CsSHMT3 gene enhances the growth and development in cucumber seedlings under salt stress.

Salt stress is one of the major factors limiting plant growth and productivity. Many studies have shown that serine hydroxymethyltransferase (SHMT) gene play an important role in growth, development and stress response in plants. However, to date, there have been few studies on whether SHMT3 can enhance salt tolerance in plants. Therefore, the effects of overexpression or silencing of CsSHMT3 gene on cucumber seedling growth under salt stress were investigated in this study. The results showed that overexpression of CsSHMT3 gene in cucumber seedlings resulted in a significant increase in chlorophyll content, photosynthetic rate and proline (Pro) content, and antioxidant enzyme activity under salt stress condition; whereas the content of malondialdehyde (MDA), superoxide anion (H2O2), hydrogen peroxide (O2·-) and relative conductivity were significantly decreased when CsSHMT3 gene was overexpressed. However, the content of chlorophyll and Pro, photosynthetic rate, and antioxidant enzyme activity of the silenced CsSHMT3 gene lines under salt stress were significantly reduced, while MDA, H2O2, O2·- content and relative conductivity showed higher level in the silenced CsSHMT3 gene lines. It was further found that the expression of stress-related genes SOD, CAT, SOS1, SOS2, NHX, and HKT was significantly up-regulated by overexpressing CsSHMT3 gene in cucumber seedlings; while stress-related gene expression showed significant decrease in silenced CsSHMT3 gene seedlings under salt stress. This suggests that overexpression of CsSHMT3 gene increased the salt tolerance of cucumber seedlings, while silencing of CsSHMT3 gene decreased the salt tolerance. In conclusion, CsSHMT3 gene might positively regulate salt stress tolerance in cucumber and be involved in regulating antioxidant activity, osmotic adjustment, and photosynthesis under salt stress. KEY MESSAGE: CsSHMT3 gene may positively regulate the expression of osmotic system, photosynthesis, antioxidant system and stress-related genes in cucumber.

SlSERK3B Promotes Tomato Seedling Growth and Development by Regulating Photosynthetic Capacity.

Brassinosteroids (BRs) are a group of polyhydroxylated steroids for plant growth and development, regulating numerous physiological and biochemical processes and participating in multi-pathway signaling in plants. 24-Epibrassinolide (EBR) is the most commonly used BR for the investigation of the effects of exogenous steroidal phytohormones on plant physiology. Although SlSERK3B is considered a gene involved in the brassinosteroid (BR) signaling pathway, its specific role in plant growth and development has not been reported in detail. In this study, tomato (Solanum lycopersicum L.) seedlings treated with 0.05 µmol L-1 EBR showed a significant increase in plant height, stem diameter, and fresh weight, demonstrating that BR promotes the growth of tomato seedlings. EBR treatment increased the expression of the BR receptor gene SlBRI1, the co-receptor gene SlSERK3A and its homologs SlSERK3B, and SlBZR1. The SlSERK3B gene was silenced by TRV-mediated virus-induced gene silencing (VIGS) technology. The results showed that both brassinolide (BL) content and BR synthesis genes were significantly up-regulated in TRV-SlSERK3B-infected seedlings compared to the control seedlings. In contrast, plant height, stem diameter, fresh weight, leaf area and total root length were significantly reduced in silenced plants. These results suggest that silencing SlSERK3B may affect BR synthesis and signaling, thereby affecting the growth of tomato seedlings. Furthermore, the photosynthetic capacity of TRV-SlSERK3B-infected tomato seedlings was reduced, accompanied by decreased photosynthetic pigment content chlorophyll fluorescence, and photosynthesis parameters. The expression levels of chlorophyll-degrading genes were significantly up-regulated, and carotenoid-synthesising genes were significantly down-regulated in TRV-SlSERK3B-infected seedlings. In conclusion, silencing of SlSERK3B inhibited BR signaling and reduced photosynthesis in tomato seedlings, and this correlation suggests that SlSERK3B may be related to BR signaling and photosynthesis enhancement.

