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Antibody-based immunoassays such as the lateral flow immunoassay (LFIA) and enzyme-linked immunosorbent assay (ELISA) are currently indispensable analytical methods widely used in many fields, mainly due to the high sensitivity and specificity of antibodies. However, the high cost of monoclonal antibodies and their susceptibility to high temperature limit the application of immunoassays. Previously, we developed a class of gold nanoparticle (AuNP)-based artificial antibodies, called Goldbody. Goldbodies not only bind antigens as specifically as monoclonal antibodies do but also have far better stability than monoclonal antibodies. To take advantage of the excellent specificity, stability, and easy functionalization of Goldbodies and use them for the substitution of monoclonal antibodies in immunoassays, herein, we synthesize a biotinylated anti-lysozyme Goldbody and successfully construct a competitive LFIA for the detection of lysozyme in the range of 17.98–226.49 ng·mL–1. At the same time, the biotinylated anti-lysozyme Goldbody can easily replace the detection antibody in the commercial BA (biotinylated antibody)-ELISA kit for the detection of lysozyme with a lower detection limit of 0.34 ng·mL–1 and a wider detection range of 0.89–20 ng·mL–1 compared with the commercial BA-ELISA kit. In addition, the biotinylated anti-lysozyme Goldbody has good thermal stability in both assays and can accurately detect spiked samples even after pretreatment at 100 °C, demonstrating the high potential of Goldbodies as a good replacement of monoclonal antibodies in immunoassays. [ABSTRACT FROM AUTHOR]

Background: Alzheimer’s disease (AD) is a common form of dementia, characterized by production and deposition of β-amyloid peptide in the brain. Thus, β-amyloid peptide is a potentially promising biomarker used to diagnose and monitor the progression of AD. Objective: The study aims to develop a biosensor based on a molecularly imprinted poly-pyrrole for detection of β-amyloid.Material and Methods: In this experimental study, an imprinted poly-pyrrole was employed as an artificial receptor synthesized by electro-polymerization of pyrrole on screen-printed carbon electrodes in the presence of β-amyloid. β-amyloid acts as a molecular template within the polymer. The biosensor was evaluated by cyclic voltammetry using ferro/ferricyanide marker. The parameters influencing the biosensor performance, including electro-polymerization cycle umbers and β-amyloid binding time were optimized to achieve the best biosensor sensitivity. Results: The β-amyloid binding affinity with the biosensor surface was evaluated by the Freundlich isotherm, and Freundlich constant and exponent were obtained as 0.22 ng mL-1 and 10.60, respectively. The biosensor demonstrated a detection limit of 1.2 pg mL-1. The biosensor was applied for β-amyloid determination in artificial cerebrospinal fluid. Conclusion: The biosensor is applicable for early Alzheimer’s disease detection.

The production of artificial anti-CB1 antibodies in nanoparticle format is described using the solid-phase imprinting approach. Instead of whole protein imprinting, a linear C-terminus sequence of the receptor comprising 15 amino acids (458-KVTMSVSTDTSAEAL-472) has been used as template, in accordance with the epitope imprinting approach. This sequence is located intracellularly, and it is involved in coupling to Gi/o proteins, being responsible for CB1 receptor desensitisation and internalisation. Developed molecularly imprinted materials were found to be in the nanometre scale, with a particle size of 126.4 ± 10.5 nm at pH 3 (25 ºC) and spherical shape. It was also observed that the size was sensible to temperature changes being reduced to 106.3 ± 15.2 nm at 35 °C. Lower critical solution temperature of this polymer was found to be ≈ 33.4 °C. The affinity and selectivity of the artificial antibody were assessed through dot blot and Western blot experiments. For the latter, recombinant fusion proteins GST-CB1414-472 and GST-CB1414-442 were produced to work respectively as target and negative control proteins. The control protein did not carry the target epitope for being devoid of last 30 amino acids at the C-terminus. The results demonstrated that the anti-CB1 material recognised selectively the target protein, thanks to the presence of the 15-amino acid sequence selected as epitope, which revealed that binding occurred at the C-terminus of the receptor itself. The methodology presented may pave the way for the development of novel imprinted nanomaterials for other proteins included in the superfamily of the G-protein-coupled receptors (GPCR). [ABSTRACT FROM AUTHOR]

