Almira Ramanaviciene

• Prof. (HP) Dr.
• Professor at Vilnius University Faculty of Chemistry and Geosciences

In recent years, many efforts have been made to develop rapid, sensitive and user-friendly glucose biosensors for monitoring blood glucose concentration in patients. In this study, the electrochemical glucose biosensors based on graphite rod (GR) electrode electrochemically modified with dendritic gold nanostructures (DGNs) and glucose oxidase (GOx...

SARS-CoV-2 vaccines provide strong protection against COVID-19. However, the emergence of SARS-CoV-2 variants has raised concerns about the efficacy of vaccines. In this study, we investigated the interactions of specific polyclonal human antibodies (pAb-SCoV2-S) produced after vaccination with the Vaxzevria vaccine with the spike proteins of three...

A surface plasmon resonance (SPR) immunosensor signal amplification strategy based on antibody-functionalized gold-coated magnetic nanoparticles (mAuNPs) was developed for ultrasensitive and quantitative detection of the CD5 biomarker using an indirect sandwich immunoassay format. The gold surface of the SPR sensor disk and mAuNPs was modified with...

Polymers represent materials that are applied in almost all areas of modern life, therefore, the characterization of polymer layers using different methods is of great importance. In this review, the main attention is dedicated to the non-invasive and label-free optical and acoustic methods, namely spectroscopic ellipsometry (SE) and quartz crystal...

Physiological and endocrine maintenance of a normal human growth hormone (hGH) concentration is crucial for growth, development, and a number of essential biological processes. In this study, we describe the preparation and characterization of magnetic nanoparticles coated with a gold shell (MNPs-Au). The optimal surface concentration of monoclonal...

Diabetes mellitus is a pathological condition that requires continuous measurement of glucose concentration in human blood. In this study, two enzymatic mediator-free glucose biosensors based on premodified graphite rod (GR) electrodes were developed and compared. GR electrode modified with electrochemically synthesized dendritic gold nanostructure...

Purpose For the diagnosis of various diseases, simultaneous sensitive detection of multiple biomarkers using low sample volumes is needed. The purpose of the present research was to develop sensitive multiplex detection model of QD-based ELISA (QLISA), through the spectroscopic QD-analyte complex measurements in microvolume liquid droplets on a gla...

All these papers address different aspects of the development and application of molecularly imprinted polymers, and some of them were dedicated to the application of Molecularly Imprinted Polymers as Tools for Analytical Chemistry and/or Medical Diagnostics.

Herein, we report the development and characterisation of an electrochemical biosensor with a polypyrrole (Ppy)-based molecularly imprinted polymer (MIP) for the serological detection of the recombinant nucleocapsid protein of SARS-CoV-2 (rN). The electrochemical biosensor utilises a Ppy-based MIP formed on a self-assembled monolayer (SAM) at the g...

Developing vascular endothelial growth factor (VEGF) protein is essential for early cancer diagnosis and cancer treatment monitoring. This study presents the design and characterisation of an electrochemical sensor utilising a self-assembling DNA aptamer structure for the sensitive and selective detection of VEGF. The aptamer structure comprisesthr...

The world’s growing energy crisis demands renewable energy sources. This issue can be solved using microbial fuel cells (MFCs). MFCs are biocatalytic systems which convert chemical energy into electrical energy, thereby reducing pollution from hazardous chemical compounds. However, during the development of MFCs, one of the most significant challen...

Background/Objectives: Electrochemotherapy (ECT) is a safe and efficient method of targeted drug delivery using pulsed electric fields (PEF), one that is based on the phenomenon of electroporation. However, the problems of electric field homogeneity within a tumor can cause a diminishing of the treatment efficacy, resulting only in partial response...

The strong immunogenicity of the SARS-CoV-2 nucleocapsid protein is widely recognized, and the detection of specific antibodies is critical for COVID-19 diagnostics in patients. This research proposed direct, label-free, and sensitive detection of antibodies against the SARS-CoV-2 nucleocapsid protein (anti-SCoV2-rN). Recombinant SARS-CoV-2 nucleoc...

This study addresses the need for enhanced antimicrobial properties of electrospun membranes, either through surface modifications or the incorporation of antimicrobial agents, which are crucial for improved clinical outcomes. In this context, chitosan—a biopolymer lauded for its biocompatibility and extracellular matrix-mimicking properties—emerge...