The Crucial Role of SlGSNOR in Regulating Postharvest Tomato Fruit Ripening.

S-nitrosoglutathione reductase (GSNOR) is a well-known regulator in controlling protein S-nitrosylation modification and nitric oxide (NO) homeostasis. Here, a GSNOR inhibitor N6022 and SlGSNOR silencing were applied to investigate the roles of SlGSNOR in tomato fruit postharvest ripening. We found that the application of N6022 and S-nitrosoglutathione (GSNO, a NO donor), and SlGSNOR silencing delayed the transition of fruit skin color by improving total chlorophyll level by 88.57%, 44.78%, and 91.03%, respectively. Meanwhile, total carotenoid and lycopene contents were reduced by these treatments. Concurrently, the activity of chlorophyll biosynthesis enzymes and the expression of related genes were upregulated, and the transcript abundances of total carotenoid bioproduction genes were downregulated, by N6022 and GSNO treatments and SlGSNOR silencing. In addition, fruit softening was postponed by N6022, GSNO, and SlGSNOR silencing, through delaying the decrease of firmness and declining cell wall composition; structure-related enzyme activity; and gene expression levels. Furthermore, N6022, GSNO, and SlGSNOR silencing enhanced the accumulation of titratable acid; ascorbic acid; total phenol; and total flavonoid, but repressed the content of soluble sugar and soluble protein accompanied with the expression pattern changes of nutrition-related genes. In addition, the endogenous NO contents were elevated by 197.55%; 404.59%; and 713.46%, and the endogenous SNOs contents were enhanced by 74.65%; 93.49%; and 94.85%; by N6022 and GSNO treatments and SlGSNOR silencing, respectively. Altogether, these results indicate that SlGSNOR positively promotes tomato postharvest fruit ripening, which may be largely on account of its negative roles in the endogenous NO level.

Brassinosteroids is involved in methane-induced adventitious root formation via inducing cell wall relaxation in marigold.

BACKGROUND: Methane (CH4) and brassinosteroids (BRs) are important signaling molecules involved in a variety of biological processes in plants. RESULTS: Here, marigold (Tagetes erecta L. 'Marvel') was used to investigate the role and relationship between CH4 and BRs during adventitious root (AR) formation. The results showed a dose-dependent effect of CH4 and BRs on rooting, with the greatest biological effects of methane-rich water (MRW, CH4 donor) and 2,4-epibrassinolide (EBL) at 20% and 1 µmol L- 1, respectively. The positive effect of MRW on AR formation was blocked by brassinoazole (Brz, a synthetic inhibitor of EBL), indicating that BRs might be involved in MRW-regulated AR formation. MRW promoted EBL accumulation during rooting by up-regulating the content of campestanol (CN), cathasterone (CT), and castasterone (CS) and the activity of Steroid 5α-reductase (DET2), 22α-hydroxylase (DWF4), and BR-6-oxidase (BR6ox), indicating that CH4 could induce endogenous brassinolide (BR) production during rooting. Further results showed that MRW and EBL significantly down-regulated the content of cellulose, hemicellulose and lignin during rooting and significantly up-regulated the hydrolase activity, i.e. cmcase, xylanase and laccase. In addition, MRW and EBL also significantly promoted the activity of two major cell wall relaxing factors, xyloglucan endotransglucosylase/hydrolase (XTH) and peroxidase, which in turn promoted AR formation. While, Brz inhibited the role of MRW on these substances. CONCLUSIONS: BR might be involved in CH4-promoted AR formation by increasing cell wall relaxation.

Characterization of the FLA Gene Family in Tomato (Solanum lycopersicum L.) and the Expression Analysis of SlFLAs in Response to Hormone and Abiotic Stresses.

