Detection of C-reactive protein using nanoparticle-enhanced surface plasmon resonance using an aptamer-antibody sandwich assay

EGaIn-Modified ePADs for Simultaneous Detection of Homocysteine and C-Reactive Protein in Saliva toward Early Diagnosis of Cardiovascular Disease

Homocysteine (Hcy) and C-reactive protein (CRP) are critical biomarkers for numerous chronic diseases, with cardiovascular disease (CVD) being the most prevalent. The ability to simultaneously detect both biomarkers in point-of-care settings is in high demand for CVD early diagnosis and prevention. Herein, we prepared the eutectic gallium indium (EGaIn) nanoparticles decorated with p-phenylenediamine (PPD) on the surface to facilitate the subsequent attachment of gold nanoparticles (AuNPs) to achieve EGaIn-PPD@Au, which was modified on the screen-printed electrochemical paper-based analytical devices (ePADs). Aptamers that are specific to Hcy and CRP were then immobilized on the EGaIn-PPD@Au surface to achieve the sensing interface on ePADs. The presence of EGaIn-PPD@Au significantly enhanced the electrical conductivity, leading to amplified electrochemical signals. This aptasensor demonstrated high specificity, capable of detecting Hcy in a range of 1-50 μM with a detection limit of 0.22 μM, and the detection range for CRP was 1-100 ng/mL with a detection limit of 0.039 ng/mL. The aptasensor also effectively detected Hcy and CRP in clinical saliva samples, yielding an area under the curve (AUC) of about 0.80 when the individual biomarker was considered and 0.93 when both biomarkers were taken into account. The positive correlation observed between salivary and blood concentrations of Hcy and CRP, coupled with their association with cardiovascular disease (CVD), suggested the potential of this methodology as a noninvasive point-of-care strategy for the early diagnosis of CVD.

Structure-Switching Electrochemical Aptasensor for Rapid, Reagentless, and Single-Step Nanomolar Detection of C-Reactive Protein

C-reactive protein (CRP) is an acute-phase reactant and sensitive indicator for sepsis and other life-threatening pathologies, including systemic inflammatory response syndrome. Currently, clinical turn-around times for established CRP detection methods take between 30 min to hours or even days from centralized laboratories. Here, we report the development of an electrochemical biosensor using redox probe-tagged DNA aptamers, functionalized onto inexpensive, commercially available screen-printed electrodes. Binding-induced conformational switching of the CRP-targeting aptamer induces a specific and selective signal-ON event, which enables single-step and reagentless detection of CRP in as little as 1 min. The aptasensor limit of detection spans approximately 20-60 nM in 50% human serum with dynamic response windows spanning 1-200 or 1-500 nM (R = 0.97/R = 0.98 respectively). The sensor is stable for at least 1 week and can be reused numerous times, as judged from repeated real-time dosing and dose-response assays. By decoupling binding events from the signal induction mechanism, structure-switching electrochemical aptamer-based sensors provide considerable advantages over their adsorption-based counterparts. Our work expands on the retinue of such sensors reported in the literature and is the first instance of structure-switching electrochemical aptamer-based sensors (SS-EABs) for reagentless, voltammetric CRP detection. We hope this study inspires further investigations into the suitability of SS-EABs for diagnostics, which will aid translational R&D toward fully realized devices aimed at point-of-care applications or for broader use by the public.

Aptamer-conjugated gold nanoparticles for portable, ultrasensitive naked-eye detection of C-reactive protein based on the Tyndall effect

BACKGROUND

C-reactive protein (CRP) represents an early clinical biomarker that indicates the presence of inflammatory or infectious conditions in the human body. Today's procedures approved by the Food and Drug Administration (FDA) imply expensive equipment and highly trained personnel to perform the test. Therefore, a new diagnostic method with high detection efficiency and less cost is urgently needed for delivering rapid and timely results in point-of-care (POC) service.

RESULTS

Herein, we propose a new, equipment-free, and portable sensing method for the future POC detection of CRP based on the Tyndall effect (TE). In our study, aptamer-conjugated citrate-stabilized gold nanoparticles (apta-AuNPs) are exploited as the sensing platform. The apta-AuNPs' interaction with CRP in a saline environment leads to their aggregation, thus enhancing the scattering of light when the solution is exposed to a 640 nm pointer laser line. Firstly, the enhancement of the scattering light as a function of increasing concentration of CRP in solution is measured spectroscopically using a typical 90-degree angle spectrofluorometer and then the measurements are compared to the classic colorimetric detection using an UV-Vis spectrophotometer. Finally, to achieve high portability and accessibility, we demonstrate that the measurement of CRP concentration can be performed with similar accuracy but in a more direct and inexpensive way by using a laser pointer pen as the excitation source and a camera of a low-budget smartphone as a quantitative reader instead of most expensive spectrofluorometer.

SIGNIFICANCE

The portable TE-based assay exhibits a wide linear dynamic range (1-60 μg/mL) for the detection of CRP with a limit of detection (LOD) of 92 ng/mL The proposed method is capable to integrate both standard and high-sensitivity CRP analysis in a single procedure with increased sensitivity and prompt delivery of analysis results. Moreover, the sensing procedure is significantly faster than the FDA approved ones with a detection time of only 10 min. Finally, as a proof-of-concept, our findings demonstrate excellent recovery for CRP detection in spiked and diluted urine samples, highlighting the strong potential of this sensing method for POC applications.

Antidote-controlled DNA aptamer modulates human factor IXa activity

Thrombosis leads to elevated mortality rates and substantial medical expenses worldwide. Human factor IXa (HFIXa) protease is pivotal in tissue factor (TF)-mediated thrombin generation, and represents a promising target for anticoagulant therapy. We herein isolated novel DNA aptamers that specifically bind to HFIXa through systematic evolution of ligands by exponential enrichment (SELEX) method. We identified two distinct aptamers, seq 5 and seq 11, which demonstrated high binding affinity to HFIXa (Kd = 74.07 ± 2.53 nM, and 4.93 ± 0.15 nM, respectively). Computer software was used for conformational simulation and kinetic analysis of DNA aptamers and HFIXa binding. These aptamers dose-dependently prolonged activated partial thromboplastin time (aPTT) in plasma. We further rationally optimized the aptamers by truncation and site-directed mutation, and generated the truncated forms (Seq 5-1t, Seq 11-1t) and truncated-mutated forms (Seq 5-2tm, Seq 11-2tm). They also showed good anticoagulant effects. The rationally and structurally designed antidotes (seq 5-2b and seq 11-2b) were competitively bound to the DNA aptamers and effectively reversed the anticoagulant effect. This strategy provides DNA aptamer drug-antidote pair with effective anticoagulation and rapid reversal, developing advanced therapies by safe, regulatable aptamer drug-antidote pair.

