Recent advances in luminescence and aptamer sensors based analytical determination, adsorptive removal, degradation of the tetracycline antibiotics, an overview and outlook.

Tetracycline antibiotics (TCs), one of the important antibiotic groups, have been widely used in human and veterinary medicines. Their residues in foodstuff, soil and sewage have caused serious threats to food safety, ecological environment and human health. Here, we reviewed the potential harms of TCs residues to foodstuff, environment and human beings, discussed the luminescence and aptamer sensors based analytical determination, adsorptive removal, and degradation strategies of TCs residues from a recent 5-year period. The advantages and intrinsic limitations of these strategies have been compared and discussed, the potential challenges and opportunities in TCs residues degradation have also been deliberated and explored.

Non-aggregation based label free colorimetric sensor for the detection of Cu2+ based on catalyzing etching of gold nanorods by dissolve oxygen.

A label-free non-aggregation colorimetric sensor has been designed for the detection of Cu(2+), based on Cu(2+) catalyzing etching of gold nanorods (AuNRs) along longitudinal axis induced by dissolve oxygen in the presence of S2O3(2-), which caused the aspect ratio (length/width) of AuNRs to decrease and the color of the solution to distinctly change. The linear range and the detection limit (LD, calculated by 10 Sb/k, n=11) of this sensor were 0.080-4.8 µM Cu(2+) and 0.22 µM Cu(2+), respectively. This sensor has been utilized to detect Cu(2+) in tap water and human serum samples with the results agreeing well with those of inductively coupled plasma-mass spectroscopy (ICP-MS), showing its remarkable practicality. In order to prove the possibility of catalyzing AuNRs non-aggregation colorimetric sensor for the detection of Cu(2+), the morphological structures of AuNRs were characterized by high resolution transmission electron microscopy (HRTEM) and the sensing mechanism of colorimetric sensor for the detection of Cu(2+) was also discussed.

Ultra-sensitive non-aggregation colorimetric sensor for detection of iron based on the signal amplification effect of Fe3+ catalyzing H2O2 oxidize gold nanorods.

Fe(3+) can catalyze H2O2 to oxidize along on the longitudinal axis of gold nanorods (AuNRs), which caused the aspect ratio of AuNRs to decrease, longitudinal plasmon absorption band (LPAB) of AuNRs to blueshift (Δλ) and the color of the solution to change obviously. Thus, a rapid response and highly sensitive non-aggregation colorimetric sensor for the determination of Fe(3+) has been developed based on the signal amplification effect of catalyzing H2O2 to oxidize AuNRs. This simple and selective sensor with a wide linear range of 0.20-30.00 µM has been utilized to detect Fe(3+) in blood samples, and the results consisted with those obtained by inductively coupled plasma-mass spectroscopy (ICP-MS). Simultaneously, the mechanism of colorimetric sensor for the detection of Fe(3+) was also discussed.

Fullerol-fluorescein isothiocyanate-concanavalin agglutinin phosphorescent sensor for the detection of alpha-fetoprotein and forecast of human diseases.

Based on the reaction of the active -OH group in fullerol (F) with the dissociated -COOH group in fluorescein isothiocyanate (FITC) to form an F-FITC and the enhanced effect of N, N-dimethylaniline (DMA) on phosphorescence signal of F-FITC, a new phosphorescent labeling reagent (DMA-F-FITC) was developed. What's more, a phosphorescent sensor for the determination of alpha-fetoprotein variant (AFP-V) has been designed via the coupling technique of the high sensitivity for affinity adsorption-solid substrate-room temperature phosphorimetry (AA-SS-RTP) with the strong specificity reaction between DMA-F-FITC-Con A and AFP-V. The DMA-F-FITC increased the number of luminescent molecules in the biological target which improved the sensitivity of phosphorescent sensor. The proposed sensor was responsive, simple, selective and sensitive, and it has been applied to the determination of trace AFP-V in human serum and the forecast of human diseases using phosphorescence emission wavelength of F or FITC, with the results agreed well with those obtained by enzyme-linked immunoassay (ELISA). Meanwhile, the mechanisms for the labeling reaction and the sensing detection of AFP-V were discussed.

Zr(H2O)2EDTA modulated luminescent carbon dots as fluorescent probes for fluoride detection.

A novel fluorescent probe (Zr(CDs-COO)(2)EDTA) has been designed for fluoride ion (F(-)) content detection based on the competitive ligand reactions carried out between the carboxylate groups (-COOH) on the surface of the luminescent carbon dots (CDs) and F(-) coordinated to Zr(H(2)O)(2)EDTA. The strong and stable fluorescence signal of this probe was quenched upon the addition of F(-) as a result of the formation of the non-fluorescent complex Zr(F)(2)EDTA, due to the stronger affinity of F(-) than the -COOH in the CDs to Zr(IV). The fluorescence change (ΔF) in this process was linear with respect to the content of F(-), ranging from 0.10 µM to 10 µM. The probe has been applied to F(-) detection in toothpaste and water samples with satisfactory results. Moreover, the mechanism of this Zr(H(2)O)(2)EDTA modulated fluorescent probe for the detection of F(-) was also discussed.

