An enzymatic immunoassay microfluidics integrated with membrane valves for microsphere retention and reagent mixing

The present study presents a new microfluidic device integrated with pneumatic microvalves and a membrane mixer for enzyme-based immunoassay of acute myocardial infarction (AMI) biomarkers, namely, myoglobin, and heart-type fatty acid binding protein (H-FABP). Superparamagnetic microspheres with carboxyl groups on their surfaces were used as antibody solid carriers. A membrane mixer consisting of four ψ-type membrane valves was assembled under the reaction chamber for on-chip performing microsphere trapping and reagent mixing. The entire immunoassay process, including microsphere capture, reagent input, mixing, and subsequent reaction, was accomplished on the device either automatically or manually. The post-reaction substrate resultant was analyzed using a microplate reader. The results show that the average absorbance value is correlated with the concentration of cardiac markers, in agreement with the results obtained using a conventional microsphere-based immunoassay; this indicated that the proposed on-chip immunoassay protocol could be used to detect both myoglobin and H-FABP. The minimum detectable concentration is 5 ng/mL for myoglobin and 1 ng/mL for H-FABP.     

Electrochemical detection of HbA1c, a marker [correction of maker] for diabetes, using a flow immunoassay system

An on-chip electrochemical flow immunoassay system for the detection of hemoglobin A1c (HbA1c) was developed using anti-human hemoglobin (Hb) IgG labeled with ferrocene monocarboxylic acid (Fc-COOH) and boronate-affinity chromatography. An on-chip column packed with boronate-activated agarose beads was used for the separation of HbA1c from both non-glycated Hb and free antibody. Anti-human Hb IgG conjugated to Fc-COOH (Fc-IgG) was used for the electrochemical detection of HbA1c. The assay procedure included immunoreactions with Fc-IgG and HbA1c, separation of immunocomplexes by boronate affinity, and electrochemical detection of Fc-IgG-HbA1c immunocomplexes. The immunoreaction mixtures were injected onto a boronate-affinity column. HbA1c-antibody complexes were then trapped onto the column by the affinity of HbA1c to boronic acid. Subsequently, elution buffer containing sorbitol was applied to elute HbA1c-antibody complexes and a current was detected by applying 600 mV versus Ag/AgCl. The elution signal was an estimation of the HbA1c amount. A linear correlation between the increase of current and HbA1c concentration was obtained up to an HbA1c concentration of 500 microg/ml. The HbA1c flow immunoassay was successfully achieved using hemolysates. This electrochemical flow immunoassay system enabled us to construct a novel point-of-care testing device for the monitoring of glycated proteins including HbA1c.     

Targeted mass spectrometric approach for biomarker discovery and validation with nonglycosylated tryptic peptides from N-linked glycoproteins in human plasma

A simple mass spectrometric approach for the discovery and validation of biomarkers in human plasma was developed by targeting nonglycosylated tryptic peptides adjacent to glycosylation sites in an N-linked glycoprotein, one of the most important biomarkers for early detection, prognoses, and disease therapies. The discovery and validation of novel biomarkers requires complex sample pretreatment steps, such as depletion of highly abundant proteins, enrichment of desired proteins, or the development of new antibodies. The current study exploited the steric hindrance of glycan units in N-linked glycoproteins, which significantly affects the efficiency of proteolytic digestion if an enzymatically active amino acid is adjacent to the N-linked glycosylation site. Proteolytic digestion then results in quantitatively different peptide products in accordance with the degree of glycosylation. The effect of glycan steric hindrance on tryptic digestion was first demonstrated using alpha-1-acid glycoprotein (AGP) as a model compound versus deglycosylated alpha-1-acid glycoprotein. Second, nonglycosylated tryptic peptide biomarkers, which generally show much higher sensitivity in mass spectrometric analyses than their glycosylated counterparts, were quantified in human hepatocellular carcinoma plasma using a label-free method with no need for N-linked glycoprotein enrichment. Finally, the method was validated using a multiple reaction monitoring analysis, demonstrating that the newly discovered nonglycosylated tryptic peptide targets were present at different levels in normal and hepatocellular carcinoma plasmas. The area under the receiver operating characteristic curve generated through analyses of nonglycosylated tryptic peptide from vitronectin precursor protein was 0.978, the highest observed in a group of patients with hepatocellular carcinoma. This work provides a targeted means of discovering and validating nonglycosylated tryptic peptides as biomarkers in human plasma, without the need for complex enrichment processes or expensive antibody preparations.     

