Recyclable magnetic Fe3O4@C for methylene blue removal under microwave-induced reaction system.

The reclamation and removal of organic pollutants are difficult issues of world concern. In this study, a microwave-induced reaction system (MIRS) is applied to synthesize the multifunctional composite of Fe3O4@C, which is employed to adsorb, separate and catalytic oxide the typical organic dye of methylene blue (MB). SEM, TEM, VSM, XPS, pHpzc, and N2 adsorption performances are carried out to characterize the Fe3O4@C. Results show that the Fe3O4@C mainly consists of activated Fe-O-C microspheres, which possess plentiful mesopore and macropore structures on surfaces. Batch adsorption experiments were carried out by varying key reaction conditions to optimize these. The maximum adsorption capacity of MB onto the Fe3O4@C was 305.0 mg g-1 in 120 min, at pH 10, and at a temperature of 323 K. MIRS was also assisted to regenerate the spent Fe3O4@C which presented good regeneration efficiency by sustaining 16 regeneration cycles without any oxidizing agent. SEM images and FTIR spectrum verified that MB would translate into greater or smaller-sized carbon microspheres. What's more, the adsorption of MB onto both initial and the 16th regenerated Fe3O4@C obeyed the Langmuir isotherm model and followed the pseudo-second-order adsorption kinetics, indicating the adsorptive stability after regeneration. In this study, the Fe3O4@C combined with MIRS may be one innovative strategy for organic pollutants' complete removal in the future.

[Effects of Different Treatment Methods on the Contents of Related Growth Factors Released by Platelet Rich Plasma].

OBJECTIVE: To evaluate the effect of sonication, repeated freeze-thaw cycles, calcium salt solution and their combination on the content of related growth factors (GFs) released by platelet rich plasma (PRP). METHODS: Twenty PRPs from healthy blood donors were divided into 9 groups, including sonication group, freeze-thaw group, calcium gluconate group, calcium chloride group, sonication + calcium gluconate group, sonication + calcium chloride group, freeze-thaw + calcium gluconate group, freeze-thaw + calcium chloride group, and sonication + freeze-thaw group. After PRP activated by above 9 methods, the content of transforming growth factor-ß1 (TGF-ß1), vascular endothelial growth factor (VEGF), and platelet-derived growth factor-BB (PDGF-BB) were detected by ELISA. RESULTS: The platelet concentration of the samples was (966.7±202.6)×109/L. The content of TGF-ß1 in sonication + freeze-thaw group was the highest, while the lowest was in freeze-thaw group. The content of VEGF in freeze-thaw + calcium chloride group was the highest, while the lowest was in calcium gluconate group. The content of PDGF-BB in sonication + freeze-thaw group was the highest, while the lowest was in calcium gluconate group. There was no significant differences in the three GFs between calcium gluconate group and calcium chloride group. CONCLUSION: Among the 9 activated methods of PRP, there is no difference between two calcium salt solutions. And the combination of repeated freeze-thaw cycles and sonication may be the best treatment method to promote PRP to release GFs, while calcium gluconate is the weakest way.

In Situ Synthetic ZIF-8/Carbon Aerogel Composites as Solid-Phase Microextraction Coating for the Detection of Phthalic Acid Esters in Water Samples.

In this study, a hybrid composite featuring zeolitic imidazolate framework-8/carbon aerogel (ZIF-8/CA) was synthesized via in situ nucleation and growth of ZIF-8 nanoparticles inside carbon aerogels. The novel material was used as the solid-phase microextraction (SPME) coating for the five phthalic acid esters (PAEs) detection by coupling with a gas chromatography-flame ionization detector (GC-FID). Compared with bare carbon aerogel, the ZIF-8/CA presented the best performance, which is attributed to the unique advantages between the high surface area of CA and high hydrophobic properties, the thermal stability of ZIF-8, and their synergistic adsorption effects, such as molecular penetration, hydrogen bond, and π-π stacking interactions. Under the optimized conditions, the as-proposed ZIF-8/CA fiber provided a wide linearity range from 0.2 to 1000 µg L-1 and a low detection limit of 0.17-0.48 µg L-1 for PAEs analysis. The intra-day and inter-day of signal fiber and the fiber-fiber relative standard deviations were observed in the ranges of 3.50-8.16%, 5.02-10.57%, and 5.66-12.11%, respectively. The method was applied to the determination of five PAEs in plastic bottled and river water samples.

