Scientific Resources
Explore publications, technical tutorials, books and datasets selected to support analytical decisions in research and product development.
How to use the Percevia scientific library
This library brings together technical material connected to Percevia's fields of work: instrumental characterization, pharmaceutical development, materials science, microbiology and biosensors. Each resource card identifies its topic, publication year and destination link so readers can reach the original source rather than relying on an isolated summary.
Use the category filters to separate papers, books, tutorials and datasets. A paper may support interpretation of a method, a tutorial may clarify an analytical workflow, and a dataset may help compare measurements or train a model. Resource inclusion does not mean that every method described is available as a commercial service; current capabilities are stated on the corresponding service page and confirmed during technical scoping.
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Design and characterization of crotamine-functionalized gold nanoparticles
This paper describes the development of a facile and environmentally friendly strategy for supporting crotamine on gold nanoparticles (GNPs). Our approach was based on the covalent binding interaction between the cell penetrating peptide crotamine, which is a snake venom polypeptide with preference to penetrate dividing cells, and a polyethylene glycol (PEG) ligand, which is a nontoxic, water-soluble and easily obtainable commercial polymer. Crotamine was derivatized with ortho-pyridyldisulfide-polyethyleneglycol-N-hydroxysuccinimide (OPSS-PEG-SVA) cross-linker to produce OPSS-PEG-crotamine as the surface modifier of GNP. OPSS-PEG-SVA can serve not only as a surface modifier, but also as a stabilizing agent for GNPs. The successful PEGylation of the nanoparticles was demonstrated using different physicochemical techniques, while the grafting densities of the PEG ligands and crotamine on the surface of the nanoparticles were estimated using a combination of electron microscopy and mass spectrometry analysis. In vitro assays confirmed the internalization of these GNPs, into living HeLa cells. The results described herein suggest that our approach may serve as a simple platform for the synthesis of GNPs decorated with crotamine with well-defined morphologies and uniform dispersion, opening new roads for crotamine biomedical applications.
High Resolution Piezoresponse Force Microscopy Study of Self-Assembled Peptide Nanotubes
Peptide nanotubes based on short dipeptide diphenylalanine (FF) attract a lot of attention due to their unique physical properties ranging from strong piezoelectricity to extraordinary mechanical rigidity. In this work, we present the results of high-resolution Piezoresponse Force Microscopy (PFM) measurements in FF microtubes prepared from the solution. Firstin-situ temperature measurements show that the effective shear piezoelectric coefficient d15 (proportional to axial polarization) significantly decreases (to about half of the initial value) under heating up to 100oC. The piezoresponse becomes inhomogeneous over the surface being higher in the center of the tubes. Further, PFM study of a composite consisting of FF microtubes and reduced graphene oxide (rGO) was performed. We show that piezoelectric properties of peptide microtubes are significantly modified and radial (vertical) piezoresponse appears in the presence of rGO as confirmed via PFM analysis. The results are rationalized in terms of molecular approach in which \u03c0 \u2013 \u03c0 molecular interaction between rGO and dipeptide is responsible for the appearance of radial component of polarization in such hybrid structures.
COVID-19 impedimetric biosensor based on polypyrrole nanotubes, nickel hydroxide and VHH antibody fragment: specific, sensitive, and rapid viral detection in saliva samples
SARS-CoV-2 rapid spread required urgent, accurate, and prompt diagnosis to control the virus dissemination and pandemic management. Several sensors were developed using different biorecognition elements to obtain high specificity and sensitivity. However, the task to achieve these parameters in combination with fast detection, simplicity, and portability to identify the biorecognition element even in low concentration remains a challenge. Therefore, we developed an electrochemical biosensor based on polypyrrole nanotubes coupled via Ni(OH)2 ligation to an engineered antigen-binding fragment of heavy chain-only antibodies (VHH) termed Sb#15. Herein we report Sb#15-His6 expression, purification, and characterization of its interaction with the receptor-binding domain (RBD) of SARS-CoV-2 in addition to the construction and validation of a biosensor. The recombinant Sb#15 is correctly folded and interacts with the RBD with a dissociation constant (KD) of 27.1 \u00b1 6.4 nmol/L. The biosensing platform was developed using polypyrrole nanotubes and Ni(OH)2, which can properly orientate the immobilization of Sb#15-His6 at the electrode surface through His-tag interaction for the sensitive SARS-CoV-2 antigen detection. The quantification limit was determined as 0.01 pg/mL using recombinant RBD, which was expressively lower than commercial monoclonal antibodies. In pre-characterized saliva, both Omicron and Delta SARS-CoV-2 were accurately detected only in positive samples, meeting all the requirements recommended by the World Health Organization for in vitro diagnostics. A low sample volume of saliva is needed to perform the detection, providing results within 15 min without further sample preparations. In summary, a new perspective allying recombinant VHHs with biosensor development and real sample detection was explored, addressing the need for accurate, rapid, and sensitive biosensors.