Multiplex signal amplification for ultrasensitive CRP assay via integrated electrochemical biosensor array using MOF-derived carbon material and aptamers

Accurate and precise detection of disease-associated proteins, such as C-reactive protein (CRP), remains a challenge in biosensor development. Herein, we present a novel approach－an integrated disposable aptasensor array－designed for precise, ultra-sensitive, and parallel detection of CRP in plasma samples. This integrated biosensing array platform enables multiplex parallel testing, ensuring the accuracy and reliability in sample analysis. The ultra-sensitivity of this biosensor is achieved through multiplex signal amplification. Leveraging the superior conductivity and extensive surface area of MOF-derived nanoporous carbon material (CMOF), the biosensor enhances recognition elements (aptamers) by catalyzing the horseradish peroxidase (HRP) label enzyme reaction to multiply the number of probe molecules. Optimized conditions yielded exceptional performance, exhibiting high accuracy (relative standard deviation, RSD≤10.0 %), a low detection limit (0.3 pg/mL, S/N = 3), ultra-sensitivity (0.16 μA/ng mL-1 mm-2), and a rapid response (seven parallel tests within 60 min). Importantly, this multi-unit integrated disposable aptasensor array accurately quantified CRP in human serum, demonstrating comparable results to commercial enzyme-linked immunosorbent assay (ELISA). This technology showcases promise for detecting various biomarkers using a unified approach, presenting an appealing strategy for early disease diagnosis and biological analysis.

Optimization of Surface Functionalizations for Ring Resonator-Based Biosensors

Liquid biopsy is expected to become widespread in the coming years thanks to point of care devices, which can include label-free biosensors. The surface functionalization of biosensors is a crucial aspect that influences their overall performance, resulting in the accurate, sensitive, and specific detection of target molecules. Here, the surface of a microring resonator (MRR)-based biosensor was functionalized for the detection of protein biomarkers. Among the several existing functionalization methods, a strategy based on aptamers and mercaptosilanes was selected as the most highly performing approach. All steps of the functionalization protocol were carefully characterized and optimized to obtain a suitable protocol to be transferred to the final biosensor. The functionalization protocol comprised a preliminary plasma treatment aimed at cleaning and activating the surface for the subsequent silanization step. Different plasma treatments as well as different silanes were tested in order to covalently bind aptamers specific to different biomarker targets, i.e., C-reactive protein, SARS-CoV-2 spike protein, and thrombin. Argon plasma and 1% v/v mercaptosilane were found as the most suitable for obtaining a homogeneous layer apt to aptamer conjugation. The aptamer concentration and time for immobilization were optimized, resulting in 1 µM and 3 h, respectively. A final passivation step based on mercaptohexanol was also implemented. The functionalization protocol was then evaluated for the detection of thrombin with a photonic biosensor based on microring resonators. The preliminary results identified the successful recognition of the correct target as well as some limitations of the developed protocol in real measurement conditions.

Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer

This article introduces distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) and carbon dots (CDs) for simultaneous quantification of cytokine biomarkers, namely C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in human biological samples for diagnosis of cytokine syndrome. Using fluorescent CDs and MIP technology, the dPAD exhibits high selectivity and sensitivity. Detection is based on fluorescence quenching of CDs achieved through the interaction of the target analytes with the MIP layer on the paper substrate. Quantitative analysis is easily accomplished by measuring the distance length of quenched fluorescence with a traditional ruler and naked eye readout enabling rapid diagnosis of cytokine syndrome and the underlying infection. Our sensor demonstrated linear ranges of 2.50-24.0 pg mL-1 (R2 = 0.9974), 0.25-3.20 pg mL-1 (R2 = 0.9985), and 1.50-16.0 pg mL-1 (R2 = 0.9966) with detection limits (LODs) of 2.50, 0.25, and 1.50 pg mL-1 for CRP, TNF-α, and IL-6, respectively. This sensor also demonstrated remarkable selectivity compared to a sensor employing a non-imprinted polymer (NIP), and precision with the highest relative standard deviation (RSD) of 5.14%. The sensor is more accessible compared to prior methods relying on expensive reagents and instruments and complex fabrication methods. Furthermore, the assay provided notable accuracy for monitoring these biomarkers in various human samples with recovery percentages ranging between 99.22% and 103.58%. By integrating microfluidic systems, nanosensing, and MIPs technology, our developed dPADs hold significant potential as a cost-effective and user-friendly analytical method for point-of-care diagnostics (POC) of cytokine-related disorders. This concept can be further extended to developing diagnostic devices for other biomarkers.

Diagnostic and Therapeutic Aptamers: A Promising Pathway to Improved Cardiovascular Disease Management

Despite advances in care, cardiovascular diseases remain the leading cause of death worldwide. As a result, identifying suitable biomarkers for early diagnosis and improving therapeutic and diagnostic strategies is crucial. Because of their significant advantages over other therapeutic approaches, nucleic-based therapies, particularly aptamers, are gaining increased attention. Aptamers are innovative synthetic polymers or oligomers of single-stranded DNA (ssDNA) or RNA molecules that can form 3-dimensional structures and thus interact with their targets with high specificity and affinity. Furthermore, they outperform classical protein-based antibodies in terms of in vitro selection, production, ease of modification and conjugation, high stability, low immunogenicity, and suitability for nanoparticle functionalization for targeted drug delivery. This work aims to review the advances made in the aptamers' field in biomarker detection, diagnosis, imaging, and targeted therapy, which highlight their huge potential in the management of cardiovascular diseases.

Exploiting the design of surface plasmon resonance interfaces for better diagnostics: A perspective review

Surface Plasmon Resonance based-sensors are promising tools for precision diagnostics as they can provide tests useful for early and, whenever possible, non-invasive disease detection and monitoring. The design of novel, robust and effective interfaces enabling the sensing of a variety of molecular interactions in a highly selective and sensitive manner is a necessary step to obtain both accurate and reliable detection by SPR. This review covers the recent research efforts in this area, specifically emphasizing well-designed interfaces and applications in real-life samples. In particular, after a short introduction which identifies some of the critical challenges, the emerging strategies for the integration of the linker, the metal substrate and the recognition element on the sensing interface will be explored and discussed in three sections, as well as the opportunities for building SPR biosensors, easy to use, and with excellent sensitivities. Finally, a summary of some of the more promising and latest diagnostic applications will be provided, presenting a new window into the near-future perspectives.