In the current study, a molecularly imprinted polymer (MIP)-based potentiometric sensor was fabricated for a label-free determination of recombinant human erythropoietin (rhEPO). The MIP sensor was operated under zero current conditions using tetra-butyl ammonium bromide as a marker ion. A highly ordered rhEPO surface imprinted layer was prepared using 3-aminopropyl triethoxysilane and tetraethoxysilane as a monomer and cross-linker, respectively, under mild reaction conditions. A two-fold increase in the signal output was obtained by polymeric surface minimization (0.5 mm) that allowed more pronounced molecular recognition (imprinting factor = 20.1). The proportion of cross-reactivity was examined using different interfering biomolecules. Results confirmed sensor specificity for both structurally related and unrelated proteins. An ~40% decrease in the response was obtained for rhEPO-β compared to rhEPO-α. The imprinted polymeric surface was evaluated using scanning electron microscopy and Fourier transform infrared spectroscopy. Under the optimal measurement conditions, a linear range of 10.00–1000.00 ng mL−1 (10−10 − 10−8 M) was obtained. The sensor was employed for the determination of rhEPO in different biopharmaceutical formulations. Results were validated against standard immunoassay. Spiked human serum samples were analyzed and the assay was validated. The presence of non-specific proteins did not significantly affect (~8%) the results of our assay. A concentration-dependent linear response was produced in an identical range with detection limit as low as 6.50 ng mL−1 (2.14 × 10−10 M). The facile fabricated MIP sensor offers a cost-effective, portable, and easy to use alternative for biosimilarity assessment and clinical application. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) is a common form of dementia, characterized by production and deposition of β-amyloid peptide in the brain. Thus, β-amyloid peptide is a potentially promising biomarker used to diagnose and monitor the progression of AD. Objective: The study aims to develop a biosensor based on a molecularly imprinted poly-pyrrole for detection of β-amyloid. Material and Methods: In this experimental study, an imprinted poly-pyrrole was employed as an artificial receptor synthesized by electro-polymerization of pyrrole on screen-printed carbon electrodes in the presence of β-amyloid. β-amyloid acts as a molecular template within the polymer. The biosensor was evaluated by cyclic voltammetry using ferro/ferricyanide marker. The parameters influencing the biosensor performance, including electro-polymerization cycle umbers and β-amyloid binding time were optimized to achieve the best biosensor sensitivity. Results: The β-amyloid binding affinity with the biosensor surface was evaluated by the Freundlich isotherm, and Freundlich constant and exponent were obtained as 0.22 ng mL-1 and 10.60, respectively. The biosensor demonstrated a detection limit of 1.2 pg mL-1. The biosensor was applied for β-amyloid determination in artificial cerebrospinal fluid. Conclusion: The biosensor is applicable for early Alzheimer's disease detection. [ABSTRACT FROM AUTHOR]

Abstract Prostate Specific Antigen (PSA) is a biomarker employed for detection of prostate cancer. An electrochemical nanobiosensor is designed and fabricated using a molecularly imprinted polymer for the simple and fast PSA detection. The imprinted polymer served as a PSA artificial receptor fabricated by electrochemical polymerization of pyrrole on screen-printed gold electrode in the presence of PSA. PSA was a molecular template for the polymer. The fabricated nanobiosensor was evaluated by differential pulse voltammetry and using K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] as an electrochemical marker. The factors influencing the performance of the sensor including electropolymerization cycle umbers (to control the thickness of the polymer film) and time of PSA binding were optimized to attain the best sensitivity. The binding affinity of the nanobiosensor surface was examined by the Freundlich isotherm with Freundlich constant and exponent of 0.89 ng mL−1 and 10.93, respectively. The nanobiosensor demonstrated a fast rebinding rate and a high capacity of PSA recognition with detection limit of 2.0 pg mL−1. Graphical abstract Image 1 Highlights • A molecularly imprinted polymer was synthesized. • The imprinted polymer was molded with prostate specific antigen. • The polymer was applied as a nanobiosensor for prostate specific antigen determination. [ABSTRACT FROM AUTHOR]