Strong piezoelectricity in single-layer graphene deposited on SiO2 grating substrates
Electromechanical response of materials is a key property for various applications ranging from actuators to sophisticated nanoelectromechanical systems. Here electromechanical properties of the single-layer graphene transferred onto SiO2 calibration grating substrates is studied via piezoresponse force microscopy and confocal Raman spectroscopy. The correlation of mechanical strains in graphene layer with the substrate morphology is established via Raman mapping. Apparent vertical piezoresponse from the single-layer graphene supported by underlying SiO2 structure is observed by piezoresponse force microscopy. The calculated vertical piezocoefficient is about 1.4\u2009nm\u2009V\u22121, that is, much higher than that of the conventional piezoelectric materials such as lead zirconate titanate and comparable to that of relaxor single crystals. The observed piezoresponse and achieved strain in graphene are associated with the chemical interaction of graphene\u2019s carbon atoms with the oxygen from underlying SiO2. The results provide a basis for future applications of graphene layers for sensing, actuating and energy harvesting.
Piezoelectric properties and Young's moduli of diphenylalanine microtubes\u2014oxide nanoparticles composites
In this work, we investigated the influence of piezoelectric ZnO and nonpiezoelectric SiO2 and TiO2 nanoparticles on the structure and some physical properties of composite structures based on microtubes of diphenylalanine. We demonstrated that all types of used nanoparticles promoted formation of voids and cavities in diphenylalanine microtubes thus reducing the effective Young's modulus and lateral piezoelectric coefficient of the composite. At the same time, embedding of piezoelectric ZnO nanoparticles provides noticeable vertical piezoresponse normally absent in single-component diphenylalanine microtubes. The obtained results demonstrate the ability to control the properties of self-assembling composite biomaterials by nanoparticles.
2D Layered Dipeptide Crystals for Piezoelectric Applications
2D piezoelectric materials such as transition metal dichalcogenides are attracting significant attention because they offer various benefits over bulk piezoelectrics. In this work, the fabrication of layered biomolecular crystals of diphenylalanine (FF) obtained via a co-assembly of l,l- and d,d- enantiomers of FF monomers is reported. Their crystal structure, thermal and chemical stabilities, and piezoelectric properties are investigated. Single crystal X-ray diffraction results show that FF enantiomers are arranged in the form of bilayers consisting of monomers with alternating chirality packed into a tape-like monoclinic structure belonging to a polar space group P21. Each bilayer (\u22481.5 nm thick) demonstrates strong out-of-plane piezoelectricity (d33 \u2248 20 pm V\u22121) that is almost an order of magnitude higher than in the archetypical piezoelectric material quartz. The grown crystals demonstrate better thermal and chemical stabilities than self-assembled hexagonal FF nanotubes studied in the past. Piezoelectric bilayers, being held via weak aromatic interaction in the bulk crystals, can be exfoliated by mechanical or chemical methods, thus resulting in a 2D piezoelectric material, which can find various applications in biocompatible and ecologically friendly electromechanical microdevices, such as sensors, actuators, and energy harvesting elements used in implantable and wearable electronics.
Diphenylalanine-Based Microribbons for Piezoelectric Applications via Inkjet Printing
Peptide-based nanostructures are very promising for nanotechnological applications because of their excellent self-assembly properties, biological and chemical flexibility, and unique multifunctional performance. However, one of the limiting factors for the integration of peptide assemblies into functional devices is poor control of their alignment and other geometrical parameters required for device fabrication. In this work, we report a novel method for the controlled deposition of one of the representative self-assembled peptides\u2014diphenylalanine (FF)\u2014using a commercial inkjet printer. The initial FF solution, which has been shown to readily self-assemble into different structures such as nano- and microtubes and microrods, was modified to be used as an efficient ink for the printing of aligned FF-based structures. Furthermore, during the development of the suitable ink, we were able to produce a novel type of FF conformation with high piezoelectric response and excellent stability. By using this method, ribbonlike microcrystals based on FF could be formed and precisely patterned on different surfaces. Possible mechanisms of structure formation and piezoelectric effect in printed microribbons are discussed along with the possible applications.
