Molecular Recognition and Specific Interactions for Biosensing Applications

Metal-Ion Optical Fingerprinting Sensor Selection via an Analyte Classification and Feature Selection Algorithm

Accurate analyte classification remains a significant challenge in sensor technologies. We present the Analyte Classification and Feature Selection Algorithm (ACFSA), a computational tool designed to identify optimal sensor combinations from unique fingerprint patterns for analyte classification. We applied the ACFSA to a library of peptide-corona-functionalized single-walled carbon nanotubes (SWCNTs), developed as a near-infrared fluorescent, semiselective fingerprinting sensor set for detecting heavy metal ions. Inspired by natural metal-ion complexation sites, each SWCNT sensor in this library features a unique peptide sequence containing various amino acids for metal binding, revealing diverse optical response patterns to the various metal ions tested. The sensor library was further diversified using different SWCNT chiralities and photochemical modifications of the peptide coronae. The ACFSA was applied to the screening data of the fluorescence response of the 30 resulting SWCNT-peptide sensors to five metal-ion analytes. Through iterative dimensionality reduction and rational sensor selection, the algorithm identified the optimal fingerprinting sensors as a minimal two-sensor set with a 0.02% classification error. The final output of the ACFSA is thus an analyte classifier that serves as a unique analyte fingerprint pattern for the selected sensors. The developed peptide-SWCNT system serves as an effective proof-of-concept, illustrating the potential of our platform as a generally applicable tool for fingerprinting analytes and optimal sensor set selection in other sensor-analyte screening experiments.

CRISPR/Cas and Argonaute-based biosensors for nucleic acid detection

Nowadays, nucleic acid detection technology has been applied to disease diagnosis, prevention, food safety, environmental testing and many other aspects. However, traditional methods still have shortcomings. Therefore, there is an urgent need for a simple, rapid, sensitive, and specific new method to supersede traditional nucleic acid detection technology. CRISPR/Cas(Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated) system and Argonaute (Ago) system play an important role in microbial immune defense. Their targeting specificity, programmability and special trans-cleavage activity make it possible to develop some new platforms for nucleic acid detection in combination with a variety of biosensors. We introduce the origins of these two systems and the biosensors developed based on CRISPR/Cas system and Ago system, respectively, especially the prospects for the future development of Cascade Amplification biosensors. This review is expected to provide useful guidance for researchers in related fields and provide inspiration for the development of Cascade Amplification biosensors in the future.

Exploring glycans as vital biological macromolecules: A comprehensive review of advancements in biomedical frontiers

This comprehensive review delves into the intricate landscape of glycans and glycoconjugates, unraveling their multifaceted roles across diverse biological dimensions. From influencing fundamental cellular processes such as signaling, recognition, and adhesion to exerting profound effects at the molecular and genetic levels, these complex carbohydrate structures emerge as linchpins in cellular functions and interactions. The structural diversity of glycoconjugates, which can be specifically classified into glycoproteins, glycolipids, and proteoglycans, underscores their importance in shaping the architecture of cells. Beyond their structural roles, these molecules also play key functions in facilitating cellular communication and modulating recognition mechanisms. Further, glycans and glycoconjugates prove invaluable as biomarkers in disease diagnostics, particularly in cancer, where aberrant glycosylation patterns offer critical diagnostic cues. Furthermore, the review explores their promising therapeutic applications, ranging from the development of glycan-based nanomaterials for precise drug delivery to innovative interventions in cancer treatment. This review endeavors to comprehensively explore the intricate functions of glycans and glycoconjugates, with the primary goal of offering valuable insights into their extensive implications in both health and disease. Encompassing a broad spectrum of biological processes, the focus of the review aims to provide a comprehensive understanding of the significant roles played by glycans and glycoconjugates.

