Multifunctional Probe Research Articles

A dual-site multifunctional fluorescent probe for selective detection of endogenous H2O2 and SO2 derivatives based on ICT process and its bioimaging application

In this paper, we reported a coumarin-based fluorescent probe for selective detection of H2O2/SO2 derivatives via ICT process. To the best of our knowledge, it was few reported with the same probe to enable visual detection of H2O2/SO2 derivatives in vivo and in vitro. H2O2 and SO32− were selectively sensed over other analytes, and the probe displayed 20-fold and 220-fold relative fluorescence intensity respectively, as well as the good linear relationship and the excellent detection limits of 2.7 * 103 nM and 19.3 nM. Furthermore, the probe was successfully used for fluorescence imaging of the HeLa cells and the mice to monitor exogenous and endogenous H2O2 and SO32−, suggesting its potential biomedical application for investigation and detection the intermediate indicator of oxidative stress in vitro and in vivo.

Lanthanide coordination polymers used for fluorescent ratiometric sensing of H2O2 and glucose

Scheme 1. Schematic description of the preparation of GOx@Tb-ATA/GDP CPs and detection of glucose. • The dual-emission multi-functional probes based on Ln CPs were facilely prepared by self-assembly. • The ratiometric fluorescence method based on double ligand Ln 3+ coordination polymers for H 2 O 2 detection was realized. • By integrating GOx through the adaptive inclusion property of CPs in the self-assembly process, a simple, highly selective and sensitive one-pot retiometric glucose assay was developed. A dual-emission lanthanide coordination polymers (Ln CPs) were facilely prepared by self-assembly of guanine diphosphate (GDP) and 2-aminoterephthalic acid (ATA) with Tb 3+ , termed as Tb-ATA/GDP CPs. GDP played as the antenna ligand to sensitize the luminescence of Tb 3+ , and ATA served as a fluorescent auxiliary ligand for the ratiometric assay. The obtained Tb-ATA/GDP CPs exhibited both blue-emission of ATA at 430 nm and characteristic green-emission of Tb 3+ under a single excitation wavelength. Upon addition of H 2 O 2 , the fluorescence of Tb 3+ could be selectively quenched and that of ATA slightly enhanced. The fluorescence intensity ratio at 430 nm and 549 nm (I 430 /I 549 ) increased linearly with increasing the concentration of H 2 O 2 in the range of 0.005–20 μM and 120–500 μM, and the detection limit was 3.42 nM. Furthermore, by integrating the glucose oxidase (GOx) through the adaptive inclusion ability of Ln CPs, GOx@Tb-ATA/GDP CPs were facilely obtained. Based on their high affinity to oxidize glucose and the fluorescence response to the generated H 2 O 2 , a simple, highly selective and sensitive one-pot ratiometric glucose assay was developed. This work will facilitate the design and construct of multi-functional fluorescent probes based on the Ln CPs, and exploit their applications in bio-sensing and environmental analysis.

Robust emission in near-infrared II of lanthanide nanoprobes conjugated with Au (LNPs-Au) for temperature sensing and controlled photothermal therapy

To address the poor activity and inaccurate in situ temperature measurements of composite photothermal probes, herein we report lanthanide nanoparticles-gold (LNPs-Au) nanoprobes for fluorescence temperature sensing and controlled photothermal therapy (PTT). The conjugation between LNPs and Au is done via electrostatic interactions. LNPs doped with rare earth cations (Yb3+, Ho3+, Er3+, and Ce3+) fluoresce strongly in the NIR-II region and their emission spectrum does not overlap with the absorption spectrum of Au. The intensities of LNPs-Au emission peaks at 1185 and 1560 nm highly depend on temperature, which is utilized in this study for the non-contact temperature measurements in the biologically relevant range. Deep tissue penetration of NIR-II radiation is observed, which is favorable for real-time temperature sensing. In addition, this radiation does not damage the normal tissue. Moreover, LNPs-Au nanoparticles reduce HeLa cell viability below 40 % and adequately inhibited tumor tissue in mice upon 808-nm irradiation. The results of this study will motivate the development of multifunctional photothermal probes for safer, controllable PTT of cancers with simultaneous temperature monitoring.