Morphology and piezoelectric characterization of thin films and microcrystals of ortho-carboranyl derivatives of (S)-glutamine and (S)-asparagine
Local morphological features and piezoelectric properties of films and bulk crystals of ortho-carboranyl derivatives of (S)-asparagine and (S)-glutamine have been investigated at nanoscale by atomic force and piezoresponse force microscopies. Both films and bulk crystals of the studied compounds demonstrated a very high piezoelectric response exceeding that of lithium niobate. The crystal structure has been studied by single crystal X-ray diffraction.
Multifunctional biosensors based on peptide\u2013polyelectrolyte conjugates
A novel enzymatic platform for the sensing of H2O2 and glucose that uses L,L-diphenylalanine micro/nanostructures (FF-MNSs) as an enzyme support is shown. This platform is obtained by the self-assembly of poly(allylamine hydrochloride) (PAH), FF-MNSs, and microperoxidase-11 (MP11) anchored onto the peptide matrix, in two different crystal structures of FF-MNSs: hexagonal (P61) and orthorhombic (P22121). The electroactive area of the electrodes increases in the presence of FF-MNSs. We also demonstrate via theoretical calculations that the valence band energy of the orthorhombic structure allows it to be doped, similarly to p-type semiconductors, where PAH acts as a doping agent for the orthorhombic peptide structure, decreasing the band-gap by around 1 eV, which results in a smaller charge transfer resistance. These results are consistent with electrochemical impedance spectroscopy measurements, which further elucidate the role of the band structure of the orthorhombic FF-MNSs in the conductivity and electron transfer rates of the hybrid material. An effective communication between the electrode and the active site of a glucose oxidase enzyme through MP11\u2013protein complexes occurs, paving the way for FF-MNSs in the orthorhombic phase for the future development of bioelectronics sensing devices.
Polycaprolactone fibers with self-assembled peptide micro/nanotubes: a practical route towards enhanced mechanical strength and drug delivery applications
Peptide-based scaffolds are a frontier research area in materials science with widespread impact in biomedical engineering. In this paper, we describe a hybrid material formulated through the conjugation of electrospun polycaprolactone (PCL) fibers and micro/nanotubes of L,L-diphenylalanine (FF-MNTs). Morphology and crystallinity of the composite matrices are investigated using a wide range of analytical techniques including electron microscopy, thermal analyses, X-ray diffraction and micro-tomography. Peptide assemblies are found to produce deep modifications on the microstructure of PCL fibers, impacting average diameters, crystallinity degree and porous size in the polymer network. These changes are correlated with mechanical properties of the resulting scaffolds, whose strength is found to exhibit a brittle-to-ductile transition upon increasing the amount of FF-MNTs and lead to enhanced Young's moduli of polymer fibers. The PCL/FF-MNTs composites were tested for the drug delivery application of a lipophilic drug, benzocaine. In vitro permeation studies have shown that these polymer/peptide hybrids are able to produce a steady release of benzocaine over periods of up to \u223c13 hours, much higher than commercially available gel formulations. Enzymatic tests have shown a significant increment in biodegradation rates in PCL/FF-MNTs hybrids containing higher peptide amounts, which exhibited almost 100% weight loss against only 10% found in pure PCL. Our findings indicate that using PCL/FF-MNTs materials is a simple route towards achieving enhanced mechanical strength of PCL networks that have the ability to promote controlled drug delivery from a completely biodegradable matrix.