This paper describes the study of an amperometric glucose biosensor based on an enzymatic biofuel cell consisting of a bioanode and a biocathode modified with the same enzyme—glucose oxidase (GOx). A graphite rod electrode (GRE) was electrochemically modified with a layer of Prussian blue (PB) nanoparticles embedded in a poly(pyrrole-2-carboxylic a...

Two types of low-cost reagentless electrochemical glucose biosensors based on graphite rod (GR) electrodes were developed. The electrodes modified with electrochemically synthesized platinum nanostructures (PtNS), 1,10-phenanthroline-5,6-dione (PD), glucose oxidase (GOx) without and with a polypyrrole (Ppy) layer-(i) GR/PtNS/PD/GOx and (ii) GR/PtNS...

This article aims to present a comparative study of three polypyrrole-based molecularly imprinted polymer (MIP) systems for the detection of the recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein (rN). The rN is known for its relatively low propensity to mutate compared to other SARSCoV-2 antigens. The afo...

To effectively control and prevent diseases on a global scale, it is essential to employ precise, sensitive, selective, and rapid immunoanalytical methods [...]

This study is dedicated to molecularly imprinted polymer-based sensor development for methylene blue detection. The sensor was designed by molecular imprinting of polypyrrole with phenothiazine derivative methylene blue (MB) as a template molecule. The molecularly imprinted polymer (MIP) was deposited directly on the surface of the indium tin oxide...

Precise blood glucose detection plays a crucial role in diagnosing and medicating diabetes, in addition to aiding diabetic patients in effectively managing their condition. In this research, a first-generation reagentless amperometric glucose biosensor was developed by combining the graphite rod (GR) electrode modification by gold nanostructures (A...

The profound understanding and detailed evaluation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (SCoV2-S) protein and specific antibody interaction mechanism is of high importance in the development of immunosensors for COVID-19. In the present work, we studied a model system of immobilized SCoV2-S protein and specific mono...

Articular cartilage is an avascular tissue with a limited capacity for self-regeneration, leading the tissue to osteoarthritis (OA). Mesenchymal stem cells (MSCs) are promising for cartilage tissue engineering, as they are capable of differentiating into chondrocyte-like cells and secreting a number of active molecules that are important for cartil...

The spike (S) protein and its receptor-binding domain (RBD) of the coronavirus SARS-CoV-2 have been continually evolving, yielding the majority of significant missense mutations and new variants of concern. In this study, we examined how monoclonal antibodies against RBD (mAbs-SCoV2-RBD) and polyclonal antibodies present in convalescent human serum...

Reagentless electrochemical glucose biosensors were developed and investigated. A graphite rod (GR) electrode modified with electrochemically synthesized dendritic gold nanostructures (DGNs) and redox mediators (Med) such as ferrocenecarboxylic acid (FCA), 1,10-phenathroline-5,6-dione (PD), N,N,N′,N′-tetramethylbenzidine (TMB) or tetrathiafulvalene...

Maxillary sinus augmentation is a commonly used procedure for the placement of dental implants. However, the use of natural and synthetic materials in this procedure has resulted in postoperative complications ranging from 12% to 38%. To address this issue, we developed a novel calcium deficient HA/β-TCP bone grafting nanomaterial using a two-step...

Bone marrow mesenchymal stem cells (BMMSCs) possess a strong ability to differentiate into the chondrogenic lineage, which is important for cartilage regeneration. External stimuli, such as electrical stimulation (ES), are frequently studied for chondrogenic differentiation of BMMSCs; however, the application of conductive polymers such as polypyrr...

This paper reports the development of a novel surface plasmon resonance (SPR) immunosensor for ultra-sensitive quantitative determination of human articular cartilage oligomeric matrix protein (COMP), a major component of the extracellular matrix and an exploratory biomarker. Capture antibodies against human COMP (anti-COMP16F12) were covalently im...

Gene delivery by the pulsed electric field is a promising alternative technology for nonviral transfection; however, the application of short pulses (i.e., nanosecond) is extremely limited. In this work, we aimed to show the capability to improve gene delivery using MHz frequency bursts of nanosecond pulses and characterize the potential use of gol...

