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Developing a functional affinity monolithic column towards in-tube solid-phase microextraction (IT-SPME) for selective sample pretreatment is critical. Herein, a high-performance capillary affinity monolithic column with an ultra-high aptamer coverage density was rapidly fabricated via a simple adsorption strategy, in which aptamers with natural sequences were directly immobilized on an ammonium-based strongly cationic matrix. Limitations of the traditional biological or covalent methods such as time-consuming modification reactions, special requirement of active groups (e.g. –NH2 and –SH) on the aptamer, and low aptamer coverage density levels were avoided. An ultra-high coverage density of 8616 pmol μL−1 was achieved with excellent stability, and the highest aptamer-modification level among all the current methods was reached. Selective recognition and high recovery yields of the model mycotoxin ochratoxin A (OTA) were achieved in 95.9 ± 0.98%–97.9 ± 0.28% (n = 3). In particular, there was little cross-reactivity towards the OTB analogue of only 0.5% even in the case of 250 fold of the analogue OTB, which was not reported in previous affinity monoliths. Upon sample analysis, satisfactory discriminations of trace OTA were obtained at 93.7 ± 1.4%–95.5 ± 2.5% (n = 3) in beer and wheat. A facile and direct method for efficiently fabricating an aptamer-based affinity monolith towards online selective IT-SPME was proposed. [ABSTRACT FROM AUTHOR]

Developing a high‐performance modification protocol is critical for efficiently fabricating affinity monolith. Herein, by using 2,4,6‐trichloro‐1,3,5‐triazine as the linker, a simple triazine‐bridged approach was proposed for efficiently fabricating aptamer‐grafted polyhedral oligomeric silsesquioxane‐polyethyleneimine affinity monolith with high specificity toward ochratoxin A. Experimental parameters, column characteristics and specificity performances of the resultant affinity monolith were investigated in detail. Under the optimal conditions, 2,4,6‐trichloro‐1,3,5‐triazine was rapidly grafted on the polyamine matrix, and effectively applied to the subsequent bridge linkage of aptamers. It was simple and effective, which resulted in a significant decrease of modification time, excellent properties including the high coverage density of aptamer up to 1799 pmol/μL and sensitive detection of ochratoxin A as low as 10 pg/mL in beer samples. This protocol provides a facile approach for fabricating aptamer‐grafted polyamine affinity monoliths with highly selective discrimination performance. [ABSTRACT FROM AUTHOR]

A novel polyhedral oligomeric silsesquioxane (POSS)-containing aptamer-modified hybrid affinity monolith with excellent hydrophilicity and unique architecture without Si–OH groups is presented herein, and the nonspecific adsorption caused by the hydrophobic nature of the monolithic column or polar interaction with silanol groups is minimized. Via a simple “one-pot” procedure, hydrophilic monomers were facilely polymerized with the POSS-methacryl substituted (POSS-MA) and aptamer; a highly hydrophilic nature was obtained and the lowest contact angle of 11° was achieved. By using ochratoxin A (OTA) as the model analyte, highly selective recognition of OTA in the mixture was achieved and the control of nonspecific interactions and the cross-reactivity of OTB and AFB1 were significantly improved. The recovery yield of OTB caused by nonspecific adsorption in the resultant monolith was only about 0.1% and remained steady even with the coexistence of a high OTB content (OTA : OTB = 1 : 50), which reached the best level to date and was obviously less than the 6.1% occurring in the hydrophobic POSS-containing control monolith, 8.3% in the POSS-PEI@AuNPs@aptamer affinity monolith and 18.7% in the silica-hybrid affinity monolith. When applied to wine and wheat samples, the nonspecific adsorption was significantly reduced and efficient discrimination of OTA was obtained with better results than that of the hydrophobic POSS-containing affinity column. This provides an attractive tool for minimizing the nonspecific adsorption for highly selective on-column recognition. [ABSTRACT FROM AUTHOR]

A convenient and high-performance AuNPs@aptamer-modified mercaptosiloxane-based hybrid affinity monolithic column with an unusually high coverage density of aptamers was facilely prepared and used for on-column selective recognition of ochratoxin A (OTA). Due to the high surface-to-volume ratio of AuNPs, the robust conjugation of Au-SH and large specific surface area of hybrid-silica monolith, high coverage density of 5′-SH-aptamers up to 3494 pmol μL−1 was achieved, which was 2.5–10 folds higher than that of other previously reported affinity monoliths modified with AuNPs@Apt. Using OTA as the model analyte, the highly selective recognition of OTA was carried out via online coupling with HPLC, and the cross-reactivity towards analogues, such as OTB and aflatoxin B1, was weak. High recovery yields of OTA were achieved at more than 92% (n = 3) even when OTB was added at a high concentration level up to 50 ng mL−1. For sample analysis, efficient discrimination of OTA was successfully obtained with a sensitive detection limit of 25 pg mL−1. The recoveries of OTA with different fortified levels were achieved at 88.6%–94.1% and 88.2%–94.3% for beer and wine samples, respectively. This protocol provides a facile approach for fabricating a desirable affinity monolith modified with abundant aptamers for highly selective and sensitive on-column extraction of target analyte OTA. [ABSTRACT FROM AUTHOR]

