Carbon nanomaterial functionalization with pesticide-detoxifying carboxylesterase.

Four carbon materials, spent coffee-ground biochar, carbon black, short CNTs, and nitrogen-doped few-layer graphene (N-graphene) were tested for their functionalization with a commercial carboxylesterase. Their robustness to variations in time and key physicochemical parameters (temperature and pH) was analysed. In general, carbon nanomaterials showed better performance than biochar, both in terms of binding capacity and resilience in harsh conditions, at statistically significant levels. Among the tested materials, functionalized N-graphene also showed the highest level of inhibition of carboxylesterase by pesticide exposure. Therefore, N-graphene was selected for biotechnological application of pesticide scavenging toxicity in T. thermophila, a ciliate bioindicator of water quality. While immobilization of the enzyme was not effective in the case of carbaryl, a methyl carbamate, in the case of the organophosphorus dichlorvos, a 1- or 30-min contact time with a water solution containing 5 times the LC100 - 0.5 mM - allowed 50% and 100% rescue of ciliate survival, respectively. These results suggest that functionalization with carboxylesterase may be of additional benefit compared to bare carbon in water clean-up procedures, especially for highly hydrophilic pesticides such as dichlorvos.

N,S-Decorated graphenes modified with 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine manganese(III) chloride-based 3D needle stochastic sensors for enantioanalysis of arginine: a key factor in the metabolomics and early detection of gastric cancer.

Arginine has an important role in the metabolomics of gastric cancer. Two 3D enantioselective needle stochastic sensors based on the physical immobilization of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine manganese(III) chloride (solution, 10-3 mol L-1) in graphene paste matrices decorated with N and S atoms were designed, characterized and validated for the enantioanalysis of arginine in whole blood and tissue samples. The signature values obtained for the enantiomers of arginine confirmed that the stochastic sensors are enantioselective. The lowest limit of quantification obtained for both enantiomers of arginine was 1 fmol L-1, while sensitivity of up to 1011 s-1 mol-1 L was recorded for the stochastic sensors. High recoveries were obtained for the determination of one enantiomer in the presence of the other one; moreover, very good correlation was found between the results obtained with the two 3D enantioselective needle stochastic sensors.

Stochastic microsensors based on modified graphene for pattern recognition of maspin in biological samples.

Maspin is a novel serine protease inhibitor differentially expressed in several types of human cancers. It proved to be a key biomarker in the assessment of gastric cancer. Therefore, we design, characterize, and validate two stochastic microsensors based on graphene co-doped with N and S, and modified with α-cyclodextrin and maltodextrin, for the pattern recognition and quantification of maspin in whole blood, gastric tumor tissue, saliva, and urine. While the sensitivities were comparable with magnitude order, the variations were in the wideness of the linear concentration range, when measurements were performed at a pH of 7.40. Very low limits of quantification were recorded at both working pHs: 7.40, and 3.00. High recoveries of maspin in whole blood, gastric tissue tumor, saliva, and urine were also recorded.

Stochastic biosensors based on N- and S-doped graphene for the enantioanalysis of aspartic acid in biological samples.

Metabolomics plays a very important role in cancer mechanism and also in the early diagnosis of cancer. The enantioanalysis of aminoacids found in biological samples may favor the development of new screening tests for the early diagnosis of cancer. Two stochastic biosensors, based on the immobilization of α-hemolysin and hemin in exfoliated reduced graphene modified with nitrogen and sulphur, were proposed for the enantioanalysis of aspartic acid in biological samples (whole blood, urine, saliva, and tissue). The proposed biosensors showed low limits of quantification, high sensitivity, and large linear concentration ranges. The recoveries of d- and l-aspartic acid in biological samples were higher than 95.00%, with a relative standard deviation lower than 1.00%.

Enantioanalysis of glutamine-a key factor in establishing the metabolomics process in gastric cancer.

Gastric cancer is the second leading cause of death in the world. Early detection will facilitate early treatment and full recovery of the patients. Metabolomics facilitated the detection of few amino acids able to be used as biomarkers. It was always assumed that the L-enantiomer of the chiral amino acid is part of the process, forgetting the twisting of DNA molecules which may also produce the D-enantiomer of the amino acid. Therefore, an enantioanalysis of amino acids such as glutamine which are part of the gastric cancer metabolomics is absolutely necessary. Four stochastic sensors based on immobilization of protoporphyrin IX, ß-cyclodextrin, and 2,2-diphenyl-1-picrylhydrazyl on graphene materials were proposed for the enantioanalysis of glutamine in whole blood samples of patients with gastric cancer. Different signatures were obtained for the enantiomers for each stochastic sensor, making possible the enantioanalysis of glutamine in large concentration ranges-from fmol/L to mmol/L; these ranges facilitating the enantioanalysis of glutamine in healthy patients as well as in patients were found in early and later stages of gastric cancer. Graphical abstract.

Enantioanalysis of tryptophan in whole blood samples using stochastic sensors-A screening test for gastric cancer.

Tryptophan is a key amino acid related to metabolomics in gastric cancer. To date, methods were developed only for the assay of l-tryptophan, the role of d-tryptophan being not yet established. Therefore, four stochastic sensors based on different graphene materials modified with ß-cyclodextrins, 2,2-diphenyl-1-picrylhydrazyl, and protoporphyrin IX were designed and used for enantioanalysis of tryptophan in whole blood samples. High sensitivities, and reliabilities were recorded when the stochastic sensors were used for the enantioanalysis of tryptophan in whole blood samples. The paper opened a new chapter in early detection of gastric cancer, based on establishing the role of d-tryptophan in metabolomics, and in early diagnosis of gastric cancer.

Pattern recognition of 8-hydroxy-2'-deoxyguanosine in biological fluids.

8-Hydroxy-2'-deoxyguanosine (8-OHdG), a product of oxidative DNA damage, which has been used as a sensitive and reliable marker of oxidative stress and carcinogenesis, is found in high levels in biological fluids of leukemia patients. A reliable screening method based on pattern recognition of 8-OHdG using stochastic sensors designed with graphene materials decorated with nanoparticles of TiO2Ag or TiO2Au was developed. 5,10,15,20-Tetraphenyl-21H,23H porphyrin (P), 2,6-bis((E)-2-(furan-2-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine (Py1), and 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine (Py2) were used as modifiers of the graphene paste in the design of sensors. The screening method used for pattern recognition was developed for two pH values accordingly with the nature of the biological fluid to be screened: pH = 3.02 for urine samples and pH = 7.49 for whole blood samples. High sensitivities and low limits of determination for 8-OHdG obtained at both pH values favored the early detection of leukemia. Recoveries over 98.00% with RSD (%) values lower than 1.00% proved the reliability of the proposed screening method. Graphical abstract Graphene based sensors detect 8-hydroxy-2'-deoxyguanosine in biological fluids.