A micro-chamber free digital bio-detection for multiplexed and ultrasensitive immunoassay based on encoded magnetic microbeads and tyramide signal amplification strategy

Single-Molecule Protein Analysis by Centrifugal Droplet Immuno-PCR with Magnetic Nanoparticles

Detecting proteins in ultralow concentrations in complex media is important for many applications but often relies on complicated techniques. Herein, a single-molecule protein analyzer with the potential for high-throughput applications is reported. Gold-coated magnetic nanoparticles with DNA-labeled antibodies were used for target recognition and separation. The immunocomplex was loaded into microdroplets generated with centrifugation. Immuno-PCR amplification of the DNA enabled the quantification of proteins at the level of single molecules. As an example, ultrasensitive detection of α-synuclein, a biomarker for neurodegenerative diseases, is achieved. The limit of detection was determined to be ∼50 aM in buffer and ∼170 aM in serum. The method exhibited high specificity and could be used to analyze post-translational modifications such as protein phosphorylation. This study will inspire wider studies on single-molecule protein detection, especially in disease diagnostics, biomarker discovery, and drug development.

Corilagin attenuates intestinal ischemia/reperfusion injury in mice by inhibiting ferritinophagy-mediated ferroptosis through disrupting NCOA4-ferritin interaction

AIMS

Intestinal ischemia reperfusion (II/R) is a common clinical emergency. Ferroptosis is reported to play a role in II/R injury. Our previous studies revealed that corilagin significantly attenuates intestinal ischemia/reperfusion injuries. However, the underlying molecular mechanism is unclear and requires further study.

MATERIALS AND METHODS

DAO, GSSG/T-GSH, MDA, and Fe2+ were measured by assay kits, 4-HNE was assessed by IHC, and 15-LOX was measured by ELISA. Mitochondrial damage was observed by TEM and cellular oxidation levels were detected by C11-BODIPY 581/591 and DHE probes. LC3, p62, Beclin1, ACSL4, GPX4, NCOA4, and ferritin expression were examined by WB in vivo and in vitro. IF, co-IF, q-PCR, and constructed NCOA4-knock-down IEC-6 cells were used to evaluate the role of NCOA4 in the effect of corilagin against II/R injury. Temporal and nucleoplasmic variations with or without corilagin were observed by WB. Co-IP and molecular docking were used to investigate the NCOA4-ferritin interaction.

KEY FINDINGS

Corilagin attenuated II/R-induced ferroptosis both in vitro and in vivo. Further study revealed that the anti-ferroptosis bioactivity of corilagin might be due to the modulation of iron homeostasis via inhibition of ferritinophagy in an NCOA4-dependent manner.

SIGNIFICANCE

Corilagin might be a potential therapeutic agent for II/R-induced tissue injury.

Digital-like Enzyme Inhibition Mechanism-Based Strategy for the Digital Sensing of Heparin-Specific Biomarkers

A new microbead (MB)-based digital flow cytometric sensing system is proposed for the sensitive detection of heparin-specific biomarkers, including heparin-binding protein (HBP) and heparinase. This strategy takes advantage of the inherent space-confined enzymatic behavior of T4 polynucleotide kinase phosphatase (T4 PNKP) around a single MB and the heparin's digital-like inhibitory effect on T4 PNKP. By integrating with an on-bead terminal deoxynucleotidyl transferase (TdT)-catalyzed fluorescence signal amplification technology, the concentration of HBP and heparinase can be digitally determined by the number of fluorescence-positive/-negative MBs which can be easily counted by flow cytometry. This is not only the first test to expand the application scenario of T4 PNKP to the digital detection of different biomarkers but also pioneers a new direction for fabricating digital biosensing platforms based on the enzyme inhibition mechanism.