Polydopamine modification of polydimethylsiloxane for multifunctional biomaterials: Immobilization and stability of albumin and fetuin-A on modified surfaces

The surface of polydimethylsiloxane (PDMS) can be modified to immobilize proteins; however, most existing approaches are limited to complex reactions and achieving multifunctional modifications is challenging. This work applies a simple technique to modify PDMS using polydopamine (PDA) and investigates immobilization of multiple proteins. The surfaces were characterized in detail and stability was assessed, demonstrating that in a buffer solution, PDA modification was maintained without an effect on surface properties. Bovine serum albumin (BSA) and bovine fetuin-A (Fet-A) were used as model biomolecules for simultaneous or sequential immobilization and to understand their use for surface backfilling and functionalization. Based on 125I radiolabeling, amounts of BSA and Fet-A on PDA were determined to be close to double that were obtained on control PDMS surfaces. Following elution with sodium dodecyl sulfate, around 67% of BSA and 63% of Fet-A were retained on the surface. The amount of immobilized protein was influenced by the process (simultaneous or sequential) and surface affinity of the proteins. With simultaneous modification, a balanced level of both proteins could be achieved, whereas with the sequential process, the initially immobilized protein was more strongly attached. After incubation with plasma and fetal bovine serum, the PDA-modified surfaces maintained over 90% of the proteins immobilized. This demonstrates that the biological environments also play an important role in the binding and stability of conjugated proteins. This combination of PDA and surface immobilization methods provides fundamental knowledge for tailoring multifunctional PDMS-based biomaterials with applications in cell-material interactions, biosensing, and medical devices.

Recent trends in macromolecule-conjugated hybrid quantum dots for cancer theranostic applications

Quantum dots (QDs) are small nanoparticles with semiconductor properties ranging from 2 to 10 nanometers comprising 10-50 atoms. The single wavelength excitation character of QDs makes it more significant, as it can excite multiple particles in a confined surface simultaneously by narrow emission. QDs are more photostable than traditional organic dyes; however, when injected into tissues, whole animals, or ionic solutions, there is a significant loss of fluorescence. HQD-based probes conjugated with cancer-specific ligands, antibodies, or peptides are used in clinical diagnosis. It is more precise and reliable than standard immunohistochemistry (IHC) at minimal protein expression levels. Advanced clinical studies use photodynamic therapy (PDT) with fluorescence imaging to effectively identify and treat cancer. Recent studies revealed that a combination of unique characteristics of QDs, including their fluorescence capacity and abnormal expression of miRNA in cancer cells, were used for the detection and monitoring progression of cancer. In this review, we have highlighted the unique properties of QDs and the theranostic behavior of various macromolecule-conjugated HQDs leading to cancer treatment.

Recent Advances in Biomolecular Detection Based on Aptamers and Nanoparticles

The fast, accurate detection of biomolecules, ranging from nucleic acids and small molecules to proteins and cellular secretions, plays an essential role in various biomedical applications. These include disease diagnostics and prognostics, environmental monitoring, public health, and food safety. Aptamer recognition (DNA or RNA) has gained extensive attention for biomolecular detection due to its high selectivity, affinity, reproducibility, and robustness. Concurrently, biosensing with nanoparticles has been widely used for its high carrier capacity, stability and feasibility of incorporating optical and catalytic activity, and enhanced diffusivity. Biosensors based on aptamers and nanoparticles utilize the combination of their advantages and have become a promising technology for detecting of a wide variety of biomolecules with high sensitivity, reliability, specificity, and detection speed. Via various sensing mechanisms, target biomolecules have been quantified in terms of optical (e.g., colorimetric and fluorometric), magnetic, and electrical signals. In this review, we summarize the recent advances in and compare different aptamer-nanoparticle-based biosensors by nanoparticle types and detection mechanisms. We also share our views on the highlights and challenges of the different nanoparticle-aptamer-based biosensors.

Advances in Electrochemical Nano-Biosensors for Biomedical and Environmental Applications: From Current Work to Future Perspectives