Surface plasmon coupling between wide-field SPR microscopy and gold nanoparticles

The coupling behavior of the wide field surface plasmon microscopy (WF-SPRM) with single-, two-, and multiple-gold nanoparticles (AuNPs) with different AuNPs sizes is investigated using theoretical, simulation, and experimental approaches. The signal intensity of a single AuNP increases from 208 a.u. to 583 a.u. as particle size increases from 40 to 80 nm, which evidences the signal-building mechanism of Rayleigh scattering theory. A discrete particle model of SPR is used to understand the interaction between an Au-layer and a single AuNP. The calculated intensity profile of the single AuNP from the discrete particle model is accepted with the experimental data. In addition, the superposition between 2-AuNPs surface plasmon waves is studied using the finite element method as well as experimental data from WF-SPRM. The surface plasmon waves around the two particles generate an interference pattern. Finally, it is demonstrated that plasmonic multiple particles scattering can be represented by an effective media, which is described by Maxwell-Garnet equations.

Nucleic Acid Aptamer-Based Biosensors: A Review

Aptamers, short strands of either DNA, RNA, or peptides, known for their exceptional specificity and high binding affinity to target molecules, are providing significant advancements in the field of health. When seamlessly integrated into biosensor platforms, aptamers give rise to aptasensors, unlocking a new dimension in point-of-care diagnostics with rapid response times and remarkable versatility. As such, this review aims to present an overview of the distinct advantages conferred by aptamers over traditional antibodies as the molecular recognition element in biosensors. Additionally, it delves into the realm of specific aptamers made for the detection of biomarkers associated with infectious diseases, cancer, cardiovascular diseases, and metabolomic and neurological disorders. The review further elucidates the varying binding assays and transducer techniques that support the development of aptasensors. Ultimately, this review discusses the current state of point-of-care diagnostics facilitated by aptasensors and underscores the immense potential of these technologies in advancing the landscape of healthcare delivery.

Aptamer-Protein Interactions: From Regulation to Biomolecular Detection

Serving as the basis of cell life, interactions between nucleic acids and proteins play essential roles in fundamental cellular processes. Aptamers are unique single-stranded oligonucleotides generated by in vitro evolution methods, possessing the ability to interact with proteins specifically. Altering the structure of aptamers will largely modulate their interactions with proteins and further affect related cellular behaviors. Recently, with the in-depth research of aptamer-protein interactions, the analytical assays based on their interactions have been widely developed and become a powerful tool for biomolecular detection. There are some insightful reviews on aptamers applied in protein detection, while few systematic discussions are from the perspective of regulating aptamer-protein interactions. Herein, we comprehensively introduce the methods for regulating aptamer-protein interactions and elaborate on the detection techniques for analyzing aptamer-protein interactions. Additionally, this review provides a broad summary of analytical assays based on the regulation of aptamer-protein interactions for detecting biomolecules. Finally, we present our perspectives regarding the opportunities and challenges of analytical assays for biological analysis, aiming to provide guidance for disease mechanism research and drug discovery.

Imaging Protein Aggregates in Parkinson's Disease Serum Using Aptamer-Assisted Single-Molecule Pull-Down

The formation of soluble α-synuclein (α-syn) and amyloid-β (Aβ) aggregates is associated with the development of Parkinson's disease (PD). Current methods mainly focus on the measurement of the aggregate concentration and are unable to determine their heterogeneous size and shape, which potentially also change during the development of PD due to increased protein aggregation. In this work, we introduce aptamer-assisted single-molecule pull-down (APSiMPull) combined with super-resolution fluorescence imaging of α-syn and Aβ aggregates in human serum from early PD patients and age-matched controls. Our diffraction-limited imaging results indicate that the proportion of α-syn aggregates (α-syn/(α-syn+Aβ)) can be used to distinguish PD and control groups with an area under the curve (AUC) of 0.85. Further, super resolution fluorescence imaging reveals that PD serums have a higher portion of larger and rounder α-syn aggregates than controls. Little difference was observed for Aβ aggregates. Combining these two metrics, we constructed a new biomarker and achieved an AUC of 0.90. The combination of the aggregate number and morphology provides a new approach to early PD diagnosis.

Sensitive dual-mode sensing platform for Amyloid β detection: Combining dual Z-scheme heterojunction enhanced photoelectrochemistry analysis and dual-wavelength ratiometric electrochemiluminescence strategy

As a tumor biomarker, the accumulation of amyloid β oligomers (Aβo) in the brain has been suggested as a key feature in the pathogenesis and progression of Alzheimer's disease (AD). In this work, we designed a novel photoelectrochemical (PEC) and electrochemiluminescence resonance energy transfer (ECL-RET) dual-mode biosensor to achieve ultra-sensitive detection of Aβo. Specifically, the electrode surface modified Carbon Dots (C Dots) and the electrodeposited polyaniline (PANI) film formed a Z-scheme heterojunction reversing the photocurrent signal, and then the Aβo specific recognition peptide was attached to the surface via amide bonding between the amino group of PANI and carbonyl group of peptide. After that, in the presence of CdTe labeled specific recognition aptamer for Aβ (CdTe-Apt), Aβo was captured to construct a sandwich-type biosensor and exhibited a significantly enhanced cathodic photocurrent response because the formed dual Z-scheme heterojunction promoted charge separation efficiency. Interestingly, the proposed biosensor also caused a ratiometric change in the ECL intensity at 555 nm and 640 nm. Therefore, the developed biosensor achieved dual-mode detection of Aβo, where the PEC detection range of Aβo was from 10 fM to 0.1 μM (with a detection limit of 4.27 fM) and the ECL method provided a linear detection range of 10 fM to 10 nM (with a detection limit of 6.41 fM). The stability and reliability of the experimental results indicate that this has been a promising biosensing pattern and could be extended to the analysis of other biomarkers.

"Two-in-one" core-shell nanozyme probes with double signal amplification for high-performing surface plasmon resonance immunosensing

Herein, a "two-in-one" Ag@Au core-shell nanozyme probe inducing double-signal amplification has been developed to significantly elevate the sensitivity of SPR sensors via sandwich immunoassay. The Ag@Au core-shell nanozyme with intrinsic peroxide-like activity was demonstrated to catalyze a polymerization reaction leading to formation of polyaniline, allowing further improvement of detection performance of SPR immunosensor. The method demonstrated here offers a universal strategy for enhanced SPR detection and further expands the application of nanozymes.