Catalytic solid substrate-room temperature phosphorimetry for the determination of residual perphenazine based on the electronic effect of rhodamine 6G.

The rhodamine 6G(+) -perphenazine (Rhod 6G(+) -PPH) compound is formed in the ester-exchange reaction between -OH of PPH and -COOC2 H5 of Rhod 6G(+) . PPH was oxidized to a red compound (PPH') in the presence of K2 S2 O8 . Interestingly, the room temperature phosphorescence (RTP) of Rhod 6G(+) was quenched because the -OH of PPH' reacted with -COOC2 H5 of Rhod 6G(+) -PPH to form Rhod 6G(+) -PPH' and PPH, which decreased the π-electron density (δ) of the carbon atom in the Rhod 6G(+) -PPH' conjugated system and enhanced the nonradiation energy loss of the excited Rhod 6G(+) of the triplet state. The PPH content was directly proportional to the ΔIp of the system. Thus, a new catalytic solid-substrate room temperature phosphorimetry (SSRTP) method was established for the determination of PPH. The method had high sensitivity (the limit of detection was 0.019 fg/spot, corresponding to a concentration of 4.8 × 10(-14) g/mL; the sampling quantity was 0.40 µL/spot), good selectivity, convenience and speed. The analytical results were in accordance with those of high-performance liquid chromatography (HPLC). The structures of Rhod 6G(+) , PPH and Rhod 6G(+) -PPH were characterized by infrared spectra. The reaction mechanism by which PPH was determined is discussed.

Ultra-sensitive complex as phosphorescence probe for the determination of trace protein.

ß-CD-HMTA-L-Tyr complex, formed in the host guest inclusion reaction carried out between host molecule ß-cyclodextrin (ß-CD) in ß-CD-HMTA (HMTA is methenamine) and guest molecule L-tryptophan (L-Tyr), possessing the characteristic of room temperature phosphorescence (RTP). Bovine serum albumin (BSA) reacted with L-Tyr to form a complex of cage structure bringing in the sharply RTP signal quenching of L-Tyr. Based on the above facts, a new ultra-sensitive solid substrate room temperature phosphorimetry (SSRTP) for the determination of trace protein has been established using ß-CD-HMTA-L-Tyr complex as a phosphorescence probe. Under the optimum conditions, the linear range of this method was 0.0040-0.56 agspot(-1) with a detection limit (D.L.) as 0.92 zgspot(-1), and the regression equations of working curve was ΔI(p)=0.8239+162.5 m(BSA) (agspot(-1), n=8) with the correlation coefficient (r) of 0.9994. The relatively standard deviation (RSD) and the recovery of SSRTP were 4.8-3.3% and 96.7-102%, respectively, indicating that this method had good repeatability. The proposed phosphorescence probe has been applied in the detection of protein in real samples and the results agreed well with those obtained with SSRTP using methylene blue-sodium tetraphenylborate as phosphorescence probe. Meanwhile, the reaction mechanism for the determination of trace protein with ß-CD-HMTA-L-Tyr complex as phosphorescence probe has been discussed.

Selective determination of cysteine using BSA-stabilized gold nanoclusters with red emission.

Gold nanoclusters (AuNCs) were synthesized by a macromolecules template using bovine serum albumin (BSA) as stabilizer which can emit red photoluminescence under illumination of ultraviolet light. The fluorescence intensity of AuNCs enhanced through decreasing the surface defects of AuNCs modified with cysteine, herein we present a novel fluorometry for determination of trace cysteine. This method with a wider linear range from 2.0 to 800 nmol mL(-1), higher sensitivity (detection limit was 1.2 nmol mL(-1)) and better selectivity has been utilized to determine cysteine content in real samples, and the results were in a good agreement with those determined by electrochemical biosensor. At the same time, the structures of AuNCs and AuNCs-cysteine were characterized by Fourier-transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy (HRTEM) and the mechanism of the proposed assay for the detection of cysteine has been discussed.

A specific Tween-80-Rhodamine S-MWNTs phosphorescent reagent for the detection of trace calcitonin.

