ABSTRACT
Photonic biosensors that use optical resonances to amplify signals from refractive index changes offer high sensitivity, real-time readout, and scalable, low-cost fabrication. However, when used with classic affinity assays, they struggle with noise from nonspecific binding and are limited by the low refractive index and small size of target biological molecules. In this Letter, we evaluate the performance of an integrated microring photonic biosensor using the high contrast cleavage detection (HCCD) mechanism, which we recently introduced. The HCCD sensors make use of dramatic optical signal amplification caused by the cleavage of large numbers of high-contrast nanoparticle reporters instead of the adsorption of labeled or unlabeled low-index biological molecules. We evaluate the advantages of the HCCD detection mechanism over conventional target-capture detection techniques with the same label and the same sensor platform, using an example of a silicon ring resonator as an optical transducer decorated with silicon nanoparticles as high-contrast reporters. In the practical realization of this detection scheme, detection specificity and signal amplification can be achieved via collateral nucleic acid cleavage caused by enzymes such as CRISPR Cas12a and Cas13 after binding to a target DNA/RNA sequence in solution.
Subject(s)
Biosensing Techniques , SiliconABSTRACT
Microplastics (MPs) have been found in aqueous environments ranging from rural ponds and lakes to the deep ocean. Despite the ubiquity of MPs, our ability to characterize MPs in the environment is limited by the lack of technologies for rapidly and accurately identifying and quantifying MPs. Although standards exist for MP sample collection and preparation, methods of MP analysis vary considerably and produce data with a broad range of data content and quality. The need for extensive analysis-specific sample preparation in current technology approaches has hindered the emergence of a single technique which can operate on aqueous samples in the field, rather than on dried laboratory preparations. In this perspective, we consider MP measurement technologies with a focus on both their eventual field-deployability and their respective data products (e.g., MP particle count, size, and/or polymer type). We present preliminary demonstrations of several prospective MP measurement techniques, with an eye towards developing a solution or solutions that can transition from the laboratory to the field. Specifically, experimental results are presented from multiple prototype systems that measure various physical properties of MPs: pyrolysis-differential mobility spectroscopy, short-wave infrared imaging, aqueous Nile Red labeling and counting, acoustophoresis, ultrasound, impedance spectroscopy, and dielectrophoresis.
ABSTRACT
INTRODUCTION: This study provides evidence of validity of the School-age Assessment of Attachment (SAA) through longitudinal comparison with the Preschool Assessment of Attachment (PAA) and with concurrent attachment assessments and measures of risk and parenting. Determining which assessment had the greatest validity with this moderate-risk sample would be of benefit to those working with troubled young people and their families. HYPOTHESES: Children's SAA classifications were expected to correspond to their PAA, a behavioral attachment assessment, parenting, and risk. An attachment questionnaire was predicted to not accurately indicate children's risk status. DESIGN: The design was an 8-year longitudinal follow-up of rural Appalachian American preschoolers. METHOD: The participants were 21 children and their caregivers. The PAA was completed at age 4. The SAA, a self-report questionnaire, and a parent-child conflict resolution task were completed at age 12. Parents completed assessments of depression, trauma, stress, and perceptions of helplessness. RESULTS: The PAA was related to the SAA and the dyadic behavioral task. The SAA was consistently associated with measures of parenting and family risk. The attachment questionnaire performed poorly for children with higher risk status, suggesting more (not less) sensitive and responsive parenting.