A fluorescent competitive assay for melamine was first developed utilizing dummy molecularly imprinted polymers (DMIPs) as artificial antibodies. This method is based on the competition between fluorescent substances and the unlabeled analyte for binding sites in synthesized DMIPs and the decreased binding of fluorescent substances to DMIPs due to increased concentrations of melamine in the solutions. DMIPs for melamine were synthesized under a hot water bath in the presence of the initiator azobisisobutyronitrile (AIBN) using 2,4-diamino-6-methyl-1,3,5-triazine (DAMT) as a dummy template, methacrylic acid (MAA) as a functional monomer, and ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent. The adsorption capacity and selectivity of DMIPs for melamine were evaluated by the isothermal adsorption curve and Scatchard analysis. The evaluation results showed that the synthesized DMIPs had specific recognition sites for melamine and the maximum adsorption amount was 1 066.33 μg g−1. Later, 5-(4,6-dichlorotriazinyl) amino fluorescein (DTAF) with a triazine ring, which slightly resembles melamine, was selected as the fluorescent substance. The fluorescent competitive assay using DMIPs as the antibody mimics was finally established by selecting and optimizing the reaction solvents, DMIPs amount, DTAF concentration, and incubation time. The optimal detection system showed a linear response within range of 0.05–40 mg L−1 and the limit of detection (LOD) was 1.23 μg L−1. It was successfully applied to the detection of melamine in spiked milk samples with satisfactory recoveries (71.9 to 86.3%). According to the comparative analysis, the result of optimized fluorescent competitive assay revealed excellent agreement with the HPLC-MS/MS result for melamine.

We report the development of a molecularly imprinted polymers–surface-enhanced Raman spectroscopy (MIPs–SERS) method for rapid detection and quantification of a herbicide residue 2,4-dichlorophenoxyacetic acid (2,4-D) in milk. MIPs were synthesized via bulk polymerization and utilized as solid phase extraction sorbent to selectively extract and enrich 2,4-D from milk. Silver nanoparticles were synthesized to facilitate the collection of SERS spectra of the extracts. Based on the characteristic band intensity of 2,4-D (391 cm −1 ), the limit of detection was 0.006 ppm and the limit of quantification was 0.008 ppm. A simple logarithmic working range (0.01–1 ppm) was established, satisfying the sensitivity requirement referring to the maximum residue level of 2,4-D in milk in both Europe and North America. The overall test of 2,4-D for each milk sample required only 20 min including sample preparation. This MIPs-SERS method has potential for practical applications in detecting 2,4-D in agri-foods. [ABSTRACT FROM AUTHOR]

To impart biomedical functions to nanoparticles (NPs), the common approach is to conjugate functional groups onto NPs by dint of the functions of those groups per se. It is still beyond current reach to create protein-like specific interactions and functions on NPs by conformational engineering of nonfunctional groups on NPs. Here, we develop a conformational engineering method to create an NP-based artificial antibody, denoted "Goldbody," through conformational reconstruction of the complementary-determining regions (CDRs) of natural antibodies on gold NPs (AuNPs). The seemingly insurmountable task of controlling the conformation of the CDR loops, which are flexible and nonfunctional in the free form, was accomplished unexpectedly in a simple way. Upon anchoring both terminals of the free CDR loops on AuNPs, we managed to reconstruct the "active" conformation of the CDR loops by tuning the span between the two terminals and, as a result, the original specificity was successfully reconstructed on the AuNPs. Two Goldbodies have been created by this strategy to specifically bind with hen egg white lysozyme and epidermal growth factor receptor, with apparent affinities several orders of magnitude stronger than that of the original natural antibodies. Our work demonstrates that it is possible to create protein-like functions on NPs in a protein-like way, namely by tuning flexible surface groups to the correct conformation. Given the apparent merits, including good stability, of Goldbodies, we anticipate that a category of Goldbodies could be created to target different antigens and thus used as substitutes for natural antibodies in various applications. [ABSTRACT FROM AUTHOR]

As an ideal biomimetic antibody, molecularly imprinted polymer (MIP) has shown great promise in immunoassays. Here, we developed a covalent imprinting method to prepare MIP artificial antibody towards clenbuterol on the well surface of a microtiter plate. Template molecule (clenbuterol) was splited by hydrolysis with functional monomer and removed by methanol/acetic acid solution, and then three-dimensional cavities were fabricated in the MIP, which can rebind template molecule via hydrogen bond interaction. Using this artificial antibody, we developed a novel biomimetic enzyme-linked immunosorbent assay (ELISA) with excellent sensitivity and specificity. The linear range for clenbuterol was 10 −5 to 1000 μg L −1 , with a detection limit of 10 −7 μg L −1 . Cross reactivity of this MIP artificial antibody to other four structural analogs was less than 0.93%. This method was applied to determine clenbuterol in real samples with satisfactory result, suggesting a promising application of the biomimetic ELISA in food and environmental analysis. [ABSTRACT FROM AUTHOR]