Fasciclin-like arabinogalactan proteins (FLAs), a subclass of arabinogalactan proteins (AGPs), participate in mediating plant growth, development, and response to abiotic stress. However, the characterization and function of FLAs in tomato are currently unknown. In this study, members of the tomato FLA family are characterized and analyzed in relation to their response to phytohormonal and abiotic stresses. The results show that a total of 24 FLA members were characterized in tomato. The structural domain analysis showed that these members have a high protein similarity. The expression profiles of different tissues indicated that the genes of most members of the tomato FLA gene family are highly expressed in roots, but to a lower extent in fruits. qRT-PCR analysis revealed that all 24 tomato FLA genes are responsive to ABA and MeJA. SlFLAs showed a positive response to salt and cold stress. SlFLA1, SlFLA12, and SlFLA14 are significantly induced under darkness. SlFLA1 and SlFLA3 are significantly induced under drought stress. This study provides a basis for a further understanding of the role of tomato FLA homologous genes in plant response to abiotic stress and lays the foundation for further research on the function of FLAs in tomato.

NO is involved in H2-induced adventitious rooting in cucumber by regulating the expression and interaction of plasma membrane H+-ATPase and 14-3-3.

MAIN CONCLUSION: NO was involved in H2-induced adventitious rooting by regulating the protein and gene expressions of PM H+-ATPase and 14-3-3. Simultaneously, the interaction of PM H+-ATPase and 14-3-3 protein was also involved in this process. Hydrogen gas (H2) and nitric oxide (NO) have been shown to be involved in plant growth and development. The results in this study revealed that NO was involved in H2-induced adventitious root formation. Western blot (WB) analysis showed that the protein abundances of plasma membrane H+-ATPase (PM H+-ATPase) and 14-3-3 protein were increased after H2, NO, H2 plus NO treatments, whereas their protein abundances were down regulated when NO scavenger carboxy-2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTI O) was added. Moreover, the mRNA abundances of the HA3 and 14-3-3(7) gene as well as the activities of PM H+-ATPase (EC 3.6.1.35) and H+ pump were in full agreement with the changes of protein abundance. Phosphorylation of PM H+-ATPase and the interaction of PM H+-ATPase and 14-3-3 protein were detected by co-immunoprecipitation analysis. H2 and NO significantly up regulated the phosphorylation of PM H+-ATPase and the interaction of PM H+-ATPase and 14-3-3 protein. Conversely, the stimulation of PM H+-ATPase phosphorylation and protein interaction were significantly diminished by cPTIO. Protein interaction activator fusicoccin (FC) and inhibitor adenosine monophosphate (AMP) of PM H+-ATPase and 14-3-3 were used in this study, and the results showed that FC significantly increased the abundances of PM H+-ATPase and 14-3-3, while AMP showed opposite trends. We further proved the critical roles of PM H+-ATPase and 14-3-3 protein interaction in NO-H2-induced adventitious root formation. Taken together, our results suggested that NO might be involved in H2-induced adventitious rooting by regulating the expression and the interaction of PM H+-ATPase and 14-3-3 protein.

Liver Cancer Detection by a Simple, Inexpensive and Effective Immunosensor with Zinc Oxide Nanoparticles.

Regular monitoring of blood α-fetoprotein (AFP) and/or carcino-embryonic antigen (CEA) levels is important for the routine screening of liver cancer. However, AFP and CEA have a much lower specificity than des-γ-carboxyprothrombin (DCP) to detect liver cancer. Therefore, the study reported here was designed, to develop a screen-printed DCP immunosensor incorporating zinc oxide nanoparticles, for accurate determination of DCP. The designed immunosensor shows low detection limits for the detection of DCP: 0.440 ng/mL (based on impedance measurement), 0.081 ng/mL (based on real part of impedance measurement) and 0.078 ng/mL (based on imaginary part of impedance measurement), within the range of 3.125 ng/mL to 2000 ng/mL. In addition, there was little interference to DCP determination by molecules such as Na⁺, K⁺, Ca(2+), Cl(-), glucose, urea, and uric acid. It is therefore concluded that the DCP immunosensor developed and reported here is simple, inexpensive and effective, and shows promise in the rapid screening of early-stage liver cancer at home with a point-of-care approach.