Silica nanoparticles for the layer-by-layer assembly of fully electro-active cytochrome c multilayers

Background

Gold nanoparticles (AuNPs) scatter light intensely at or near their surface plasmon wavelength region. Using AuNPs coupled with dynamic light scattering (DLS) detection, we developed a facile nanoparticle immunoassay for serum protein biomarker detection and analysis. A serum sample was first mixed with a citrate-protected AuNP solution. Proteins from the serum were adsorbed to the AuNPs to form a protein corona on the nanoparticle surface. An antibody solution was then added to the assay solution to analyze the target proteins of interest that are present in the protein corona. The protein corona formation and the subsequent binding of antibody to the target proteins in the protein corona were detected by DLS.

Results

Using this simple assay, we discovered multiple molecular aberrations associated with prostate cancer from both mice and human blood serum samples. From the mice serum study, we observed difference in the size of the protein corona and mouse IgG level between different mice groups (i.e., mice with aggressive or less aggressive prostate cancer, and normal healthy controls). Furthermore, it was found from both the mice model and the human serum sample study that the level of vascular endothelial growth factor (VEGF, a protein that is associated with tumor angiogenesis) adsorbed to the AuNPs is decreased in cancer samples compared to non-cancerous or less malignant cancer samples.

Conclusion

The molecular aberrations observed from this study may become new biomarkers for prostate cancer detection. The nanoparticle immunoassay reported here can be used as a convenient and general tool to screen and analyze serum proteins and to discover new biomarkers associated with cancer and other human diseases.     

Multiplexed MRM‐based quantitation of candidate cancer biomarker proteins in undepleted and non‐enriched human plasma

An emerging approach for multiplexed targeted proteomics involves bottom‐up LC‐MRM‐MS, with stable isotope‐labeled internal standard peptides, to accurately quantitate panels of putative disease biomarkers in biofluids. In this paper, we used this approach to quantitate 27 candidate cancer‐biomarker proteins in human plasma that had not been treated by immunoaffinity depletion or enrichment techniques. These proteins have been reported as biomarkers for a variety of human cancers, from laryngeal to ovarian, with breast cancer having the highest correlation. We implemented measures to minimize the analytical variability, improve the quantitative accuracy, and increase the feasibility and applicability of this MRM‐based method. We have demonstrated excellent retention time reproducibility (median interday CV: 0.08%) and signal stability (median interday CV: 4.5% for the analytical platform and 6.1% for the bottom‐up workflow) for the 27 biomarker proteins (represented by 57 interference‐free peptides). The linear dynamic range for the MRM assays spanned four orders‐of‐magnitude, with 25 assays covering a 10³–10⁴ range in protein concentration. The lowest abundance quantifiable protein in our biomarker panel was insulin‐like growth factor 1 (calculated concentration: 127 ng/mL). Overall, the analytical performance of this assay demonstrates high robustness and sensitivity, and provides the necessary throughput and multiplexing capabilities required to verify and validate cancer‐associated protein biomarker panels in human plasma, prior to clinical use.     

Quantification of Cardiovascular Biomarkers in Patient Plasma by Targeted Mass Spectrometry and Stable Isotope Dilution