Investigation on protein dimerization and evaluation of medicine effects by single molecule force spectroscopy

Monitoring the dimerization state of the mesenchymal-epithelial transition factor (Met) was essential for in-depth understanding of the tumor signal transduction network. At present, the dimerization activation pathway of Met protein was mainly studied at the macro level, while the research at the single molecule level was far from comprehensive. Herein, the dimerization activation of Met protein's extracellular domain induced by ligand hepatocyte growth factor (HGF) was dynamically studied by single-molecule force spectroscopy. Met protein was immobilized on a biomimetic lipid membrane for ensuring its physiological environment, and then the Met dimers were recognized by bivalent probe which was formed by two Met-binding aptamers. Then the dimeric state of Met protein could be distinguished from monomeric state of Met protein through some parameters, (such as unimodal ratio, bimodal ratio and separation work). The unimodal indicates the occurrence of single molecule binding event, and the bimodal represents the occurrence of double binding event (also represents the presence of Met dimer). Before HGF treatment, most of the Met protein on the lipid membrane was still in the form of monomer, so the unimodal ratio in the force curve was larger (78.8 ± 5.2%), and the bimodal ratio was smaller (17.0 ± 4.1%). After HGF treatment, the unimodal ratio decreased to 54.0 ± 7.4%, and the bimodal ratio increased to 43.2 ± 7.3%. It was due to the formation of dimers after the binding of Met protein on the fluidity lipid membrane with HGF. In addition, the average separation work increased to about 2 times after HGF treatment. Given that studies of Met protein dimerization inhibitors have contributed to the development of more potent and safe inhibitors to significantly inhibit tumor metastasis, the effects of different medicines (including anticoagulant medicines, different antibiotics and anti-cancer medicines) on the dimerization activation of Met protein were then explored by the platform described above. The results showed that anticoagulant medicines heparin and its analogs can significantly inhibit HGF-mediated Met protein activation, while different antibiotics and anticancer medicines had no significant effect on the dimerization of Met protein. This work provided a platform for studying protein dimerization as well as for screening Met protein dimerization inhibitors at the single-molecule level.

Sandwich-Type Electrochemical Aptasensor for Highly Sensitive and Selective Detection of Pseudomonas Aeruginosa Bacteria Using a Dual Signal Amplification Strategy

An electrochemical aptasensor developed to realize the detection of Pseudomonas aeruginosa (P. aeruginosa) bacteria based on a signal amplification strategy. The carbon screen-printed electrode (CSPE) surface was modified by MIL-101(Cr)/Multi-walled carbon nanotubes (MWCNT), which significantly increased the effective surface area of the electrode, thus resulting in further F23 aptamer immobilization at the surface of the modified electrode. As a result, the P. aeruginosa can be efficiently captured onto the surface of the aptasensor. Moreover, aptamer immobilized on the two-dimensional graphitic carbon nitride complex with silver nanoparticles (AgNPs/c-g-C₃N₄/Apt) was used as an electrochemical signal label, connected to P. aeruginosa bacteria at the modified electrode. This strategy increased the aptamer surface density and the sensitivity for detecting P. aeruginosa. Also, the resultant material was thoroughly characterized using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis techniques. A highly sensitive voltammetric aptasensor for P. aeruginosa detection was obtained via this strategy at the limit of detection of 1 Colony-forming unit (CFU)/mL (σ = 3). Therefore, this proposed strategy with dual signal amplification can be a promising platform for simple, practical, reliable, and sensitive method for P. aeruginosa.

Aptamer-Based Biosensors for the Colorimetric Detection of Blood Biomarkers: Paving the Way to Clinical Laboratory Testing

Clinical diagnostics for human diseases rely largely on enzyme immunoassays for the detection of blood biomarkers. Nevertheless, antibody-based test systems have a number of shortcomings that have stimulated a search for alternative diagnostic assays. Oligonucleotide aptamers are now considered as promising molecular recognizing elements for biosensors (aptasensors) due to their high affinity and specificity of target binding. At the moment, a huge variety of aptasensors have been engineered for the detection of various analytes, especially disease biomarkers. However, despite their great potential and excellent characteristics in model systems, only a few of these aptamer-based assays have been translated into practice as diagnostic kits. Here, we will review the current progress in the engineering of aptamer-based colorimetric assays as the most suitable format for clinical lab diagnostics. In particular, we will focus on aptasensors for the detection of blood biomarkers of cardiovascular, malignant, and neurodegenerative diseases along with common inflammation biomarkers. We will also analyze the main obstacles that have to be overcome before aptamer test systems can become tantamount to ELISA for clinical diagnosis purposes.

A Fiber-Based SPR Aptasensor for the In Vitro Detection of Inflammation Biomarkers

It is widely accepted that the abnormal concentrations of different inflammation biomarkers can be used for the early diagnosis of cardiovascular disease (CVD). Currently, many reported strategies, which require extra report tags or bulky detection equipment, are not portable enough for onsite inflammation biomarker detection. In this work, a fiber-based surface plasmon resonance (SPR) biosensor decorated with DNA aptamers, which were specific to two typical inflammation biomarkers, C-reactive protein (CRP) and cardiac troponin I (cTn-I), was developed. By optimizing the surface concentration of the DNA aptamer, the proposed sensor could achieve a limit of detection (LOD) of 1.7 nM (0.204 μg/mL) and 2.5 nM (57.5 ng/mL) to CRP and cTn-I, respectively. Additionally, this biosensor could also be used to detect other biomarkers by immobilizing corresponding specific DNA aptamers. Integrated with a miniaturized spectral analysis device, the proposed sensor could be applied for constructing a portable instrument to provide the point of care testing (POCT) for CVD patients.

