SU-8 epoxy-based negative photoresist has been extensively employed as a structural material for fabrication of numerous biological microelectro-mechanical systems (Bio-MEMS) or lab-on-a-chip (LOC) devices. However, SU-8 has a high autofluorescence level that limits sensitivity of microdevices that use fluorescence as the predominant detection workhorse. Here, we show that deposition of a thin gold nanoparticles layer onto the SU-8 surface significantly reduces the autofluorescence of the coated SU-8 surface by as much as 81% compared to bare SU-8. Furthermore, DNA probes can easily be immobilized on the Au surface with high thermal stability. These improvements enabled sensitive DNA detection by simple DNA hybridization down to 1 nM (a two orders of magnitude improvement) or by solid-phase PCR with sub-picomolar sensitivity. The approach is simple and easy to perform, making it suitable for various Bio-MEMs and LOC devices that use SU-8 as a structural material.
References
[1]
Abgrall, P.; Conedera, V.; Camon, H.; Gue, A.; Nguyen, N. SU-8 as a structural material for labs-on-chips and microelectromechanical systems. Electrophoresis 2007, 28, 4539–4551, doi:10.1002/elps.200700333.
[2]
Pai, J.; Wang, Y.; Salazar, G.T.; Sims, C.E.; Bachman, M.; Li, G.P.; Allbritton, N.L. Photoresist with low fluorescence for bioanalytical applications. Anal. Chem. 2007, 79, 8774–8780.
[3]
Desai, S.P.; Taff, B.A.; Voldman, J. A photopatternable silicone for biological applications. Langmuir 2008, 24, 575–581.
[4]
Tao, S.L.; Popat, K.; Desai, T.A. Off-wafer fabrication and surface modification of asymmetric 3D SU-8 microparticles. Nat. Protoc. 2006, 1, 3153–3158.
[5]
Sethi, D.; Kumar, A.; Gandhi, R.P.; Kumar, P.; Gupta, K.C. New protocol for oligonucleotide microarray fabrication using SU-8-coated glass microslides. Bioconjug. Chem. 2010, 21, 1703–1708, doi:10.1021/bc100262n.
[6]
Broder, G.R.; Ranasinghe, R.T.; She, J.K.; Banu, S.; Birtwell, S.W.; Cavalli, G.; Galitonov, G.S.; Holmes, D.; Martins, H.F.P.; MacDonald, K.F.; Neylon, C.; Zheludev, N.; Roach, P.L.; Morgan, H. Diffractive micro bar codes for encoding of biomolecules in multiplexed assays. Anal. Chem. 2008, 80, 1902–1909.
[7]
Joshi, M.; Kale, N.; Lal, R.; Rao, V.R.; Mukherji, S. A novel dry method for surface modification of SU-8 for immobilization of biomolecules in Bio-MEMS. Biosens. Bioelectron. 2007, 22, 2429–2435, doi:10.1016/j.bios.2006.08.045.
[8]
Park, S.; Lazarides, A.; Mirkin, C.; Brazis, P.; Kannewurf, C.; Letsinger, R. The electrical properties of gold nanoparticle assemblies linked by DNA. Angew. Chem. Int. Ed. 2000, 39, 3845–3848.
[9]
Cao, C.; Sim, S.J. Resonant Rayleigh light scattering response of individual Au nanoparticles to antigen-antibody interaction. Lab Chip 2009, 9, 1836–1839, doi:10.1039/b901327j.
[10]
Cao, C.; Gontard, L.C.; Thuy Tram, L.L.; Wolff, A.; Bang, D.D. Dual enlargement of gold nanoparticles: From mechanism to scanometric detection of pathogenic bacteria. Small 2011, 7, 1701–1708, doi:10.1002/smll.201100294.
[11]
Dubertret, B.; Calame, M.; Libchaber, A. Single-mismatch detection using gold-quenched fluorescent oligonucleotides. Nat. Biotechnol. 2001, 19, 365–370, doi:10.1038/86762.
[12]
Tan, W.S.; Lewis, C.L.; Horelik, N.E.; Pregibon, D.C.; Doyle, P.S.; Yi, H. Hierarchical assembly of viral nanotemplates with encoded microparticles via nucleic acid hybridization. Langmuir 2008, 24, 12483–12488.
[13]
Truong, T.; Nguyen, N. A polymeric piezoelectric micropump based on lamination technology. J. Micromech. Microeng. 2004, 14, 632–638, doi:10.1088/0960-1317/14/4/026.
[14]
Leff, D.; Brandt, L.; Heath, J. Synthesis and characterization of hydrophobic, organically-soluble gold nanocrystals functionalized with primary amines. Langmuir 1996, 12, 4723–4730, doi:10.1021/la960445u.