Characterization of the GGP gene family in potato (Solanum tuberosum L.) and Pepper (Capsicum annuum L.) and its expression analysis under hormonal and abiotic stresses.

GDP-L-galactose phosphorylase (GGP) is a key rate-limiting enzyme in plant ascorbic acid synthesis, which plays an important role in plant growth and development as well as stress response. However, the presence of GGP and its function in potato and pepper are not known. In this study, we first identified two GGP genes in each potato and pepper genomes using a genome-wide search approach. We then analyzed their physicochemical properties, conserved domains, protein structures and phylogenetic relationships. Phylogenetic tree analysis revealed that members of the potato and pepper GGP gene families are related to eggplant (Solanum melongena L.), Arabidopsis (Arabidopsis thaliana L.), tobacco (Nicotiana tabacum L.) and tomato (Solanum lycopersicum L.), with tomato being the most closely related. The promoter sequences mainly contain homeopathic elements such as light-responsive, hormone-responsive and stress-responsive, with light-responsive elements being the most abundant. By analyzing the structure of the genes, it was found that there is no transmembrane structure or signal peptide in the GGP gene family of potatoes and peppers, and that all of its members are hydrophilic proteins. The expression profiles of different tissues show that StGGP1 has the highest expression levels in leaves, StGGP2 has the highest expression levels in stamens, and CaGGPs have the highest expression levels in the early stages of fruit development (Dev1). It was found that StGGPs and CaGGPs genes showed different response to phytohormones and abiotic stresses. Abscisic acid (ABA) treatment induced the most significant change in the expression of StGGPs, while the expression of CaGGPs showed the most pronounced change under methyl jasmonate (MeJA) treatment. StGGPs responded mainly to dark treatment, whereas CaGGPs responded mainly to NaCl stress. These results provide an important basis for a detailed study about the functions of GGP homologous genes in potato and pepper in response to abiotic stresses.

Crucial roles of trehalose and 5-azacytidine in alleviating salt stress in tomato: Both synergistically and independently.

Trehalose may improve plant stress tolerance by regulating gene expression under different abiotic stresses. DNA methylation is involved in plant growth and development, but also in response to abiotic stresses. 5-azacytidine is a widely used inhibitor of DNA methylation. In this study, tomato (Solanum lycopersicum L. 'Ailsa Craig') was used as experimental material to explore the effects of trehalose and DNA methylation on the growth and development in tomato seedlings under salt stress. 10 mM trehalose, 50 µM 5-azacytidine, and their combined treatments could significantly increase growth parameters in tomato under salt stress, indicating trehalose and 5-azacytidine might play crucial roles in alleviating salt stress both synergistically and independently. Additionally, trehalose significantly down-regulated the expression of DNA methylase genes (SlDRM5, SlDRM1L1, SlCMT3 and SlCMT2) and up-regulated the expression of DNA demethylases genes under salt stress, suggesting that trehalose might regulate DNA methylation under salt stress condition. Under salt stress, trehalose and 5-azacytidine treatments enhanced antioxidant enzyme activity and induced antioxidant enzyme gene expression in tomato seedlings. Meanwhile, trehalose and 5-azacytidine increased ABA content by regulating the expression of ABA metabolism-related genes, thereby enhancing salt tolerance in tomato. Altogether, these results suggest that trehalose conferred salt tolerance in tomato seedlings probably by DNA demethylation and enhancing antioxidant capability and ABA accumulation.

Hydrogen Gas Improves the Postharvest Quality of Lanzhou Lily (Lilium davidii var. unicolor) Bulbs.