Efficient Reduction of Cr(VI) with Carbon Quantum Dots.

Hexavalent chromium (Cr(VI)) pollution is a global problem, and the reduction of highly toxic Cr(VI) to less toxic Cr(III) is considered to be an effective method to address Cr(VI) pollution. In this study, low-toxicity carbon quantum dots (CQDs) were used to reduce Cr(VI) in wastewater. The results show that CQDs can directly reduce Cr(VI) at pH 2 and can achieve a reduction efficiency of 94% within 120 min. It is observed that under pH higher than 2, CQDs can activate peroxymonosulfate (PMS) to produce reactive oxygen species (ROS) for the reduction of Cr(VI) and the reduction efficiency can reach 99% within 120 min even under neutral conditions. The investigation of the mechanism shows that the hydroxyl groups on the surface of CQDs can be directly oxidized by Cr(VI) because of the higher redox potential of Cr(VI) at pH 2. As the pH increases, the carbonyl groups on the surface of CQDs can activate PMS to generate ROS, O2 •-, and 1O2, which result in Cr(VI) being reduced. To facilitate the practical application of CQDs, the treatment of Cr(VI) in real water samples by CQDs was simulated and the method reduced Cr(VI) from an initial concentration of 5 mg/L to only 8 µg/L in 150 min, which is below the California water quality standard of 10 µg/L. The study provides a new method for the removal of Cr(VI) from wastewater and a theoretical basis for practical application.

Carboxylation modified meso-porous carbon aerogel templated by ionic liquid for solid-phase microextraction of trace tetracyclines residues using HPLC with UV detection.

A carbon aerogel composite templated and catalyzed by ionic liquid was fabricated to obtain a meso-porous and cross-linked structure while avoiding the freeze and supercritical drying. It was then carboxylated to obtain favorable surface groups. The easily prepared material displayed excellent extraction effect of six tetracyclines (TCs) compared to the non-carboxylated carbon aerogel. A direct immersion solid-phase microextraction method to determine six TCs in aqueous samples was developed coupling with high-performance liquid chromatography (HPLC) with UV-Vis detector set at 355 nm. The experimental parameters affecting the analytical performance of this method, including sample pH, ionic strength, extraction and desorption time, extraction volume, and temperature, were optimized. Adsorption kinetics and thermodynamics models were used to clarify the extraction mechanism. Under the optimized conditions, this method has a wide linear range of 2-1000 µg L-1, low limits of detection of 0.36-0.71 µg L-1, repeatability of 1.85-10.96%, and reproducibility of 4.92-13.47% for six TCs. The method was successfully applied to detect TC residues in egg and poultry farm wastewater samples.

Carbon aerogel as a solid-phase microextraction fiber coating for the extraction and detection of trace tetracycline residues in food by coupling with high-performance liquid chromatography.

A direct immersion solid-phase microextraction method for determining tetracyclines (TCs) was developed by coupling with high-performance liquid chromatography. A carbon aerogel (CA) was synthesized as a fiber coating with high extractive properties and a low density of 0.1855 g cm-3via ambient pressure drying and carbonization. The as-synthesized CA exhibited a high specific surface area and a cross-linked structure; it was characterized via scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis, etc. The extraction performance for six TCs was investigated, and the main experimental parameters were optimized by the Box-Behnken design. Adsorption kinetics, Langmuir and Freundlich models were used to clarify the extraction mechanism. This method showed wide linear ranges of 1-500 µg L-1, low limits of detection of 0.52-1.05 µg L-1, good repeatability of 1.37-12.47%, and satisfactory inter-fiber reproducibility of 8.51-15.81% relative standard deviation for the detection of six TCs. Moreover, this study provided an interesting insight into the detection of TCs residues in food samples.

Simultaneous Oxidation and Sequestration of Arsenic(III) from Aqueous Solution by Copper Aluminate with Peroxymonosulfate: A Fast and Efficient Heterogeneous Process.