Decorating Zirconium on Graphene Oxide to Design a Multifunctional Nanozyme for Eco-Friendly Detection of Hydrogen Peroxide

Peroxidase enzymes are crucial in analytical chemistry owing to significant peroxide analytes and their key role in hydrogen peroxide (H2O2) detection. Therefore, exploiting appropriate catalysts for the peroxidase like reactions has become crucial for achieving desired analytical performance. Zirconium (Zr) has attracted growing interest, as a safe and stable potential eco-friendly catalyst for various organic transformations that address increasing environmental challenges. Hence, aiming at fast, sensitive and selective optical detection of H2O2, a colorimetric platform is presented here, based on the excellent peroxidase enzyme-like activity of Zr decorated on graphene oxide (GO). The synergistic effect achieved due to intimate contact between an enzyme like Zr and the high surface area 0f GO ensures efficient electron transfer that increases the chemical and catalytic activity of the composite and advances the decomposition of H2O2 into hydroxyl radicals. The designed probe, thus, efficiently catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), via hydroxyl radicals, thereby transforming the colorless TMB into blue oxidized TMB within 2 min. The catalytic mechanism of the Zr-GO enzyme mimic is proposed herein and verified using a fluorescent probe terephthalic acid (TA) and other scavenger experiments. The multifunctional optical probe allows sensitive and highly selective recognition of H2O2 in a linear range from 100 to 1000 µM with a low detection limit of 0.57 µM. Essentially, the direct accessibility of Zr prevents having to use the complicated preparation and purification procedures mostly practiced for conventional biozymes and nanozymes. The devised method offers several gains, including being green and an inexpensive catalyst, having lower LOD, being fast, cost-effective and sensitive, and having selective work-up procedures.

An ultra-sensitive fluorescent sensor based on Zn-MOF for selective detection of riboflavin in food

Riboflavin can not only promote cell metabolism, but also prevent cardiovascular diseases. People usually need to obtain riboflavin from food or medicine, so the determination of riboflavin is significant for safety and quality control. An ingenious zinc-based metal-organic framework (Zn-MOF) was synthesized which can be used for rapid fluorescence detection of riboflavin with an ultralow detection limit of 2 ​× ​10−8 ​mol/L. The quenching mechanism is mainly attributed to the fluorescence resonance energy transfer and the absorption competition. In addition, this Zn-MOF can be used as a multifunctional fluorescence probe to specifically recognize acetylacetone and Cr2O72−/CrO42−. Most importantly, it has been applied to the quantitative analysis of milk and energy drinks with satisfactory recovery (100.71%–103.42%). It is the first attempt to use MOF as fluorescence probe to determine riboflavin without additional surface modification and functionalization, which provides a promising functional platform for detecting riboflavin in food industry.

Bifunctional ratiometric fluorescent probe for sensing anthrax spore biomarker and tetracycline at different excitation channels

Multifunctional fluorescent probes have received increasing attention for the sake of atom economy and high-density integration. Herein, CdTe quantum dots (QDs) modified with Eu3+ were synthesized as the bifunctional ratiometric fluorescent probe for sensing two hazardous substances tetracycline (TC) and anthrax spore biomarker 2,6-dipicolinic acid (DPA) at different excitation channels, based on the discrepant excitation wavelengths of Eu3+ and the fluorescence quenching of CdTe QDs after interaction with them. Both DPA and TC enhanced the red emission of Eu3+ via antenna effect but caused the green emission of CdTe QDs to quench. Interestingly, the excitation wavelengths of Eu3+ after coordinating with DPA and TC were 275 and 386 nm, respectively. On this basis, CdTe QDs-Eu3+ achieved the bifunctional ratiometric detection of DPA (λex = 275 nm) and TC (λex = 386 nm) with different excitation channels. Both DPA and TC were selectively detected by CdTe QDs-Eu3+ with rapid response (DPA-1 min, TC-1 min) and high sensitivity (DPA-LOD 0.3 μM, TC-LOD 2.2 nM). CdTe QDs-Eu3+ were applied to analyzing DPA and TC in food, biological and environmental samples. Satisfactory spiked recoveries (80.0–119.0 %) and relative standard deviations (0.5–8.4 %) were obtained for measuring DPA and TC in these samples.