Hydrogen gas (H2) is an important molecular messenger in animal and plant cells and is involved in various aspects of plant processes, including root organogenesis induction, stress tolerance and postharvest senescence. This study investigated the effect of H2 fumigation on the quality of Lanzhou lily scales. The results indicated the H2 remarkably declined the color variation and browning degree in Lanzhou lily scales by suppressing the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO). Moreover, H2 significantly alleviated the degradation of soluble proteins and soluble sugars in Lanzhou lily scales during postharvest storage, mitigating the decline in nutritional quality. This alleviating effect of H2 might be achieved by increasing the endogenous H2 concentration. Collectively, our data provide new insights into the postharvest quality reduction of Lanzhou lily scales mitigated by H2 fumigation.

Trehalose alleviates salt tolerance by improving photosynthetic performance and maintaining mineral ion homeostasis in tomato plants.

Trehalose (Tre), which was an osmoprotective or stabilizing molecule, played a protective role against different abiotic stresses in plants and showed remarkable perspectives in salt stress. In this study, the potential role of Tre in improving the resistance to salt stress in tomato plants was investigated. Tomato plants (Micro Tom) were treated with Hoagland nutrient solution (CK), 10 mM Tre (T), 150 mM sodium chloride (NaCl, S), and 10 mM Tre+150 mM NaCl (S+T) for 5 days. Our results showed that foliar application of Tre alleviated the inhibition of tomato plant growth under salt stress. In addition, salt stress decreased the values of net photosynthetic rate (Pn, 85.99%), stomata conductance (gs, 57.3%), and transpiration rate (Tr, 47.97%), but increased that of intercellular carbon dioxide concentration (Ci, 26.25%). However, exogenous application of Tre significantly increased photosynthetic efficiency, increased the activity of Calvin cycle enzymes [ribulose diphosphate carboxylase/oxygenase (Rubisco), fructose-1,6-bisphosphate aldolase (FBA), fructose-1, 6-bisphosphatase (FBPase), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and transketolase (TK)], up-regulated the expression of genes encoding enzymes, induced stomatal opening, and alleviated salt-induced damage to the chloroplast membrane and structure. In the saline environment, photosynthetic electron transport was restricted, resulting the J-I-P phase to decrease. At the same time, the absorption, capture, and transport energies per excited cross-section and per active reaction center decreased, and the dissipation energy increased. Conversely, Tre reversed these values and enhanced the photosystem response to salt stress by protecting the photosynthetic electron transport system. In addition, foliage application with Tre significantly increased the potassium to sodium transport selectivity ratio (S K-Na ) by 16.08%, and increased the levels of other ions to varying degrees. Principal component analysis (PCA) analysis showed that exogenous Tre could change the distribution of elements in different organs and affect the expressions of SlSOS1, SlNHX, SlHKT1.1, SlVHA, and SlHA-A at the transcriptional level under salt stress, thereby maintaining ion homeostasis. This study demonstrated that Tre was involved in the process of mitigating salt stress toxicity in tomato plants and provided specific insights into the effectiveness of Tre in mediating salt tolerance.

Trehalose Alleviated Salt Stress in Tomato by Regulating ROS Metabolism, Photosynthesis, Osmolyte Synthesis, and Trehalose Metabolic Pathways.

Trehalose plays a critical role in plant response to salinity but the involved regulatory mechanisms remain obscure. Here, this study explored the mechanism of exogenous trehalose-induced salt tolerance in tomato plants by the hydroponic test method. Our results indicated that 10 mM trehalose displayed remarkable plant biomass by improving growth physiology, which were supported by the results of chlorophyll fluorescence and rapid light-response curve. In the salinity environment, trehalose + NaCl treatment could greatly inhibit the decrease of malondialdehyde level, and it increases the contents of other osmotic substances, carbohydrates, K+, and K+/Na+ ratio. Meanwhile, trehalose still had similar effects after recovery from salt stress. Furthermore, trehalose pretreatment promoted trehalose metabolism; significantly increased the enzymatic activity of the trehalose metabolic pathway, including trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), and trehalase (TRE); and upregulated the expression of SlTPS1, SlTPS5, SlTPS7, SlTPPJ, SlTPPH, and SlTRE under saline conditions. However, the transcriptional levels of SlTPS1, SlTPS5, and SlTPS7 genes and the activity of TPS enzyme were reversed after recovery. In addition, we found that hydrogen peroxide (H2O2) and superoxide anion (O2 -) were accumulated in tomato leaves because of salt stress, but these parameters were all recovered by foliar-applied trehalose, and its visualization degree was correspondingly reduced. Antioxidant enzyme activities (SOD, POD, and CAT) and related gene expression (SlCu/Zn-SOD, SlFe-SOD, SlMn-SOD, SlPOD, and SlCAT) in salt-stressed tomato leaves were also elevated by trehalose to counteract salt stress. Collectively, exogenous trehalose appeared to be the effective treatment in counteracting the negative effects of salt stress.