The major problem in arsenic (As(III)) removal using adsorbents is that the method is time-consuming and inefficient owing to the fact that most of the adsorbents are more effective for As(V). Herein, we report a new discovery regarding the significant simultaneous oxidation and sequestration of As(III) by a heterogeneous catalytic process of copper aluminate (CuAl2O4) coupled with peroxymonosulfate (PMS). Oxidation and adsorption promote each other. With the help of the active radicals, the As(III) removal efficiency can be increased from 59.4 to 99.2% in the presence of low concentrations of PMS (50 µM) and CuAl2O4 (300 mg/L) in solution. CuAl2O4/PMS can work effectively in a wide pH range (3.0-9.0). Other substances, such as nitrate, sulfate, chloride, carbonate, and humic acid, exert an insignificant effect on As(III) removal. Based on X-ray photoelectron spectroscopy (XPS) analysis, the exposed reductive copper active sites might drive the redox reaction of Cu(II)/Cu(I), which plays a key role in the decomposition of PMS and the oxidation of As(III). The exhausted CuAl2O4 could be refreshed for cycling runs with insignificant capacity loss by the combined regeneration strategy because of the stable spinel structure. According to all results, the CuAl2O4/PMS with favorable oxidation ability and stability could be employed as a promising candidate in real As(III)-contaminated groundwater treatment.

Synchronous oxidation and sequestration for As(iii) from aqueous solution by modified CuFe2O4 coupled with peroxymonosulfate: a fast and stable heterogeneous process.

Bifunctional heterogeneous catalytic processes for highly efficient removal of arsenic (As(iii)) are receiving increased attention. However, the agglomerated nature and stability of nanoparticles are major concerns. Herein, we report a new process regarding the anchoring of CuFe2O4 nanoparticles on a substrate material, a kind of Fe-Ni foam, to form porous CuFe2O4 foam (CuFe2O4-foam) by in situ synthesis. The prepared material was then applied to activate peroxymonosulfate (PMS) for fast and efficient removal of As(iii) from water. The results of removal experiments show that the complete removal of arsenic (<10 µg L-1) from 1 mg L-1 As(iii) aqueous solution can be achieved within shorter time (<10 min) using this adsorbent coupled with PMS. The maximum adsorption capability of As(iii) and As(v) on the prepared adsorbent is observed to be about 105.78 mg g-1 and 120.32 mg g-1, respectively. CuFe2O4-foam/PMS couple could work effectively in a wide pH range (3.0-9.0) and temperature range (10-60 °C), which is more beneficial to its application in actual water treatment engineering. The exhausted adsorbents can be refreshed for cyclic runs (at least 7 cycles) with insignificant capacity loss using alkaline solution as a regeneration strategy, suggesting this process has good stability. Investigation of the mechanism reveals that the route to the removal of As(iii) is synchronous oxidation and sequestration in the arsenic removal process. The large As(iii) removal capability and stability of CuFe2O4-foam/PMS show its potential as a promising candidate in real As(iii)-contaminated groundwater treatment.

Data for a new spinel catalyst to activate peroxymonosulfate for highly efficient degrading organic contaminants in water based on non-radical process.

The aim of this research is to degrade organic contaminants in aqueous solution via lead ferrite (PbFe2O4) as a catalyst to activate peroxymonosulfate (PMS). PbFe2O4 was synthesized by a citrate combustion method and analyzed by SEM, TEM and XRD. A simulated solution including thionine were used, with different conditions tested to optimize the degradation process, including comparing PbFe2O4 to other catalysts, PbO and Fe2O3, and tracking active oxygen species. The concentrations of thionine and PMS were tracked with a UV-Vis spectrophotometer in the treatment process. The data are presented as graphs and tables. A detailed analyses of this report can be found in the article "New insight into the mechanism of peroxymonosulfate activation by nanoscaled lead-based spinel for organic matters degradation: a singlet oxygen-dominated oxidation process" published in Journal of colloid and interface science.

New insight into the mechanism of peroxymonosulfate activation by nanoscaled lead-based spinel for organic matters degradation: A singlet oxygen-dominated oxidation process.

