Exploring the potential of molecularly imprinted polymers and metal/metal oxide nanoparticles in sensors: recent advancements and prospects

Metal/metal oxide nanoparticles have gained increasing attention in recent years due to their outstanding features, including optical and catalytic properties, as well as their excellent conductivity. The implementation of metal/metal oxide nanoparticles, combined with molecularly imprinted polymers (MIPs) has paved the way for a new generation of building blocks to engineer and enhance the fascinating features of advanced sensors. This review critically evaluates the impact of combining metal/metal oxide nanoparticles with MIPs in sensors. It covers synthesis strategies, advantages of coupling these materials with MIPs, and addresses questions about the selectivity of these hybrid materials. In the end, the current challenges and future perspectives of this field are discussed, with a particular focus on the potential applications of these hybrid composites in the sensor field. This review highlights the exciting opportunities of using metal/metal oxide nanoparticles along with MIPs for the development of next-generation sensors.

Unlocking the Potential of Molecularly Imprinted Polydopamine in Sensing Applications

Molecularly imprinted polymers (MIPs) are synthetic receptors that mimic the specificity of biological antibody-antigen interactions. By using a "lock and key" process, MIPs selectively bind to target molecules that were used as templates during polymerization. While MIPs are typically prepared using conventional monomers, such as methacrylic acid and acrylamide, contemporary advancements have pivoted towards the functional potential of dopamine as a novel monomer. The overreaching goal of the proposed review is to fully unlock the potential of molecularly imprinted polydopamine (MIPda) within the realm of cutting-edge sensing applications. This review embarks by shedding light on the intricate tapestry of materials harnessed in the meticulous crafting of MIPda, endowing them with tailored properties. Moreover, we will cover the diverse sensing applications of MIPda, including its use in the detection of ions, small molecules, epitopes, proteins, viruses, and bacteria. In addition, the main synthesis methods of MIPda, including self-polymerization and electropolymerization, will be thoroughly examined. Finally, we will examine the challenges and drawbacks associated with this research field, as well as the prospects for future developments. In its entirety, this review stands as a resolute guiding compass, illuminating the path for researchers and connoisseurs alike.

Smart Multiplex Point-of-Care Platform for Simultaneous Drug Monitoring

Recently, illicit drug use has become more widespread and is linked to problems with crime and public health. These drugs disrupt consciousness, affecting perceptions and feelings. Combining stimulants and depressants to suppress the effect of drugs has become the most common reason for drug overdose deaths. On-site platforms for illicit-drug detection have gained an important role in dealing, without any excess equipment, long process, and training, with drug abuse and drug trafficking. Consequently, the development of rapid, sensitive, noninvasive, and reliable multiplex drug-detecting platforms has become a major necessity. In this study, a multiplex laser-scribed graphene (LSG) sensing platform with one counter, one reference, and three working electrodes was developed for rapid and sensitive electrochemical detection of amphetamine (AMP), cocaine (COC), and benzodiazepine (BZD) simultaneously in saliva samples. The multidetection sensing system was combined with a custom-made potentiostat to achieve a complete point-of-care (POC) platform. Smartphone integration was achieved by a customized application to operate, display, and send data. To the best of our knowledge, this is the first multiplex LSG-based electrochemical platform designed for illicit-drug detection with a custom-made potentiostat device to build a complete POC platform. Each working electrode was optimized with standard solutions of AMP, COC, and BZD in the concentration range of 1.0 pg/mL-500 ng/mL. The detection limit of each illicit drug was calculated as 4.3 ng/mL for AMP, 9.7 ng/mL for BZD, and 9.0 ng/mL for COC. Healthy and MET (methamphetamine) patient saliva samples were used for the clinical study. The multiplex LSG sensor was able to detect target analytes in real saliva samples successfully. This multiplex detection device serves the role of a practical and affordable alternative to conventional drug-detection methods by combining multiple drug detections in one portable platform.

