for various applications (Yeh et al 2010;Cheng and Jiang 2009;Saha et al 2009;Kwon et al 2007). Here, wettability and structure-induced spreading on micropillar arrays is investigated for liquid-vapor and liquid-liquid systems.…”