Aptamers Targeting Cardiac Biomarkers as an Analytical Tool for the Diagnostics of Cardiovascular Diseases: A Review

The detection of cardiac biomarkers is used for diagnostics, prognostics, and the risk assessment of cardiovascular diseases. The analysis of cardiac biomarkers is routinely performed with high-sensitivity immunological assays. Aptamers offer an attractive alternative to antibodies for analytical applications but, to date, are not widely practically implemented in diagnostics and medicinal research. This review summarizes the information on the most common cardiac biomarkers and the current state of aptamer research regarding these biomarkers. Aptamers as an analytical tool are well established for troponin I, troponin T, myoglobin, and C-reactive protein. For the rest of the considered cardiac biomarkers, the isolation of novel aptamers or more detailed characterization of the known aptamers are required. More attention should be addressed to the development of dual-aptamer sandwich detection assays and to the studies of aptamer sensing in alternative biological fluids. The universalization of aptamer-based biomarker detection platforms and the integration of aptamer-based sensing to clinical studies are demanded for the practical implementation of aptamers to routine diagnostics. Nevertheless, the wide usage of aptamers for the diagnostics of cardiovascular diseases is promising for the future, with respect to both point-of-care and laboratory testing.

Single-Molecule Identification of the Conformations of Human C-Reactive Protein and Its Aptamer Complex with Solid-State Nanopores

Human C-reactive protein (CRP) is an established inflammatory biomarker and was proved to be potentially relevant to disease pathology and cancer progression. A large body of methodologies have been reported for CRP analysis, including electrochemical/optical biosensors, aptamer, or antibody-based detection. Although the detection limit is rather low until pg/uL, most of which are time-consuming and relatively expensive, and few of them provided CRP single-molecule information. This work demonstrated the nanopore-based approach for the characterization of CRP conformation under versatile conditions. With an optimized pore of 14 nm in diameter, we achieved the detection limit as low as 0.3 ng/μL, voltage polarity significantly influences the electro-osmotic force and CRP translocation behavior, and the pentameric conformation of CRP may dissociate into pro-inflammatory CRP isoforms and monomeric CRP at bias potential above 300 mV. CRP tends to translocate through nanopores faster along with the increase in pH values, due to more surface charge on both CRP and pore inner wall and stronger electro-osmotic force. The CRP could specifically bind with its aptamer of different concentrations to form complexes, and the complexes exhibited distinguishable nanopore translocation behavior compared with CRP alone. The variation of the molar ratio of aptamer significantly influences the orientation of CRP translocation. The plasma test under physiological conditions displayed the ability of the nanopore system on the CRP identification with a concentration of 3 ng/μL.

Towards a protein-selective Raman enhancement by a glycopolymer-based composite surface

Surface-enhanced Raman scattering (SERS), which is based on the surface plasmon resonance (LSPR) of noble metal nanostructures, is widely used in the biological field due to its advantages of non-damaging samples and detection up to the molecular level. For biological SERS detection, preparation of substrates with biocompatibility and specific adsorption, leading to selective enhancement of the target biomolecules, are important design strategies. Utilizing the specific interaction between a carbohydrate and protein, a glycopolymer-based composite surface is fabricated to realize specific SERS detection of proteins. Herein, we use N-3,4-dihydroxybenzeneethyl methacrylamide (DMA), 2-deoxy-2-(methacrylamido)glucopyranose (MAG) and methacrylic acid (MAA) as monomers in a sunlight-induced RAFT polymerization to synthesize a dopamine-containing glycopolymer. The glycopolymers are used to prepare a SERS substrate. The composite surface shows specific protein adsorption capacity, and the selective Raman enhancement of specific proteins was successfully achieved between the two different proteins Con A and BSA. This provides a feasible approach to design a SERS surface for protein detection and the study of the interaction between sugar and proteins.

Micro- and nanosensors for detecting blood pathogens and biomarkers at different points of sepsis care

Severe infections can cause a dysregulated response leading to organ dysfunction known as sepsis. Sepsis can be lethal if not identified and treated right away. This requires measuring biomarkers and pathogens rapidly at the different points where sepsis care is provided. Current commercial approaches for sepsis diagnosis are not fast, sensitive, and/or specific enough for meeting this medical challenge. In this article, we review recent advances in the development of diagnostic tools for sepsis management based on micro- and nanostructured materials. We start with a brief introduction to the most popular biomarkers for sepsis diagnosis (lactate, procalcitonin, cytokines, C-reactive protein, and other emerging protein and non-protein biomarkers including miRNAs and cell-based assays) and methods for detecting bacteremia. We then highlight the role of nano- and microstructured materials in developing biosensors for detecting them taking into consideration the particular needs of every point of sepsis care (e.g., ultrafast detection of multiple protein biomarkers for diagnosing in triage, emergency room, ward, and intensive care unit; quantitative detection to de-escalate treatment; ultrasensitive and culture-independent detection of blood pathogens for personalized antimicrobial therapies; robust, portable, and web-connected biomarker tests outside the hospital). We conclude with an overview of the most utilized nano- and microstructured materials used thus far for solving issues related to sepsis diagnosis and point to new challenges for future development.

Aptasensors versus immunosensors—Which will prevail?

Since the invention of the first biosensors 70 years ago, they have turned into valuable and versatile tools for various applications, ranging from disease diagnosis to environmental monitoring. Traditionally, antibodies have been employed as the capture probes in most biosensors, owing to their innate ability to bind their target with high affinity and specificity, and are still considered as the gold standard. Yet, the resulting immunosensors often suffer from considerable limitations, which are mainly ascribed to the antibody size, conjugation chemistry, stability, and costs. Over the past decade, aptamers have emerged as promising alternative capture probes presenting some advantages over existing constraints of immunosensors, as well as new biosensing concepts. Herein, we review the employment of antibodies and aptamers as capture probes in biosensing platforms, addressing the main aspects of biosensor design and mechanism. We also aim to compare both capture probe classes from theoretical and experimental perspectives. Yet, we highlight that such comparisons are not straightforward, and these two families of capture probes should not be necessarily perceived as competing but rather as complementary. We, thus, elaborate on their combined use in hybrid biosensing schemes benefiting from the advantages of each biorecognition element.

Rapid and Highly Sensitive Detection of C-Reaction Protein Using Robust Self-Compensated Guided-Mode Resonance BioSensing System for Point-of-Care Applications

The rapid and sensitive detection of human C-reactive protein (CRP) in a point-of-care (POC) may be conducive to the early diagnosis of various diseases. Biosensors have emerged as a new technology for rapid and accurate detection of CRP for POC applications. Here, we propose a rapid and highly stable guided-mode resonance (GMR) optofluidic biosensing system based on intensity detection with self-compensation, which substantially reduces the instability caused by environmental factors for a long detection time. In addition, a low-cost LED serving as the light source and a photodetector are used for intensity detection and real-time biosensing, and the system compactness facilitates POC applications. Self-compensation relies on a polarizing beam splitter to separate the transverse-magnetic-polarized light and transverse-electric-polarized light from the light source. The transverse-electric-polarized light is used as a background signal for compensating noise, while the transverse-magnetic-polarized light is used as the light source for the GMR biosensor. After compensation, noise is drastically reduced, and both the stability and performance of the system are enhanced over a long period. Refractive index experiments revealed a resolution improvement by 181% when using the proposed system with compensation. In addition, the system was successfully applied to CRP detection, and an outstanding limit of detection of 1.95 × 10-8 g/mL was achieved, validating the proposed measurement system for biochemical reaction detection. The proposed GMR biosensing sensing system can provide a low-cost, compact, rapid, sensitive, and highly stable solution for a variety of point-of-care applications.