CD34+ HSPCs-derived exosomes contain dynamic cargo and promote their migration through functional binding with the homing receptor E-selectin

Exosomes are tiny vesicles released by cells that carry communications to local and distant locations. Emerging research has revealed the role played by integrins found on the surface of exosomes in delivering information once they reach their destination. But until now, little has been known on the initial upstream steps of the migration process. Using biochemical and imaging approaches, we show here that exosomes isolated from both leukemic and healthy hematopoietic stem/progenitor cells can navigate their way from the cell of origin due to the presence of sialyl Lewis X modifications surface glycoproteins. This, in turn, allows binding to E-selectin at distant sites so the exosomes can deliver their messages. We show that when leukemic exosomes were injected into NSG mice, they traveled to the spleen and spine, sites typical of leukemic cell engraftment. This process, however, was inhibited in mice pre-treated with blocking E-selectin antibodies. Significantly, our proteomic analysis found that among the proteins contained within exosomes are signaling proteins, suggesting that exosomes are trying to deliver active cues to recipient cells that potentially alter their physiology. Intriguingly, the work outlined here also suggests that protein cargo can dynamically change upon exosome binding to receptors such as E-selectin, which thereby could alter the impact it has to regulate the physiology of the recipient cells. Furthermore, as an example of how miRNAs contained in exosomes can influence RNA expression in recipient cells, our analysis showed that miRNAs found in KG1a-derived exosomes target tumor suppressing proteins such as PTEN.

Creating Stretchable Electronics from Dual Layer Flex-PCB for Soft Robotic Cardiac Mapping Catheters

The authors present in this study the development of a novel method for creating stretchable electronics from dual-layer flex printed circuit boards (flex-PCBs) as a platform for soft robotic sensor arrays (SRSAs) for cardiac voltage mapping applications. There is a crucial need for devices that utilize multiple sensors and provide high performance signal acquisition for cardiac mapping. Previously, our group demonstrated how single-layer flex-PCB can be postprocessed to create a stretchable electronic sensing array. In this work, a detailed fabrication process for creating a dual-layer multielectrode flex-PCB SRSA is presented, along with relevant parameters to achieve optimal postprocessing with a laser cutter. The dual-layer flex-PCB SRSA's ability to acquire electrical signals is demonstrated both in vitro as well as in vivo on a Leporine cardiac surface. These SRSAs could be extended into full-chamber cardiac mapping catheter applications. Our results show a significant contribution towards the scalable use of dual-layer flex-PCB for stretchable electronics.

A Portable Molecularly Imprinted Sensor for On-Site and Wireless Environmental Bisphenol A Monitoring

The detection of pollutant traces in the public and environmental waters is essential for safety of the population. Bisphenol A (BPA) is a toxic chemical widely used for the production of food storage containers by plastic industries to increase the storage ability. However, the insertion of BPA in water medium leads to serious health risks. Therefore, the development of low-cost, practical, sensitive, and selective devices to monitor BPA levels on-site in the environment is highly needed. Herein, for the first time, we present a homemade portable potentiostat device integrated to a laser-scribed graphene (LSG) sensor for BPA detection as a practical environmental pollutant monitoring tool. Recently, there has been an increasing need regarding the development of graphene-based electrochemical transducers (e.g., electrodes) to obtain efficient biosensing platforms. LSG platform is combined with molecularly imprinted polymer (MIP) matrix. LSG electrodes were modified with gold nanostructures and PEDOT polymer electrodeposition to create a specific MIP biomimetic receptor for ultrasensitive BPA detection. The sensing device has a Bluetooth connection, wirelessly connected to a smartphone providing high sensitivity and sensitivity (LOD: 3.97 nM in a linear range of .01–10 µM) toward BPA. Two commercial bottled water samples, tap water, commercial milk, and baby formula samples have been used to validate the reliability of the portable sensor device.