A direct competitive chemiluminescence enzyme immunoassay was developed by using the molecularly imprinted 96-well plate as an artificial antibody to detect chloramphenicol (CAP). The artificial antibody was synthesised on the well surface of MaxiSorp polystyrene 96-well plate and CAP was conjugated with the horseradish peroxidase. The results showed that the imprinted plate exhibited antibody-like binding ability. The plate showed fast adsorption rate, 66% adsorption was finished within 20 min. The cross-reactivity for CAP, florfenicol and thiamphenicol were 100%, 1.25% and 2.08%, respectively. And the imprinted plate could be reused for many times without loss of sensitivity. The IC50and the detection limit values under optimum conditions were 30±2 µg·L−1and 0.9±0.01 µg·L−1, respectively. The plate was used to detect CAP in sea cucumber, which showed excellent recoveries ranging from 89% to 98.7%. And the result correlated well with that obtained by the CAP enzyme-linked immunosorbent assay (ELISA) kit. [ABSTRACT FROM PUBLISHER]

Serum is a readily available source for noninvasive studies in clinical research, but it contains abundant proteins such as albumin and immunoglobulin G that can hinder the presence of low-abundant proteins as well as decrease sample loading capacity of analytical methods. Therefore, depletion of these two proteins is required to observe low-abundance serum proteins. Molecularly imprinted polymers are template-induced artificial antibodies with the ability to recognize and selectively bind the target molecule. In this study, artificial albumin and immunoglobulin G antibodies were developed by using two epitopes of human serum albumin and immunoglobulin G as templates. Acrylic acid, acrylamide, and N-acryl tyramine were the corresponding monomers; N,N′-ethylene bisacrylamide served as a cross-linker, and cellulosic fibers were used as a supporting matrix. The adsorption capacity of these artificial antibodies was 15.2 mg, 10 mg, and 15 μL per gram for human serum albumin, immunoglobulin G, and human serum, respectively. The dissociation constant ( Kd) of these artificial antibodies toward the human serum albumin and immunoglobulin G was 1 μ M and 0.6 μ M, respectively. The biomimetic properties of these artificial antibodies, coupled with their economical and rapid production, high specificity and their reusability, make them attractive for protein separation and analysis. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

In this study, a new way to substitute the biology antibody was introduced by using a hydrophilic molecularly imprinted film, which was directly prepared on the well surface of MaxiSorp polystyrene 96-well plate by the bulk polymerization technique. This imprinted film exhibited good recognition and fast adsorption-desorption dynamics toward olaquindox. Using it as the recognition element, a fast and new direct competitive biomimetic enzyme-linked immunosorbent assay (BELISA) method for the determination of olaquindox in chick feed was developed. This BELISA method had low cross-reactivities of 6.2% and 12% for two analogues. Under the optimal conditions, the sensitivity (IC50) and the limit of detection (IC15) were 700 ± 60 µg L−1and 17.0 ± 1.6 µg L−1, respectively. The blank chick feed samples spiked with olaquindox at three levels were determined by this developed method with recoveries ranging from 82.0–96.0%. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increasing demand on the determination of trace trichlorfon residues in fresh vegetables. In this study, a sensitive direct competitive biomimetic enzyme-linked immunosorbent assay (BELISA) method was developed for the determination of trichlorfon based on a hydrophilic imprinted membrane, which was directly synthesized on the well surface of MaxiSorp polystyrene 96-well plate through bulk polymerization technology. This novel imprinted membrane was characterized with high binding ability and specificity. Under the optimal conditions, the sensitivity (IC, half maximal inhibitory concentration) and the limit of detection (LOD, IC) of this method were 6800 ± 60 μg/L and 6.8 ± 0.20 μg/L, respectively. This BELISA method had been applied to the determination of trichlorfon with good recoveries ranging from 106.0 to 110.5%, and the results were correlated with that obtained by the gas chromatography method. Moreover, this method was applied to quantitative detection of trichlorfon residues in the leek samples. [ABSTRACT FROM AUTHOR]