The present study proposed a simple sensitive and specific immunoassay for the quantification of calcitonin (CT) in human serum with water-soluble multi-walled carbon nanotubes (MWNTs). The COOH group of MWNTs could react with the NH group of rhodamine S (Rhod.S) molecules to form Rhod.S-MWNTs, which could emit room temperature phosphorescence (RTP) on acetate cellulose membrane (ACM) and react with Tween-80 to form micellar compound. Tween-80-Rhod.S-MWNTs (TRM), as a phosphorescent labelling reagent, could dramatically enhance the RTP signal of the system. The developed TRM phosphorescent reagent was used to label anti-calcitonin antibody (Ab(CT)) to form the TRM-Ab(CT) labelling product, which could take high specific immunoreaction with CT, and the ΔI(p) (= I(p2)-I(p1), I(p2) and I(p1) were the phosphorescence intensity of the test solution and the blank sample, respectively) of the system was linear to the content of CT. Hence, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) was established for the determination of CT in human serum. This sensitive (limit of quantification (LOQ) was 8.0×10(-14) g mL(-1)), accurate, selective and precise method has been applied to determine CT in human serum and predict primary osteoporosis and fractures, with the results in good agreement with those obtained by chemiluminescence immunoassay (CLIA). Simultaneously, the structure of MWNTs was characterized with scanning electron microscopy (SEM) and infrared spectroscopy (IR), and the reaction mechanisms of both labelling Ab(CT) with TRM and SSRTPIA for the determination of trace CT were discussed.

CdS/TiO2-fluorescein isothiocyanate nanoparticles as fluorescence resonance energy transfer probe for the determination of trace alkaline phosphatase based on affinity adsorption assay.

The CdS/TiO(2)-fluorescein isothiocyanate (FITC) luminescent nanoparticles (CdS/TiO(2)-FITC) with the particle size of 20 nm have been synthesized by sol-gel method. CdS/TiO(2)-FITC could emit the fluorescence of both FITC and CdS/TiO(2). The fluorescence resonance energy transfer (FRET) occurred between the donor CdS/TiO(2) and the acceptor FITC in the CdS/TiO(2)-FITC. Taking advantages of the excellent characteristics of FRET, a new CdS/TiO(2)-FITC FRET labeling reagent and a CdS/TiO(2)-FITC-wheat germ agglutinin (CdS/TiO(2)-FITC-WGA) fluorescent probe have been developed. The FRET occurring between the donor CdS/TiO(2) and the acceptor FITC in the labelled product CdS/TiO(2)-FITC-WGA-AP, formed in the affinity adsorption reaction between the WGA in this CdS/TiO(2)-FITC-WGA fluorescent probe and alkaline phosphatase (AP), sharply enhanced the fluorescence signal of FITC and quench the fluorescence signal of CdS/TiO(2). Moreover, the ΔF (the change of the fluorescence signal) of FITC and CdS/TiO(2) were proportional to the content of AP, respectively. Thus, a new method that CdS/TiO(2)-fluorescein isothiocyanate nanoparticles for the determination of trace AP based on FRET-affinity adsorption assay has been established. The limit of quantification (LOQ) of the method was 1.3×10(-17) g AP mL(-1) for CdS/TiO(2) and 1.1×10(-17) g AP mL(-1) for FITC, respectively. This sensitive, rapid, high selective and precise method has been applied to the determination of AP in human serum and the prediction of human disease with the results agreed well with enzyme-linked immunosorbent assay (ELISA) in Zhangzhou Municipal Hospital of Fujian Province. Simultaneously, the reaction mechanism for the determination of AP was also discussed.

Coupling technique of self-ordered ring and phosphorimetry for the determination of alkaline phosphatase and diseases prediction.

Rhodamine S could emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM) in the presence of heavy atom perturber Pb(2+). When Rhodamine S-piperidine solution was dropped on PAM, the red (Rhod.S)(n)-P-SOR (Rhod.S, (Rhod.S)(n), P and SOR refer to alizarin red S, multiple Rhod.S molecules, piperidine and self-ordered ring, respectively) formed on PAM, leading to the enhancement of room temperature phosphorimetry (RTP) intensity (I(p), 117.2) of (Rhod.S)(n)-P-SOR system, which was 2.4 times higher than that without SOR (I(p), 48.1). Wheat germ agglutinin (WGA) was labelled with (Rhod.S)(n)-P-SOR by the -NH- of Rhod.S reacting with the -COOH of WGA to form WGA-(Rhod.S)(n)-P-SOR. The formation of WGA-AP-WGA-(Rhod.S)(n)-P-SOR in the affinity adsorption (AA) reaction carried out between the -COOH of WGA in WGA-(Rhod.S)(n)-P-SOR and the -NH(2) of alkaline phosphatase (AP) caused the RTP intensity (ΔI(p)) of the WGA-AP-WGA-(Rhod.S)(n)-P-SOR system 7.8 times larger than that without (Rhod.S)(n)-P-SOR. Therefore, the coupling technique of SOR and solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace AP has been established. This method possessed good selectivity, high sensitivity (Detection limit (L.D) was 3.4×10(-16)gmL(-1)) and accuracy, and it has been applied to the determination of trace AP in human serum and the forecast of human diseases, and the results agreed well with those obtained by enzyme-linked immunoassay (ELISA). Besides, the mechanism of the coupling technique for the determination of AP was discussed.

