Imprinted Hydrogel Nanoparticles for Protein Biosensing: A Review

Quasi-solid hydrogel electrolyte/nitrogen dot-based electrochemiluminescence sensor for enrofloxacin detection in milk

In this study, a novel quasi-solid hydrogel-based electrochemiluminescence (ECL) sensor was developed to detect enrofloxacin (ENR) in milk. First, nitrogen-rich quantum dots ((5-AT-co-CA)-N-dots) with high luminescence efficiency were synthesized and served cathodic ECL luminophores. Second, the P(AM-co-AMPS)-PEDOT:PSS (PAMES) hydrogel was prepared as a quasi-solid electrolyte. The hydrogel exhibited high ionic conductivity (52.5 mS cm-1), excellent adhesion properties, high transparency (83 %), and high water content (89 %). The ECL signal of (5-AT-co-CA)-N-dots was enhanced by 4.3 times in is PAMES hydrogel compared to the solution. The solventless sensing system based on quasi-solid hydrogel electrolyte addressed the limitations of leakage and instability of traditional liquid electrolytes, thereby improving the portability and environmental adaptability of the sensor. Furthermore, a molecularly imprinted sensing system was constructed to detect ENR based on the PAMES hydrogel. This novel ECL sensor significantly simplified the operations and expanded s potential sensing applications.

CA 15-3-specific molecularly imprinted polymer nanoparticles-based voltammetric sensor for breast cancer monitoring

Cancer antigen 15-3 (CA 15-3) is a critical biomarker for breast cancer, used to monitor disease severity and recurrence. Furthermore, its detection can be beneficial in post-operative treatment. Thus, biosensors that can track CA 15-3 levels in patients would provide useful data for disease monitoring. This study proposed molecularly imprinted polymer nanoparticles (nanoMIPs) specific for CA 15-3 detection; furthermore, the synthesized nanoMIPs were combined with an electrochemical sensor for breast cancer monitoring. The CA 15-3-specific nanoMIPs were generated via solid-phase synthesis. For sensor fabrication, a screen-printed carbon electrode (SPCE) was decorated with multi-walled carbon nanotubes and Au nanoparticles to improve the sensitivity. 4-aminothiophenol (4-ATP) enabled linking the synthesized CA 15-3-specific nanoMIPs to the electrode via the reaction with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). Characterizations via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and the electrochemical method suggested the successful modification of the SPCE surface. Square wave voltammetry (SWV) was used to evaluate the sensor's performance in detecting CA 15-3. The sensor exhibited a wide detection range from 1 to 100 U/mL of CA 15-3 and a limit of detection (LOD) of 0.14 U/mL. The detection range covered the reference level (30 U/mL) of CA 15-3, allowing for distinguishing between healthy people and patients. The sensor allowed for the accurate and reliable determination of CA 15-3 concentrations in serum samples after pretreatment. In addition, the proposed sensor offers advantages in terms of easy fabrication and detection, low costs, and disposability. Therefore, it could serve as an alternative device for breast cancer monitoring.

High-Sensitive Hydrogel Optofluidic Microcavities for Heavy Metal Ion Detection

Hydrogels have emerged as promising sensors for detecting heavy metal ions in fluids and have been extensively developed. However, monitoring of multiple target analytes in Chinese herbs remains challenging due to subtle chemical signals and the complex composition of the extracted solutions. To address these challenges, we developed a hydrogel optofluidic sensor to amplify analyte signals through strong light-matter interactions within the hydrogel. This sensing platform integrates a hydrogel film encapsulated in a whispering-gallery-mode (WGM) microcavity for the detection of heavy metal ions, such as Pb2+ and Hg2+. The 3D cross-linked hydrophilic polymer network facilitates ion penetration from analyte solutions, inducing distinct WGM resonance shifts. The red shift in the spectral wavelength serves as a parameter to quantify the content of heavy metal ions. By modification of the hydrogel with aptamers, the optofluidic sensors achieve high sensitivity and selectivity. Finally, the platform's performance was demonstrated using Chinese herbs with varying Pb2+ concentrations, highlighting its practical applicability in real-world scenarios. The proposed hydrogel microcavity exhibit a promising method for development of functional hydrogel sensors and healthcare applications.

