Nanopore film based enrichment and quantification of low abundance hepcidin from human bodily fluids

Neuron-Inspired Nanofluidic Biosensors for Highly Sensitive and Selective Imidacloprid Detection

Pesticides have caused concerns about food safety due to their residual effects in vegetables and fruits. Imidacloprid, as the frequently used neonicotinoid pesticide, could harm cardiovascular and respiratory function and cause reproductive toxicity in humans. Therefore, reliable methods for portable, selective, and rapid detection are desirable to develop. Herein, we report a neuron-inspired nanofluidic biosensor based on a tyrosine-modified artificial nanochannel for sensitively detecting imidacloprid. The functional tyrosine is modified on the outer surface of porous anodic aluminum oxide to rapidly capture imidacloprid through π-π interactions and hydrogen bonds. The integrated nanofluidic biosensor has a wide concentration range from 10-8 to 10-4 g/mL with an ultralow detection limit of 6.28 × 10-9 g/mL, which outperforms the state-of-the-art sensors. This work provides a new perspective on detecting imidacloprid residues as well as other hazardous pesticide residues in environmental and food samples.

Antifouling Electrochemical Biosensor Based on the Designed Functional Peptide and the Electrodeposited Conducting Polymer for CTC Analysis in Human Blood

Circulating tumor cells (CTCs) are considered reliable cancer biomarkers for the liquid biopsy of many types of tumors. The direct detection of CTCs in human blood with normal biosensors, however, remains challenging because of severe biofouling in blood that contains various proteins and a large number of cells. Herein, we report the construction of an antifouling electrochemical biosensor capable of assaying CTCs directly in blood, based on a designed multifunctional peptide and the electrodeposited conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). The designed peptide possesses antifouling capability in complex biological media and specific recognition ability to capture breast cancer cells MCF-7. Meanwhile, electrodeposited PEDOT can promote electron transfer at the sensing interface, improve the signal-to-noise ratio for the detection, and thus enhance the sensitivity of the biosensor. The integration of the multifunctional peptide and conducting polymer PEDOT ensures that the developed biosensor is able to perform directly in blood samples without purification or separation. The antifouling electrochemical biosensor for the detection of MCF-7 cells exhibits a wide linear range over 4 orders, with a limit of detection (LOD) of 17 cells mL^-1. More interestingly, even when performing in 25% human blood, the biosensor still retains a linear response with an LOD of 22 cells mL^-1, without suffering significantly from biofouling in real blood. This work provides a promising strategy for the direct analysis of CTCs in human blood without a complicated pretreatment, and it may find practical application in the liquid biopsy of cancers.

Iron disorders and hepcidin

Iron is an essential element due to its role in a wide variety of physiological processes. Iron homeostasis is crucial to prevent iron overload disorders as well as iron deficiency anemia. The liver synthesized peptide hormone hepcidin is a master regulator of systemic iron metabolism. Given its role in overall health, measurement of hepcidin can be used as a predictive marker in disease states. In addition, hepcidin-targeting drugs appear beneficial as therapeutic agents. This review emphasizes recent development on analytical techniques (immunochemical, mass spectrometry and biosensors) and therapeutic approaches (hepcidin agonists, stimulators and antagonists). These insights highlight hepcidin as a potential biomarker as well as an aid in the development of new drugs for iron disorders.

Opportunities and challenges of the tag-assisted protein purification techniques: Applications in the pharmaceutical industry

Tag-assisted protein purification is a method of choice for both academic researches and large-scale industrial demands. Application of the purification tags in the protein production process can help to save time and cost, but the design and application of tagged fusion proteins are challenging. An appropriate tagging strategy must provide sufficient expression yield and high purity for the final protein products while preserving their native structure and function. Thanks to the recent advances in the bioinformatics and emergence of high-throughput techniques (e.g. SEREX), many new tags are introduced to the market. A variety of interfering and non-interfering tags have currently broadened their application scope beyond the traditional use as a simple purification tool. They can take part in many biochemical and analytical features and act as solubility and protein expression enhancers, probe tracker for online visualization, detectors of post-translational modifications, and carrier-driven tags. Given the variability and growing number of the purification tags, here we reviewed the protein- and peptide-structured purification tags used in the affinity, ion-exchange, reverse phase, and immobilized metal ion affinity chromatographies. We highlighted the demand for purification tags in the pharmaceutical industry and discussed the impact of self-cleavable tags, aggregating tags, and nanotechnology on both the column-based and column-free purification techniques.