Background Articular cartilage is an avascular tissue with limited capacity to self-regeneration, which leads to challenges treating injuries or diseases such as osteoarthritis (OA). Mesenchymal stem cells (MSCs) are a promising tool for cartilage tissue engineering, as they are capable to differentiate into chondrogenic lineage cells and secrete a...

Detecting bacteria—Listeria monocytogenes—is an essential healthcare and food industry issue. The objective of the current study was to apply platinum (Pt) and screen-printed carbon (SPCE) electrodes modified by molecularly imprinted polymer (MIP) in the design of an electrochemical sensor for the detection of Listeria monocytogenes. A sequence of...

In this study, ZnO nanostructures with different types of morphologies and particle sizes were evaluated and applied for the development of an immunosensor. The first material was composed of spherical, polydisperse nanostructures with a particle size in the range of 10–160 nm. The second was made up of more compact rod-like spherical nanostructure...

The appearance of the biomarkers in body fluids like blood, urine, saliva, tears, etc. can be used for the identification of many diseases. This article aimed to summarize the studies about electrochemical biosensors with molecularly imprinted polymers as sensitive and selective layers on the electrode to detect protein-based biomarkers of such neu...

Today, optical, electrochemical, and acoustic affinity biosensors; immunosensors; and immunoanalytical systems play an important role in the detection and characterization of a number of biological substances, including viral antigens, specific antibodies, and clinically important biomarkers [...]

In this article, we report the development of an electrochemical biosensor for the determination of the SARS-CoV-2 spike protein (rS). A gold disc electrode was electrochemically modified to form the nanocrystalline gold structure on the surface. Then, it was further altered by a self-assembling monolayer based on a mixture of two alkane thiols: 11...

Nanostructured materials formed from metal oxides offer a number of advantages, such as large surface area, improved mechanical and other physical properties, as well as adjustable electronic properties that are important in the development and application of chemical sensors and biosensor design. Nanostructures are classified using the dimensions...

The application of antibody-functionalized quantum dots (QDs) in different areas has been widely described in the literature. However, a standard routine method for obtaining information on the conjugation efficiency of QDs with antibodies in terms of the interaction of the functionalized QDs with a specific antigen is still lacking. Herein, surfac...

In this study, graphite rod (GR) electrodes were electrochemically modified by dendritic gold nanostructures (DGNs) followed by immobilization of glucose oxidase (GOx) in the presence of mediator phenazine methosulfate (PMS). Modified with polyaniline (PANI) or polypyrrole (Ppy), GOx/DGNs/GR electrodes were used in glucose biosensor design. Differe...

In this research, we assessed the applicability of electrochemical sensing techniques for detecting specific antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike proteins in the blood serum of patient samples following coronavirus disease 2019 (COVID-19). Herein, screen-printed carbon electrodes (SPCE) with electrod...

This work presents the development of a membraneless single-enzyme biofuel cell powered by glucose (GBFC). The GBFC biocathode is based on a graphite rod electrode (GRE) coated with a layer of Prussian blue (PB) nanoparticles entrapped into poly(pyrrole-2-carboxylic acid) (PPCA) shell, an additional layer of PPCA, and covalently to polymer linked g...

The serologic diagnosis of coronavirus disease 2019 (COVID-19) and the evaluation of vaccination effectiveness are identified by the presence of antibodies specific to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this paper, we present the electrochemical-based biosensing technique for the detection of antibodies specific to the...

Detailed evaluations of the antigen and antibody interaction rate and strength of the immune complex formed are very important for medical and bioanalytical applications. These data are crucial for the development of sensitive and fast immunosensors suitable for continuous measurements. Therefore, combined spectroscopic ellipsometry (SE) and quartz...

The aim of this work was to compare two different conducting polymers (pyrrole and aniline) in the design of the molecularly imprinted polymer (MIP). An L-tryptophan was selected as a template molecule in such MIP-based layers deposited on the graphite electrode. Further, the MIPs with L-tryptophan imprints were applied in the design of electrochem...

Herein we report the electrochemical system for the detection of specific antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins in blood serum patient samples after coronavirus disease 2019 (COVID-19). For this purpose, the recombinant SARS-CoV-2 spike protein (SCoV2-rS) was covalently immobilised on the surface o...

