Optical protein sensor for detecting cancer markers in saliva.

A surface immobilized optical protein sensor has been utilized to detect Interleukin-8 (IL-8) protein, an oral cancer marker, and can reach limit of detection (LOD) at 1.1 pM in buffer without using enzymatic amplification. Only after applying enzymatic amplification to increase the signal level by a few orders of magnitude, ELISA can reach the LOD of 1 pM level. We then develop the confocal optics based sensor for further reducing the optical noise and can extend the LOD of the surface immobilized optical protein sensor two orders in magnitude. These improvements have allowed us to detect IL-8 protein at 4.0 fM in buffer. In addition, these sensitive LODs were achieved without the use of enzymatic signal amplification, such that the simplified protocol can further facilitate the development of point-of-care devices. The ultra sensitive optical protein sensor presented in this paper has a wide number of applications in disease diagnoses. Measurements for detecting biomarkers in clinical sample are much more challenging than the measurements in buffer, due to high background noise contributed by large collections of non-target molecules. We used clinical saliva samples to validate the functionality of the optical protein sensor. Clinical detection of disease-specific biomarkers in saliva offers a non-invasive, alternative approach to using blood or urine. Currently, the main challenge of using saliva as a diagnostic fluid is its inherently low concentration of biomarkers. We compare the measurements of 40 saliva samples; half from oral cancer patients and half from a control group. The data measured by the optical protein sensor is compared with the traditional Enzyme-Linked Immunosorbant Assay (ELISA) values to validate the accuracy of our system. These positive results enable us to proceed to using confocal optical protein sensor to detect other biomarkers, which have much lower concentrations.

Cell relaxation after electrodeformation: effect of latrunculin A on cytoskeletal actin.

Precise measurement of the mechanical properties of a cell provides useful information about its structural organization and physiological state. It is interesting to understand the effect of individual components on the mechanical properties of the entire cell. In this study, we investigate the influence of the cytoskeletal actin on the viscoelastic properties of a cell. Actin-specific agents, including latrunculin A and jasplakinolide, are used to alter the organization of the cytoskeletal actin. Brassica oleracea protoplasts are treated with the drugs and deformed under an external electric potential. The relaxation processes of single protoplasts after electrodeformation are measured. The data are analyzed by a model-independent spectrum recovery algorithm. Two distinct characteristic time constants are obtained from the relaxation spectra. Treatment with latrunculin A increases both of the relaxation time constants. The longest relaxation times for control, latrunculin A treated, and jasplakinolide treated cells are determined to be 0.28, 1.0, and 0.21 s, respectively.