Verification of candidate biomarkers requires specific assays to selectively detect and quantify target proteins in accessible biofluids. The primary objective of verification is to screen potential biomarkers to ensure that only the highest quality candidates from the discovery phase are taken forward into preclinical validation. Because antibody reagents for a clinical grade immunoassay often exist for a small number of candidates, alternative methodologies are required to credential new and unproven candidates in a statistically viable number of serum or plasma samples. Using multiple reaction monitoring coupled with stable isotope dilution MS, we developed quantitative, multiplexed assays in plasma for six proteins of clinical relevance to cardiac injury. The process described does not require antibodies for immunoaffinity enrichment of either proteins or peptides. Limits of detection and quantitation for each signature peptide used as surrogates for the target proteins were determined by the method of standard addition using synthetic peptides and plasma from a healthy donor. Limits of quantitation ranged from 2 to 15 ng/ml for most of the target proteins. Quantitative measurements were obtained for one to two signature peptides derived from each target protein, including low abundance protein markers of cardiac injury in the nanogram/milliliter range such as the cardiac troponins. Intra- and interassay coefficients of variation were predominantly <10 and 25%, respectively. The configured multiplex assay was then used to measure levels of these proteins across three time points in six patients undergoing alcohol septal ablation for hypertrophic obstructive cardiomyopathy. These results are the first demonstration of a multiplexed, MS-based assay for detection and quantification of changes in concentration of proteins associated with cardiac injury in the low nanogram/milliliter range. Our results also demonstrate that these assays retain the necessary precision, reproducibility, and sensitivity to be applied to novel and uncharacterized candidate biomarkers for verification of proteins in blood.Discovery of disease-specific biomarkers with diagnostic and prognostic utility has become an important challenge in clinical proteomics. In general, unbiased discovery experiments often result in the confident identification of thousands of proteins, hundreds of which may vary significantly between case and control samples in small discovery studies. However, because of the stochastic sampling of proteomes in discovery “omics” experiments, a large fraction of the protein biomarkers “discovered” in these experiments are false positives arising from biological or technical variability. Clearly discovery omics experiments do not lead to biomarkers of immediate clinical utility but rather produce candidates that must be qualified and verified in larger sample sets than were used for discovery (1).Traditional, clinical validation of biomarkers has relied primarily on immunoassays because of their specificity and sensitivity for the target analyte and high throughput capability. However, antibody reagents for a clinical grade immunoassay often only exist for a short list of candidates. The development of a reliable sandwich immunoassay for one target protein is expensive, has a long development time, and is dependent upon the generation of high quality protein antibodies. For the large majority of new, unproven candidate biomarkers, an intermediate verification technology is required that has shorter assay development time lines, lower assay cost, and effective multiplexing of dozens of candidates in low sample volumes. Ideally the approach should be capable of analyzing hundreds of samples of serum or plasma with good precision. The desired outcome of verification is a small number of highly credentialed candidates suitable for traditional preclinical and clinical validation studies.Multiple reaction monitoring (MRM)¹ coupled with stable isotope dilution (SID) MS has recently been shown to be well suited for direct quantification of proteins in plasma (2–4) and has emerged as the core technology for candidate biomarker verification. MRM assays can be highly multiplexed such that a moderate number of candidate proteins (in the range of 10–50) can be simultaneously targeted and measured in the statistically viable number of patient samples required for verification (hundreds of serum samples). However, sensitivity for unambiguous detection and quantification of proteins by MS-based assays is often constrained by sample complexity, particularly when the measurements are being made in complex fluids such as plasma.Many biomarkers of current clinical importance, such as prostate-specific antigen and the cardiac troponins, reside in the low nanogram/milliliter range in plasma and, until recently, have been inaccessible by non-antibody approaches. Our laboratory has recently shown for the first time that a combination of abundant protein depletion with limited fractionation at the peptide level prior to SID-MRM-MS provides robust limits of quantitation (LOQs) in the 1–20 ng/ml range with coefficient of variation (CV) of 10–20% at the LOQ for proteins in plasma (3).Here we demonstrate that this work flow can be extended to configure assays for a number of known markers of cardiovascular disease and, more importantly, can be deployed to measure their concentrations in clinical samples. We modeled a verification study comprising six patients undergoing alcohol septal ablation treatment for hypertrophic obstructive cardiomyopathy, a human model of “planned” myocardial infarction (PMI), and obtained targeted, quantitative measurements for moderate to low concentrations of cardiac biomarkers in plasma. This work provides additional evidence that MS-based assays can be configured and applied to verification of new protein targets for which high quality antibody reagents are not available.     

Nanostructured optical microchips for cancer biomarker detection

Herein we report the label-free detection of a cancer biomarker using newly developed arrayed nanostructured Fabry-Perot interferometer (FPI) microchips. Specifically, the prostate cancer biomarker free prostate-specific antigen (f-PSA) has been detected with a mouse anti-human PSA monoclonal antibody (mAb) as the receptor. Experiments found that the limit-of-detection of current nanostructured FPI microchip for f-PSA is about 10pg/mL and the upper detection range for f-PSA can be dynamically changed by varying the amount of the PSA mAb immobilized on the sensing surface. The control experiments have also demonstrated that the immunoassay protocol used in the experiments shows excellent specificity and selectivity, suggesting the great potential to detect the cancer biomarkers at trace levels in complex biofluids. In addition, given its nature of low cost, simple-to-operation and batch fabrication capability, the arrayed nanostructured FPI microchip-based platform could provide an ideal technical tool for point-of-care diagnostics application and anticancer drug screen and discovery.     