Kill three birds with one stone: Zr-MOF-mediated composite multi-functional materials to enhance the efficiency for fluorescent and colorimetric dual-signal readout bioassay

In this work, we report a fluorescent and colorimetric dual readout bioassay for deoxynivalenol detection to ensure public food safety. A multifunctional fluorescent and colorimetric signal probe was constructed to develop the bioassay for deoxynivalenol detection based on the characteristics of Zr-MOF (PCN-224; i.e., high porosity, a large surface area, and excellent fluorescence quenching performance). Platinum nanoparticles (Pt NPs) were grown in situ outside, while glucose oxidase was stored inside (PPG). Glucose oxidase and Pt NPs are both enriched by Zr-MOF, achieving the first signal amplification, and cascade catalysis by the glucose-TMB system for colorimetric signal readout leads to the second signal amplification. PPG was quenched through the spontaneous formation of ZrOP bonds with fluorescent DNA to achieve a highly sensitive fluorescent readout. The self-supplied H2O2 in the colorimetric detection further improved the self-accuracy of the dual-mode analysis strategy (the accuracy of independent signal readout modes from two different signal transduction mechanisms). This multifunctional PPG probe avoids the time-consuming assembly of different probes and reduces error accumulation from uncontrollable factors in complex experimental procedures. It allows for the sensitive and accurate detection of deoxynivalenol with excellent limits of detection (5.3 pg/mL for the fluorescent assay and 34 pg/mL for the colorimetric method). Overall, this work demonstrates a viable approach for the construction of a dual-signal biosensing platform based on multifunctional MOF probes for biological analysis.

Biodistribution Profile of Magnetic Nanoparticles in Cirrhosis-Associated Hepatocarcinogenesis in Rats by AC Biosusceptometry

Since magnetic nanoparticles (MNPs) have been used as multifunctional probes to diagnose and treat liver diseases in recent years, this study aimed to assess how the condition of cirrhosis-associated hepatocarcinogenesis alters the biodistribution of hepatic MNPs. Using a real-time image acquisition approach, the distribution profile of MNPs after intravenous administration was monitored using an AC biosusceptometry (ACB) assay. We assessed the biodistribution profile based on the ACB images obtained through selected regions of interest (ROIs) in the heart and liver position according to the anatomical references previously selected. The signals obtained allowed for the quantification of pharmacokinetic parameters, indicating that the uptake of hepatic MNPs is compromised during liver cirrhosis, since scar tissue reduces blood flow through the liver and slows its processing function. Since liver monocytes/macrophages remained constant during the cirrhotic stage, the increased intrahepatic vascular resistance associated with impaired hepatic sinusoidal circulation was considered the potential reason for the change in the distribution of MNPs.