In this research the molecular imprinting technology was applied for the formation of glyphosate-sensitive layer. The glyphosate imprinted conducting polymer polypyrrole (MIPpy) was deposited on a gold chip/electrode and used as an electrochemical surface plasmon resonance (ESPR) sensor. The results described in this study disclose some restriction...

Monitoring and tracking infection is required in order to reduce the spread of the coronavirus disease 2019 (COVID-19), induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To achieve this goal, the development and deployment of quick, accurate, and sensitive diagnostic methods are necessary. The determination of the SARS-CoV-2...

Fast and sensitive determination of biomarkers and biologically active compounds is very important in biomedical diagnostics, food and beverage industry, and environmental analysis. Some promising directions in analytical and bioanalytical application of conducting polymers (CPs) are discussed. Recently polypyrrole, polyaniline, polythiophene, and...

Currently, the detection of various biomarkers using immunosensors has received considerable attention from scientists. Various biomarker detection methods and different analytical signal amplification strategies offer new possibilities for the development of sensitive, selective, rapid, and low-cost immunosensors employed in biological samples. In...

The aim of this work was to compare two different conducting polymers (pyrrole and aniline) in the design of the molecularly imprinted polymer (MIP). An L-tryptophan was selected as a template molecule in such MIP-based layers deposited on the graphite electrode. Further, the MIPs with L-tryptophan imprints were applied in the design of electrochem...

Polypyrrole (Ppy) and poly(methylene blue) (PMB) heterostructure (Ppy-PMB) was electrochemically formed on the indium tin oxide (ITO) coated glass slides, which served as working electrodes. For electropolymerization, a solution containing pyrrole, methylene blue, and a saccharide (lactose, sucrose, or heparin) that served as dopant was used. The a...

Low-cost 1D plasmonic photonic structures supporting Tamm plasmon polaritons and cavity modes were employed for optical signal enhancement, modifying the commercially available quartz crystal microbalance with dissipation (QCM-D) sensor chip in a combinatorial spectroscopic ellipsometry and quartz microbalance method. The Tamm plasmon optical state...

This study describes the application of a polypyrrole-based sensor for the determination of SARS-CoV-2-S spike glycoprotein. The SARS-CoV-2-S spike glycoprotein is a spike protein of the coronavirus SARS-CoV-2 that recently caused the worldwide spread of COVID-19 disease. This study is dedicated to the development of an electrochemical determinatio...

In this study, we reported the development of Prussian blue (PB), poly(pyrrole-2-carboxylic acid) (PPCA), and glucose oxidase (GOx) biocomposite modified graphite rod (GR) electrode as a potential biocathode for single enzyme biofuel cell fuelled by glucose. In order to design the biocathode, the GR electrode was coated with a composite of PB parti...

Scanning electrochemical microscopy enhanced by electrochemical impedance spectroscopy (SEIM) was applied to detect immobilized antibodies labelled with horseradish peroxidase (Ab-HRP). The localized HRP activity was investigated by the SEIM redox competition (RC-SEIM) mode using hydrogen peroxide as a substrate and hexacyanoferrate as a redox medi...

In this research, we have demonstrated a one-step electrochemical deposition of dendritic gold nanostructures (DGNs) on a graphite rod (GR) electrode without any template, seeds, surfactants, or stabilizers. Three electrochemical methods, namely, constant potential amperometry (CPA), pulse amperometry, and differential pulse voltammetry, were used...

Biosensors for the determination of glucose concentration have a great significance in clinical diagnosis, and in the food and pharmaceutics industries. In this research, short-chain polyaniline (PANI) and polypyrrole (Ppy)-based nanocomposites with glucose oxidase (GOx) and 6 nm diameter AuNPs (AuNPs(6 nm)) were deposited on the graphite rod (GR)...

The indium tin oxide (ITO)-coated glass was used as a working electrode for electrochemical deposition of conducting polymer polypyrrole (Ppy). Before polymerization, the electrode surface was additionally modified with triethoxymethylsilane (TEMS) to provide better adhesion of polypyrrole to the surface of ITO. The polymerization of Ppy was perfor...

The review focuses on the overview of electrochemical sensors based on molecularly imprinted polymers (MIPs) for the determination of uric acid. The importance of robust and precise determination of uric acid is highlighted, a short description of the principles of molecular imprinting technology is presented, and advantages over the others affinit...