Inherent Surface Activation of Laser-Scribed Graphene Decorated with Au and Ag Nanoparticles: Simultaneous Electrochemical Behavior toward Uric Acid and Dopamine

Laser-scribed graphene electrodes (LSGEs) have attracted great attention for the development of electrochemical (bio)sensors due to their excellent electronic properties, large surface area, and high porosity, which enhances the electrons' transfer rate. An increasing active surface area and defect sites are the quickest way to amplify the electrochemical sensing attributes of the electrodes. Here, we have found that the activation procedure coupled to the electrodeposition of metal nanoparticles resulted in a significant amplification of the active area and the analytical performance. This preliminary study is supported by the demonstration of the simultaneous electrochemical sensing of dopamine (DA) and uric acid (UA) by the electrochemically activated LSGEs (LSGE*s). Furthermore, the electrodeposition of two different metal nanoparticles, gold (Au) and silver (Ag), was performed in multiple combinations on working and reference electrodes to investigate the enhancement in the electrochemical response of LSGE*s. Current enhancements of 32, 27, and 35% were observed from LSGE* with WE:Au/RE:LSG/CE:LSGE, WE:Au/RE:Au/CE:LSGE, and WE:Au/RE:Ag/CE:LSGE, compared to the same combinations of LSGEs without any surface activation. A homemade and practical potentiostat, KAUSTat, was used in these electrochemical depositions in this study. Among all of the combinations, the surface area was increased 1.6-, 2.0-, and 1.2-fold for WE:Au/RE:LSG/CE:LSGE, WE:Au/RE:Au/CE:LSGE, and WE:Au/RE:Ag/CE:LSGE prepared from LSGE*s, respectively. To evaluate the analytical performance, DA and UA were detected simultaneously in the presence of ascorbic acid. The LODs of DA and UA are calculated to be ∼0.8 and ∼0.6 μM, respectively. Hence, this study has the potential to open new insights into new surface activation strategies with a combination of one-step nanostructured metal depositions by a custom-made potentiostat. This novel strategy could be an excellent and straightforward method to enhance the electrochemical transducer sensitivity for various electrochemical sensing applications.

Gold nanostructured laser-scribed graphene: A new electrochemical biosensing platform for potential point-of-care testing of disease biomarkers

Improvements in the laser-scribed graphene (LSG)-based electrodes are critical to overcoming limitations of bare LSG electrodes in terms of sensitivity, direct immobilization of detection probes for biosensor fabrication, and ease of integration with point-of-care (POC) devices. Herein, we introduce a new class of nanostructured gold modified LSG (LSG-AuNS) electrochemical sensing system comprising LSG-AuNS working electrode, LSG reference, and LSG counter electrode. LSG-AuNS electrodes are realized by electrodeposition of gold chloride (HAuCl₄) solution, which gave~2-fold enhancement in sensitivity and electrocatalytic activity compared to bare LSG electrode and commercially available screen-printed gold electrode (SPAuE). We demonstrate LSG-AuNS electrochemical aptasensor for detecting human epidermal growth factor receptor 2 (Her-2) with a limit of detection (LOD) of 0.008 ng/mL and a linear range of 0.1-200 ng/mL. LSG-AuNS-aptasensor can easily detect different concentrations of Her-2 spiked in undiluted human serum. Finally, to show the LSG-AuNS sensor system's potential to develop POC biosensor devices, we integrated LSG-AuNS electrodes with a handheld electrochemical system operated using a custom-developed mobile application.

Electrochemical sensors and biosensors using laser-derived graphene: A comprehensive review

Laser-derived graphene (LDG) technology is gaining attention as a promising material for the development of novel electrochemical sensors and biosensors. Compared to established methods for graphene synthesis, LDG provides many advantages such as cost-effectiveness, fast electron mobility, mask-free, green synthesis, good electrical conductivity, porosity, mechanical stability, and large surface area. This review discusses, in a critical way, recent advancements in this field. First, we focused on the fabrication and doping of LDG platforms using different strategies. Next, the techniques for the modification of LDG sensors using nanomaterials, conducting polymers, biological and artificial receptors are presented. We then discussed the advances achieved for various LDG sensing and biosensing schemes and their applications in the fields of environmental monitoring, food safety, and clinical diagnosis. Finally, the drawbacks and limitations of LDG based electrochemical biosensors are addressed, and future trends are also highlighted.