Crystalline iron-based nanoparticles with spinel structure have received great attention for catalyzing peroxymonosulfate (PMS). This study introduces lead ferrite (PbFe2O4) as a novel, simple, and efficient catalyst to activate PMS for the degradation of organic contaminants in aqueous solution. The results indicated that, under pH 9.0, nearly 100% of 10 µM thionine was removed in 20 min. Operation factors, including pH, oxidant concentrations, catalyst dosage, and coexisting ions, were investigated and found to be influential for the thionine removal. PbFe2O4 showed higher catalytic activity and lower ions leaching than well-crystallized lead oxide (PbO) and ferric oxide (Fe2O3). The results from the characterization of the PbFe2O4 with X-ray diffraction (XRD) before and after reaction suggested that the structure and properties of the catalyst kept stable, and the recovered catalyst exhibited good catalytic performance during the recycling batch experiments. Free radical quenching experiments and electron paramagnetic resonance (EPR) spectra revealed that singlet-oxygen (1O2) is the dominant active oxygen species rather than sulfate radical for thionine degradation in PbFe2O4/PMS system. Meanwhile, the possible pathways of 1O2 generation were proposed: the redox reaction between Pb(Ⅳ)/Pb(II) and PMS may play an key role in PMS activation. This study provides an interesting insight in PMS activation by the high-efficient non-radical process, and the PbFe2O4 could be as efficient and recyclable heterogeneous catalyst for organic degradation.

Label-free analytical performances of a peptide-based QCM biosensor for trypsin.

A label-free biosensor was fabricated for the detection of trypsin by using a peptide-functionalized quartz crystal microbalance gold electrode. The synthetized peptide chains were immobilized tightly on the QCM electrode via a self-assembly method, which formed a thin and approximate rigid layer of peptides. The detection signal was achieved by calculating the mass changes on the QCM electrode because the peptide chains could be specifically cleaved in the carboxyl terminuses of arginine and lysine by trypsin. When gold nanoparticles were coupled to the peptide chains, the sensing signal would be amplified 10.9 times. Furthermore, the sensor interface shows a lower resonance resistance change when the peptide chain is immobilized horizontally. Independent detections in parallel on different electrodes have a wide linear range. Under the optimum conditions, the signal-amplified biosensor allowed the measurement of trypsin over the range of 0-750 ng mL-1 with a detection limit of 8.6 ng mL-1. Moreover, for screening the inhibitor of trypsin, the IC50 values were obtained to be 1.85 µg mL-1 for benzamidine hydrochloride and 20.5 ng mL-1 for the inhibitor from soybean.

A fluorescence sensing platform of theophylline based on the interaction of RNA aptamer with graphene oxide.

RNA, with a structure similar to DNA, should exhibit similar behaviors when it interacts with graphene. In this work, we designed a sensing platform of theophylline based on the interaction of an RNA aptamer with graphene oxide (GO) using the fluorescence as a sensing signal. Firstly, quantum dots (QDs) were modified with the selected ssRNA that can be used as an aptamer to recognize the theophylline. The fluorescence of QDs will be quenched in the presence of GO due to the noncovalent assembly between ssRNA aptamer and GO, leading to fluorescence resonance energy transfer (FRET) from QDs to GO, fluorescence "turn-off". Then, in the presence of theophylline, the ssRNA aptamer recognizes theophylline to form a dsRNA-theophylline complex. The weak affinity between the complex and GO makes QDs move away from the GO surface, leading to the fluorescence recovery of QDs, fluorescence "turn-on". Because of the high fluorescence quenching efficiency, unique structure of GO and specificity of the RNA aptamer, the proposed sensing platform exhibits high sensitivity and excellent selectivity for the determination of theophylline. The excellent performance of the sensor based on GO provides new opportunities for sensitive and selective detection of biorecognition events.

[Coagulation Properties for Whole Blood Stored at 4℃].

OBJECTIVE: To study the coagulation properties the refrigerated whole blood stored at 4℃. METHODS: Ten units of whole blood were obtained from healthy volunteer donors and stored at 4±2℃ for 21 days. Samples were collected on the day after donation and on days 2, 4, 6, 8, 10, 14 and 21 for delection including complete blood count, electrolyte, APTT, PT, Fg, blood coagulation factors, and thromboelastography(TEG). RESULTS: The levels of Hb, WBC, Plt, sodium and potassium in each sample accorded with standard of storing whole blood. The level of Hb, WBC, Plt and Na+ decreased along with prolonging of storage time, while the K+ level increased along with prolonging of stored time, APTT and PT prolonged along with prolonging of thored time, PT>17 min at d 21, the Fg level change was no-obvious, The level of factor Ⅴ and Ⅷ decreased more than 50 % of baseline on d 6 and 4 respectively; the levels of factor Ⅱ, Ⅶ, Ⅸ, Ⅹ, Ⅺ, Ⅻ showed decreasing trend, but their levels were less than 40 % of baseline values at d 21. TEG test showed that no abnormalily of R value was found, the abnormal valnes of K and Angle were observed at d 21, the abnormal value of MA was observed at d 14. CONCLUSION: The whole blood stored for 10 days possesses normal coagulation function showing important significance for treatment of hemorrhage from war injury and surgical openation of heart and chest.