A multifunctional fluorescent probe for dual-color visualization of intracellular mitochondria and lipid droplets and monitoring of SO2 in vivo

Mitochondria and lipid droplets (LDs) are organelles involved in intracellular lipid and energy metabolism, and their complicated interplays are critical for maintaining cellular homeostasis. However, the fluorescent probes capable of simultaneously and discriminatively visualizing mitochondria and LDs are severely insufficient, which greatly limits the investigation of the interaction between two organelles in cells. In addition, abnormal SO2 levels can have harmful effects on living organisms. Monitoring the changes of SO2 levels in vivo is of great significance for biological and medical research. In this work, a SO2-dependent strategy was proposed for the first time to construct the new functional fluorescence conversion probe MLD-SO2 for two-color visualization of mitochondria and LDs. Under normal physiological conditions, the cationic form enabled the probe to selectively target the mitochondria and emit red fluorescence. In addition, based on SO2-driven nucleophilic addition reaction, the probe MLD-SO2 was converted to the neutral lipophilic structure in the presence of SO2, which targeted to LDs and displayed a strong blue emission. Importantly, mitochondria and LDs could be visualized simultaneously in the red and blue emission channels under the appropriate amount of SO2 exposure. Furthermore, the probe MLD-SO2 has been successfully employed to monitor the SO2 changes in zebrafish and mung bean sprouts. The remarkable imaging performances render the novel probe MLD-SO2 as a powerful tool for deciphering the interactions between mitochondrial and LDs and monitoring SO2 in different organisms.

Multimodal molecular imaging in the second near-infrared window.

Near-infrared-II (NIR-II) fluorescence imaging has rapidly developed for the noninvasive investigation of physiological and pathological activities in living organisms with high spatiotemporal resolution. However, the penetration depth of fluorescence restricts its ability to provide deep anatomical information. Scientists integrate NIR-II fluorescence imaging with other imaging modes (such as photoacoustic and magnetic resonance imaging) to create multimodal imaging that can acquire detailed anatomical and quantitative information with deeper penetration by using multifunctional probes. This reviewoffers acomprehensive picture of NIR-II-based dual/multimodal imaging probes and highlightsadvances in bioimaging and therapy. In addition, seminal studies and trends in multimodal imaging probes activated by NIR-II laser are summarizedand several key points regarding future clinical translation are elucidated.

Application of Near‐Infrared Fluorescence Imaging in Thrombosis Detection

AbstractIn recent years, researchers have developed a variety of near infrared (NIR) fluorescent probes to achieve visual detection of thrombotic plaques in vivo. In this review, after clarifying the advantages of NIR probes in sensing thrombus in vivo, the structures and design strategies underlying always‐on and turn‐on NIR thrombus probes are discussed. Subsequently, by summarizing and classifying the biomarkers overexpressed in thrombus, we highlight the recent advances in thrombus NIR fluorescent probes in biomedical applications. Furthermore, specific issues and opportunities in this field are explored at the end of the review, which will facilitate the inventive design of new multifunctional fluorescent probes and actively promote their future clinical translation.

Multifunctional Nanosnowflakes for T1-T2 Double-Contrast Enhanced MRI and PAI Guided Oxygen Self-Supplementing Effective Anti-Tumor Therapy.

IntroductionAccurate tumor diagnosis is essential to achieve the ideal therapeutic effect. However, it is difficult to accurately diagnose cancer using a single imaging method because of the technical limitations. Multimodal imaging plays an increasingly important role in tumor treatment. Photodynamic therapy (PDT) has received widespread attention in tumor treatment due to its high specificity and controllable photocytotoxicity. Nevertheless, PDT is susceptible to tumor microenvironment (TME) hypoxia, which greatly reduces the therapeutic effect of tumor treatment.MethodsIn this study, a novel multifunctional nano-snowflake probe (USPIO@MnO2@Ce6, UMC) for oxygen-enhanced photodynamic therapy was developed. We have fabricated the honeycomb-like MnO2 to co-load chlorin e6 (Ce6, a photosensitizer) and ultrasmall superparamagnetic iron oxide (USPIO, T1-T2 double contrast agent). Under the high H2O2 level of tumor cells, UMC efficiently degraded and triggered the exposure of photosensitizers to the generated oxygen, accelerating the production of reactive oxygen species (ROS) during PDT. Moreover, the resulting USPIO and Mn2+ allow for MR T1-T2 imaging and transformable PAI for multimodal imaging-guided tumor therapy.ResultsTEM and UV-vis spectroscopy results showed that nano-snowflake probe (UMC) was successfully synthesized, and the degradation of UMC was due to the pH/ H2O2 responsive properties. In vitro results indicated good uptake of UMC in 4T-1 cells, with maximal accumulation at 4 h. In vitro and in vivo experimental results showed their imaging capability for both T1-T2 MR and PA imaging, providing the potential for multimodal imaging-guided tumor therapy. Compared to the free Ce6, UMC exhibited enhanced treatment efficiency due to the production of O2 with the assistance of 660 nm laser irradiation. In vivo experiments confirmed that UMC achieved oxygenated PDT under MR/PA imaging guidance in tumor-bearing mice and significantly inhibited tumor growth in tumor-bearing mice, exhibiting good biocompatibility and minimal side effects.ConclusionThe multimodal imaging contrast agent (UMC) not only can be used for MR and PA imaging but also has oxygen-enhanced PDT capabilities. These results suggest that UMC may have a good potential for further clinical application in the future.

