PAS1-modified optical SIS sensor for highly sensitive and specific detection of toluene

Single-Cell Detection of Erwinia amylovora Using Bio-Functionalized SIS Sensor

Herein, we developed a bio-functionalized solution-immersed silicon (SIS) sensor at the single-cell level to identify Erwinia amylovora (E. amylovora), a highly infectious bacterial pathogen responsible for fire blight, which is notorious for its rapid spread and destructive impact on apple and pear orchards. This method allows for ultra-sensitive measurements without pre-amplification or labeling compared to conventional methods. To detect a single cell of E. amylovora, we used Lipopolysaccharide Transporter E (LptE), which is involved in the assembly of lipopolysaccharide (LPS) at the surface of the outer membrane of E. amylovora, as a capture agent. We confirmed that LptE interacts with E. amylovora via LPS through in-house ELISA analysis, then used it to construct the sensor chip by immobilizing the capture molecule on the sensor surface modified with 3'-Aminopropyl triethoxysilane (APTES) and glutaraldehyde (GA). The LptE-based SIS sensor exhibited the sensitive and specific detection of the target bacterial cell in real time. The dose-response curve shows a linearity (R2 > 0.992) with wide dynamic ranges from 1 to 107 cells/mL for the target bacterial pathogen. The sensor showed the value change (dΨ) of approximately 0.008° for growing overlayer thickness induced from a single-cell E. amylovora, while no change in the control bacterial cell (Bacillus subtilis) was observed, or negligible change, if any. Furthermore, the bacterial sensor demonstrated a potential for the continuous detection of E. amylovora through simple surface regeneration, enabling its reusability. Taken together, our system has the potential to be applied in fields where early symptoms are not observed and where single-cell or ultra-sensitive detection is required, such as plant bacterial pathogen detection, foodborne pathogen monitoring and analysis, and pathogenic microbial diagnosis.

Normal-incidence type solution immersed silicon (SIS) biosensor for ultra-sensitive, label-free detection of cardiac troponin I

Early diagnosis of acute myocardial infarction (AMI) significantly reduce the mortality rate and can be achieved via high-sensitive detection of AMI specific cardiac troponin I (cTnI) biomarker. Here, we present normal-incident type solution-immersed silicon (NI-SIS) ellipsometric biosensor, designed for ultra-high sensitive, high-throughput, label-free detection of the target protein. The NI-SIS sensors are equipped with a specially designed prism that maintains the angle of incidence close to the Brewster angle during operation, which significantly reduces SIS noise signals induced by the refractive index fluctuations of the surrounding medium, improves the signal-to-noise ratio, in-results lowers the detection limit. We applied NI-SIS biosensor for ultra-sensitive detection of cTnI biomarkers in human serum. The optimized sensor chip fabrication and detection operation procedures are proposed. The wide linear concentration ranges of fg/mL to ng/mL is achieved with the detection limit of 22.0 fg/mL of cTnI. The analytical correlation was assessed by linear regression analysis with the results of the Pathfast reference system. These impressive biosensing capabilities of NI-SIS technology have huge potentials for accurate detection of target species in different application areas, such as diagnosis, drug discovery, and food contaminations.