Polycaprolactone\u2013Polyaniline Blend: Effects of the Addition of Cysteine on the Structural and Molecular Properties
Organic molecule conjugates usually arrange themselves into complex multiphase systems that are sensitive to processing and local chemical environment. Moreover, these conjugates are able to self-assemble at different scales, varying from nano- to macroscale. In addition, intermolecular interactions introduce structural variations in the molecular packing and large-scale ordering, which directly affects different physicochemical properties of the materials. Herein, we study the synthesis of polymer blends based on poly(\u03b5)-caprolactone (PCL) with polyaniline (PANI) doped with the amino acid N-acetyl-l-cysteine (NAC). Samples were prepared either through solution casting or via electrospinning methods. The materials were characterized regarding their morphological, structural, and molecular properties at different length scales. From the results obtained, the relationship between changes in blend properties and different NAC concentrations was determined. Deep structural details have been unveiled by using different characterization techniques, including X-rays microcomputed tomography (Micro-CT), small- and wide-angle scattering (SAXS and WAXS), and differential scanning calorimetry (DSC). Our findings indicated that NAC enhances organization and crystallinity index of the blends and that a close relationship appears between the synthesis method and the internal micronanostructure. It is also shown that NAC modifies the molecular properties of PANI. Through spectroscopic techniques (UV\u2013vis and resonant Raman), it was shown that NAC favors the formation of different forms of PANI. In addition, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) showed the formation of a supramolecular structure maintained by sulfur-\u03c0 (SH-\u03c0) intermolecular interactions between PANI and NAC.
Synthesis and piezoelectric properties of N-phthaloylglutamic acid derivatives
The (S,S)- and (R,R)-enantiomers of dimethyl 2,4-diphthalimidoglutarate were synthesized by nucleophilic substitution of bromine in dimethyl (2S,4RS)-4-bromo-N-phthaloyl-glutamate upon treatment with potassium phthalimide, followed by separation. The crystal structure of the obtained compounds was studied by X-ray diffraction. Crystals of enantiomerically pure dimethyl 4-hydroxy- and 4-phthalimido-N-phthaloylglutamates were found to possess a noticeable piezoelectric activity.
Freeze-drying of silica nanoparticles: redispersibility toward nanomedicine applications
To study freeze-drying of silica nanoparticles (SiO2NPs) in order to find suitable conditions to produce lyophilized powders with no aggregation after resuspension and storage. Methods: SiO2NPs were synthesized using a St\u00f6ber-based procedure, and characterized by scanning electron microscopy, dynamic light scattering and nitrogen adsorption/desorption isotherms. SiO2NPs hydrodynamic diameters were compared prior and after freeze-drying in the presence/absence of carbohydrate protectants. Results: Glucose was found to be the most suitable protectant against the detrimental effects of lyophilization. The minimum concentration of carbohydrate required to effectively protect SiO2NPs from aggregation during freeze-drying is influenced by the nanoparticle's size and texture. Negligible aggregation was observed during storage. Conclusion: Carbohydrates can be used during SiO2NPs freeze-drying process to obtain redispersable solids that maintain original sizes without residual aggregation.
Piezoactive amino acid derivatives containing fragments of planar-chiral ortho-carboranes
A series of novel (S)-amino acid derivatives bearing planar-chiral (3-acylamino-1,2-dicarba-closo-dodecaboran-1-yl)acetyl substituents was synthesized. Carboranyl amino esters were obtained in a diastereomerically pure form (according to chiral HPLC). Single crystals of individual diastereomers were studied by optical microscopy, X-ray diffraction analysis and piezoresponse force microscopy. The piezoelectric activity of some compounds was shown to exceed that of most known organic piezoelectrics.
Self-Assembly of a Designed Alternating Arginine/Phenylalanine Oligopeptide
A model octapeptide peptide consisting of an alternating sequence of arginine (Arg) and phenylalanine (Phe) residues, namely, [Arg-Phe]4, was prepared, and its self-assembly in solution studied. The simple alternating [Arg-Phe]4 peptide sequence allows for unique insights into the aggregation process and the structure of the self-assembled motifs. Fluorescence and UV\u2013vis assays were used to determine critical aggregation concentrations, corresponding to the formation of oligomeric species and \u03b2-sheet rich structures organized into both spheroidal aggregates and highly ordered fibrils. Electron and atomic force microscopy images show globular aggregates and long unbranched fibers with diameters ranging from \u223c4 nm up to \u223c40 nm. Infrared and circular dichroism spectroscopy show the formation of \u03b2-sheet structures. X-ray diffraction on oriented stalks show that the peptide fibers have an internal lamellar structure, with an orthorhombic unit cell with parameters a \u223c 27.6 \u00c5, b \u223c 9.7 \u00c5, and c \u223c 9.6 \u00c5. In situ small-angle X-ray scattering (SAXS) shows the presence of low molecular weight oligomers in equilibrium with mature fibers which are likely made up from 5 or 6 intertwined protofilaments. Finally, weak gel solutions are probed under gentle shear, suggesting the ability of these arginine-rich fibers to form networks.