Modern life quality is strongly supported by the advances made in biosensors, which has been attributed to their crucial and viable contribution in point-of-care (POC) technology developments. POC devices are exploited for the fast tracing of disease progression, rapid analysis of water, and food quality assessment. Blood glucose meters, home pregnancy strips, and COVID-19 rapid tests all represent common examples of successful biosensors. Biosensors can provide great specificity due to the incorporation of selective bio-recognition elements and portability at significantly reduced costs. Electrochemical biosensor platforms are one of the most advantageous of these platforms because they offer many merits, such as being cheap, selective, specific, rapid, and portable. Furthermore, they can be incorporated into smartphones and various analytical approaches in order to increase their sensitivity and many other properties. As a very broad and interdisciplinary area of research and development, biosensors include all disciplines and backgrounds from materials science, chemistry, physics, medicine, microbiology/biology, and engineering. Accordingly, in this state-of-the-art article, historical background alongside the long journey of biosensing construction and development, starting from the Clark oxygen electrode until reaching highly advanced wearable stretchable biosensing devices, are discussed. Consequently, selected examples among the miscellaneous applications of nanobiosensors (such as microbial detection, cancer diagnosis, toxicity analysis, food quality-control assurance, point of care, and health prognosis) are described. Eventually, future perspectives for intelligent biosensor commercialization and exploitation in real-life that is going to be supported by machine learning and artificial intelligence (AI) are stated.

A critical review on microbe-electrode interactions towards heavy metal ion detection using microbial fuel cell technology

Implicit interaction of electroactive microbes with solid electrodes is an interesting phenomenon in nature, which supported development of bioelectrochemical systems (BESs), especially the microbial fuel cell (MFCs) for valorization of low-value waste streams into bioelectricity. Intriguingly, the metabolism of interacted microbes with electrode is affected by the microenvironment at electrodes, which influences the current response. For instance, when heavy metal ions (HMIs) are imposed in the medium, the current production decreases due to their intrinsic toxic effect. This event provides an immense opportunity to utilize MFC as a sensor to selectively detect HMIs in the environment, which has been explored vastly in recent decade. In this review, we have concisely discussed the microbial interaction with electrodes and mechanism of detection of HMIs using an MFC. Recent advancement in sensing elements and their application is elaborated with a future perspective section for follow-up research and development in this field.

Electrochemical Impedance Spectroscopy (EIS): Principles, Construction, and Biosensing Applications

Electrochemical impedance spectroscopy (EIS) is a powerful technique used for the analysis of interfacial properties related to bio-recognition events occurring at the electrode surface, such as antibody–antigen recognition, substrate–enzyme interaction, or whole cell capturing. Thus, EIS could be exploited in several important biomedical diagnosis and environmental applications. However, the EIS is one of the most complex electrochemical methods, therefore, this review introduced the basic concepts and the theoretical background of the impedimetric technique along with the state of the art of the impedimetric biosensors and the impact of nanomaterials on the EIS performance. The use of nanomaterials such as nanoparticles, nanotubes, nanowires, and nanocomposites provided catalytic activity, enhanced sensing elements immobilization, promoted faster electron transfer, and increased reliability and accuracy of the reported EIS sensors. Thus, the EIS was used for the effective quantitative and qualitative detections of pathogens, DNA, cancer-associated biomarkers, etc. Through this review article, intensive literature review is provided to highlight the impact of nanomaterials on enhancing the analytical features of impedimetric biosensors.

Out-of-Equilibrium Measurements of Kinetic Constants on a Biosensor

Conventional measurements of kinetic constants currently in use are performed at equilibrium and may require large volumes, especially at a low association rate constant k_on. If the measurements are made out of equilibrium, the values obtained may be biased by dilution of the sample with the flow of the running buffer. In some applications, the available sample volume can be very critical and requires the development of tools to measure kinetic constants with low volumes. In this paper, by combining an experimental, numerical and modeling approach, we propose a surface plasmon resonance-based method that relies on an out-of-equilibrium measurement using the effect of dilution by flow to its advantage. This new method should have a significant impact in biochemistry and medical research.

Self Assembled Recombinant Proteins on Metallic Nanoparticles As Bimodal Imaging Probes