Amplified QCM biosensor for type IV collagenase based on collagenase-cleavage of gold nanoparticles functionalized peptide.

The present study develops a rapid, simple and efficient method for the determination of type IV collagenase by using a specific peptide-modified quartz crystal microbalance (QCM). A small peptide (P1), contains a specific sequence (Pro-Gly) and a terminal cysteine, was synthetized and immobilized to the surface of QCM electrode via the reaction between Au and thiol of the cysteine. The peptide bond between proline and glycine can be specific hydrolyzed cleavage by type IV collagenase, which enabled the modified electrode with a high selectivity toward type IV collagenase. The cleaving process caused a frequency change of QCM to give a signal related to the concentration of type IV collagenase. The morphologies of the modified electrodes were characterized by scanning electron microscope (SEM) and the specific hydrolyzed cleavage process was monitored by QCM. When P1 was modified with gold nanoparticles (P1-Au NPs), the signal could be amplified to further enhance the sensitivity of the designed sensor due to the high-mass of the modified Au NPs. Compared the direct unamplified assay, the values obtained for the limit of detection for type IV collagenase was 0.96 ng mL-1, yielding about 6.5 times of magnitude improvement in sensitivity. This signal enhanced peptide based QCM biosensor for type IV collagenase also showed good selectivity and sensitivity in complex matrix.

A novel signal-on photoelectrochemical immunosensor for detection of alpha-fetoprotein by in situ releasing electron donor.

A signal-on photoelectrochemical (PEC) immunosensor was constructed for detecting tumor marker in this work. α-fetoprotein (AFP) was chosen as a model analyte to investigate the prepared procedure and the analytical performance of the exploited sensor. In order to construct the sensor, CdSe QDs were used as photoactive material, biotin conjugated AFP antibody (Bio-anti-AFP) as detecting probe, streptavidin (SA) as signal capturing unit, biotin functionalized apoferritin encapsulated ascorbic acid (Bio-APOAA) as amplification unit, which were assembled onto the electrodes. The sensing strategy was based on in situ enzymatic hydrolysis of Bio-APOAA to release ascorbic acid (AA) as sacrificial electron donor to produce photocurrent. The photocurrent from the immunosensor was monitored as a result of AFP concentrations. The constructed sensing platform displayed high selectivity and good sensitivity for detecting AFP. Under optimal conditions, a wide linear range from 0.001 to 1000ng/mL and a low detection limit of 0.31pg/mL were obtained. The developed immunosensor is expected to be used to determine AFP and other tumor markers in human plasma in clinical laboratories either for pre-cancer screening or cancer monitoring. Moreover, this sensing platform further has the potential to use for the detection of trypsin activity and the corresponding inhibitor-screening.

Nano-encapsulant of ascorbic acid-loaded apoferritin-assisted photoelectrochemical sensor for protease detection.

A signal-on photoelectrochemical (PEC) biosensor based on nano-encapsulant of ascorbic acid-loaded apoferritin-assisted for protease detection is described. The loaded ascorbic acid could be released from the central cavity of apoferritin into the buffer solution as sacrificial electron donor to capture the photo-generated holes of CdTe quantum dots when light is turned on. In this system, the biosensor relied on monitoring the photocurrent intensity as a result of enzymatic substrate proteolysis in the homogeneous aqueous solution. A low detection limit of 2.7ngmL-1 for trypsin in the linear range from 30 to 450ngmL-1 is achieved. We believe that such a sensing system not only holds the potential ability as a probe for trypsin activity assay, but also could be used for the corresponding inhibitor-screening. It might provide a potentially feasible alternative tool for determining trypsin in human serum in a clinical laboratory. The established method could open a different perspective for PEC enzyme detection and provide a new platform for future development of PEC analysis with other clinically important proteins.

A Novel Photoelectrochemical Biosensor for Tyrosinase and Thrombin Detection.