Determination of trace human chorionic gonadotropin by using multiwall carbon nanotubes as phosphorescence labeling reagent.

Taking advantage of the cutting effect of the strong oxidation of benzoyl peroxide [(C(6)H(5)CO)(2)O(2)] on the end of multiwall carbon nanotubes (MWNTs) to obtain water-soluble multiwall nanotubes (MWNTs') and the spiking effect of polyacrylamide (PA) on the room temperature phosphorescence (RTP) of MWNTs', a new phosphorescent labeling reagent, MWNTs'-PA, has been developed in this study. The product ß-Ab(HCG)-MWNTs'-PA obtained by MWNTs'-PA labeling human chorionic gonadotropin-ß-subunit three-dimensional core monoclonal antibody (ß-Ab(HCG)) not only could maintain good RTP characteristics of MWNTs' but also could take specific immunoreaction with ß-HCG to form ß-HCG- ß-Ab(HCG)-MWNTs'-PA, resulting in the increase of MWNTs' RTP signal. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of ß-HCG has been established. The limits of detection (LODs) of the new method were 0.021pgspot(-1) for the direct way at 447/615nm (λ(ex)(max)/λ(em)(max)) and 0.016pgspot(-1) for the sandwich way at 447/614nm (λ(ex)(max)/λ(em)(max)). This sensitive, accurate, and precise method was used to determine ß-HCG and diagnose human diseases by the direct way or the sandwich way, with the results coinciding with those obtained by chemiluminescence immunoassay. Meanwhile, the mechanisms of MWNTs' labeling ß-Ab(HCG) and determining ß-HCG are also discussed.

A promising CdSe@CdS-quantum dots-cysteine for the determination of trace IgE by solid substrate room temperature phosphorescence immunoassay.

The labelling reagent CdSe@CdS-QDs-Cys (QDs-Cys) with the grain diameter of 4.5 nm was synthesized by modifying CdSe@CdS quantum dots (QDs) with cysteine (Cys). At the same time, QDs-Cys-Ab(IgE), a phosphorescent quantum dot probe, was developed based on the labelling reaction between -COOH of QDs-Cys and -NH(2) of goat anti human IgE antibody (Ab(IgE)). This probe with excellent biocompatibility and high specificity could not only emit strong and stable room temperature phosphorescence (RTP), but also could carry out specific immunoassay (IA) with immunoglobulin E (IgE), causing the RTP of the system to sharply enhance. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of IgE was established. The limit of quantification (LOQ) of the method was 0.12 fg spot(-1), corresponding concentration was 3.0 × 10(-13) g mL(-1) and sampling quantity was 0.40 µL spot(-1). This highly selective, sensitive and accurate SSRTPIA has been applied to determine IgE in biological samples and diagnose diseases, and the results agreed well with those obtained by enzyme-link immunoassay (ELISA). Meanwhile, the mechanisms of QDs-Cys labelling Ab(IgE) and the determination of IgE by SSRTPIA were also discussed.

Catalytic solid substrate room temperature phosphorimetry for the determination of trace rhamnose based on its condensation reaction with calcein.

Calcein (R) could not only emit strong and stable room temperature phosphorescence (RTP) on filter paper using I(-) as perturber, but also could be oxidized by H(2)O(2) to form a non-phosphorescence compound (R'), resulting in the quenching of RTP signal of R. Moreover, the ortho-hydrogen of phenolic hydroxyl in R took condensation reaction with rhamnose (Rha) to produce non-phosphorescence compound (R-Rha) causing the RTP signal of R to further quench, and R-Rha was oxidized by H(2)O(2) to form R' and Rha, bringing about the sharp RTP signal quenching of R. Thus, a new solid substrate room temperature phosphorimetry (SSRTP) for the determination of trace Rha based on its strong catalytic effect on H(2)O(2) oxidizing R has been established, with the detection limit (LD) of 7.8zgspot(-1) (corresponding concentration: 2.0×10(-17) gm l(-1), sample volume: 0.40 µl spot(-1)). This method has been applied to determine trace Rha in cigarettes and jujubes, with the results coinciding well with those determined by a high performance liquid chromatography (HPLC). The component of R-Rha also was analyzed by means of HPLC, mass spectrometer and nuclear magnetic resonance (NMR) measurements. The mechanism of catalytic SSRTP for the determination of trace Rha was discussed.