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A novel colorimetric aptasensor has been developed for highly sensitive tetracycline (TC) detection based on the peroxidase-like activity of Fe3O4@Cu nanoparticles and "sandwich" oligonucleotide hybridization. The Fe3O4@Cu nanoparticles with high peroxidase-like activity were successfully synthesized under mild conditions. Then, a "sandwich" oligonucleotide hybridization probe (a short amino-modified complementary sequence of a portion of the TC aptamer (cDNA1), TC aptamers, and a long complementary to 5′ terminal TC aptamer sequence (cDNA2)) was created in 96-wells plates via DNA hybridization in the absence of TC from the detection system. The unique "sandwich" oligonucleotide hybridization probe adsorbed large numbers of Fe3O4@Cu nanozymes while further enhancing its peroxidase-like activity. Based on the 3,3′,5,5′-tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) reporting system, the blue color of the solution decreased linearly with the increase of TC concentration, ranging from 10−3 to 103 μg/L with an ultralow limit of detection (LOD) of 0.91 ng/L (2 pM). The proposed method was successfully applied to detect TC in spiked milk samples, with recoveries of 81.8 to 112%, demonstrating the excellent potential for highly sensitive TC detection in milk. [ABSTRACT FROM AUTHOR]

Objective: To discuss the clinical significance of fluid management of severe patients according to arterial pressure-based cardiac output (APCO) monitoring volume responsiveness index., Methods: A retrospective cohort study was conducted. The severe patients were selected from the intensive care unit (ICU) of the First Hospital of Jilin University from June 1st, 2012 to December 31st, 2013. The hemodynamic parameters were monitored by APCO, and the fluid resuscitation was managed by stroke volume variation (SVV) and passive leg-raising test (PLR) when the acute physiology and chronic health evaluation II (APACHEII) score ≥ 15, heart rate >100 bpm with the result that the preload and heart function could not be evaluated. The heart rate, SVV, lactic acid (Lac) and central venous pressure (CVP) and curative effect were recorded before and after carrying out fluid management strategy. The criteria of clinical effective was defined as heart rate decreased and (or) stroke volume (SV) increased ≥ 10%, accompanied by blood Lac and SVV decreased, other than, the cases did not meet above criteria were considered ineffective., Results: Sixty-eight patients were enrolled in the study. (1) Before carrying out fluid management strategy: 40 cases with CVP>12 cmH₂O (1 cmH₂O=0.098 kPa), and 16 cases with 5-12 cmH₂O, 12 with <5 cmH₂O. SVV>13% in 35 cases, SVV <13% in 9 cases. PLR positive in 18 cases, and PLR negative in 6 cases. It was implicated that the patients with poor preload (SVV>13% and PLR positive) accounted by 77.9% (53/68). (2) There were 49 effective cases and 19 ineffective cases 4 hours after carrying out fluid management strategy, and the effective rate was 72.06% (49/68). While there were 56 effective cases and 12 ineffective cases after 12 hours, and the total effective rate was 82.35% (56/68). (3) In effective group, heart rate, SVV, Lac after fluid management strategy were significantly lower than those before fluid management strategy [4 hours after fluid management strategy: heart rate (bpm) 112.45 ± 13.53 vs. 129.55 ± 15.49, SVV (15.47 ± 6.32)% vs. (21.20 ± 7.40)%, Lac (mmol/L) 4.16 ± 3.12 vs. 6.21 ± 4.11; 12 hours after fluid management strategy: heart rate (bpm) 110.02 ± 13.92 vs. 129.61 ± 14.93, SVV (14.61 ± 15.52)% vs. (20.66 ± 7.40)%, Lac (mmol/L) 3.35 ± 2.26 vs. 6.11 ± 4.02, P<0.05 or P<0.01], while there was no significant difference in those markers between before and after fluid management strategy in ineffective group [4 hours after fluid management strategy: heart rate (bpm) 119.53 ± 11.68 vs. 125.79 ± 11.58, SVV (16.95 ± 6.48)% vs. (18.47 ± 4.96)%, Lac (mmol/L) 5.55 ± 3.80 vs. 6.54 ± 3.72; 12 hours after fluid management strategy: heart rate (bpm) 115.92 ± 11.71 vs. 123.40 ± 11.59, SVV (17.17 ± 6.09)% vs. (19.42 ± 8.25)%, Lac (mmol/L) 6.33 ± 3.40 vs. 7.21 ± 3.81, all P>0.05]. CVP only at 12 hours after fluid management strategy in effective group was significantly higher than that before fluid management strategy (cmH₂O: 12.8 8 ± 3.38 vs. 11.27 ± 4.97, P<0.05)., Conclusions: SVV monitored by APCO is a good indicator of volume responsiveness index, which can be used as an important reference combined with PLR for fluid management of severe patients.