Utilizing human blood plasma for proteomic biomarker discovery

Candidate proteomic biomarker discovery from human plasma holds both incredible clinical potential as well as significant challenges. The dynamic range of proteins within plasma is known to exceed 10(10), and many potential biomarkers are likely present at lower protein abundances. At present, proteomic based MS analyses provide a dynamic range typically not exceeding approximately 10(3) in a single spectrum, and approximately 10(4)-10(6) when combined with on-line separations (e.g., reversed-phase gradient liquid chromatography), and thus are generally insufficient for low level biomarker detection directly from human plasma. This limitation is providing an impetus for the development of experimental methodologies and strategies to increase the possible number of detections within this biofluid. Discussed is the diversity of available approaches currently used by our laboratory and others to utilize human plasma as a viable medium for biomarker discovery. Various separation, depletion, enrichment, and quantitative efforts as well as recent improvements in MS capabilities have resulted in measurable improvements in the detection and identification of lower abundance proteins (by approximately 10-10(2)). Despite these improvements, further advances are needed to provide a basis for discovery of candidate biomarkers at very low levels. Continued development of depletion and enrichment techniques, coupled with improved pre-MS separations (both at the protein and peptide level) holds promise in extending the dynamic range of proteomic analysis.     

Micropreparative fractionation of the complexome by blue native continuous elution electrophoresis

The large‐scale analysis of protein complexes is an emerging challenge in the field of proteomics. Currently, there are few methods available for the fractionation of protein complexes that are compatible with downstream proteomic techniques. Here, we describe the technique of blue native continuous elution electrophoresis (BN‐CEE). It combines the features of blue native PAGE (BN‐PAGE) and continuous elution electrophoresis (CEE), generating liquid‐phase fractions of protein complexes of up to 800 kDa. The resulting complexes can be further analysed by BN‐PAGE, by SDS‐PAGE and/or by MS. This can help define the constituent proteins of many complexes and their stoichiometry. As BN‐CEE is also micropreparative, with a capacity to separate milligram quantities of protein complexes, it will assist the study of proteins of lower abundance. In this regard, the acrylamide concentration and elution rate during separation can be controlled to help ‘zoom in’ on particular high mass regions and thus complexes of interest. We illustrate the utility of the technique in the analysis of Saccharomyces cerevisiae cellular lysate.     

Functional proteomics of circadian expressed proteins from Chlamydomonas reinhardtii

In this study, functional proteomics was successfully applied for the characterization of circadian expressed, basic proteins. For this purpose, we have chosen the green model alga Chlamydomonas reinhardtii since its entire nuclear genome is available and it is ideally suited for biochemical enrichment procedures. Proteins from cells harvested during subjective day and night were heparin affinity purified. They were separated by two-dimensional gel electrophoresis suited for basic proteins and analyzed after tryptic digestion by electrospray ionization mass spectrometry. We can show for the first time that the expressions of a protein disulfide isomerase-like protein and a tetratricopeptide repeat protein change in a circadian manner. Interestingly, both proteins are known to be interaction partners in multiprotein complexes including RNA binding proteins.     

Miniaturized amperometric flow immunoassay system using a glass fiber membrane modified with anion

This paper describes a miniaturized amperometric flow immunoassay system using a glass fiber membrane modified with anion. The glass fiber membrane was functionally modified with gamma-glycidoxypropyltrimethoxysilane and sodium thiosulfate and was used for separation of protein. Anti-human chorionic gonadotrophin (HCG) immunoglobulin G (IgG) antibody conjugated with ferrocenemonocarboxylic acid (Fc), namely, Fc-conjugated IgG (Fc-IgG), was used as a novel analytical reagent. HCG and Fc-IgG complexes were separated from free Fc-IgG based on differences in isoelectric point (pI) using the glass fiber membrane modified with a thiosulfonyl acid functional group. The assay yields a linear relationship between current and HCG concentration in the range of 0-2000 mIU/mL. This simple technique enables the assay of HCG within 2 min. The modified glass fiber membrane was regenerated by occasional elution with malonate buffer (pH 6.0) containing 0.5 M NaCl, to remove free Fc-IgG. Free Fc-IgG recovered in this manner could be reused up to eight times without significant decreases in sensitivity. This miniaturized amperometric flow immunoassay requires only minute quantities of serum and generates highly reproducible results.     

A novel binding assay for detection of 14-3-3 protein in cerebrospinal fluid from Creutzfeldt-Jakob patients.

