Label-free, single molecule detection of cytokines using optical microcavities

Interleukin-2 (IL2) is a cytokine that regulates T-cell growth and is used in cancer therapies. By sensitizing a microcavity sensor surface with anti-IL2 and monitoring the resonant frequency, single molecules of IL2 can be detected

Label-free detection of cytokines using optical microcavities

Ultra-high-Q microresonators have demonstrated sensitive and specific chemical and biological detection. The sensitivity is derived from the long photon lifetime inside the cavity and specificity is achieved through surface functionalization. Here, ultra-high-Q microcavities demonstrate label-free, single molecule detection of Interleukin-2 (IL-2) in fetal bovine serum (FBS). IL-2 is a cytokine released in response to immune system activation. The surface of the microtoroids was sensitized using anti-IL-2. The detection mechanism relies upon a thermo-optic mechanism to enhance resonant wavelength shifts induced through binding of a molecule

Characterization of high-Q optical microcavities using confocal microscopy

Confocal microscopy was initially developed to image complex circuits and material defects. Previous imaging studies yielded only qualitative data about the location and number of defects. In the present study, this noninvasive method is used to obtain quantitative information about the Q factor of an optical resonant cavity. Because the intensity of the fluorescent signal measures the number of defects in the resonant cavity, this signal is a measure of the number of surface scattering defects, one of the dominant loss mechanisms in optical microcavities. The Q of the cavities was also determined using conventional linewidth measurements. Based upon a quantitative comparative analysis of these two techniques, it is shown that the Q can be determined without a linewidth measurement, allowing for a noninvasive characterization technique

Label-free single-molecule all-optical sensor

Recently, quality factors greater than 100 million were demonstrated using planar arrays of silica microtoroid resonators. These high Q factors allow the toroidal resonators to perform very sensitive detection experiments. By functionalizing the silica surface of the toroid with biotin, the toroidal resonators become both specific and sensitive detectors for Streptavidin. One application of this sensor is performing detection in lysates. To mimic this type of environment, additional solutions of Streptavidin were prepared which also contained high concentrations (nM and μM) of tryptophan

BioMeT and algorithm challenges: A proposed digital standardized evaluation framework

Technology is advancing at an extraordinary rate. Continuous flows of novel data are being generated with the potential to revolutionize how we better identify, treat, manage, and prevent disease across therapeutic areas. However, lack of security of confidence in digital health technologies is hampering adoption, particularly for biometric monitoring technologies (BioMeTs) where frontline healthcare professionals are struggling to determine which BioMeTs are fit-for-purpose and in which context. Here, we discuss the challenges to adoption and offer pragmatic guidance regarding BioMeTs, cumulating in a proposed framework to advance their development and deployment in healthcare, health research, and health promotion. Furthermore, the framework proposes a process to establish an audit trail of BioMeTs (hardware and algorithms), to instill trust amongst multidisciplinary users

Click chemistry surface functionalization for resonant micro-cavity sensors

Micro-cavity resonant sensors have outer surfaces that are functionalized using click chemistry, e.g., involving a cycloaddition reaction of an alkyne functional group and an azide functional group. A first polymer linking element binds to an outer surface of the micro-cavity and has an azide functional group, which bonds to an alkyne functional group of a second polymer linking element as a result of a cycloaddition reaction. A functionalization element such as an antibody, antigen or protein for sensing a target molecule is bound to the second linking element

Label-Free, Single-Molecule Detection with Optical Microcavities

Current single-molecule detection techniques require labeling the target molecule. We report a highly specific and sensitive optical sensor based on an ultrahigh quality (Q) factor (Q > 10^8) whispering-gallery microcavity. The silica surface is functionalized to bind the target molecule; binding is detected by a resonant wavelength shift. Single-molecule detection is confirmed by observation of single-molecule binding events that shift the resonant frequency, as well as by the statistics for these shifts over many binding events. These shifts result from a thermo-optic mechanism. Additionally, label-free, single-molecule detection of interleukin-2 was demonstrated in serum. These experiments demonstrate a dynamic range of 10^(12) in concentration, establishing the microcavity as a sensitive and versatile detector

Large amplitude variability from the persistent ultracompact X-ray binary in NGC 1851

Using archival RXTE data, we show that the ultracompact X-ray binary in NGC 1851 exhibits large amplitude X-ray flux varations of more than a factor of 10 on timescales of days to weeks and undergoes sustained periods of months where the time-averaged luminosty varies by factors of two. Variations of this magnitude and timescale have not been reported previously in other ultracompact X-ray binaries. Mass transfer in ultracompact binaries is thought to be driven by gravitational radiation and the predicted transfer rates are so high that the disks of ultracompact binaries with orbits as short as that of this object should not be susceptible to ionization instabilities. Therefore the variability characteristics we observe were unexpected, and need to be understood. We briefly discuss a few alternatives for producing the observed variations in light of the fact that the viscous timescale of the disk is of order a week, comparable to the shorter time scale variation that is observed but much less than the longer term variation. We also discuss the implications for interpretation of observations of extragalactic binaries if the type of variability seen in the source in NGC 1851 is typical.Comment: 7 pages, 5 figures, accepted for publication in MNRA