Nanogel imprinting improving affinity and selectivity of domain-limited ssDNA aptamer to Pb2+: Interaction mechanisms revealed by molecular dynamics simulation

Aptamer conformations are susceptible to environmental conditions, which makes it difficult to achieve stable targets detection in complex environments with aptasensors. Imprinting strategy was proposed to immobilize the specific conformation of aptamers, aiming to enhance their recognition anti-interference. However, it is mechanistically unclear how the imprinted polymers affect aptamers' recognition, which limits application of the strategy. Herein, MD simulation was applied to explore the structural reason why nanogel imprinting improves binding affinity and selectivity of T30695 aptamer to Pb2+ observed experimentally. Results show the imprinted polymers stabilize the domain-limited T30695 by noncovalent interactions. The coating process undergoes three evolution stages, finally achieving a polymer-aptamer-polymer sandwich-shaped conformation. Notably, it was found the polymers provide additional non-specific binding of Pb2+ at acylamine group of acrylamide monomers, which accounts for the improved binding affinity with association constant Ka 2.5 times larger. More importantly, imprinting enhances selectivity of aptamer to Pb2+ by changing coordination mode of interfering ions (Ca2+, K+, Mg2+, NH4+ and Cu2+), which significantly destroys G-quadruplex conformation and thus its binding ability. This work revealed mechanistic effects of imprinting strategy on aptamers recognition at molecular level, which can guide rational design of high-performance aptamer-based biosensors applied in various detection areas.

Molecularly imprinted hydrogels embedded with two-dimensional photonic crystals for the detection of dexamethasone/betamethasone sodium phosphate

Dexamethasone sodium phosphate (DSP) and betamethasone sodium phosphate (BSP) imprinted hydrogels embedded with two-dimensional photonic crystals (2DPC) were developed as hormones-sensitive photonic hydrogel sensors with highly sensitive, selective, anti-interference and reproducible recognition capability. The DSP/BSP molecularly imprinted photonic hydrogels (denoted as DSP-MIPH and BSP-MIPH) can specifically recognize DSP/BSP by rebinding the DSP/BET molecules to nanocavities in the hydrogel network. This recognition is enabled by the similar shape, size, and binding sites of the nanocavities to the target molecules. The rebinding of hormones molecules causes the hydrogel to swell, resulting in a particle spacing increase of the embedded 2DPC of the hydrogel. The particle spacing increase can be used as sensing signal and can be acquired by simply measuring the Debye diffraction diameters of the photonic hydrogel sensor before and after exposure with a laser pointer and a ruler. The particle spacing increments of the DSP-MIPH and BSP-MIPH sensors linearly change when DSP and BSP concentrations changes within the ranges 0.025-1 μM, 10-100 μM, and 100-500 μM, and the limits of detection (LoD) are 21.8 nM for DSP and 12.6 nM for BSP, respectively. These photonic hydrogel sensors were successfully applied to the determination of DSP/BSP contents in the real pharmaceutical injections, providing an ideal strategy for the development of portable hormones sensors.

Construction of a monoclonal molecular imprinted sensor with high affinity for specific recognition of influenza a virus subtype

Although molecular imprinting technology has been widely used in the construction of virus sensors, it is still a great challenge to identify subtypes viruses specifically because of their high similarity in morphology, size and structure. Here, a monoclonal molecular imprinted polymers (MIPs) sensor for recognition of H5N1 is constructed to permit the accurate distinguishing of H5N1 from other influenza A virus (IAV) subtypes. Firstly, H5N1 are immobilized on magnetic microspheres to produce H5N1-MagNPs, then the high affinity nanogel H5N1-MIPs is prepared by solid phase imprinting technique. When H5N1-MIPs is combined with MagNP-H5N1, different concentrations of H5N1 are added for competitive substitution. The quantitative detection of H5N1 is realized by the change of fluorescence intensity of supernatant. As expected, the constructed sensor shows satisfactory selectivity, and can identify the target virus from highly similar IAV subtypes, such as H1N1, H7N9 and H9N2. The sensor was highly sensitive, with a detection limit of 0.58 fM, and a selectivity factor that is comparable to that of other small MIPs sensors is achieved. In addition, the proposed sensor is cheap, with a cost of only RMB 0.08 yuan. The proposed monoclonal sensor provides a new method for the specific recognition of designated virus subtype, which is expected to be used for large-scale screening and accurate treatment of infected people.

