TABLE I.
Comparison of anti-NSA performance of various surface passivation methods of PDMS.
| Ref./Year | PDMS surface modification | Analytes | Adsorption and desorption coefficient | Comments |
|---|---|---|---|---|
| 18/2015 | Self-assembled peptides coating | BSAa and LYZb | … | The adsorption of BSA and LYZ was reduced by 96%–98%, and there was no difference between BSA and LYZ. The coating could only be conducted after chip assembly and was realized in the phosphate buffer at a specific pH of 9.5. Practical application: adsorption of platelet from whole blood was detected |
| 30/2012 | Plasma polymer coating (tetraglyme, ppTTg) | FINc | … | 4-step ppTTg coating process could resist protein adsorption (<10 ng/cm2), while the requirement for the surface to be open for the coating process may be a limitation, and all devices sealing were relied on a clamp system and operational pressure |
| 21/2010 | Photocatalyzed Polysaccharides coating: carboxymethyl cellulose (CMC), carboxymethyl −1, 3-dextran (CMD), and alginic acid (AA) | BSA and LYZ | … | Selectively (isoelectric point of protein (PI) dependent) protein repelling property was demonstrated, and the modification could only be conducted after PDMS bonding |
| 23/2010 | Self-assembled alkanethiol monolayers (SAM) | LYZ and FIN | … | The SAM reduced the adsorption by around 75%, and there was no difference between LYZ and FIN. The modification was conducted after PDMS chip assembly and required a complex surface pretreatment. |
| 24/2007 | Coating of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers | BSA | … | The MPC coating on PDMS inhibit the adsorption by ∼75%. The modification was carried out after PDMS microchannel preparation |
| 29/2006 | Grafting epoxy-modified hydrophilic polymers | BSA and LYZ | … | Surface adsorption of BSA and LYZ was reduced to less than 10% relative to that on the native PDMS surface, but 10%–15% increase in protein adsorption was observed after 6 days. There is no difference between BSA and LYZ. The coating was carried out after PDMS device preparation with plasma bonding |
| 20/2005 | n-Dodecyl-b-d-Maltoside (DDM) | BSA | … | The adsorption was reduced by a factor of 100. The coating process is complex, and could only be conducted after chip assembly when a small percentage of DDM is tolerated in the reaction system. Practical application: adsorption of cytochrome c (an antibody) and β2 adrenergic receptor (a transmembrane protein) were tested |
| 22/2005 | Platinum-catalyzed covalent immobilization of polyethylene oxide (PEO) | BSA and FIN | … | The adsorption was reduced by more than 90% and no difference for BSA and FIN, but molecular weight of PEO may affect protein. The PEO coating process was conducted on the PDMS specimen and bonding for device assembly was not tested |
| 25/2005 | Fluorous surfactant treatment | BSA and FIN | Adsorption rate | The adsorption of BSA and FIN could be prevented and no significances, while the coating was conducted after microfluidic channel assembly |
| 31/2004 | Polyacrylamide coating through atom-transfer radical polymerization | BSA | … | Surface modification reduced both reversible and irreversible adsorption of BSA, while a rigorous operation was required for the coating. Practical application: demonstrated separation of LYZ and cytochrome c in 35 s showed evidence of no adsorption |
| 27/2003 | Polytetrafluoroethylene (PTFE) cover | BSA | … | Adsorption of BSA was dropped on the PTFE covered surface. But the formation of fine structures required 115 °C under pressure of 40 kPa after cover |
| 37/2003 | Chemical vapor deposition (CVD) of poly(p-xylylene carboxylic acid pentafluorophenolester-co-p-xylylene)26 (PPX-PPF) | … | … | Immobilization of biotin and streptavidin demonstrated the decreased protein adsorption on the PPX-PPF modified PDMS surface, and the process is compatible with complex biological application, while bonding of the microchannel required oxidization-facilitated adhesive epoxy bond |
| This work | Parylene C caulking inside PDMS matrix via chemical vapor deposition (CVD) | BSA | Yes | pcPDMS process was able to reduce the NSA of BSA by 64.8% in a continuous flow reaction case (at a flow rate of 2000 nL/min) and 95.5% in a heterogeneous sensing case. The pcPDMS bonding could be realized via easily available oxygen plasma treatment. Practical application: Taq polymerase for PCR |
a
Bovine serum albumin.
b
Lysozyme.
c
Fibrinogen.