[15]
Oldenburg, S.; Averitt, R.; Westcott, S.; Halas, N. Nanoengineering of optical resonances. Chem. Phys. Lett. 1998, 288, 243–247, doi:10.1016/S0009-2614(98)00277-2.
[16]
Limmer, S.; Chou, T.; Cao, G. Formation and optical properties of cylindrical gold nanoshells on silica and titania nanorods. J. Phys. Chem. B 2003, 107, 13313–13318, doi:10.1021/jp034992h.
[17]
Bang, D.D.; Pedersen, K.; Madsen, M. Development of a PCR assay suitable for Campylobacter spp. mass screening programs in broiler production. J. Rapid Meth. Autom. Microbiol. 2001, 9, 97–113, doi:10.1111/j.1745-4581.2001.tb00233.x.
[18]
Birtwell, S.W.; Banu, S.; Zheludev, N.I.; Morgan, H. Holographically encoded microparticles for bead-based assays. J. Phys. D: Appl. Phys. 2009, 42, doi:10.1088/0022-3727/42/5/055507.
[19]
Wang, Z.; Skirtach, A.G.; Xie, Y.; Liu, M.; Moehwald, H.; Gao, C. Core-shell poly(allyamine hydrochloride)-pyrene nanorods decorated with gold nanoparticles. Chem. Mater. 2011, 23, 4741–4747, doi:10.1021/cm201711d.
[20]
You, C.; Miranda, O.R.; Gider, B.; Ghosh, P.S.; Kim, I.; Erdogan, B.; Krovi, S.A.; Bunz, U.H.F.; Rotello, V.M. Detection and identification of proteins using nanoparticle-fluorescent polymer “chemical nose” sensors. Nat. Nanotechnol. 2007, 2, 318–323, doi:10.1038/nnano.2007.99.
[21]
Park, C.; Im, M.S.; Lee, S.; Lim, J.; Kim, C. Tunable fluorescent dendron-cyclodextrin nanotubes for hybridization with metal nanoparticles and their biosensory function. Angew. Chem. Int. Ed. 2008, 47, 9922–9926, doi:10.1002/anie.200804087.
[22]
Fan, C.; Wang, S.; Hong, J.; Bazan, G.; Plaxco, K.; Heeger, A. Beyond superquenching: Hyper-efficient energy transfer from conjugated polymers to gold nanoparticles. Proc. Natl. Acad. Sci. USA 2003, 100, 6297–6301.
[23]
Mayilo, S.; Kloster, M.A.; Wunderlich, M.; Lutich, A.; Klar, T.A.; Nichtl, A.; Kuerzinger, K.; Stefani, F.D.; Feldmann, J. Long-range fluorescence quenching by gold nanoparticles in a sandwich immunoassay for cardiac troponin T. Nano Lett. 2009, 9, 4558–4563, doi:10.1021/nl903178n.
[24]
Marie, R.; Schmid, S.; Johansson, A.; Ejsing, L.E.; Nordstrom, M.; Hafliger, D.; Christensen, C.B.V.; Boisen, A.; Dufva, M. Immobilisation of DNA to polymerised SU-8 photoresist. Biosens. Bioelectron. 2006, 21, 1327–1332, doi:10.1016/j.bios.2005.03.004.
[25]
Gudnason, H.; Dufva, M.; Bang, D.D.; Wolff, A. An inexpensive and simple method for thermally stable immobilization of DNA on an unmodified glass surface: UV linking of poly(T)10-poly(C)10-tagged DNA probes. BioTechniques 2008, 45, 261–271.
[26]
Sun, Y.; Dhumpa, R.; Bang, D.D.; Hogberg, J.; Handberg, K.; Wolff, A. A lab-on-a-chip device for rapid identification of avian influenza viral RNA by solid-phase PCR. Lab Chip 2011, 11, 1457–1463, doi:10.1039/c0lc00528b.
[27]
Parkhill, J.; Wren, B.; Mungall, K.; Ketley, J.; Churcher, C.; Basham, D.; Chillingworth, T.; Davies, R.; Feltwell, T.; Holroyd, S.; Jagels, K.; Karlyshev, A.; Moule, S.; Pallen, M.; Penn, C.; Quail, M.; Rajandream, M.; Rutherford, K.; van Vliet, A.; Whitehead, S.; Barrell, B. The genome sequence of the food-borne pathogen Campylobacter jejuni reveals hypervariable sequences. Nature 2000, 403, 665–668.
[28]
Cao, C.; Kim, J.; Kim, B.; Chae, H.; Yoon, H.; Yang, S.; Sim, S. A strategy for sensitivity and specificity enhancements in prostate specific antigen-alpha(1)-antichymotrypsin detection based on surface plasmon resonance. Biosens. Bioelectron. 2006, 21, 2106–2113, doi:10.1016/j.bios.2005.10.014.