Nanomaterial-based aptasensors as an efficient substitute for cardiovascular disease diagnosis: Future of smart biosensors

As a major cause of deaths in developed countries, cardiovascular disease (CVD) has been a big burden for human health systems. Its early and rapid detection is crucial to efficiently apply appropriate on time therapy and to ultimately reduce the associated mortality rate. Aptamers, known as single-stranded DNA/RNA or oligonucleotides containing receptors and/or catalytic properties, have been widely employed in biodetection platforms due to their beneficial properties. Like antibodies, aptamers have served as artificial target receptors in affinity biosensors. Currently, advanced biosensors with improved sensitivity and specificity are fabricated by the synergistic combination of aptamers and diverse nanomaterials. Herein, we review the current development and applications of nanomaterial-based aptasensors for the recognition of CVD biomarkers with special emphasis on electrochemical and optical technologies. The performance of aptasensors has been assessed further in terms of key quality assurance metrics along with discussions on recent technologies developed for the amplification of signals with enhanced portability.

SPR detection of protein enhanced by seedless synthesized gold nanorods

Surface plasmon resonance (SPR) is a label-free, real-time bio-sensing technique with high potential in the diagnostic area, especially when a signal amplification strategy is used to improve the detection limit. We report here a simple method for enhancing the detection limit of bovine serum albumin (BSA), by attaching gold nanorods (AuNRs). AuNRs were obtained by a seedless synthesis technique and characterized using scanning electron microscopy (SEM), UV-VIS spectroscopy, FT-IR spectroscopy and dynamic light scattering (DLS). Finite element method (FEM) simulations were employed to explore the enhancement of the SPR signal by adding AuNRs on the SPR sensor's metallic layer. SPR spectroscopy was used to analyze the changes in the refractive index brought by the immobilization of unconjugated BSA and BSA modified with AuNRs. The results confirmed that the AuNRs conjugated with the protein increase the SPR signal ~ 10 times, leading to a limit of detection of 1.081 × 10^-8 M (0.713 μg/mL).

Advances in aptamer-based sensing assays for C-reactive protein

C-reactive protein (CRP), a non-specific acute-phase indicator of inflammation, has been widely recognized for its value in clinical diagnostic applications. With the advancement of testing technologies, there have been many reports on fast, simple, and reliable methods for CRP testing. Among these, the aptamer-based biosensors are the focus and hotspot of research for achieving high-sensitivity analysis of CRP. This review summarizes the progress of in vitro aptamer screening for CRP and the recent advances in aptamer-based CRP sensor applications, thus developing insight for the new CRP aptasensor design strategy.

Roadmap on Universal Photonic Biosensors for Real-Time Detection of Emerging Pathogens

The COVID-19 pandemic has made it abundantly clear that the state-of-the-art biosensors may not be adequate for providing a tool for rapid mass testing and population screening in response to newly emerging pathogens. The main limitations of the conventional techniques are their dependency on virus-specific receptors and reagents that need to be custom-developed for each recently-emerged pathogen, the time required for this development as well as for sample preparation and detection, the need for biological amplification, which can increase false positive outcomes, and the cost and size of the necessary equipment. Thus, new platform technologies that can be readily modified as soon as new pathogens are detected, sequenced, and characterized are needed to enable rapid deployment and mass distribution of biosensors. This need can be addressed by the development of adaptive, multiplexed, and affordable sensing technologies that can avoid the conventional biological amplification step, make use of the optical and/or electrical signal amplification, and shorten both the preliminary development and the point-of-care testing time frames. We provide a comparative review of the existing and emergent photonic biosensing techniques by matching them to the above criteria and capabilities of preventing the spread of the next global pandemic.

Aptamer-based biosensors for the diagnosis of sepsis

Sepsis, the syndrome of infection complicated by acute organ dysfunction, is a serious and growing global problem, which not only leads to enormous economic losses but also becomes one of the leading causes of mortality in the intensive care unit. The detection of sepsis-related pathogens and biomarkers in the early stage plays a critical role in selecting appropriate antibiotics or other drugs, thereby preventing the emergence of dangerous phases and saving human lives. There are numerous demerits in conventional detection strategies, such as high cost, low efficiency, as well as lacking of sensitivity and selectivity. Recently, the aptamer-based biosensor is an emerging strategy for reasonable sepsis diagnosis because of its accessibility, rapidity, and stability. In this review, we first introduce the screening of suitable aptamer. Further, recent advances of aptamer-based biosensors in the detection of bacteria and biomarkers for the diagnosis of sepsis are summarized. Finally, the review proposes a brief forecast of challenges and future directions with highly promising aptamer-based biosensors.

Recent Advancements in Aptamer-Based Surface Plasmon Resonance Biosensing Strategies

Surface plasmon resonance (SPR) can track molecular interactions in real time, and is a powerful as well as widely used biological and chemical sensing technique. Among the different SPR-based sensing applications, aptamer-based SPR biosensors have attracted significant attention because of their simplicity, feasibility, and low cost for target detection. Continuous developments in SPR aptasensing research have led to the emergence of abundant technical and design concepts. To understand the recent advances in SPR for biosensing, this paper reviews SPR-based research from the last seven years based on different sensing-type strategies and sub-directions. The characteristics of various SPR-based applications are introduced. We hope that this review will guide the development of SPR aptamer sensors for healthcare.