Genome-wide identification and expression analysis of serine hydroxymethyltransferase (SHMT) gene family in tomato (Solanum lycopersicum).

Serine hydroxymethyltransferase (SHMT) is one of the most important enzyme families in one-carbon metabolic pathway and photorespiration within plant cells. Recently studies reported the active roles of plant SHMTs in defending abiotic stresses. However, genome-scale analysis of SHMT in tomato is currently unknown. In this study, seven SHMT genes were identified in the tomato genome using a genome-wide search approach. In addition, their physicochemical properties, protein secondary structure, subcellular localization, gene structure, conserved motifs, phylogenetic and collinear relationships were analyzed. Our results demonstrated that tomato SHMT members were divided into two group and four subgroups, and they were conserved with the orthologs of other plants. Analysis of cis-acting elements showed that each of the SlSHMT genes contained different kinds of hormones and stress-related cis-acting elements in their promoter regions. Finally, qRT-PCR analysis indicated that SlSHMTs were expressed at different levels in different tissues, and they responded to UV, cold, heat, NaCl, H2O2, ABA and PEG treatments. These results provided definite evidence that SlSHMTs might involve in growth, development and stress responses in tomato, which laid a foundation for future functional studies of SlSHMTs.

Roles of Small-Molecule Compounds in Plant Adventitious Root Development.

Adventitious root (AR) is a kind of later root, which derives from stems and leaf petioles of plants. Many different kinds of small signaling molecules can transmit information between cells of multicellular organisms. It has been found that small molecules can be involved in many growth and development processes of plants, including stomatal movement, flowering, fruit ripening and developing, and AR formation. Therefore, this review focuses on discussing the functions and mechanisms of small signaling molecules in the adventitious rooting process. These compounds, such as nitric oxide (NO), hydrogen gas (H2), hydrogen sulfide (H2S), carbon monoxide (CO), methane (CH4), ethylene (ETH), and hydrogen peroxide (H2O2), can be involved in the induction of AR formation or development. This review also sums the crosstalk between these compounds. Besides, those signaling molecules can regulate the expressions of some genes during AR development, including cell division genes, auxin-related genes, and adventitious rooting-related genes. We conclude that these small-molecule compounds enhance adventitious rooting by regulating antioxidant, water balance, and photosynthetic systems as well as affecting transportation and distribution of auxin, and these compounds further conduct positive effects on horticultural plants under environmental stresses. Hence, the effect of these molecules in plant AR formation and development is definitely a hot issue to explore in the horticultural study now and in the future.

Research Progress on the Functions of Gasotransmitters in Plant Responses to Abiotic Stresses.

Abiotic stress is one of the major threats affecting plant growth and production. The harm of abiotic stresses includes the disruption of cellular redox homeostasis, reactive oxygen species (ROS) production, and oxidative stress in the plant. Plants have different mechanisms to fight stress, and these mechanisms are responsible for maintaining the required homeostasis in plants. Recently, the study of gasotransmitters in plants has attracted much attention, especially for abiotic stress. In the present review, abiotic stressors were mostly found to induce gasotransmitter production in plants. Meanwhile, these gasotransmitters can enhance the activity of several antioxidant enzymes, alleviate the harmfulness of ROS, and enhance plant tolerance under various stress conditions. In addition, we introduced the interaction of gasotransmitters in plants under abiotic stress. With their promising applications in agriculture, gasotransmitters will be adopted in the near future.