A new direct competitive enzyme-linked immunosorbent assay (ELISA) with molecularly imprinted film as artificial antibody was developed to detect ractopamine (RAC) in urine and pork samples. The imprinted film was directly synthesized on the well surface of 96-well plate by an organic-inorganic hybrid technology and evaluated by fourier transform infrared (FT-IR), static, and kinetic adsorption experiments. The imprinted film exhibited an antibody-like binding ability and rapid adsorption speed. The established ELISA method gave a good sensitivity (IC, 15.77 μg L) and a low detection limit (IC, 0.01 μg L) for RAC under the optimum conditions, and it was applied to the determination of RAC in urine and pork samples spiked at three levels with recoveries ranging from 77.7% to 108.9% (urine) and from 93.5% to 101.1% (pork). The obtained results, which correlated well with those gained from the traditional high performance liquid chromatography (HPLC) method, demonstrated that the developed ELISA method was reliable for RAC determination in real samples. [ABSTRACT FROM AUTHOR]

Abstract: A novel artificial antibody for troponin T (TnT) was synthesized by molecular imprint (MI) on the surface of multiwalled carbon nanotubes (MWCNT). This was done by attaching TnT to the MWCNT surface, and filling the vacant spaces by polymerizing under mild conditions acrylamide (monomer) in N,N′-methylenebisacrylamide (cross-linker) and ammonium persulphate (initiator). After removing the template, the obtained biomaterial was able to rebind TnT and discriminate it among other interfering species. Stereochemical recognition of TnT was confirmed by the non-rebinding ability displayed by non-imprinted (NI) materials, obtained by imprinting without a template. SEM and FTIR analysis confirmed the surface modification of the MWCNT. The ability of this biomaterial to rebind TnT was confirmed by including it as electroactive compound in a PVC/plasticizer mixture coating a wire of silver, gold or titanium. Anionic slopes of 50mV decade−1 were obtained for the gold wire coated with MI-based membranes dipped in HEPES buffer of pH 7. The limit of detection was 0.16μgmL−1. Neither the NI-MWCNT nor the MWCNT showed the ability to recognize the template. Good selectivity was observed against creatinine, sucrose, fructose, myoglobin, sodium glutamate, thiamine and urea. The sensor was tested successfully on serum samples. It is expected that this work opens new horizons on the design of new artificial antibodies for complex protein structures. [Copyright &y& Elsevier]

Immunoassay, based on a selective affinity of the biological antibody for its antigen, is one of the most usual analytical methods in food safety and environmental chemistry. However, it presents several drawbacks because of the nature of the antibody. Molecular imprinting technique, due to its high selectivity and stability, ease of preparation and low cost, has shown great potential in producing artificial antibodies in biomimetic immunoassays. This article focuses on the recent states, advantages, current problems and outlooks of molecularly imprinted radio, fluoro, enzyme-linked and chemiluminescent immunoassays, and biomimetic immunosensor, with special emphasis on the challenges in developing biomimetic enzyme-linked immunosorbent assays (BELISAs). The biomimetic immunoassay method will provide an important new analysis platform in food safety, although the sensitivity and specificity is relatively low. As a new simple analysis method, the biomimetic immunoassay has attractive prospect, although some limitations were existed in real-sample assay. In this critical review, some promising solutions for overcoming its drawbacks were put forward, which may promote the more quick development and extensive application of this method in food safety. [ABSTRACT FROM AUTHOR]

Herein, a strategy for a metal ion-imprinted artificial antibody with recognition sites tagged by fluorescein was carried out to construct the selective sites with a sensitive optical response signal to the specific metal ion. The synthesized silica nanoparticles were modified by the derivative residue group of 3-aminopropyltriethoxysilane conjugated with a 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl) molecule through the hydrolysis and condensation reactions. The as-prepared silica nanoparticles were encapsulated by metal ion (Cu 2+ , Cd 2+ , Hg 2+ , and Pb 2+ )-imprinted polymers with nanostructured layers through the copolymerization of ethyl glycol dimethyl methacrylate (EGDMA) as a cross-linker, AIBN as an initiator, metal ions as template molecules, AA as a functional monomer, and acetonitrile as a solvent. The layers of molecular imprinted polymers (MIPs) with a core-shell structure removed template molecules by EDTA-2Na to retain the cavities and spatial sizes to match the imprinted metal ions. The microsensor arrays were achieved by the self-assembly technique of SiO 2 @MIP nanoparticles on the etched silicon wafer with regular dot arrays. The nanostructured-shell layers with fluorescence-tagged recognition sites rebound metal ions by the driving force of concentration difference demonstrates the high selective recognition and sensitive detection to heavy metal ions through the decline of fluorescence intensity. The LOD concentration for four metal ions is down to 10 -9 mol·L -1 . The method will provide biomimetic synthesis, analyte screen, and detection of highly dangerous materials in the environment for theoretical foundation and technological support.