Self-Assembly of Peptide Nanostructures onto an Electrode Surface for Nonenzymatic Oxygen Sensing
We report here the fabrication of a biomimetic sensor for direct oxygen reduction; the sensor consists of multicopper oxidases derived from cyclic-tetrameric copper(II) species containing the ligand (4-imidazolyl)ethylene-2-amino-1-ethylpyridine (apyhist) that are self-assembled with l-diphenylalanine micro/nanostructures (FF-MNTs). The [Cu4(apyhist)4]4+/FF-MNT complex was immobilized onto the surface of a glassy carbon (GC) electrode by poly ion complex formation with a Nafion film. This hybrid membrane allows regular proton transport to a Cu-based molecular oxygen reduction reaction catalyst, and the imidazole group in the imine ligand (apyhist) acts as a local buffer in the vicinity of the O2 reducing center, thus aiding the catalyst in retaining its selectivity for 4e\u2013/4H+ oxygen reduction reaction. This nanocomposite provided improved sensing characteristics in the electrode interface with respect to the electroactive surface area, the diffusion coefficient, and the electron transfer kinetics. In addition, the hybrid film [Cu4(apyhist)4]4+/FF-MNT-coated GC electrode was successfully used as an enzymeless electrochemical sensor for the detection of dissolved oxygen in aqueous media at two concentration intervals, viz., 0.2\u20133.0 mg L\u20131 and greater than 3.0 mg L\u20131, with sensitivities of 25.0 and 80.2 \u03bcA L mg\u20131 cm\u20132, respectively, and a detection limit of 0.1 mg L\u20131. Evaluated in terms of relative standard deviation, the repeatability of the proposed sensor was less than 9.0% for ten measurements of a solution of 6.5 mg L\u20131 oxygen. Experimental efforts were conducted to use this proposed platform for O2 determination with real samples. Results from theoretical investigations using density functional theory support the hypothesis that the [Cu4(apyhist)4]4+ complex can act as the sole source of protons and electrons in the O2 reduction reaction.
Self-Assembly of Arg\u2013Phe Nanostructures via the Solid\u2013Vapor Phase Method
We report here the fabrication of a biomimetic sensor for direct oxygen reduction; the sensor consists of multicopper oxidases derived from cyclic-tetrameric copper(II) species containing the ligand (4-imidazolyl)ethylene-2-amino-1-ethylpyridine (apyhist) that are self-assembled with l-diphenylalanine micro/nanostructures (FF-MNTs). The [Cu4(apyhist)4]4+/FF-MNT complex was immobilized onto the surface of a glassy carbon (GC) electrode by poly ion complex formation with a Nafion film. This hybrid membrane allows regular proton transport to a Cu-based molecular oxygen reduction reaction catalyst, and the imidazole group in the imine ligand (apyhist) acts as a local buffer in the vicinity of the O2 reducing center, thus aiding the catalyst in retaining its selectivity for 4e\u2013/4H+ oxygen reduction reaction. This nanocomposite provided improved sensing characteristics in the electrode interface with respect to the electroactive surface area, the diffusion coefficient, and the electron transfer kinetics. In addition, the hybrid film [Cu4(apyhist)4]4+/FF-MNT-coated GC electrode was successfully used as an enzymeless electrochemical sensor for the detection of dissolved oxygen in aqueous media at two concentration intervals, viz., 0.2\u20133.0 mg L\u20131 and greater than 3.0 mg L\u20131, with sensitivities of 25.0 and 80.2 \u03bcA L mg\u20131 cm\u20132, respectively, and a detection limit of 0.1 mg L\u20131. Evaluated in terms of relative standard deviation, the repeatability of the proposed sensor was less than 9.0% for ten measurements of a solution of 6.5 mg L\u20131 oxygen. Experimental efforts were conducted to use this proposed platform for O2 determination with real samples. Results from theoretical investigations using density functional theory support the hypothesis that the [Cu4(apyhist)4]4+ complex can act as the sole source of protons and electrons in the O2 reduction reaction.