Combining multiple modalities is at the center of developing new methods for sensing and imaging that are required for comprehensive understanding of events at the molecular level. Various imaging modalities have been developed using metallic nanoparticles owning to their exceptional physical and chemical properties. Due to their localized surface plasmon resonance characteristics, gold and silver nanoparticles exhibit unique optoelectronic properties commonly used in biomedical sciences and engineering. Self assembled monolayers or physical adsorption have previously been adapted to functionalize the surfaces of nanoparticles with biomolecules for targeted imaging. However, depending on differences among the functional groups used on the nanoparticle surface, wide variation in the displayed biomolecular property to recognize its target may result. In the last decade, the properties of inorganic binding peptides have been proven advantageous to assemble selective functional nano-entities or proteins onto nanoparticles surfaces. Herein we explored formation of self-assembled hybrid metallic nano-architectures that are composed of gold and silver nanoparticles with fluorescent proteins, for use as bimodal imaging probes. We employed metal binding peptide-based assembly to self assemble green fluorescence protein onto metallic substrates of various geometries. Assembly of the green fluorescent proteins, genetically engineered to incorporate gold- or silver-binding peptides onto metallic nanoparticles, resulted in the generation of hybrid-, biomodal-imaging probes in a single step. Green fluorescent activity on gold and silver surfaces can be been monitored using both plasmonic and fluorescent signatures. Our results demonstrate a novel bimodal imaging system that can be finely tuned with respect to nanoparticle size and protein concentration. Resulting hybrid probes may mitigate the limitation of depth penetration into biological tissues as well as providing high signal-to-noise ratio and sensitivity.

Physical Structure and Electrochemical Response of Diamond-Graphite Nanoplatelets: From CVD Synthesis to Label-Free Biosensors

Hybrid diamond-graphite nanoplatelet (DGNP) thin films are produced and applied to label-free impedimetric biosensors for the first time, using avidin detection as a proof of concept. The DGNPs are synthesized by microwave plasma chemical vapor deposition through H₂/CH₄/N₂ gas mixtures in a reproducible and rapid single-step process. The material building unit consists of an inner two-dimensional-like nanodiamond with preferential vertical alignment covered by and covalently bound to nanocrystalline graphite grains, exhibiting {111}_diamond||{0002}_graphite epitaxy. The DGNP films' morphostructural aspects are of interest for electrochemical transduction, in general, and for Faradaic impedimetric biosensors, in particular, combining enhanced surface area for biorecognition element loading and facile Faradaic charge transfer. Charge transfer rate constants in phosphate buffer saline/[Fe(CN)₆]^4- solution are shown to increase up to 5.6 × 10^-3 cm s^-1 upon N₂ addition to DGNP synthesis. For the impedimetric detection of avidin, biotin molecules are covalently bound as avidin specific recognition elements on (3-aminopropyl)triethoxysilane-functionalized DGNP surfaces. Avidin quantification is attained within the 10-1000 μg mL^-1 range following a logarithmic dependency. The limits of detection and of quantitation are 1.3 and 6.4 μg mL^-1 (19 and 93 nM), respectively, and 2.3 and 13.8 μg mL^-1 (33 and 200 nM) when considering the nonspecific response of the sensors.

Anisotropic noble metal nanoparticles: Synthesis, surface functionalization and applications in biosensing, bioimaging, drug delivery and theranostics

Anisotropic nanoparticles have fascinated scientists and engineering communities for over a century because of their unique physical and chemical properties. In recent years, continuous advances in design and fabrication of anisotropic nanoparticles have opened new avenues for application in various areas of biology, chemistry and physics. Anisotropic nanoparticles have the plasmon absorption in the visible as well as near-infrared (NIR) region, which enables them to be used for crucial applications such as biological imaging, medical diagnostics and therapy ("theranostics"). Here, we describe the progress in anisotropic nanoparticles achieved since the millennium in the area of preparation including various shapes and modification of the particle surface, and in areas of application by providing examples of applications in biosensing, bio-imaging, drug delivery and theranostics. Furthermore, we also explain various mechanisms involved in cellular uptake of anisotropic nanoparticles, and conclude with our opinion on various obstacles that limit their applications in biomedical field.

STATEMENT OF SIGNIFICANCE

Anisotropy at the molecular level has always fascinated scientists and engineering communities for over a century, however, the research on novel methods through which shape and size of nanoparticles can be precisely controlled has opened new avenues for anisotropic nanoparticles in various areas of biology, chemistry and physics. In this manuscript, we describe progress achieved since the millennium in the areas of preparation of various shapes of anisotropic nanoparticles, investigate various methods involved in modifying the surface of these NPs, and provide examples of applications in biosensing and bio-imaging, drug delivery and theranostics. We also present mechanisms involved in cellular uptake of nanoparticles, describe different methods of preparation of anisotropic nanoparticles including biomimetic and photochemical synthesis, and conclude with our opinion on various obstacles that limit their applications in biomedical field.