Construction of libraries of artificial antibodies has been reported by several groups of investigators. Various forms of antibody fused to a surface protein, cpIII, are expressed on the surface of filamentous phage. Since phages that encode desired antibodies can be easily grown in Escherichia coli after selection with target antigens, the phage-display antibody system appears to be very useful for various biological purposes. In this brief review, recent progress in research into the production of artificial antibodies is summarized and the strategies used for the construction of libraries of artificial antibodies are compared. [ABSTRACT FROM AUTHOR]

• Silica-based rhEPO-MIP was prepared in polystyrene microplate. • MIP preparation was optimized using factorial and response surface designs. • The stability of rhEPO during the MIP preparation condition was investigated using a validated stability indicating SEC method. • rhEPO-MIP was selective for template protein in preference to hyperglycosylated and pegylated counterparts. • Determination of rhEPO in pharmaceutical formulations containing albumin stabilizer was achieved and the results were cross-validated with validated ELISA assay and RP-HPLC method. • Biosimilarity assessment was carried out using the prepared rhEPO-MIP. Synthesis and applications of molecularly imprinted polymers (MIP) are rapidly growing. In this study, a biomimetic MIP was prepared through silanes polymerization on the surface of 96-well microplates using recombinant human erythropoietin-alfa (rhEPO) as a template molecule. The rhEPO was immobilized onto the plate surface using bi-functional cross-linker and a thin imprinted layer following sol-gel procedure was constructed. After template extraction, uniform three-dimensional cavities compatible with the configuration of rhEPO were obtained. The rhEPO-MIP preparation was optimized using 2-level factorial design and response surface design where polymerization time and interactions between the different variable were found to be the most significant factors. Size-exclusion chromatography (SEC) was used to monitor the stability of the rhEPO under the investigated polymerization conditions. Determination of rhEPO using the MIP microplate showed good dynamic response fitting to the 4 PL regression model (0.9962) over a concentration range of 10.00 - 100.00 ng mL−1. Adsorption of rhEPO onto MIP followed the Langmuir isotherm model (r = 0.9957, χ2 =0.02786) with pseudo-second-order kinetics (r = 0.9984). The surface of the rhEPO-MIP was characterized using scanning electron microscopy (SEM) while step-by-step surface modification was tracked using Fourier transform infrared (FTIR) spectroscopy. The rhEPO-MIP was able to distinguish between the rhEPO-alfa template and modified rhEPO molecules; rhEPO-beta, hyperglycosylated and pegylated forms (imprinting factors < 2) and in the commonly used formulation additive human serum albumin (HSA) (R% = 113.96 -95.22%). The rhEPO-MIP was applied to compare the receptor-binding pattern to rhEPO and its biosimilars / structural analogues. The results were cross-validated using the conventional assay protocol (RP-HPLC and ELISA) and an acceptable correlation was observed with RP-HPLC (maximum deviation is 7.78%). This work confirmed the applicability of rhEPO-MIP with its unique binding features for batch release, stability and biosimilarity assessment as well as subsequent evaluation of batch-to-batch consistency during bioproduction of target analytes. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) is a common form of dementia, characterized by production and deposition of β-amyloid peptide in the brain. Thus, β-amyloid peptide is a potentially promising biomarker used to diagnose and monitor the progression of AD., Objective: The study aims to develop a biosensor based on a molecularly imprinted poly-pyrrole for detection of β-amyloid., Material and Methods: In this experimental study, an imprinted poly-pyrrole was employed as an artificial receptor synthesized by electro-polymerization of pyrrole on screen-printed carbon electrodes in the presence of β-amyloid. β-amyloid acts as a molecular template within the polymer. The biosensor was evaluated by cyclic voltammetry using ferro/ferricyanide marker. The parameters influencing the biosensor performance, including electro-polymerization cycle umbers and β-amyloid binding time were optimized to achieve the best biosensor sensitivity., Results: The β-amyloid binding affinity with the biosensor surface was evaluated by the Freundlich isotherm, and Freundlich constant and exponent were obtained as 0.22 ng mL -1 and 10.60, respectively. The biosensor demonstrated a detection limit of 1.2 pg mL -1 . The biosensor was applied for β-amyloid determination in artificial cerebrospinal fluid., Conclusion: The biosensor is applicable for early Alzheimer's disease detection., (Copyright: © Journal of Biomedical Physics and Engineering.)