Molecular modeling and computational study of the chiral-dependent structures and properties of self-assembling diphenylalanine peptide nanotubes
The structure and properties of diphenylalanine (FF) peptide nanotubes (PNT) based on phenylalanine were investigated by various molecular modeling methods. The main approach employed semi-empirical quantum-chemical methods (PM3 and AM1). Ab initio, density functional theory methods and molecular mechanical approaches were also used. Both model structures and structures extracted from experimental crystallographic databases obtained by X-ray methods were examined. A comparison of optimized model structures and structures obtained by natural self-assembly revealed important differences depending on chirality: D and L. In both the cases, the effect of chirality on the results of self-assembly of FF PNT was established: PNT based on the D-FF has large condensation energy E0 in the transverse direction, and form thicker and shorter PNT bundles than those based on L-FF. A topological difference was established: model PNT were optimized into structures consisting of rings, while naturally self-assembled PNT consisted of helical turns. The latter nanotubes differed from the original L-FF and D-FF and formed helix structures of different chirality signs in accordance with the alternation rule of chirality due to macromolecule hierarchy. A topological transition between ring and helix turn PNT structures is discussed: self-assembled natural helix structures are favorable and their energy is lower by a value of the order of one to several eV.
Piezoelectric properties of diphenylalanine microtubes prepared from the solution
Biomimetic self-assembling peptides form a variety of structures that can be used for the fabrication of functional devices. We are witnessing the emergence of a new era of bionanotechnology that opens up new possibilities for novel electronic, photonic and energy functionalities based on supramolecular green and lightweight structures. In this work, we study the emergent piezoelectric properties of linear dipeptide diphenylalanine (FF) that can self-assemble in the shape of microtubes. The matrix of piezoelectric coefficients is derived for the first time based on the hexagonal symmetry of FF structures and different configurations of the tubes are tested by the advanced Piezoresponse Force Microscopy (PFM). Strong piezoelectric anisotropy of piezoelectric coefficients is explained by the self-assembled structure of FF peptides. Possible applications of piezoelectric microtubes in functional devices are discussed.
Peptide-Based Assemblies on Electrospun Polyamide-6/Chitosan Nanofibers for Detecting Visceral Leishmaniasis Antibodies
An alternative label-free electrochemical immunosensor for the rapid detection of Leishmania braziliensis was developed by immobilizing a peptide-based probe of the promastigote surface antigen (PSA-38S) onto electrospun polyamide-6 (PA6)/chitosan nanofibers. An increase in chitosan content in the spinning solution leads to a decrease in the diameter of the formed fibers, whereas the differential scanning calorimetry (DSC) and X-ray diffraction (XRD) data showed a decrease in crystallinity upon increasing the chitosan content in the formulation. In addition, the incorporation of chitosan into the PA6 nanofibers tends to decrease the resistance to the charge-transfer process at the electrode surface. A 40 wt % chitosan content was used for immobilization of the peptide antigen, which was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The detection was performed by measuring the relative change in impedance before and after the anti-Leishmania braziliensis reaction by EIS. Under the optimized conditions, the relative change in impedance was proportional to the logarithmic value of PSA concentrations in the range of 2.5 to 10 pg\u00b7mL\u20131(r2 = 0.9946) with a detection limit of 0.2 pg\u00b7mL\u20131, which was slightly lower than that of the enzyme-linked immunosorbent assay. Additionally, the sensor was tested against two nonspecific antibodies (T. cruzi and \u03b2-actin), whereas multivariate analysis using unsupervised pattern recognition through principal component analysis was successfully applied to identification of the pattern relative to each antibody. Finally, the optimized electrochemical immunoassay can be a favorable approach for Leishmania detection tests, as it is able to differentiate negative and positive visceral leishmaniasis human serum samples.