A novel photoelectrochemical biosensor for step-by-step assay of tyrosinase and thrombin was fabricated based on the specific interactions between the designed peptide and the target enzymes. A peptide chain with a special sequence which contains a positively charged lysine-labeled terminal, tyrosine at the other end and a cleavage site recognized by thrombin between them was designed. The designed peptide can be fixed on surface of the CdTe quantum dots (QDs)-modified indium-tin oxide (ITO) electrode through electrostatic attraction to construct the photoelectrochemical biosensor. The tyrosinase target can catalyze the oxidization of tyrosine by oxygen into ortho-benzoquinone residues, which results in a decrease in the sensor photocurrent. Subsequently, the cleavage site could be recognized and cut off by another thrombin target, restoring the sensor photocurrent. The decrease or increase of photocurrent in the sensor enables us to assay tyrosinase and thrombin. Thus, the detection of tyrosinase and thrombin can be achieved in the linear range from 2.6 to 32 µg/mL and from 4.5 to 100 µg/mL with detection limits of 1.5 µg/mL and 1.9 µg/mL, respectively. Most importantly, this strategy shall allow us to detect different classes of enzymes simultaneously by designing various enzyme-specific peptide substrates.

Label-free detection of pathogenic bacteria via immobilized antimicrobial peptides.

A novel label-free strategy for the detection of bacteria was developed by using a specific antimicrobial peptide (AMP)-functionalized quartz crystal microbalance (QCM) electrode. This electrode interface was successfully applied to detect pathogenic Escherichia coli O157:H7 based on the specific affinity between the small synthetic antimicrobial peptide and the bacterial cell of pathogenic E. coli O157:H7. The concentrations of pathogenic E. coli O157:H7 were sensitively measured by the frequency response of the QCM with a detection limit of 0.4 cfu µL(-1). The detection can be fulfilled within 10 min because it does not require germiculture process. On the other hand, if the specific antimicrobial peptides were immobilized on a gold electrode, this label-free strategy can also be performed by electrochemical impedance spectroscopy (EIS). Compared with QCM technique, the EIS measurement gives a lower sensitivity and needs a longer assay time. The combination of antimicrobial peptides with the real-time responses of QCM, as well as electronic read-out monitoring of EIS, may open a new way for the direct detection of bacteria.

Direct electrochemistry of hemoglobin at a graphene gold nanoparticle composite film for nitric oxide biosensing.

A simple two-step method was employed for preparing nano-sized gold nanoparticles-graphene composite to construct a GNPs-GR-SDS modified electrode. Hemoglobin (Hb) was successfully immobilized on the surface of a basal plane graphite (BPG) electrode through a simple dropping technique. Direct electrochemistry and electrocatalysis of the hemoglobin-modified electrode was investigated. The as-prepared composites showed an obvious promotion of the direct electro-transfer between hemoglobin and the electrode. A couple of well-defined and quasi-reversible Hb CV peaks can be observed in a phosphate buffer solution (pH 7.0). The separation of anodic and cathodic peak potentials is 81 mV, indicating a fast electron transfer reaction. The experimental results also clarified that the immobilized Hb retained its biological activity for the catalysis toward NO. The biosensor showed high sensitivity and fast response upon the addition of NO, under the conditions of pH 7.0, potential -0.82 V. The time to reach the stable-state current was less than 3 s, and the linear response range of NO was 0.72-7.92 µM, with a correlation coefficient of 0.9991.

A theophylline quartz crystal microbalance biosensor based on recognition of RNA aptamer and amplification of signal.

A quartz crystal microbalance (QCM) biosensor for theophylline was developed by recognition of RNA aptamer and gold nanoparticle amplification technique. Firstly, a designed small single-stranded RNA, RNA1, was immobilized onto the QCM electrode through a thiol linker. Then, the complementary stranded RNA2, which can combine with RNA1 to form a double-stranded RNA with a recognition unit of theophylline, could be self-assembled on the QCM electrode surface through a hybrid reaction in the presence of theophylline. The recognition process could cause a frequency change of QCM to give the signal related to theophylline. When RNA2 was tethered to gold nanoparticles, the signal could be amplified to further enhance the sensitivity of the designed sensor. Under the optimal conditions, the QCM-based biosensor showed excellent sensitivity (limit of detection, 8.2 nM) and specificity with a dissociation constant of Kd = 5.26 × 10(-7) M. The sensor can be used to quantitatively detect theophylline in serum, suggesting that it can be applied in complex biological samples.