Here we describe a simple and fast microplate assay for 14-3-3 protein, which is based on the binding of 14-3-3 protein to a chemically synthesized peptide containing the phosphorylated recognition sequence of this protein. The peptide is covalently bound to maleimide-activated microplates through reaction of the sulfhydryl group of a N-terminal cysteine residue linked to the peptide. The peptide- 14-3-.3 complexes formed are detected using--as a second recognition principle--an anti-14-3-3 protein antibody. This assay was used for measurement of 14-3-3 protein in brain (bovine) and in cerebrospinal fluid from patients with Creutzfeldt-Jakob disease (CJD) and control cases with diseases other than CJD. This novel assay allowed also the detection of low 14-3-3 protein levels present in cerebrospinal fluid, without further concentration, in contrast to conventional immunoblotting or immunoassay procedures.     

Antibody array analysis with label-based detection and resolution of protein size

Elements from DNA microarray analysis, such as sample labeling and micro-spotting of capture reagents, have been successfully adapted to multiplex measurements of soluble cytokines. Application in cell biology is hampered by the lack of mono-specific antibodies and the fact that many proteins occur in complexes. Here, we incorporated a principle from Western blotting and resolved protein size as an additional parameter. Proteins from different cellular compartments were labeled and separated by size exclusion chromatography into 20 fractions. All were analyzed with replicate antibody arrays. The elution profiles of all antibody targets were compiled to color maps that resemble Western blots with bands of antibody reactivity across the size separation range (670-10 kDa). A new solid phase designed for processing in microwell plates was developed to handle the large number of samples. Antibodies were bound to protein G-coupled microspheres surface-labeled with 300 combinations of four fluorescent dyes. Fluorescence from particle color codes and the protein label were measured by high-speed flow cytometry. Cytoplasmic protein kinases were detected as bands near predictable elution points. For proteins with atypical elution characteristics or multiple contexts, two or more antibodies were used as internal references of specificity. Membrane proteins eluted near the void volume, and additional bands corresponding to intracellular forms were detected for several targets. Elution profiles of cyclin-dependent kinases (cdks), cyclins, and cyclin-dependent kinase inhibitors, were compatible with their occurrence in complexes that vary with the cell cycle phase and subcellular localization. A two-dimensional platform circumvents the need for mono-specific capture antibodies and extends the utility of antibody array analysis to studies of protein complexes.     

Construction of electrochemical flow immunoassay system using capillary columns and ferrocene conjugated immunoglobulin G for detection of human chorionic gonadotrophin

In this paper is reported a miniaturized flow immunoassay system. Ferrocenecarboxylic acid (Fc) conjugated with anti-HCG immunoglobulin G (IgG) antibody (Fc–IgG) was prepared, and used as a novel analytical reagent. The system consists of the immunoreaction section, the capillary column packed with cation exchange resin, and the flow cell for electrochemical detection of Fc–IgG. Antibody–antigen complexes were separated from their free conjugate on the basis of differences in isoelectric point (pI) using a cation exchange capillary column. The assay yielded a linear relationship between signal and HCG concentration in the range 0–2000 mIU/ml. This simple technique enables the assay of HCG within 2 min. The cation exchange capillary column was regenerated by occasional elution with malonate buffer (pH 6.0) containing 0.5 M NaCl, to remove free conjugate. Free conjugate recovered in this manner could be reused up to eight times without significant decreases in the sensitivity of the immunoassay. This electrochemical flow immunoassay requires only minute quantities of serum and generates highly reproducible results.     

Autoantibody biomarker opens a new gateway for cancer diagnosis

The list of cancer markers of current interest has grown considerably, but none of the markers used in clinical work is a true tumor marker. These cancer biomarkers are based on the determination of tumor antigens. Here, we report a single method of autoantibody enzyme immunoassay (EIA) screens for a spectrum of serum tumor markers. A comparison of the autoantibody-based EIA to conventional antigen EIA kits, using receiver operating characteristic (ROC) plots, showed that the autoantibody EIA can significantly enhance the sensitivity and specificity of tumor markers. The detection of serum autoantibodies for a spectrum of serum tumor markers, as demonstrated here, suggests that most, if not all, serum cancer biomarkers produce autoantibodies. A unique autoantibody biomarker screening method, as presented here, might therefore facilitate achieving the accurate and early diagnosis of cancer.     