Process, advances, and perspectives of graphene oxide-SELEX for the development of aptamer molecular probes: A comprehensive review

BACKGROUND

Aptamers are screened via the systematic evolution of ligands by exponential enrichment (SELEX) and are widely used in molecular diagnostics and targeted therapies. The development of efficient and convenient SELEX technology has facilitated rapid access to high-performance aptamers, thereby advancing the aptamer industry. Graphene oxide (GO) serves as an immobilization matrix for libraries in GO-SELEX, making it suitable for screening aptamers against diverse targets.

RESULTS

This review summarizes the detailed steps involved in GO-SELEX, including monitoring methods, various sublibrary acquisition methods, and practical applications from its inception to the present day. In addition, the potential of GO-SELEX in the development of broad-spectrum aptamers is explored, and its current limitations for future development are emphasized. This review effectively promotes the application of the GO-SELEX technique by providing valuable insights and assisting researchers interested in conducting related studies.

SIGNIFICANCE AND NOVELTY

To date, no review on the topic of GO-SELEX has been published, making it challenging for researchers to initiate studies in this area. We believe that this review will broaden the SELEX options available to researchers, ensuring that they can meet the growing demand for molecular probes in the scientific domain.

Boosting Electrochemical Sensing Performances Using Molecularly Imprinted Nanoparticles

Nanoparticles of molecularly imprinted polymers (nanoMIPs) combine the excellent recognition ability of imprinted polymers with specific properties related to the nanosize, such as a high surface-to-volume ratio, resulting in highly performing recognition elements with surface-exposed binding sites that promote the interaction with the target and, in turn, binding kinetics. Different synthetic strategies are currently available to produce nanoMIPs, with the possibility to select specific conditions in relation to the nature of monomers/templates and, importantly, to tune the nanoparticle size. The excellent sensing properties, combined with the size, tunability, and flexibility of synthetic protocols applicable to different targets, have enabled the widespread use of nanoMIPs in several applications, including sensors, imaging, and drug delivery. The present review summarizes nanoMIPs applications in sensors, specifically focusing on electrochemical detection, for which nanoMIPs have been mostly applied. After a general survey of the most widely adopted nanoMIP synthetic approaches, the integration of imprinted nanoparticles with electrochemical transducers will be discussed, representing a key step for enabling a reliable and stable sensor response. The mechanisms for electrochemical signal generation will also be compared, followed by an illustration of nanoMIP-based electrochemical sensor employment in several application fields. The high potentialities of nanoMIP-based electrochemical sensors are presented, and possible reasons that still limit their commercialization and issues to be resolved for coupling electrochemical sensing and nanoMIPs in an increasingly widespread daily-use technology are discussed.

Innovative technologies for the fabrication of 3D/4D smart hydrogels and its biomedical applications - A comprehensive review

Repairing and regenerating damaged tissues or organs, and restoring their functioning has been the ultimate aim of medical innovations. 'Reviving healthcare' blends tissue engineering with alternative techniques such as hydrogels, which have emerged as vital tools in modern medicine. Additive manufacturing (AM) is a practical manufacturing revolution that uses building strategies like molding as a viable solution for precise hydrogel manufacturing. Recent advances in this technology have led to the successful manufacturing of hydrogels with enhanced reproducibility, accuracy, precision, and ease of fabrication. Hydrogels continue to metamorphose as the vital compatible bio-ink matrix for AM. AM hydrogels have paved the way for complex 3D/4D hydrogels that can be loaded with drugs or cells. Bio-mimicking 3D cell cultures designed via hydrogel-based AM is a groundbreaking in-vivo assessment tool in biomedical trials. This brief review focuses on preparations and applications of additively manufactured hydrogels in the biomedical spectrum, such as targeted drug delivery, 3D-cell culture, numerous regenerative strategies, biosensing, bioprinting, and cancer therapies. Prevalent AM techniques like extrusion, inkjet, digital light processing, and stereo-lithography have been explored with their setup and methodology to yield functional hydrogels. The perspectives, limitations, and the possible prospects of AM hydrogels have been critically examined in this study.

