Methods of reducing non-specific adsorption in microfluidic biosensors

Abstract

Non-specific adsorption (NSA) of biomolecules is a persistent challenge in microfluidic biosensors. Microfluidic biosensors often have immobilized bioreceptors such as antibodies, enzymes, DNAs, etc, via linker molecules such as SAMs (self-assembled monolayers) to enhance immobilization. However, the linker molecules are very susceptible to NSA, causing false responses and decreasing sensitivity. In this paper, we present design methods to reduce the NSA of alkanethiol SAMs, which are popular linker molecules on microfluidic biosensors. Three design parameters were studied for two different chain-length SAMs (n = 2 and 10): (i) SAM incubation time, (ii) surface roughness [0.8 nm and 4.4 nm RMS (root mean square)] and (iii) gold crystal re-growth along (1 1 1) the target orientation. NSA was monitored by surface plasmon resonance (SPR). The results suggest that increased SAM incubation time reduces NSA, and that short-chain SAMs respond more favorably than the long-chain SAMs. Both SAMs were shown to be sensitive to surface roughness, and long-chain SAMs reduced NSA by 75%. Gold crystal re-growth along (1 1 1) the target orientation profoundly reduced NSA on the short-chain SAM. On a gold surface where surface roughness was 0.8 nm and there was strong directional alignment along the (1 1 1) gold crystal, final concentrations of nonspecifically bound proteins were 0.05 ng mm −2 (fibrinogen) and 0.075 ng mm −2 (lysozyme)-significantly lower than other known methods. The results show that optimizing three parameters (SAM incubation time, gold surface roughness and gold crystal orientation) improved SAM sensitivity for fibrinogen-anti-fibrinogen conjugates by a factor of 5 in 2.94 pM, suggesting that the methods are effective for reducing NSA in microfluidic biosensors.

Introducing surface-tethered poly(acrylic acid) brushes as 3D functional thin film for biosensing applications

“…The precursor layer onto which the bioactive molecules (probes) are immobilized is conventionally based on a self-assembled monolayer (SAM) of end-functionalized alkanethiol, especially for gold-coated substrates, but the density of this cannot be greatly enhanced [1][2][3]. Variation of the alkyl chain length, which is generally used for controlling the distance between the measurement platform and the sensing probes, is also limited due to the fact that long alkyl chains tend to induce non-specific adsorption of the bioactive molecules during the immobilization [4]. This often causes an adverse effect on the biosensor efficiency.…”

Different approaches to PVP/graphene composite film fabrication using electrohydrodynamic atomization technique

“…At each flow rate, the strength of the electric field was increased by gradually increasing the potential difference between the anode nozzle and the grounded stage [17][18][19]. At each flow rate step, applying different magnitudes of voltage gave different modes of atomization and hence various modes were observed such as the dripping to the multi-jet [20][21][22].…”

Non-specific adsorption of serum and cell lysate on 3D biosensor platforms: A comparative study based on SPRi

“…SPR sensing has been significantly developed in recent years to quantify biomarkers in complex matrixes, such as serum (Choi et al, 2010;Su et al, 2008 andLadd et al, 2009), plasma (Teramura et al, 2007), saliva (Yang et al, 2005) and cell lysate (Kyo et al, 2005). SPR biosensors have been shown to be suited for the detection of several cancer biomarkers (Sankiewicz et al, 2015) in solubilized samples, such as oropharyngeal squamous cell carcinoma (Liu et al, 2012), prostate cancer (Choi et al, 2010), colorectal, gastric, and pancreatic cancer (Su et al, 2008), intestinal cancer (Ladd et al, 2009), liver cancer (Teramura et al, 2007) and ovarian cancer (Liu et al, 2012) among others. However, serum and cell lysate screening on SPRi provide real time detection results in less time with low human error, but due to their protein and lipid rich matrix respectively, they expected to significantly foul on sensor surface.…”