A chitosan gold nanoparticles molecularly imprinted polymer based ciprofloxacin sensor

In this work, we present a novel study on the development of an electrochemical biomimetic sensor to detect the ciprofloxacin (CIP) antibiotic. A chitosan gold nanoparticles decorated molecularly imprinted polymer (Ch-AuMIP) was used to modify the glassy carbon electrode (GCE) for preparation of the sensor. The Ch-AuMIP was characterized to understand various properties like chemical composition, morphology, roughness, and conduction using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and cyclic voltammetry (CV) respectively. Several experimental conditions affecting the Ch-AuMIP/GCE sensor such as the CIP removal agent, the extraction time, the volume of Ch-AuMIP drop-cast onto GCE and the rebinding time were studied and optimized. The Ch-AuMIP sensor sensitivity was studied in the concentration range of 1-100 μmol L-1 exhibiting a limit of detection of 210 nmol L-1. The synergistic combination of Au nanoparticles and Ch-MIP helps detect the CIP antibiotic with good sensitivity and selectivity, respectively. We investigated the selectivity aspect by using some possible interfering species and the developed sensing system showed good selectivity for CIP with a 66% response compared to the other compounds (≤45% response). The proposed sensing strategy showed its applicability for successful detection of CIP in real samples like tap water, mineral water, milk, and pharmaceutical formulation. The developed sensor showed good selectivity towards CIP even among the analogue molecules of Norfloxacin (NFX) and Ofloxacin (OFX). The developed sensor was successfully applied to determine the CIP in different samples with a satisfactory recovery in the range of 94 to 106%.

A label-free aptasensor FET based on Au nanoparticle decorated Co3O4 nanorods and a SWCNT layer for detection of cardiac troponin T protein

Acute myocardial infarction (AMI) is a serious health problem that must be identified in its early stages. Considerable progress has been made in understanding the condition of AMI through ascertaining the role of biomarkers, such as myoglobin, cardiac troponin proteins (T and I), creatine kinase-MB, and fatty acid-binding protein (FABP). A field-effect transistor (FET) is an effective platform; however, innovations are required in all layers of the FET for it to become robust and highly sensitive. For the first time, we made use of the synergistic combination of noble metal nanoparticles (AuNPs) with Co₃O₄ for the detection of cardiac troponin T (cTnT) in a FET platform. We determined the morphology of Au-decorated Co₃O₄ NRs and their electronic properties by characterizing the channel layer using electron microscopies and transient measurements. Subsequently, we performed the detection of cardiac troponin T by immobilizing its complementary biotinylated DNA aptamer on the channel surface using a drop-casting method. To understand the changes in drain current caused by this interaction, we probed our SWCNT-Co₃O₄ NR transistor with limited gate and drain bias (≤1 V), achieving a sensitivity of 0.5 μA μg^-1 mL^-1 for the Au-decorated NRs. A 250% increase in the sensitivity and a limit of detection (LOD) of 0.1 μg mL^-1 were achieved by using this device. Finally, selectivity studies proved that this synergistic combination works well in the FET configuration for the successful detection of cTnT.

Study of solvent effect on the synthesis of magnetic molecularly imprinted polymers based on ultrasound probe: Application for sulfonamide detection

In this work, a comparative study of the effect of various solvents on the synthesis of magnetic molecularly imprinted polymers (MMIPs) based on the use of high-power ultrasound probe is reported for the first time. Dimethylsulfoxide (DMSO), dimethylformamide (DMF), ethanol, acetonitrile and acetone were studied as solvents for the synthesis of MMIPs. Several crucial experimental conditions such as the time of synthesis and the applied amplitude were investigated. DMSO, DMF and ethanol were successfully used for ultrasound-assisted synthesis of MMIPs. However, for the polymerization performed using acetonitrile and acetone, no significant conversion to product was observed. Under optimal conditions for each solvent tested, the synthesized MMIPs were characterized using several techniques such as Scanning/Transmission Electron Microscopy (SEM and STEM modes), X-Ray Diffraction, Fourier Transform Infra-Red Spectroscopy, Thermal Gravimetric Analysis and Vibrating Sample Magnetometer system. The study of adsorption time of MMIPs showed that fast adsorption occurred due to the presence of specific imprinted sites on the surface. Moreover, isotherm study showed that the experimental equilibrium data fitted well with Freundlich model. The results of selectivity study indicated that MMIPs could selectively recognize the target molecule. Due to its high adsorption properties and easiness of preparation, MMIP-DMSO was used successfully as adsorbent material in solid-phase extraction coupled to a colorimetric method for sulfamethoxazole (SMX). After optimizing analytical conditions, a calibration plot was performed in the concentration range from 0.2 to 5 µg·mL^-1 with limits of detection and quantitation of 0.06 and 0.2 µg·mL^-1, respectively. The developed procedure was applied successfully for SMX determination in spiked tap and mineral waters showing satisfactory recoveries. Besides, reusability study demonstrated that MMIP could be reused at least 8 times keeping good binding capacity.