Accurate quantitation of trace-level ATP biomarkers often suffers from interference of sample matrix and remains a challenge. Herein, a novel magnetic biological nanosensor (MBNS) integrating tetrahedral framework nucleic acid (tFNA)-confined aptamers and ultrasensitive laser-induced fluorescence (LIF) was tailored and evaluated. The fluorescent aptamer nanoprobe hybridized with FAM-labelled cDNA was particularly incorporated into the inner cavity of tFNA, enabling a dual-mode mechanism that integrates molecular size selection and aptamer affinity recognition. By this strategy, the benefits of tFNA molecular sieve, the super sensitive properties of LIF, and the specific recognition of "aptamer gene codes" were integrated, as triggered the superior response of ATP. The structures, properties and reaction mechanism of tFNA, as well as tFNA modified with aptamer probe at different sites, were characterized in detail. A high level of anti-interference was achieved, shielding against non-specific adsorption even in matrices with high protein and analogue content, 103∼105 times higher than ATP. The release of fluorescent beacon from aptamer probe was facilely driven by specific binding of ATP, and an ultra-sensitive detection of 75 pmol/L ATP was obtained without amplification. It was 2–3 orders of magnitude more sensitive than most fluorescent aptasensors. Applied to serum samples, the stability and reproducibility of the resultant aptasensor have been validated with the intra- and inter-assay RSD in 1.6–6.4 % and -1.5–8.4 %, respectively. Acceptable recoveries of 96.5–106.8 % were achieved, consistent with the LC-MS method. It was expected to open a simple and efficient protocol for highly specific and ultrasensitive ATP detection in clinical diagnostics. [Display omitted] • A novel tFNAs-confined aptasensor encapsulating fluorescent aptamer was proposed. • Dual recognition mechanism enables size selectivity and aptamer-affinity recognition. • High anti-interference performance was obtained in protein and analogue matrix. • Ultra-sensitive detection of pmol/L ATP in serum was achieved using LIF. • Excellent applicability exhibits a high recovery yield of ATP at 96.5–106.8 %. [ABSTRACT FROM AUTHOR]

In this paper, a novel adsorbent based on aptamer was prepared via "thiol-ene" click chemistry reaction and used for selective adsorbing the trace phthalic acid esters (PAEs) from drinking water and juice samples, which depended on the group selectivity of aptamers to the ester and the benzoyl groups of PAEs. The morphological structures of the obtained adsorbents were characterized by Fourier Transform infrared spectroscopy (FT-IR), fluorescence spectra, Energy Dispersive Spectrometer (EDS), Brunauer-Emmett-Teller (BET). The selectivity of the prepared adsorbent was evaluated and the results showed that the recovery of the adsorbent with aptamer for PAEs was 66.10–108.90%, while the recovery of adsorbent without aptamer was only 32.41–37.59%. The limit of detection (LOD) (S/N = 3) and limit of quantitation (LOQ) (S/N = 10) of PAEs coupled with HPLC-UV were obtained in the range of 0.11–0.88 μg L−1 and 0.22–1.33 μg L−1, respectively. This work gave a facile and efficient approach to for specific enrichment and highly sensitivity detection of PAEs. 1. Aptamer-based adsorbent was prepared with a facile "one-pot" process via "thiol-ene" click chemistry reaction.2. The obtained adsorbent could recognize and detect four PAEs simultaneously due to the selectivity of the aptamer to the ester and the benzoyl groups.3. The recovery of the aptamer-based adsorbent for four PAEs was 66.10–108.90%, while the recovery of the control adsorbent was only 32.41–37.59%.4. The LOD of DBP in drinking water samples was 0.55 μg L-1, which was below 3.0 μg L-1 that was the limit standard from GB3838-2002. Image 1 • A novel aptamer-based adsorbent for PAEs was prepared via "thiol-ene" click chemistry reaction. • The obtained adsorbent could recognize and detect four PAEs simultaneously. • The selectivity of the aptamer-based adsorbent for PAEs was superior to the control adsorbent. • The LOD of PAEs in drinking water samples was obtained in the range of 0.11–0.88 μg L−1. [ABSTRACT FROM AUTHOR]