Metal-enhanced sensing platform for the highly sensitive detection of C-reactive protein antibody and rhodamine B with applications in cardiovascular diseases and food safety

The potential applications of metal-enhanced fluorescence (MEF) devices include biosensors for the detection of trace amounts in biosciences, biotechnology, and pathogens that are relevant to medical diagnostics and food control. In the present study, the silver (Ag) film thickness (56 nm) of an MEF system was calibrated to maximize the depth-to-width ratio (Γ) of the surface plasmon resonance (SPR) active metal from reflectance dip curves. Upon plasmon coupling with thermally evaporated Ag, we demonstrated a 2.21-fold enhancement compared to the pristine flat substrate with the coefficient of variation (CV) ≈0.22% and the limit of detection (LOD) 0.001 mg L^-1 of the concentration of an Alexa Fluor 488-labeled anti-C-reactive protein antibody (CRP@Alexa fluor 488). The structure was developed to simplify the in situ generation of biosensors for the surface-enhanced Raman spectroscopy (SERS) to determine Rhodamine B (RhB) with a highly robust performance. The procedure presented a simple and rapid sample pretreatment for the determination of RhB with a limit of quantification of 10^-10 M and a satisfactory linear response (0.98). The results showed the excellent performance of the surface plasmon coupled emission (SPCE), which opens up possibilities for the accurate detection of small-volume and low-concentration target analytes due to the improved sensitivity and signal-to-noise ratio (SNR).

Recent Advances in CRP Biosensor Based on Electrical, Electrochemical and Optical Methods

C-reactive protein (CRP) is an acute-phase reactive protein that appears in the bloodstream in response to inflammatory cytokines such as interleukin-6 produced by adipocytes and macrophages during the acute phase of the inflammatory/infectious process. CRP measurement is widely used as a representative acute and chronic inflammatory disease marker. With the development of diagnostic techniques measuring CRP more precisely than before, CRP is being used not only as a traditional biomarker but also as a biomarker for various diseases. The existing commercialized CRP assays are dominated by enzyme-linked immunosorbent assay (ELISA). ELISA has high selectivity and sensitivity, but its limitations include requiring complex analytic processes, long analysis times, and professional manpower. To overcome these problems, nanobiotechnology is able to provide alternative diagnostic tools. By introducing the nanobio hybrid material to the CRP biosensors, CRP can be measured more quickly and accurately, and highly sensitive biosensors can be used as portable devices. In this review, we discuss the recent advancements in electrochemical, electricity, and spectroscopy-based CRP biosensors composed of biomaterial and nanomaterial hybrids.

Nanodiagnostic Attainments and Clinical Perspectives on C-Reactive Protein: Cardiovascular Disease Risks Assessment

Cardiovascular disease (CVD) has become one of the leading causes of morbidity and mortality in both men and women. According to the World Health Organization (WHO), ischemic heart disease is the major issue due to the narrowing of the coronary artery by plaque formation on the artery wall, which causes an inadequate flow of oxygen and blood to the heart and is called 'coronary artery disease'. The CVD death rate increased by up to 15% in 2016 (~17.6 million) compared to the past decade. This tremendous increment urges the development of a suitable biomarker for rapid and early diagnosis. Currently, C-reactive protein (CRP) is considered an outstanding biomarker for quick and accurate outcomes in clinical analyses. Various techniques have also been used to diagnose CVD, including surface plasmon resonance (SPR), colorimetric assay, enzyme-linked immunosorbent assay (ELISA), fluoro-immunoassays, chemiluminescent assays, and electrical measurements. This review discusses such diagnostic strategies and how current, cutting-edge technologies have enabled the development of high-performance detection methodologies. Concluding remarks have been made concerning the clinical significance and the use of nanomaterial in medical diagnostics towards nanotheranostics.

Recent advances in functionalization of plasmonic nanostructures for optical sensing

This review summarizes the progress that has been made in the use of nanostructured SPR-based chemical sensors and biosensors. Following an introduction into the field, a first large section covers principles of nanomaterial-based SPR sensing, mainly on methods using noble metal nanoparticles (spheres, cubes, triangular plates, etc.). The next section covers methods for functionalization of plasmonic nanostructures, with subsections on functionalization using (a) amino acids and proteins; (b) oligonucleotides, (c) organic polymers, and (d) organic compounds. Several tables are presented that give an overview on the wealth of methods and materials published. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. This review is not intended to be a comprehensive compilation of the literature in the field but rather is a systematic overview of the state of the art in surface chemistry of plasmonic nanostructures. The ability of various ligands and receptors for functionalization of nanoparticles as well as their sensing capability is discussed.

Aptamers for Proteins Associated with Rheumatic Diseases: Progress, Challenges, and Prospects of Diagnostic and Therapeutic Applications

Nucleic acid aptamers capable of affine and specific binding to their molecular targets have now established themselves as a very promising alternative to monoclonal antibodies for diagnostic and therapeutic applications. Although the main focus in aptamers’ research and development for biomedicine is made on cardiovascular, infectious, and malignant diseases, the use of aptamers as therapeutic or diagnostic tools in the context of rheumatic diseases is no less important. In this review, we consider the main features of aptamers that make them valuable molecular tools for rheumatologists, and summarize the studies on the selection and application of aptamers for protein biomarkers associated with rheumatic diseases. We discuss the progress in the development of aptamer-based diagnostic assays and targeted therapeutics for rheumatic disorders, future prospects in the field, and issues that have yet to be addressed.

Plasmonic Optical Biosensors for Detecting C-Reactive Protein: A Review

C-reactive protein (CRP), a potent acute-phase reactant that increases rapidly in response to inflammation, tissue damage or infections, is also considered an indicator of the risk of cardiovascular diseases and neurological disorders. Recent advances in nanofabrication and nanophotonic technologies have prompted the optical plasmonic phenomena to be tailored for specific detection of human serum CRP into label-free devices. We review the CRP-specific detection platforms with high sensitivity, which feature the thin metal films for surface plasmon resonance, nano-enhancers of zero dimensional nanostructures, and metal nanoparticles for localized surface plasmon resonance. The protocols used for various types of assay reported in literature are also outlines with surface chemical pretreatment required for specific detection of CRPs on a plasmonic surface. Properties including sensitivity and detection range are described for each sensor device reviewed, while challenges faced by plasmonic CRP sensors are discussed in the conclusion, with future directions towards which research efforts need to be made.

Impedimetric Aptamer-Based Biosensors: Applications

Impedimetric aptamer-based biosensors show high potential for handheld devices and point-of-care tests. In this review, we report on recent advances in aptamer-based impedimetric biosensors for applications in biotechnology. We detail on analytes relevant in medical and environmental biotechnology as well as food control, for which aptamer-based impedimetric biosensors were developed. The reviewed biosensors are examined for their performance, including sensitivity, selectivity, response time, and real sample validation. Additionally, the benefits and challenges of impedimetric aptasensors are summarized.