Circulating levels of hydroxylated bradykinin function as an indicator of tissue HIF-1α expression

The critical roles of oxygen homeostasis in metabolism are indisputable and hypoxic responses are correlated with the pathogenesis of gastrointestinal, pulmonary, renal diseases and cancers. Evaluating tissue hypoxia to predict treatment outcome is challenging, however, due to the lack of rapid, accurate and non-invasive methods. Hypoxia enhances prolyl-4-hydroxylase α1 (P4HA1) expression, which can convert bradykinin (BK) to hydroxyprolyl-BK (Hyp-BK), leading us to hypothesize that circulating Hyp-BK/BK ratios may reflect tissue hypoxia and predict treatment outcomes. Direct quantification of Hyp-BK peptides in serum or plasma by conventional MALDI-TOF MS analysis is technically challenging. In our study, a nanopore-based fractionation and enrichment protocol was utilized to allow the simple workflow for circulating Hyp-BK/BK analysis. Hypoxia is linked to poor prognosis due to its role in promoting pancreatic cancer progression and metastasis. Here we show that P4HA1 expression was increased in pancreatic tumors versus adjacent tissue, associated with poor survival, and corresponded with tumor expression of the hypoxia inducible factor 1α (HIF-1α) and carbonic anhydrase 9 (CA9). Hypoxia-induced P4HA1 expression and BK conversion to Hyp-BK were found to be HIF-1α dependent, pre-treatment serum Hyp-BK/BK ratios corresponded with tissue HIF-1α and P4HA1 expression, and high Hyp-BK/BK levels corresponded with poor response to therapy. These results suggest that pre-treatment circulating Hyp-BK/BK ratios may have value as a non-invasive, surrogate indicator of tissue hypoxia and tumor responses to therapy.

Strategies for Characterization of Low-Abundant Intact or Truncated Low-Molecular-Weight Proteins From Human Plasma

Low-molecular-weight region (LMW, MW≤30kDa) of human serum/plasma proteins, including small intact proteins, truncated fragments of larger proteins, along with some other small components, has been associated with the ongoing physiological and pathological events, and thereby represent a treasure trove of diagnostic molecules. Great progress in the mining of novel biomarkers from this diagnostic treasure trove for disease diagnosis and health monitoring has been achieved based on serum samples from healthy individuals and patients and powerful new approaches in biochemistry and systems biology. However, cumulative evidence indicates that many potential LMW protein biomarkers might still have escaped from detection due to their low abundance, the dynamic complexity of serum/plasma, and the limited efficiency of characterization approaches. Here, we provide an overview of the current state of knowledge with respect to strategies for the characterization of low-abundant LMW proteins (small intact or truncated proteins) from human serum/plasma, involving prefractionation or enrichment methods to reduce dynamic range and mass spectrometry-based characterization of low-abundant LMW proteins.

Correlation of serum hepcidin levels with disease progression in hepatitis B virus-related disease assessed by nanopore film based assay

Chronic hepatitis B virus (HBV) infection often develop into cirrhosis, and both are major risk factors of hepatocellular carcinoma. However, effective approaches for the monitoring of HBV-related disease progress are still in need. Increased iron storage has an important role in HBV-related diseases. Hepcidin is a key regulator of iron homeostasis whose expression changes are often indicative of abnormal iron metabolism. There are few reports of hepcidin levels in patients with HBV infections, and the available results are inconsistent. In this study, using a recently validated nanopore silica film based method, we measured serum hepcidin levels in 46 HBV-related patients and 20 healthy controls. Patients were divided into three groups: chronic hepatitis B without cirrhosis; HBV-related cirrhosis; and HBV-related cirrhosis with hepatocellular carcinoma. Compared to healthy controls, the mean serum hepcidin level was significantly higher in CHB patients without cirrhosis, and in those with hepatocellular carcinoma, but not in those with cirrhosis. Iron-loading, viral infection and liver dysfunction are determined to be the major regulators of hepcidin in these patients. These observations suggest correlations between serum hepcidin and progression of chronic HBV infection, and may shed a new light on the development of biomarkers for HBV-related disease surveillance.