Okadaic acid (OA) biotoxin acts a well-established inhibitor of protein phosphatase even a tumor promoter of human being, arouse great attention in safety monitoring. However, the powerful and convenient nanosensing technologies for addressing the demands such as rapidity, high sensitivity, and stability in the in-field test of OA shellfish toxin is still scarce. Herein, a high-performance magnetic biometric nanosensor (MBNS) integrating oriented aptamers and ultrasensitive laser-induced fluorescence (LIF) was firstly proposed for the in-field detection of trace OA in seafoods. High-density aptamers hybridized with FAM-labeled cDNA were tethered to the surface of AuNPs on magnetic MIL-101@Fe 3 O 4 , and then finely regulated by mercaptohexyl alcohol (MCH) to be orderly assembled, as was successfully utilized to engineer an active biological nanosensor for highly specific recognition of OA. Aptamers anchored on magnetic Fe 3 O 4 @MOF@AuNPs activate a biometric microreactor of OA, in which the superior LIF properties, conformation regulation of aptamer, and the specific recognition using aptamer genes were adopted. The magnetic nanosensor with an excellent specificity and super sensitivity for OA analysis was achieved within 20 min. Moreover, the content of captured OA could facilely be recorded by measuring the fluorescence intensity, and the limit of detection (LOD) and limit of quantitation of OA (LOQ) reached 0.015 and 0.050 ng/mL respectively, which was far better than most aptamer-based biometric sensing methods. The feasibility for accurate test of trace OA toxin in the fortified shellfish samples was validated with the recovery yields of 88.2–107.5% and RSD of 0.5–7.6%, respectively. The result demonstrated that the oriented-aptamer encoded MNS had significant practical values in rapid and ultrasensitive detection of OA biotoxin and the related safety applications. A new magnetic nanosensor integrating oriented aptamers and LIF was presented for specific and ultrasensitive test of OA with an extremely low LOD of 15 pg/mL. [Display omitted] • Magnetic nanosensor integrating oriented aptamers and LIF is firstly proposed. • Bio-interface assembled with massive aptamer-codes exhibits perfect specificity. • Aptamer conformation is regulated for excellent recognition performance. • Ultrasensitive test of OA is obtained with a better result than most aptsensors. • Low-cost, accurate and reproducible aptamer-LIF protocol is achieved. [ABSTRACT FROM AUTHOR]

A novel aptamer-based polyhedral oligomeric silsesquioxane (POSS)-containing hybrid affinity monolith has been prepared with a facile “one-pot” process simultaneously via “free radical polymerization” and “thiol-ene” click reaction, and used for on-line selective extraction and practical analysis to trace ochratoxin A (OTA). By using the ternary porogenic mixture composed of water/DMF/PEG, a homogeneous polymerization mixture with POSS chemicals, acrylate-based monomers and aptamer aqueous solution was obtained, and the copolymerization of POSS chemicals, polymer monomers and aptamer aqueous solution was systematically studied. Characterizations such as the morphology, FT-IR and fluorescence spectra, mechanical stability, dynamic binding capacity, cross-reactivity and selectivity of the resultant affinity monolith were also evaluated. Attributed to the porous monolithic structure and aptamer-based affinity interaction, acceptable selective recognition and recovery yields towards trace OTA were obtained. With a 5-fold volume enrichment, the limit of detection (LOD) and limit of quantitation (LOQ) of OTA in fortified beer samples were gained at 0.025 ng/mL (S/N = 3) and 0.045 ng/mL (S/N = 10), respectively. It could be competent for the sensitive measure of actual OTA residues in real beer samples. In comparison with the previously reported strategies containing common “sol-gel” chemistry, the proposed protocol to fabricating aptamer-modified POSS-containing hybrid affinity monolith showed a simpler preparation with acceptable selectivity and higher recovery to trace OTA. [ABSTRACT FROM AUTHOR]

A novel aptamer-functionalized metal-organic framework nanofibrous composite (viz. PAN/UiO@UiO2-N 3 -aptamer) with a high aptamer coverage density was proposed based on the electrospinning and seeded growth method, and used for specific affinity recognition of trace Microcystin-LR (MC-LR). Heterobifunctional ligand was used to modify the metal–organic framework nanoparticles (MOF NPs) surface, which could passivate the MOF surface with respect to unmodified DNA, followed by coupling massive aptamers on MOF of the solid-phase microextraction (SPME) fiber using click chemistry. Characterizations including morphology, spectra analysis, mechanical stability, binding capacity and specificity were fulfilled. Applied to the analysis of MC-LR, the good selective and sensitive recognition were obtained with the detection limit as low as 0.003 ng/mL, which was better than most non-specific SPME or solid-phase extraction (SPE) protocols. The stability and reproducibility were acceptable, and the intra-day, inter-day and column-to-column relative standard deviations (RSDs) for the recovery of MC-LR were gained in the range from 2.5% to 14.3%, respectively. Satisfactory recoveries of MC-LR in environmental water samples were measured as 96.3 ± 4.7% - 98.9 ± 2.7% (n = 3) in tap water, 94.4 ± 2.5% - 96.1 ± 3.5% (n = 3) in pond water, and 97.0 ± 2.1% - 97.9 ± 3.1% (n = 3) in river water, respectively. This work demonstrated that the electrospun nanofibrous composite with massive aptamers would be a better alternative for ultra-trace MC-LR detection with good selectivity, matrix-resistance ability and high resolution. Novel DBCO-aptamer-modified "MOF-cloth" electrospun nanofibers were presented for highly specific SPME of ultra-trace MC-LR toxin. [Display omitted] • Novel aptamer-modified MOF-coated electrospun nanofibrous membrane was proposed. • Massive DBCO-modified aptamers were effectively coupled to the MOF surface using "click chemistry" method. • High specific surface area, good hydrophilicity and excellent robustness were obtained. • Ultra-trace MC-LR was highly selectivity discriminated and showed better results than control SPME or commericial SPE column. [ABSTRACT FROM AUTHOR]