A Facile, Label-free and Versatile Fluorescence Sensing Nanoplatform Based on Titanium Carbide Nanosheets for the Detection of Various Targets.

The construction of a universal nanoplatform for sensitive detection of multiple targets of interest is of great importance in different research fields. Herein, by ingeniously integrating the target recognition sequences and G-rich sequences into a single-stranded multifunctional DNA probe and adopting Ti3C2 nanosheets as an efficient fluorescence quencher, a simple, low-cost and easy operation fluorescence sensing nanoplatform was proposed. Without an analytical target, the hydrogen bond and metal chelate interaction between the target recognition region of the DNA probe and Ti3C2 nanosheet induce the selective self-assembly of highly fluorescent thioflavin T (ThT)-intercalated DNA probe onto the surface of Ti3C2 nanosheets, resulting in dramatic decrease of fluorescence emitted by ThT-G-quadruplex. In the presence of a target, the target recognition region will selectively bind with the target and the constrained DNA probe is released from the Ti3C2 nanosheets surface, leading to enhanced fluorescence recovery of ThT-G-quadruplex. As a proof of concept, the sensitive and selective detection of p53 gene, Hg2+, and adenosine with the assistance of Ti3C2 nanosheets-based fluorescence sensing nanoplatform were successfully realized. Moreover, it is also applicable for the evaluation the level of these analytical targets in real samples. By simply switching the recognition sequences of DNA probe, the universal sensing strategy could also be applied for detecting many other types of targets. The simple and universal sensing nanoplatform is expected to promote wide applications in environment monitoring and bioanalysis.

Synthesis and evaluation of a multifunctional probe with a high affinity for prostate-specific membrane antigen (PSMA) and bone

Prostate cancer frequently metastasizes to the bone. Because patients with bone metastases suffer from skeletal-related events, the diagnosis and treatment of bone metastases in the early stage are important. In this study, to improve the sensitivity of detecting bone metastases in patients with prostate cancer, we designed, synthesized, and evaluated a multifunctional radiotracer, [67Ga]Ga-D11-PSMA-617 ([67Ga]3), with an undeca-aspartic acid as a bone-seeking moiety between [67Ga]Ga-DOTA and a prostate-specific membrane antigen (PSMA) ligand based on the lysine-urea-glutamate motif. [67Ga]3 showed a high affinity for hydroxyapatite and high uptake in PSMA-positive LNCaP cells. Moreover, in biodistribution experiments using tumor-bearing mice, [67Ga]3 exhibited high accumulation in the bone and PSMA-positive tumor although the accumulation of [67Ga]3 in the PSMA-positive tumor was lower than that of [67Ga]Ga-PSMA-617. This study provides valuable information for developing radiotheranostic probes combining multiple carriers with different mechanisms.

