Detecting cancer cells with a highly sensitive LbL-based biosensor.

Early diagnosis of cancer is crucial for therapeutic methods to be more effective and to decrease the mortality rate due to this disease. Current diagnostic methods include imaging techniques that require expensive equipment and specialized personnel, making it difficult to apply them to many patients. To overcome these limitations, many biosensors have been developed to monitor cancer biomarkers. Here, we report on the electrochemical biosensor for selective detection of tumor cells using a simple and low-cost methodology. Layer-by-layer (LbL) self-assembly was used to modify indium tin oxide (ITO) electrodes with alternating layers of polyallylamine hydrochloride (PAH) and folic acid (FA), which binds to overexpressed folate receptors alpha (FRα) in tumor cells. The LbL-based biosensor showed high sensitivity in detecting cervical cancer cells (HeLa cells) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linear dependence with the logarithm cell concentration was observed and excellent detection limits were found, 4 cells mL-1 and 19 cells mL-1 for EIS and CV measurements, respectively. The developed biosensor also presented great reproducibility (RSD = 1.7%) and repeatability (RSD = 1.8%). The selectivity was confirmed after the biosensor interaction with healthy cells (HMEC cells), which did not produce significant changes in the electrochemical signals. Furthermore, it was demonstrated that selective detection of tumor cells occurs via an interaction with FA. The LbL-based biosensor provides a simple, accurate, and cost-effective platform to be applied in the early diagnosis of cancer.

Optimized PAH/Folic acid layer-by-layer films as an electrochemical biosensor for the detection of folate receptors.

Folate receptor alpha (FR-α) is a glycoprotein overexpressed in tumor cell surfaces, especially in gynecologic cancers, and can be used as a biomarker for diagnostics. Currently, FRα is quantified by positron emission tomography (PET) or fluorescence imaging techniques. However, these methods are costly and time-consuming. We report on the development of an electrochemical biosensor for FRα detection based on the use of nanostructured layer-by-layer (LbL) films as modified electrodes. Multilayer films were deposited on indium tin oxide (ITO) electrodes by the alternately assembling of positively charged polyallylamine hydrochloride (PAH) and negatively charged folic acid (FA), used as the biorecognition element. UV-vis and FTIR spectroscopies revealed the successful PAH and FA adsorption on ITO. Devices performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The [PAH/FA] films presented a good reproducibility (RSD of 1.12%) and stability when stored in the Tris-HCl solution (RSD 6.7%). The biosensor electrochemical response exhibited a linear relationship with FRα concentration in the range from 10 to 40 nM. The limit of detection reached for CV and EIS measurements were 0.7 and 1.5 nM, respectively. As a proof-of-concept, we show that the devices can differenciate tumor cells from healthy cell, showing an excellent selectivity. The biosensor device based on [PAH/FA] films represents a promising strategy for a simple, rapid, and low-cost cancer diagnosis through FRα quantification on the surface of cancer cells.

Anti-PSMA monoclonal antibody increases the toxicity of paclitaxel carried by carbon nanotubes.

Multiple-wall carbon nanotubes (CNTs) were functionalized with polyethyleneimine in order to incorporate paclitaxel (PTX), the first line chemotherapeutic agent for prostate cancer. These particles were then covered with antibodies for the prostate-specific membrane antigen (PSMA), to address them to prostate cancer cells. LNCaP prostate cancer cells (PSMA+), HCT-116 and CaCo-2 colon cancer cells (PSMA-), as well as human peripheral monocytes and lymphocytes (PSMA-), were in vitro exposed to fluorescent CNT composites. The interaction/adherence of those composites to target cells was analyzed by fluorescence microscopy and flow cytometry, showing a diffuse interaction of CNTs and CNT-PTX with all cell types. Analysis of cytotoxicity revealed that both prostate (PSMA+) and colorectal cancer cells (PSMA-) were more susceptible to PTX complexed with CNTs than to pure PTX or CNTs alone, while the incorporation of anti-PSMA (CNT-PTX-PSMA) improved the toxicity on LNCaP cells but not on PSMA- targets. No toxicity was observed in human monocytes and lymphocytes but composites induced phenotypical changes in monocytes. Our results demonstrate the feasibility of using anti-PSMA antibody to address drug-loaded CNT to cancer cells as a strategy for improving the effectiveness of antineoplastic agents.