A Mechanical Sensor Designed for Dynamic Joint Angle Measurement.

Background. The measurement of the functional range of motion (FROM) of lower limb joints is an essential parameter for gait analysis especially in evaluating rehabilitation programs. Aim. To develop a simple, reliable, and affordable mechanical goniometer (MGR) for gait analysis, with six-degree freedom to dynamically assess lower limb joint angles. Design. Randomized control trials, in which a new MGR was developed for the measurements of FROM of lower limb joints. Setting. Reliability of the designed MGR was evaluated and validated by a motion analysis system (MAS). Population. Thirty healthy subjects participated in this study. Methods. Reliability and validity of the new MGR were tested by intraclass correlation coefficient (ICC), Bland-Altman plots, and linear correlation analysis. Results. The MGR has good inter- and intrarater reliability and validity with ICC ≥ 0.93 (for both). Moreover, measurements made by MGR and MAS were comparable and repeatable with each other, as confirmed by Bland-Altman plots. Furthermore, a very high degree of linear correlation (R ≥ 0.92 for all joint angle measurements) was found between the lower limb joint angles measured by MGR and MAS. Conclusion. A simple, reliable, and affordable MGR has been designed and developed to aid clinical assessment and treatment evaluation of gait disorders.

A new approach for noninvasive transdermal determination of blood uric acid levels.

The aims of this study were to investigate the most effective combination of physical forces from laser, electroporation, and reverse iontophoresis for noninvasive transdermal extraction of uric acid, and to develop a highly sensitive uric acid biosensor (UAB) for quantifying the uric acid extracted. It is believed that the combination of these physical forces has additional benefits for extraction of molecules other than uric acid from human skin. A diffusion cell with porcine skin was used to investigate the most effective combination of these physical forces. UABs coated with ZnO2 nanoparticles and constructed in an array configuration were developed in this study. The results showed that a combination of laser (0.7 W), electroporation (100 V/cm(2)), and reverse iontophoresis (0.5 mA/cm(2)) was the most effective and significantly enhanced transdermal extraction of uric acid. A custom-designed UAB coated with ZnO2 nanoparticles and constructed in a 1×3 array configuration (UAB-1×3-ZnO2) demonstrated enough sensitivity (9.4 µA/mM) for quantifying uric acid extracted by the combined physical forces of laser, electroporation, and RI. A good linear relationship (R(2)=0.894) was demonstrated to exist between the concentration of uric acid (0.2-0.8 mM) inside the diffusion cell and the current response of the UAB-1×3-ZnO2. In conclusion, a new approach to noninvasive transdermal extraction and quantification of uric acid has been established.

Carbon nanotube composites for glucose biosensor incorporated with reverse iontophoresis function for noninvasive glucose monitoring.

This study aims to develop an amperometric glucose biosensor, based on carbon nanotubes material for reverse iontophoresis, fabricated by immobilizing a mixture of glucose oxidase (GOD) and multiwalled carbon nanotubes (MWCNT) epoxy-composite, on a planar screen-printed carbon electrode. MWCNT was employed to ensure proper incorporation into the epoxy mixture and faster electron transfer between the GOD and the transducer. Results showed this biosensor possesses a low detection potential (+500 mV), good sensitivity (4 microA/mM) and an excellent linear response range (r(2) = 0.999; 0-4 mM) of glucose detection at +500 mV (versus Ag/AgCl). The response time of the biosensor was about 25 s. In addition, the biosensor could be used in conjunction with reverse iontophoresis technique. In an actual evaluation model, an excellent linear relationship (r(2) = 0.986) was found between the glucose concentration of the actual model and the biosensor's current response. Thus, a glucose biosensor based on carbon nanotube composites and incorporated with reverse iontophoresis function was developed.