Molecular dynamics simulations of nanoscale engravings on an alkanethiol monolayer

Thermal stability of nanoscale engravings on alkanethiol monolayer.

Recent advances in electrospun metal-oxide nanofiber based interfaces for electrochemical biosensing

Synthesis of various electrospun metal-oxide nanofibers and their application towards electrochemical enzymatic and enzyme-free biosensor platforms has been critically discussed.

A prospective overview of the essential requirements in molecular modeling for nanomedicine design

Nanotechnology has presented many new challenges and opportunities in the area of nanomedicine design. The issues related to nanoconjugation, nanosystem-mediated targeted drug delivery, transitional stability of nanovehicles, the integrity of drug transport, drug-delivery mechanisms and chemical structural design require a pre-estimated and determined course of assumptive actions with property and characteristic estimations for optimal nanomedicine design. Molecular modeling in nanomedicine encompasses these pre-estimations and predictions of pertinent design data via interactive computographic software. Recently, an increasing amount of research has been reported where specialized software is being developed and employed in an attempt to bridge the gap between drug discovery, materials science and biology. This review provides an assimilative and concise incursion into the current and future strategies of molecular-modeling applications in nanomedicine design and aims to describe the utilization of molecular models and theoretical-chemistry computographic techniques for expansive nanomedicine design and development.

Biosensor Technology and the Clinical Biochemistry Laboratory – Issue of Signal Interference from the Biological Matrix

This chapter discusses the potential use of biosensor technology in the clinical biochemistry laboratory. Various relevant key aspects of biosensor technology are introduced such as the chemistry of attachment of probes to device surfaces and a summary of the main categories of sensors based on electrochemistry, acoustic-wave physics and optical science. Important performance characteristics of typical clinical measurements are appraised with examples being presented. Following this discussion, the relevant issues of device selectivity, sensitivity, dynamic range and calibration with respect to target concentration, and possibility for label-free operation are evaluated. A critical issue for potential clinical measurement is the mandatory requirement for devices to function in biological fluids and matrices, with avoidance of signal interference caused by nonspecific surface adoption. Solutions for the latter problem are summarized. The chapter closes with a look at the possible features of biosensor technology that could be employed in the clinical biochemistry laboratory.

Oriented immobilization of His-tagged protein on a redox active thiol derivative of DPTA-Cu(II) layer deposited on a gold electrode--the base of electrochemical biosensors

This paper concerns the development of an electrochemical biosensor for the determination of Aβ_16–23′ and Aβ_1–40 peptides. The His-tagged V and VC1 domains of Receptor for Advanced Glycation end Products (RAGE) immobilized on a gold electrode surface were used as analytically active molecules. The immobilization of His₆–RAGE domains consists of: (i) formation of a mixed layer of N-acetylcysteamine (NAC) and the thiol derivative of pentetic acid (DPTA); (ii) complexation of Cu(II) by DPTA; (iii) oriented immobilization of His₆–RAGE domains via coordination bonds between Cu(II) sites from DPTA–Cu(II) complex and imidazole nitrogen atoms of a histidine tag. Each modification step was controlled by cyclic voltammetry (CV), Osteryoung square-wave voltammetry (OSWV), and atomic force microscopy (AFM). The applicability of the proposed biosensor was tested in the presence of human plasma, which had no influence on its performance. The detection limits for Aβ_1–40 determination were 1.06 nM and 0.80 nM, in the presence of buffer and human plasma, respectively. These values reach the concentration level of Aβ_1–40 which is relevant for determination of its soluble form in human plasma, as well as in brain. This indicates the promising future application of biosensor presented for early diagnosis of neurodegenerative diseases.