Photoelectrochemical and visual dual-mode sensor for efficient detection of Cry1Ab protein based on the proximity hybridization driven specific desorption of multifunctional probe

Currently, the development of sensitive and visual strategy for Cry1Ab detection, particularly using a switchable dual-mode detection system based on a single component, remains a great challenge. Here, a photoelectrochemical (PEC) and visual dual-mode sensor was designed for Cry1Ab detection based on a proximity hybridization driven multifunctional probe. In the presence of Cry1Ab, specific desorption of the antibody-DNA conjugate was achieved via sufficient proximity hybridization, leading to the selective release of the multifunctional signal probe, i.e., antibody-labeled single-stranded DNA-gold nanoparticles (Ab1-S1-AuNPs). The released Ab1-S1-AuNPs reduced the photocurrent signal and produced a colored response, thereby achieving PEC and visual dual-mode detection based on a single component. Owing to the different signal generation mechanisms, two independent signals were obtained simultaneously, which provided self-verification to improve reliability and accuracy. Taking advantage of the PEC sensitive detection and visual prediction, the dual-mode sensor achieved efficient detection of the Cry1Ab protein. The developed sensor was successfully used to determine Cry1Ab in corn, wheat, and soil samples with satisfactory results. This method offers a promising biosensing platform for the on-site detection of Cry1Ab protein.

Electrochemiluminescence resonance energy transfer biosensing platform between g-C3N4 nanosheet and Ru–SiO2@FA for dual-wavelength ratiometric detection of SARS-CoV-2 RdRp gene

Rational detection of syndrome coronavirus 2 (SARS-CoV-2) is crucial to prevention, control, and treatment of disease. Herein, a dual-wavelength ratiometric electrochemiluminescence (ECL) biosensor based on resonance energy transfer (RET) between g-C3N4 nanosheets and Ru–SiO2@folic acid (FA) nanomaterials was designed to realize ultrasensitive detection of SARS-CoV-2 virus (RdRp gene). Firstly, the unique g-C3N4 nanosheets displayed very intense and stable ECL at 460 nm, then the triple helix DNA was stably and vertically bound to g-C3N4 on electrode by high binding affinity between ssDNA and g-C3N4. Meanwhile, trace amounts of target genes were converted to a large number of output by three-dimensional (3D) DNA walker multiple amplification, and the output bridged a multifunctional probe Ru–SiO2@FA to electrode. Ru–SiO2@FA not only showed high ECL at 620 nm, but also effectively quenched g-C3N4 ECL. As a result, ECL decreased at 460 nm and increased at 620 nm, which was used to design a rational ECL biosensor for detection of SARS gene. The results show that the biosensor has excellent detection sensitivity for RdRp gene with a dynamic detection range of 1 fM to 10 nM and a limit of detection (LOD) of 0.18 fM. The dual-wavelength ratio ECL biosensor has inestimable value and application prospects in the fields of biosensing and clinical diagnosis.

Development of dual-fluorophore and dual-site multifunctional fluorescent probe for detecting HClO and H2S based on rhodamine-coumarin units

HClO and H2S commonly coexist in organisms and act synergistically to maintain the redox dynamic balance in vivo; however, it is difficult to trace precisely and simultaneously HClO and H2S by single recognition-type fluorescent probes. In this paper, a novel probe (MTRN) was designed for detecting specifically HClO and H2S with dual-emission property by using an acrylate and a phenyl isothiocyanate as recognition sites. MTRN possessed outstanding performances including ultrasensitivity (LOD = 3.39 nM), high specificity and short response time (<2 min) for HClO under excitation of 530 nm with the fluorescence’s color change from dark to red. Moreover, upon treating with H2S, the fluorescence peak centered at 488 nm of MTRN enhanced obviously within 1 min and color changed from colorless to blue, the LOD was found to be 0.13 µM. The possible reaction mechanism for HClO and H2S in CH3CN/PBS (9/1, v/v) was substantiated via 1H NMR and HRMS. Above all, MTRN was successfully used to detect HClO and H2S in HeLa cells and made into test strips to detect HClO and H2S.