A highly tuneable inverse emulsion polymerization for the synthesis of stimuli-responsive nanoparticles for biomedical applications

Polymeric nanomaterials have seen widespread use in biomedical applications as they are highly tuneable to achieve the desired stimuli-responsiveness, targeting, biocompatibility, and degradation needed for fields such as drug delivery and biosensing. However, adjustments to composition and the introduction of new monomers often necessitate reoptimization of the polymer synthesis to achieve the target parameters. In this study, we explored the use of inverse emulsion polymerization to prepare a library of polymeric nanoparticles with variations in pH and temperature response and examined the impact of overall batch volume and the volume of the aqueous phase on nanoparticle size and composition. We were able to prepare copolymeric nanoparticles using three different nonionic and three different anionic comonomers. Varying the non-ionizable comonomers, acrylamide (AAm), 2-hydroxyethyl methacrylate, and N-isopropylacrylamide (NIPAM), was found to alter the mass percentage of methacrylic acid (MAA) incorporated (from 26.7 ± 3.5 to 45.8 ± 1.8 mass%), the critical swelling pH (from 5.687 ± 0.194 to 6.637 ± 0.318), and the volume swelling ratio (from 1.389 ± 0.064 to 2.148 ± 0.037). Additionally, the use of NIPAM was found to allow for temperature-responsive behavior. Varying the ionizable comonomers, MAA, itaconic acid, and 2-acrylamido-2-methylpropane sulfonic acid (AMPSA), was found to significantly alter the critical swelling pH and, in the case of AMPSA, remove the pH-responsive behavior entirely. Finally, we found that for the base P(AAm-co-MAA) formulation, the pH-responsive swelling behavior was independent of the scale of the reaction; however, variations in the aqueous volume relative to the volume of the continuous phase significantly affected both the nanoparticle size and the critical swelling pH.

Molecularly Imprinted Polymers: Shaping the Future of Early-Stage Bone Loss Detection-A Review

Osteoporosis is the deterioration of bone mineral density (BMD) because of an imbalance between bone resorption and formation, which might happen due to lots of factors like age, hormonal imbalance, and several others. While this occurrence is prevalent in both genders, it is more common in women, especially postmenopausal women. It is an asymptomatic disease that is underlying until the first incidence of a fracture. The bone is weakened, making it more susceptible to fracture. Even a low trauma can result in a fracture, making osteoporosis an even more alarming disease. These fractures can sometimes be fatal or can make the patient bedridden. Osteoporosis is an understudied disease, and there are certain limitations in diagnosing and early-stage detection of this condition. The standard method of dual X-ray absorptiometry can be used to some extent and can be detected in standard radiographs after the deterioration of a significant amount of bone mass. Clinically assessing osteoporosis using biomarkers can still be challenging, as clinical tests can be expensive and cannot be accessed by most of the general population. In addition, manufacturing antibodies specific to these biomarkers can be a challenging, time-consuming, and expensive method. As an alternative to these antibodies, molecularly imprinted polymers (MIPs) can be used in the detection of these biomarkers. This Review provides a comprehensive exploration of bone formation, resorption, and remodeling processes, linking them to the pathophysiology of osteoporosis. It details biomarker-based detection and diagnosis methods, with a focus on MIPs for sensing CTX-1, NTX-1, and other biomarkers. The discussion compares traditional clinical practices with MIP-based sensors, revealing comparable sensitivity with identified limitations. Additionally, the Review contrasts antibody-functionalized sensors with MIPs. Finally, our Review concludes by highlighting the potential of MIPs in future early-stage osteoporosis detection.

Ultra-Sensitive Portable Visual Paper-Based Viral Molecularly Imprinted Sensor without Autofluorescence Interference

Detection of the virus is the primary factor to discover and block the occurrence and development of the virus epidemic. Here, an ultrasensitive paper-based virus molecular imprinting sensor is developed to detect two viruses simultaneously in which the detection limit of the influenza virus (H5N1) is 16.0 aM (9.63 × 103 particles/mL) while that of the Hepatitis B Virus (HBV) is 129 fM (7.77 × 107 particles/mL). This paper-based sensor is low cost and is easy to cut, store, and carry. In addition, the visual semiquantitative detection of two viruses is achieved by using two aptamer-functionalized persistent luminescent nanoparticles as signal probes. These probes and the imprinted cavities on the paper-based material formed sandwich-type double recognition of the target viruses. This sensor has extremely high sensitivity to the H5N1 virus, which is of great value to solve the influenza epidemic with the most outbreaks in history, and also opens up a new way for the prevention and control of other virus epidemics. This cheap and portable visual sensor provides the possibility for self-service detection and can greatly reduce the pressure on medical staff and reduce the risk of virus infection caused by the concentration of people to be tested.