Small extracellular vesicles (sEVs) are increasingly recognized as noninvasive diagnostic markers for many diseases. Hence, it is highly desirable to isolate sEVs rapidly for downstream molecular analyses. However, conventional methods for sEV isolation (such as ultracentrifugation and immune-based isolation) are time-consuming and expensive and require large sample volumes. Herein, we developed artificial magnetic colloid antibodies (MCAs) via surface imprinting technology for rapid isolation and analysis of sEVs. This approach enabled the rapid, purification-free, and low-cost isolation of sEVs based on size and shape recognition. The MCAs presented a higher capture yield in 20 min with more than 3-fold enrichment of sEVs compared with the ultracentrifugation method in 4 h. Moreover, the MCAs also proposed a reusability benefiting from the high stability of the organosilica recognition layer. By combining with volumetric bar-chart chip technology, this work provides a sensitive, rapid, and easy-to-use sEV detection platform for point-of-care (POC) diagnostics.

Since circulating tumor cells (CTCs) in the blood carry the genetic and phenotypic information of tumor tissues, they are regarded as important markers for liquid biopsy, especially for the early diagnosis of cancer, determination of treatment options and evaluation of prognosis. However, the capture and detection of CTCs is challenging because of their extremely low concentration in blood. In this review, recent advances in capture methods of CTCs based on their biophysical properties, affinity, and artificial antibodies are summarized. The advantages and drawbacks of these methods are discussed from the aspects of capture efficiency, capture purity and maintenance of activity after release. Future trends in CTCs capture are also discussed.

To impart biomedical functions to nanoparticles (NPs), the common approach is to conjugate functional groups onto NPs by dint of the functions of those groups per se. It is still beyond current reach to create protein-like specific interactions and functions on NPs by conformational engineering of nonfunctional groups on NPs. Here, we develop a conformational engineering method to create an NP-based artificial antibody, denoted "Goldbody," through conformational reconstruction of the complementary-determining regions (CDRs) of natural antibodies on gold NPs (AuNPs). The seemingly insurmountable task of controlling the conformation of the CDR loops, which are flexible and nonfunctional in the free form, was accomplished unexpectedly in a simple way. Upon anchoring both terminals of the free CDR loops on AuNPs, we managed to reconstruct the "active" conformation of the CDR loops by tuning the span between the two terminals and, as a result, the original specificity was successfully reconstructed on the AuNPs. Two Goldbodies have been created by this strategy to specifically bind with hen egg white lysozyme and epidermal growth factor receptor, with apparent affinities several orders of magnitude stronger than that of the original natural antibodies. Our work demonstrates that it is possible to create protein-like functions on NPs in a protein-like way, namely by tuning flexible surface groups to the correct conformation. Given the apparent merits, including good stability, of Goldbodies, we anticipate that a category of Goldbodies could be created to target different antigens and thus used as substitutes for natural antibodies in various applications., Competing Interests: The authors declare no conflict of interest., (Copyright © 2017 the Author(s). Published by PNAS.)

Molecular imprinting, which involves the formation of artificial recognition elements or cavities with complementary shape and chemical functionality to the target species, is a powerful method to overcome a number of limitations associated with natural antibodies. An important but often overlooked consideration in the design of artificial biorecognition elements based on molecular imprinting is the nonspecific binding of interfering species to noncavity regions of the imprinted polymer. Here, we demonstrate a universal method, namely, PEGylation of the noncavity regions of the imprinted polymer, to minimize the nonspecific binding and significantly enhance the selectivity of the molecular imprinted polymer for the target biomolecules. The nonspecific binding, as quantified by the localized surface plasmon resonance shift of imprinted plasmonic nanorattles upon exposure to common interfering proteins, was found to be more than 10 times lower compared to the non-PEGylated counterparts. The method demonstrated here can be broadly applied to a wide variety of functional monomers employed for molecular imprinting. The significantly higher selectivity of PEGylated molecular imprints takes biosensors based on these artificial biorecognition elements closer to real-world applications.