Resolving the chemical nature of nanodesigned silica surface obtained via a bottom-up approach

The covalent grafting on silica surfaces of a functional dendritic organosilane coupling agent inserted, in a long alkyl chain monolayer, is described. In this paper, we show that depending on experimental parameters, particularly the solvent, it is possible to obtain a nanodesigned surface via a bottom-up approach. Thus, we succeed in the formation of both homogeneous dense monolayer and a heterogeneous dense monolayer, the latter being characterized by a nanosized volcano-type pattern (4-6 nm of height, 100 nm of width, and around 3 volcanos/μm(2)) randomly distributed over the surface. The dendritic attribute of the grafted silylated coupling agent affords enough anchoring sites to immobilize covalently functional gold nanoparticles (GNPs), coated with amino PEG polymer to resolve the chemical nature of the surfaces and especially the volcano type nanopattern structures of the heterogeneous monolayer. Thus, the versatile surface chemistry developed herein is particularly challenging as the nanodesign is straightforward achieved in a bottom-up approach without any specific lithography device.

Biosensor based on laccase immobilized on plasma polymerized allylamine/carbon electrode

In this work, a simple and rapid method was used to functionalize carbon electrode in order to efficiently immobilize laccase for biosensor application. A stable allylamine coating was deposited using a low pressure inductively excited RF tubular plasma reactor under mild plasma conditions (low plasma power (10 W), few minutes) to generate high density amine groups (N/C ratio up to 0.18) on rough carbon surface electrodes. The longer was the allylamine plasma deposition time; the better was the surface coverage. Laccase from Trametes versicolor was physisorbed and covalently bound to these allylamine modified carbon surfaces. The laccase activities and current outputs measured in the presence of 2,2'-azinobis-(3-ethylbenzothiazole-6-sulfonic acid) (ABTS) showed that the best efficiency was obtained for electrode plasma coated during 30 min. They showed also that for all the tested electrodes, the activities and current outputs of the covalently immobilized laccases were twice higher than the physically adsorbed ones. The sensitivity of these biocompatible bioelectrodes was evaluated by measuring their catalytic efficiency for oxygen reduction in the presence of ABTS as non-phenolic redox substrate and 2,6-dimethoxyphenol (DMP) as phenolic one. Sensitivities of around 4.8 μA mg(-1)L and 2.7 μA mg(-1)L were attained for ABTS and DMP respectively. An excellent stability of this laccase biosensor was observed for over 6 months.

Reusable nanostencils for creating multiple biofunctional molecular nanopatterns on polymer substrate

In this paper, we demonstrate a novel method for high throughput patterning of bioprobes with nanoscale features on biocompatible polymer substrate. Our technique, based on nanostencil lithography, employs high resolution and robust masks integrated with array of reservoirs. We show that the smallest pattern size can reach down to 100 nm. We also show that different types of biomolecules can be patterned on the same substrate simultaneously. Furthermore, the stencil can be reused multiple times to generate a series of identical patterns at low cost. Finally, we demonstrate that biomolecules can be covalently patterned on the surface while retaining their biofunctionalities. By offering the flexibility on the nanopattern design and enabling the reusability of the stencil, our approach significantly simplifies the bionanopatterning process and therefore could have profound implications in diverse biological and medical applications.

AFM Specific Identification of Bacterial Cell Fragments on Biofunctional Surfaces

Biointerfaces with a highly sensitive surface designed for specific interaction with biomolecules are essential approaches for providing advanced biochemical and biosensor assays. For the first time, we have introduced a simple AFM-based recognition system capable of visualizing specific bacterial nanofragments and identifying the corresponding bacterial type. For this we developed AFM-adjusted procedures for preparing IgG-based surfaces and subsequently exposing them to antigens. The AFM images reveal the specific binding of Escherichia coli cell fragments to the prepared biofunctional surfaces. Moreover, the binding of bacterial cell fragments to the affinity surfaces can be characterized quantitatively, indicating a 30-fold to 80-fold increase in the quantity of bound antigenic material in the case of a specific antigen-antibody pair. Our results demonstrate significant opportunities for developing reliable sensing procedures for detecting pathogenic bacteria, and the cell can still be identified after it is completely destroyed.