Multifunctional probe based on modified Ag&Mn:ZnInS QDs for dual-mode fluorescence and magnetic resonance imaging of intracellular glutathione

Glutathione (GSH) plays vital roles in a variety of biological processes, and the development of simple and effective GSH detection method is an important research topic. Herein, a multifunctional probe based on Ag&Mn:ZnInS quantum dots (QDs) was developed for bimodal imaging of GSH. MnO2, as an efficient fluorescence quencher, was in-situ grown on the surface of QDs, and then modified with hyaluronic acid (HA) to improve the stability and targeted recognition capability of the probe due to the binding between HA and CD44 receptors. After MnO2 was deconstructed by GSH, the fluorescence of the probe was recovered and the generated Mn2+ could serve as good magnetic resonance imaging (MRI) contrast agent. Moreover, the near-infrared emission probe was successfully employed in living cell and zebrafish imaging due to its low toxicity and high anti-biological interference performance. This strategy provides a simple dual-mode fluorescence/MRI imaging of GSH, which may have a broad application in biological detection.

Multifunctional Peptides Modified Conductive Nano-Network Based on GO and Gold Nano Triangular: Sensitive Detection of PD-L1 Exosomes in Serum

Early diagnosis and reasonable treatment of cancer can effectively reduce the progression and decrease the proliferation. Exosomes are considered to be an excellent biomarker due to their special role in cancer development and post-treatment evaluation. Here, a simple and effective method for constructing two-dimensional heterostructure modified films on the electrode surface is reported to realize the electrochemical detection of exosomes. Flake gold nano triangle (AuNTs) as spacer, effectively inhibits the decline of electron transport capacity caused by the van der Waals stacking effect of graphene, a layered conductive network based on GO/AuNTs heterojunction was constructed on glassy carbon electrode. Multifunctional peptides with antifouling and specific binding characteristics for target exosomes were carefully anchored onto the surface of GO/AuNTs conductive network composite through Au-S. Combined with the innovative micro nanostructure on the electrode surface and the multifunctional peptides probe, the fabricated sensor shows an excellent limit of detection of 76 particles/ml with a detection range of 102 to 106 particles ml−1. The proposed sensor provides a powerful platform for direct measurement of exosomes, opening new opportunities for highly sensitive determination of other biomarkers.

Brain-Implantable Multifunctional Probe for Simultaneous Detection of Glutamate and GABA Neurotransmitters: Optimization and In Vivo Studies.

Imbalances in levels of glutamate (GLU) and gamma-aminobutyric acid (GABA) and their sub-second signaling dynamics occur in several brain disorders including traumatic brain injury, epilepsy, and Alzheimer’s disease. The present work reports on the optimization and in vivo testing of a silicon (Si) multifunctional biosensor probe for sub-second simultaneous real-time detection of GLU and GABA. The Si probe features four surface-functionalized platinum ultramicroelectrodes (UMEs) for detection of GLU and GABA, a sentinel site, and integrated microfluidics for in-situ calibration. Optimal enzyme concentrations, size-exclusion phenylenediamine layer and micro spotting conditions were systematically investigated. The measured GLU sensitivity for the GLU and GABA sites were as high as 219 ± 8 nA μM−1 cm−2 (n = 3). The measured GABA sensitivity was as high as 10 ± 1 nA μM−1 cm−2 (n = 3). Baseline recordings (n = 18) in live rats demonstrated a useful probe life of at least 11 days with GLU and GABA concentrations changing at the levels of 100′s and 1000′s of μM and with expected periodic bursts or fluctuations during walking, teeth grinding and other activities and with a clear difference in the peak amplitude of the sensor fluctuations between rest (low) and activity (higher), or when the rat was surprised (a reaction with no movement). Importantly, the probe could improve methods for large-scale monitoring of neurochemical activity and network function in disease and injury, in live rodent brain.