Non-specific Adsorption of Crude Cell Lysate on Surface Plasmon Resonance Sensors Alexandra Aube ́ , † Julien Breault-Turcot, † Pierre Chaurand, † Joelle N. Pelletier, †,‡,§ and Jean-Franc ̧ ois Masson* ,†,∥ † De ́ partement de Chimie, and ‡ De ́ partement de Biochimie, Universite ́ de Montre ́ al, C.P. 6128 succursale Centre-ville, Montreal, Quebec H3C 3J7, Canada § PROTEO, The Quebec Network for Research on Protein Structure, Function and Engineering, Universite ́ Laval, Quebec City, Quebec G1V 0A6, Canada ∥ Centre for Self-Assembled Chemical Structures (CSACS), McGill University, Montreal, Quebec H3A 2K6, Canada ABSTRACT: Non-specific adsorption of the molecular components of biofluids is ubiquitous in the area of biosensing technologies, severely limiting the use of biosensors in real- world applications. The surface chemistries developed to prevent non-specific adsorption of crude serum are not necessarily suited for sensing in other biosamples. In particular, the diagnostic potential of differential expression of proteins in tissues makes cell lysate attractive for disease diagnostics using solid biopsies. However, crude cell lysate poses a significant challenge for surface chemistries because of a large concentration of highly adherent lipids. Contrary to the non- specific adsorption in crude serum being suppressed by hydrophilic surfaces, the surface plasmon resonance (SPR) analysis of serine-, aspartic-acid-, histidine-, leucine-, and phenylalanine-based peptide monolayers revealed that hydrophobic and positively charged peptides decreased non-specific adsorption when using lysate from HEK 293FT cells. A polyethylene glycol (PEG) monolayer resulted in 2-fold greater fouling than the best peptide [3-MPA−(His) 2 (Leu) 2 (Phe) 2 −OH] under the same conditions. Matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometry (MALDI−TOF/TOF MS) analysis of the adsorbate from cell lysate confirmed that lipids are the main source of non-specific adsorption. Importantly, the mass spectrometry (MS) study revealed that both the number of lipids identified and their intensity decreased with decreasing non-specific adsorption. A peptide monolayer thus provides an efficient mean to suppress non-specific adsorption from this human cell lysate. ■ INTRODUCTION The healthcare industry constantly searches for methodologies to improve diagnostic techniques, in terms of analysis time, sensitivity, and selectivity. Despite the numerous technological and medical advances, cancer remains one of the biggest scourges of humanity. The need is thus well-justified to develop early and reliable cancer diagnostic technologies to improve the chance of remission of cancer patients. 1 Enzyme-linked immunosorbent assays (ELISAs) and various biosensing technologies are the staple methodologies for identifying and quantifying cancer biomarkers. These technologies rely mainly on solubilized proteins found in serum because of the non- invasive nature of sample collection. Nonetheless, not all proteins are of diagnostic interest. Many biosensors have been developed using a large variety of selective bioreceptors, such as enzymes, antibodies, or DNA. 2 Different techniques, such as mass spectrometry (MS) 3,4 or fluorescence spectroscopy employed for protein arrays, 5 provide analytical detection of the results on the sensor. Surface plasmon resonance (SPR) is an analytical tool of particular interest because it allows real-time monitoring of multiple biomarkers with sensitivity and rapidity. SPR sensing has been significantly developed in recent years to quantify biomarkers in complex matrixes, such as serum, 6−8 plasma, 9 or saliva. 10 SPR biosensors have been shown to be suited to detection of several cancer biomarkers in solubilized samples, such as oropharyngeal squamous cell carcinoma, 10 prostate cancer, 6 colorectal, gastric, and pancreatic cancer, 7 intestinal cancer, 8 liver cancer, 9 and ovarian cancer, 11 among others. However, several types of cancer do not exhibit a significant protein or metabolomic response in biofluids, such as blood, serum, urine, or saliva. In those cases, biopsies are taken from the suspected tumor site to verify the presence of cancerous cells. The staple diagnostic method, immunostaining and microscopic readout, is lengthy, requires highly skilled pathologists, and suffers from subjective interpretation. This procedure is thus prone to human error, which may delay the assessment of the presence of cancer and retard the onset of Received: May 15, 2013 Revised: July 9, 2013 Published: July 11, 2013 Article pubs.acs.org/Langmuir © 2013 American Chemical Society 10141 dx.doi.org/10.1021/la401837y | Langmuir 2013, 29, 10141−10148