Development of polypyrrole (nano)structures decorated with gold nanoparticles toward immunosensing for COVID-19 serological diagnosis
The rapid and reliable detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroconversion in humans is crucial for suitable infection control. In this sense, many studies have focused on increasing the sensibility, lowering the detection limits and minimizing false negative/positive results. Thus, biosensors based on nanoarchitectures of conducting polymers are promising alternatives to more traditional materials since they can hold improved surface area, higher electrical conductivity and electrochemical activity. In this work, we reported the analytical comparison of two different conducting polymers morphologies for the development of an impedimetric biosensor to monitor SARS-CoV-2 seroconversion in humans. Biosensors based on polypyrrole (PPy), synthesized in both globular and nanotubular (NT) morphology, and gold nanoparticles are reported, using a self-assembly monolayer of 3-mercaptopropionic acid and covalently linked SARS-CoV-2 Nucleocapsid protein. First, the novel hybrid materials were characterized by electron microscopy and electrochemical measurements, and the biosensor step-by-step construction was characterized by electrochemical and spectroscopic techniques. As a proof of concept, the biosensor was used for the impedimetric detection of anti-SARS-CoV-2 Nucleocapsid protein monoclonal antibodies. The results showed a linear response for different antibody concentrations, good sensibility and possibility to quantify 7.442 and 0.4 ng/mL of monoclonal antibody for PPy in the globular and NT morphology, respectively. The PPy-NTs biosensor was able to discriminate serum obtained from COVID-19 positive versus negative clinical samples and is a promising tool for COVID-19 immunodiagnostic, which can contribute to further studies concerning rapid, efficient, and reliable detections.
Electrodes Based on PEDOT Nanotubes Decorated with Gold Nanoparticles for Biosensing and Energy Storage
Poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT-NTs) were electrochemically synthesized onto a stainless steel mesh electrode followed by one-pot electrodeposition of gold nanoparticles (AuNPs) at the nanotubular surface. The hybrid nanomaterial has shown remarkable electrochemical properties with the diminishment of the charge transfer resistance besides the possibility of further electrode modification by the thiol bonding at the AuNPs. The modified electrodes were deeply characterized by electrochemical techniques, in special by electrochemical impedance spectroscopy, which provides valuable information about the interfacial processes. The morphology of the nanomaterial was characterized by scanning electron microscopy and transmission electron microscopy images. The biosensing properties were evaluated through the avidin/biotin pair. The methodology of construction of the biosensor was further adapted to explore a cancer biomarker detection, the folate binding protein (FBP), which presented high sensitivity with a limit of detection of 4.5 pmol L\u20131, one of the lowest found in literature. Also, the hybrid material was used in the development of supercapacitors, the inclusion of AuNPs provided a remarkable durability of the PEDOT-NTs modified electrodes presenting long cycling stability (over 3000 cycles) and high energy density, compared with bare PEDOT nanotubes modified electrodes.
Piezoactive dense diphenylalanine thin films via solid-phase crystallization
Piezoactive biomaterials are currently in the forefront of the worldwide research due to the multitude of applications ranging from implantable biosensors to biocompatible energy harvesters. Among them, biomolecular piezoelectrics based on amino acids and dipeptides (as exemplified by diphenylalanine, FF) are the most studied. Major problem is an inability to control the self-assembly process to produce dense films with controlled orientation and thickness. To overcome this, we propose a novel method of the formation of crystalline piezoactive FF films via solid phase crystallization directly from the amorphous phase. The process starts from the spin-coating of FF monomers in an organic solution. These layers are then exposed to a controlled humidity that triggers nucleation and growth of highly oriented piezoactive areas (domains). The crystallization process proceeds without changing the morphology and results in dense films with controlled thickness. Large ferroelectric-like domains possess uniform piezoresponse of about 30 pm/V with the in-plane polarization. The growth kinetics is controlled by the temperature and humidity, suggesting that fully in-plane oriented films can be obtained. It is hypothetized that the solid-phase crystallization can be applied to other bioorganic piezoelectrics and thus open an avenue for further use of these materials in implantable piezotronics and beyond.
Recent trends of micro and nanostructured conducting polymers in health and environmental applications
Conducting polymers are, without question, outstanding materials. Their unique combination between metal-like, electrical, magnetic, and optical properties and the processability of polymeric materials consolidated their use in the electrochemical sciences over the past decades. However, the versatile character of these polymers combined with the advent of nanoscience has expanded their horizon of applications, now entering the fields of biomedicine and life science, as well as the environmental sciences. This review brings the latest advances on the use of conducting polymers micro and nanostructures in biomedical applications, such as controlled drug release, artificial muscles, and tissue engineering, where their stimuli responsiveness has shown new and exciting possibilities. Moreover, this review shows that the use of conducting polymers in effective extraction and pre-concentration of trace amount pollutants from complex matrices resulted in extraction capacities often superior to the materials currently commercialized. More than extracting contaminants, conducting polymers have shown further promissing results in the degradation of organic contaminants through photoelectrocatalysis. New features in the synthesis of these polymers are also addressed.