Herein, a facile protocol of simple DNA adsorption on UV-initiated polymerization supports was proposed for effectively fabricating aptamer-based affinity monolithic column. Hydrophilic cationic monolith with an excellent mechanical stability was achieved within 7 min and then massive aptamers were directly bound by DNA charge-dependent adsorption. Strong cationic quaternary ammonium-based monomer was employed to provide effective and stable positive charge surface for aptamer immobilization in a wide range of pH. An ultra-high aptamer coverage density of 6813 pmol/μL was achieved to gain a highly specific online recognition performance. Limitations such as low aptamer capacity, tedious modification and time-consuming reactions in the traditional biological or covalent modification strategies were avoided. By using ochratoxin A (OTA) as the given analyte, the selective recognition and high recoveries were successfully achieved, and little cross-reactivity towards OTB analogue was only 0.5% even if the content of OTB got up to 125 folds of OTA. Applied to sample analysis, the satisfactory discriminations of trace OTA were obtained at 93.9 ± 1.9% – 96.5 ± 1.7%（n = 3）in beer, wheat and chicken liver samples. It might light a cost-effective access to efficiently preparing high-performance affinity monoliths towards the selective in-tube microextraction of OTA. A simple and green access to efficiently preparing aptamer-affinity monolith for the high-performance online selective IT-SPME of mycotoxin. [Display omitted] • DNA adsorption protocol was used for building hydrophilic aptamer affinity monolith. • Aptamer charge adsorption on ammonium-based matrix was simple and efficient. • Ultra-high aptamer capacity was gained and better than most biological and chemical modes. • High-performance selective IT-SPME with low non-specific adsorption were achieved. • Robustness of monolith and good recognition performance were demonstrated. [ABSTRACT FROM AUTHOR]

Via the facile photopolymerization and thiol-ene click chemistry, a hydrophilic polyhedral oligomeric silsesquioxane (POSS)-containing affinity monolithic column with a high load of aptamers and fast preparation was presented, and successfully applied to the efficient specific recognition and sensitive detection of zearalenone (ZEN) by coupling with HPLC. Optimization of polymerization reaction and polymer recipe were studied, and characteristics such as structural morphology, affinity performance and specificity to ZEN were evaluated. A highly hydrophilic POSS-based aptamer affinity monolith was rapidly prepared in 1.1 h, and a high capacity of aptamer reached 2772.61 pmol/μL that was much higher than that of the current POSS-based aptamer affinity monoliths. By this way, the hydrophilic nature and aptamer coverage indensity in POSS monoliths were well improved. The mixed-mode mechanism including aptamer affinity recognition and hydrophilic interaction were employed for the specific analysis of ZEN. Applied to the monitoring of ZEN, a good selective recognition and sensitive detection were obtained with the detection limit (LOD) of 0.02 ng/mL. The stability and reproducibility were acceptable and the intra-day, inter-day and column-to-column relative standard deviations (RSDs) of the ZEN recovery were gained in the range from 2.28% to 5.32%, respectively. Satisfactory recoveries of ZEN in rice samples were realized ad 98.6 ± 2.8%–100.8 ± 2.0%. It might provide a preferable access to online specific analysis of ZEN via the hydrophilic POSS-based affinity monolith with a large capacity of aptamers and a high preparation efficiency. A new POSS-based aptamer monolith with hydrophilic and affinity mixed-mode interactions was proposed for online high-efficient specific detection of ZEN. Image 1 • POSS-based hydrophilic affinity monolith with massive aptamers was achieved. • Aptamer affinity and hydrophilic interaction mixed mechanisms were employed. • Aptamer capacity of 2772 pmol/μL reached the best level of current POSS monolith. • Highly specific online recognition was achieved with a low cross-interference. • Sensitive analysis of ZEN in rices was obtained with high recoveries. [ABSTRACT FROM AUTHOR]