Fast route for the synthesis of decorated nanostructured magnetic molecularly imprinted polymers using an ultrasound probe

In this paper, we report for the first time a novel, simple and fast method for the synthesis of magnetic molecularly imprinted polymers (Mag-MIPs) based on high-energy ultrasound probe. Sulfamethoxazole (SMX) was used as template molecule, methacrylic acid as functional monomer, ethylene glycole dimethacrylate as crosslinking agent and magnetic nanoparticles (NPs) as the supporting core. The effects of time (5, 7.5 and 10 min) and the applied amplitude (20, 30, 40, 50 and 60%) using the ultrasound probe for the synthesis of Mag-MIPs were studied and optimized. By applying the proposed synthesis method, the US-magMIPs synthesis time was satisfactorily reduced from several hours to a few minutes (7.5 min) in a simple way. For comparison purposes, the Mag-MIP and the non imprinted polymer (MagNIP) were also synthesized employing an ultrasound bath assisted approach (2 h, 65 °C). Magnetic NPs and US-magMIPs synthesized by both ways were investigated by means of several characterization techniques such as Fourier Transform Infrared (FT-IR) spectroscopy, Scanning/Transmission electron microscopy (SEM and STEM modes), X-Ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and Dynamic Light Scattering (DLS). The results obtained confirms clearly the formation of magnetic NPs and their successful decoration by the imprinted polymer in both synthesis ways. The sulfonamide binding efficiency of US-magMIPs synthesized by the ultrasound probe and ultrasound bath were investigated according to the adsorption isotherm. The obtained results showed that the US-magMIP synthesized with the probe has more binding capacity compared to the one synthesized with US bath. The adsorption time was studied and both synthesized US-magMIPs reached the maximum adsorption capacity toward SMX after 1 h and the US-magMIP probe tends to have more easiness to bind SMX in less time. The selectivity studies of the synthesized US-magMIPs based on probe and bath showed a high affinity for SMX compared to its structural analogues such as sulfadiazine, sulfamerazine and sulfacetamide.

A sensitive method for the determination of Sulfonamides in seawater samples by Solid Phase Extraction and UV-Visible spectrophotometry

The authors have developed a sensitive spectrophotometric method for determination of sulfonamide derivatives such as sulfanilamide (SAA), sulfadiazine (SDZ), sulfacetamide (SCT) sulfamethoxazole (SMX), sulfamerazine (SMR), sulfadimethoxine (SDX), sulfamethiazole (SMT) and Sulfathiazole (STZ). This method is based on the Bratton-Marshall reaction, which involves the diazotization of sulfonamides with sodium nitrite under acidic conditions, followed by coupling with N-(1-naphtyl) ethylenediamine dihydrochloride (NED) to form a pink colored compound. Therefore, the Bratton-Marshall method was modified by optimizing the reaction conditions, which allows us to determine a low concentration range of sulfonamides compared to the reported methods. The limits of detection and quantification obtained were 0.019-0.05 and 0.06-0.16μgmL^-1, respectively. In comparison with other reported methods using different coupling agents, the proposed method was found to be the most simple and sensitive for sulfonamides determination. In this paper, the modified method was successfully employed for the determination of sulfonamides in drinking water, seawater and pharmaceutical and veterinary formulations. The purpose of this work is to optimize and develop a simple method for extraction and concentration of sulfonamides present as residues in seawater and their quantification with the recommended spectrophotometric method. Solid phase extraction (SPE) of sulfonamides from seawater samples was evaluated using Oasis HLB cartridges (3mL, 540mg). The recovery efficiency was investigated in the sulfonamides concentration range comprised between 0.19 and 126ngmL^-1. The ease of use of this extraction method makes it very useful for routine laboratory work.