Weak protein–protein interactions revealed by immiscible filtration assisted by surface tension

Biological mechanisms are often mediated by transient interactions between multiple proteins. The isolation of intact protein complexes is essential to understanding biochemical processes and an important prerequisite for identifying new drug targets and biomarkers. However, low-affinity interactions are often difficult to detect. Here, we use a newly described method called immiscible filtration assisted by surface tension (IFAST) to isolate proteins under defined binding conditions. This method, which gives a near-instantaneous isolation, enables significantly higher recovery of transient complexes compared to current wash-based protocols, which require reequilibration at each of several wash steps, resulting in protein loss. The method moves proteins, or protein complexes, captured on a solid phase through one or more immiscible-phase barriers that efficiently exclude the passage of nonspecific material in a single operation. We use a previously described polyol-responsive monoclonal antibody to investigate the potential of this new method to study protein binding. In addition, difficult-to-isolate complexes involving the biologically and clinically important Wnt signaling pathway were isolated. We anticipate that this simple, rapid method to isolate intact, transient complexes will enable the discoveries of new signaling pathways, biomarkers, and drug targets.     

Protein biomarker validation via proximity ligation assays

The ability to detect minute amounts of specific proteins or protein modifications in blood as biomarkers for a plethora of human pathological conditions holds great promise for future medicine. Despite a large number of plausible candidate protein biomarkers published annually, the translation to clinical use is impeded by factors such as the required size of the initial studies, and limitations of the technologies used. The proximity ligation assay (PLA) is a versatile molecular tool that has the potential to address some obstacles, both in validation of biomarkers previously discovered using other techniques, and for future routine clinical diagnostic needs. The enhanced specificity of PLA extends the opportunities for large-scale, high-performance analyses of proteins. Besides advantages in the form of minimal sample consumption and an extended dynamic range, the PLA technique allows flexible assay reconfiguration. The technology can be adapted for detecting protein complexes, proximity between proteins in extracellular vesicles or in circulating tumor cells, and to address multiple post-translational modifications in the same protein molecule. We discuss herein requirements for biomarker validation, and how PLA may play an increasing role in this regard. We describe some recent developments of the technology, including proximity extension assays, the use of recombinant affinity reagents suitable for use in proximity assays, and the potential for single cell proteomics. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.     

Sensitive detection of cardiac biomarker using ZnS nanoparticles as novel signal transducers

C-reactive protein (CRP), a 115 kDa pentameric protein, is one of the important cardiac biomarkers that are indicative of coronary heart events. Sensitive detection of CRP in human serum is critical for the diagnosis of coronary heart disease. This work presents a sensitive sandwich immunoassay for the detection of CRP in human serum using zinc sulfide (ZnS) nanoparticles as novel fluorescence signal transducers. In this assay, monoclonal anti-CRP antibodies are used to capture CRP in human serum, and then the captured CRPs are incubated with biotinylated monoclonal anti-CRP and Neutravidin coated ZnS nanoparticle to form sandwich immunocomplexes. Quantification of CRP occurs when zinc ions released from ZnS nanoparticle labels are mixed with zinc-ion sensitive fluorescence indicator Fluozin-3 for fluorescence generation. The developed assay presents a detection limit around 10 pM and a detection range with more than two orders of magnitude.     

Extraction of equine chorionic gonadotrophin from pregnant mare plasma by direct adsorption on chromatographic media

Equine chorionic gonadotrophin (eCG) is a hormone of practical value in veterinary medicine and animal production. Here we report a novel preparation procedure based on its direct adsorption onto anionic-exchange resins in a batch-wise mode. The active plasma is previously conditioned to reduce pH and ionic strength to required levels. After the adsorption stage, a 90% recovery of the initial eCG is achieved, with a concentration factor of about 50 and an enrichment factor around 500, with high preservation of biological activity. Further purification is carried out by cation-exchange column chromatography. The recovery for the whole process is higher than 70%, and the final potency of the preparation is close to 4000 IU/mg. The process is well suited for its application to the industrial scale.     

Human saliva proteome analysis and disease biomarker discovery

Human saliva is an attractive body fluid for disease diagnosis and prognosis because saliva testing is simple, safe, low-cost and noninvasive. Comprehensive analysis and identification of the proteomic content in human whole and ductal saliva will not only contribute to the understanding of oral health and disease pathogenesis, but also form a foundation for the discovery of saliva protein biomarkers for human disease detection. In this article, we have summarized the proteomic technologies for comprehensive identification of proteins in human whole and ductal saliva. We have also discussed potential quantitative proteomic approaches to the discovery of saliva protein biomarkers for human oral and systemic diseases. With the fast development of mass spectrometry and proteomic technologies, we are enthusiastic that saliva protein biomarkers will be developed for clinical diagnosis and prognosis of human diseases in the future.