Profiling of Cross-Functional Peptidases Regulated Circulating Peptides in BRCA1 Mutant Breast Cancer

Women with inherited BRCA1 mutations are more likely to develop breast cancer (BC); however, not every carrier will progress to BC. The aim of this study was to identify and characterize circulating peptides that correlate with BC patients carrying BRCA1 mutations. Circulating peptides were enriched using our well-designed nanoporous silica thin films (NanoTraps) and profiled by mass spectrometry to identify among four clinical groups. To determine the corresponding proteolytic processes and their sites of activity, purified candidate peptidases and synthesized substrates were assayed to verify the processes predicted by the MERPOS database. Proteolytic processes were validated using patient serum samples. The peptides, KNG1K438-R457 and C 3fS1304-R1320, were identified as putative peptide candidates to differentiate BRCA1 mutant BC from sporadic BC and cancer-free BRCA1 mutant carriers. Kallikrein-2 (KLK2) is the major peptidase that cleaves KNG1K438-R457 from kininogen-1, and its expressions and activities were also found to be dependent on BRCA1 status. We further determined that KNG1K438-R457 is cleaved at its C-terminal arginine by carboxypeptidase N1 (CPN1). Increased KLK2 activity, with decreased CPN1 activity, results in the accumulation of KNG1K438-R457 in BRCA1-associated BC. Our work outlined a useful strategy for determining the peptide-petidase relationship and thus establishing a biological mechanism for changes in the peptidome in BRCA1-associated BC.

Biomarker Characterization by MALDI-TOF/MS

Mass spectrometric techniques frequently used in clinical diagnosis, such as gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, ambient ionization mass spectrometry, and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF/MS), are discussed. Due to its ability to rapidly detect large biomolecules in trace amounts, MALDI-TOF/MS is an ideal tool for characterizing disease biomarkers in biologic samples. Clinical applications of MS for the identification and characterization of microorganisms, DNA fragments, tissues, and biofluids are introduced. Approaches for using MALDI-TOF/MS to detect various disease biomarkers including peptides, proteins, and lipids in biological fluids are further discussed. Finally, various sample pretreatment methods which improve the detection efficiency of disease biomarkers are introduced.

Hepcidin levels in hyperprolactinemic women monitored by nanopore thin film based assay: correlation with pregnancy-associated hormone prolactin

Hepcidin is a central regulator in human iron metabolism. Although it is often regarded as a promising indicator of iron status, the lack of effective quantification method has impeded the comprehensive assessment of its physiological and clinical significance. Herein we applied a newly established, nanopore film enrichment based hepcidin assay to examine the correlation between hepcidin and prolactin, the hormone with an important role during pregnancy and lactation. Women with pathologically elevated prolactin secretion (hyperprolactinemia) were found to have lower serum hepcidin compared to those with normal prolactin levels, without showing significant difference in other hepcidin-regulating factors. Moreover, prolactin-reducing drug bromocriptine mesylate resulted in elevated expression of the hepcidin in hyperprolactinemia patients. These findings suggest a possible role of prolactin in regulation of hepcidin, and may render hepcidin a useful biomarker for progress monitoring and treatment of iron-related diseases under hyperprolactinemic conditions.

FROM THE CLINICAL EDITOR

The level of hepcidin has been shown to reflect the underlying iron status of the patient. Nonentheless, there is an urgent need of reliable, fast and easy-to-do hepcidin assay in the clinical setting. In this paper, the authors described a further modification of their previously described nanopore silica film-based enrichment approach for quantification of hepcidin and found correlation between hepcidin and prolactin. This new knowledge may add to current understanding of iron homeostasis during pregnancy.