The application of antibody-aptamer hybrid biosensors in clinical diagnostics and environmental analysis

The growing number of various diseases and the increase of environmental contamination are the causes for the development of novel methods for their detection. The possibility of the application of affinity-based biosensors for such purposes seems particularly promising as they provide high selectivity and low detection limits. Recently, the usage of hybrid antibody-aptamer sandwich constructs was shown to be more advantageous in terms of working parameters in comparison to aptamer-based and immune-based biosensors. This review is focused on the usage of hybrid antibody-aptamer receptor layers for the determination of clinically and environmentally important target molecules. In this work, antibodies and aptamer molecules are characterized and the methods of their immobilization as well as analytical signal generation are shown. This is followed by the critical presentation of examples of hybrid sandwich biosensors that have been elaborated in the past 12 years.

A signal-enhanced and sensitive lateral flow aptasensor for the rapid detection of PDGF-BB

Platelet-derived growth factor BB (PDGF-BB) is a potential biomarker of tumor angiogenesis. For the first time, we developed a highly sensitive aptasensor for PDGF-BB with an enhanced test line signal by using two different gold nanoparticles (AuNPs). Herein, we describe a highly sensitive biosensor for PDGF-BB detection that combines biotinylated aptamer on a sample pad and poly thymine-Cy3-AuNP-monoclonal antibody complexes against PDGF-BB immobilized on conjugate pad A. Streptavidin (SA) and rabbit anti-mouse polyclonal antibody were also immobilized in the nitrocellulose membrane at the test and control zones, respectively. When the target PDGF-BB protein was added, it first bound the aptamer, and later the monoclonal antibody to form a biotinylated complex that was captured by SA, resulting in a visual red line on the test zone. In addition, to enhance the sensitivity, another monoclonal antibody against Cy3 was conjugated on AuNP B and immobilized on conjugate pad B to form a AuNPs (A&B)-antibody-(PDGF-BB-Cy3)-aptamer-biotin-SA complex on the test line when a loading buffer was subsequently added. This approach showed a linear response to PDGF-BB from 3 ng mL⁻¹ to 300 ng mL⁻¹ with a limit of detection as low as 1 ng mL⁻¹ obtained in 10 minutes. Our biosensor displayed results through red lines readable by the naked eye. Interestingly, our approach has been successfully applied for real sample verification, proving its applicability for cancer monitoring and diagnosis.

Platelet-derived growth factor BB (PDGF-BB) is a potential biomarker of tumor angiogenesis.

Selection of Affinity Reagents to Neutralize the Hemolytic Toxicity of Melittin Based on a Self-Assembled Nanoparticle Library

Antibodies are the most common affinity reagents for specific target recognition. However, their applications are limited by high cost and low stability. Thus, seeking substitutes for antibodies is of great significance. In this work, we designed a library containing 82 self-assembled nanoparticles (SNPs) based on the self-assembly of β-cyclodextrin polymers and adamantane derivatives, and then screened out eight types of SNPs capable of suppressing the toxicity of melittin using a hemolytic activity neutralization assay. The affinities of the SNPs to melittin were demonstrated using surface plasmon resonance (SPR). As evidenced by cytotoxicity experiments, SNPs could also suppress the toxicity of melittin to other cells. In addition, to verify the universality of our method, 11 types of SNPs capable of neutralizing another toxic peptide, phenolic soluble polypeptide (PSMα3) secreted by Staphylococcus aureus, were selected from the same SNP library. Our self-assembly-based method for the library preparation has the advantages of flexible design, mild experimental condition, and simple operation, which is expected to seek artificial affinity reagents for more species.

A simple aptamer-based colorimetric assay for rapid detection of C-reactive protein using gold nanoparticles

C-reactive protein (CRP) is a clinical biomarker for inflammatory diseases. In this work, we present a simple and fast colorimetric method for CRP detection that employs citrate-capped gold nanoparticles (AuNPs) and a CRP-binding aptamer as sensing elements. The aptamer consisted in a guanine rich single-stranded DNA (ssDNA) that adsorbs onto the surface of the AuNPs. In the presence of the CRP, the ssDNA releases from the AuNPs surface to interact preferentially with the protein to form guanine-quadruplexes. The exposure of the unprotected AuNPs to buffer salts leads to aggregation and subsequent color change from red-wine to blue-purple that was readily seen by the naked eye. The AuNPs aggregation was monitored using UV-Vis spectroscopy and the CRP concentration in the samples could be correlated with the aggregation ratio (A_670nm/A_520nm). A linear sensing range of 0.889-20.7 μg/mL was found. The detection limit (LOD) was 1.2 μg/mL which is comparable to the typical clinical cutoff concentration in high-sensitivity CRP assays (1 μg/mL) and lower than the detection limit of nephelometric methods used in clinical practice. This method can provide a fast (5 min analysis time), simple, and sensitive way for CRP detection, with negligible interference of bovine serum albumin (BSA) up to concentrations of 100 nM.

Development of a Cuvette-Based LSPR Sensor Chip Using a Plasmonically Active Transparent Strip

This research demonstrates the development of a transmission-mode localized surface plasmon resonance (LSPR) sensor chip using a cuvette cell system for the sensitive detection of a biomolecule marker such as C-reactive protein (CRP). In order to develop a highly sensitive LSPR sensor chip, plasmonically active gold nanoparticles (AuNPs) were decorated onto various transparent substrates in the form of a uniform, high-density single layer using a self-assembly process. The transparent substrate surface was modified with amine functional groups via (3-Aminopropyl)triethoxysilane (APTES) treatment, and the ligand concentration and temperature (0.5% APTES at 60°C) were then optimized to control the binding energy with AuNPs. The optimized plasmonically active strip was subsequently prepared by dipping the amine-functionalized substrate into AuNPs for 8 h. The optimized plasmonic strip functionalized with anti-CRP was transformed into a portable LSPR sensor chip by placing it inside a cuvette cell system, and its detection performance was evaluated using CRP as a model sample. The detection limit for CRP using our LSPR sensor chip was 0.01 μg/mL, and the detection dynamic range was 0.01–10 μg/mL with a %CV of <10%, thus confirming its selectivity and good reproducibility. These findings illustrate that the highly sensitive portable LSPR biosensor developed in this study is expected to be widely used in a diverse range of fields such as diagnosis, medical care, environmental monitoring, and food quality control.