Solvent effect and time-dependent behavior of C-terminus-cysteine-modified cecropin P1 chemically immobilized on a polymer surface

Sum frequency generation (SFG) vibrational spectroscopy has been applied to the investigation of peptide immobilization on a polymer surface as a function of time and peptide conformation. Surface immobilization of biological molecules is important in many applications such as biosensors, antimicrobial materials, biobased fuel cells, nanofabrication, and multifunctional materials. Using C-terminus-cysteine-modified cecropin P1 (CP1c) as a model, we investigated the time-dependent immobilization behavior in situ in real time. In addition, potassium phosphate buffer (PB) and mixtures of PB and trifluoroethanol were utilized to examine the effect of peptide secondary structure on CP1c immobilization to polystyrene maleimide (PS-MA). The orientation of immobilized CP1c on PS-MA was determined using polarized SFG spectra. It was found that the peptide solution concentration, solvent composition, and assembly state (monomer vs dimer) prior to immobilization all influence the orientation of CP1c on a PS-MA surface. The detailed relationship between the interfacial peptide orientation and these immobilization conditions is discussed.

Strategies for patterning biomolecules with dip-pen nanolithography

Dip-pen nanolithography (DPN) is an atomic force microscopy (AFM)-based lithography technique, which has the ability to fabricate patterns with a feature size down to approximately 15 nm using both top-down and bottom-up approaches. DPN utilizes the water meniscus formed between an AFM tip and a substrate to transfer ink molecules onto surfaces. A major application of this technique is the fabrication of micro- and nano-arrays of patterned biomolecules. To achieve this goal, a variety of chemical approaches has been used. This review concisely describes the development of DPN in the past decade and presents the related chemical strategies that have been reported to fabricate biomolecular patterns with DPN at micrometer and nanometer scale, classified into direct- and indirect DPN methodologies, discussing tip-functionalization strategies as well.

Anti-fouling bioactive surfaces

Bioactive surfaces refer to surfaces with immobilized bioactive molecules aimed specifically at promoting or supporting particular interactions. Such surfaces are of great importance for various biomedical and biomaterials applications. In the past few years, considerable effort has been made to create bioactive surfaces by forming specific biomolecule-modified surfaces on a non-biofouling "base" or "background". Hydrophilic and bioinert polymers have been widely used as anti-fouling layers that resist non-specific protein interactions. They can also serve as "spacers" to effectively move the immobilized biomolecule away from the surface, thus enhancing its bioactivity. In this review we summarize several successful approaches for the design and preparation of bioactive surfaces based on different types of anti-fouling/spacer materials. Some perspectives on future research in this area are also presented.

Orientation difference of chemically immobilized and physically adsorbed biological molecules on polymers detected at the solid/liquid interfaces in situ

A surface sensitive second order nonlinear optical technique, sum frequency generation vibrational spectroscopy, was applied to study peptide orientation on polymer surfaces, supplemented by a linear vibrational spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy. Using the antimicrobial peptide Cecropin P1 as a model system, we have quantitatively demonstrated that chemically immobilized peptides on polymers adopt a more ordered orientation than less tightly bound physically adsorbed peptides. These differences were also observed in different chemical environments, for example, air versus water. Although numerous studies have reported a direct correlation between the choice of immobilization method and the performance of an attached biological molecule, the lack of direct biomolecular structure and orientation data has made it difficult to elucidate the relationship between structure, orientation, and function at a surface. In this work, we directly studied the effect of chemical immobilization method on biomolecular orientation/ordering, an important step for future studies of biomolecular activity. The methods for orientation analysis described within are also of relevance to understanding biosensors, biocompatibility, marine-antifouling, membrane protein functions, and antimicrobial peptide activities.

Na⁺,K⁺-ATPase as the Target Enzyme for Organic and Inorganic Compounds

This paper gives an overview of the literature data concerning specific and non specific inhibitors of Na⁺,K⁺-ATPase receptor. The immobilization approaches developed to improve the rather low time and temperature stability of Na⁺,K⁺-ATPase, as well to preserve the enzyme properties were overviewed. The functional immobilization of Na⁺,K⁺-ATPase receptor as the target, with preservation of the full functional protein activity and access of various substances to an optimum number of binding sites under controlled conditions in the combination with high sensitive technology for the detection of enzyme activity is the basis for application of this enzyme in medical, pharmaceutical and environmental research.