In this research, scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were applied for the evaluation of surface characteristics of electrochemical (amperometric) biosensor based on two composite structures consisting of perforated polycarbonate membrane modified by carbon-nanomaterials and glucose oxidase. T...

With the increasing importance of healthcare and clinical diagnosis, as well as the growing demand for highly sensitive analytical instruments, immunosensors have received considerable attention. In this review, electrochemical immunosensor signal amplification strategies using metal nanoparticles (MNPs) and quantum dots (Qdots) as tags are overvie...

The coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was proclaimed a global pandemic in March 2020. Reducing the dissemination rate, in particular by tracking the infected people and their contacts, is the main instrument against infection spreading. Therefore, the creation and imp...

The growing demand and need for new analytical instruments that are highly sensitive, fast, and user-friendly for detecting various analytes has opened up new possibilities and led to the development of novel sensors and biosensors. [...]

Electrochromism is the phenomenon, which is based on the change of material color when particular voltage is applied to electrochemical system. This feature is of high importance for a wide range of actuating devices such as smart windows, screens, thermal modulators and various sensors. During this research we have formed and investigated polypyrr...

During the pandemic, different methods for SARS-CoV-2 detection and COVID-19 diagnostics were developed, including antibody and antigen tests. For a better understanding of the interaction mechanism between SARS-CoV-2 virus proteins and specific antibodies, total internal reflection ellipsometry based evaluation of the interaction between SARS-CoV-...

The control of glucose concentration is a crucial factor in clinical diagnosis and the food industry. Electrochemical biosensors based on reduced graphene oxide (rGO) and conducting polymers have a high potential for practical application. A novel thermal reduction protocol of graphene oxide (GO) in the presence of malonic acid was applied for the...

The colorimetric sensors for reducing sugars based on a redox reaction between AuCl4⁻ ions and fructose, glucose, lactose, or mannose are presented. Gold nanoparticles (AuNPs) that formed at room temperature as a product of this reaction were registered using spectrophotometer. Lengthening reaction time had a positive effect on the sensitivity of t...

ZnO materials exhibit a rich family of nanostructures, which show great potential for the sensitivity improvement of optical detection systems. In this work, ∼350 nm ZnO nanowires (ZnO-NWs) were electrochemically deposited on ZnO and an indium tin oxide coated glass (ZnO-NWs/ZnO/ITO/glass) substrate. ZnO-NWs were modified with N-(3-aminopropyl)trie...

Nanocomposites based on two conducting polymers, polyaniline (PANI) and polypyrrole (Ppy), with embedded glucose oxidase (GOx) and 6 nm size gold nanoparticles (AuNPs(6nm)) or gold-nanoclusters formed from chloroaurate ions (AuCl4⁻), were synthesized by enzyme-assisted polymerization. Charge (electron) transfer in systems based on PANI/AuNPs(6nm)-G...

Enzyme-assisted synthesis of electrochemically active nanocomposite structures based on π - π conjugated polymers polyaniline (PANI) and polypyrrole (Ppy) is reported. The synthesis of both conducting polymers was induced by hydrogen peroxide, which is generated during catalytic action of glucose oxidase (GOx), and this polymerisation was performed...

Conjugated polymers (CPs) are attractive materials for use in different areas; nevertheless, the enhancement of electrochromic stability and switching time is still necessary to expand the commercialization of electrochromic devices. To our best knowledge, this is the first study demonstrating the employment of electrodeposited gold nanostructures...

This study reports non-ezymatic electrocatalytic amperometric glucose biosensor based on a graphite rod electrode (GRE) modified with biomimetic-composite consisting of Ni nanoparticles (Ni-NPs) and polypyrrole (Ppy) prepared by 1 cycle electro polymerization of pyrrole monomer (Ni-NPs/Ppy(1)/GRE). During the modification of GRE, the electropolymer...

An electrochemically synthesised porous anodic aluminium oxide (pAAO) layer has been analysed by means of spectroscopic ellipsometry. The determined thickness of the formed pAAO layer obtained from spectroscopic ellipsometry measurements and modelling was 322.75 ± 0.12 nm. The radius of the nanopores estimated from SEM images was 39 ± 5 nm and the...

A pencil graphite electrode was used for electrochemical synthesis of polypyrrole in an aqueous solution. Two key features of the polymerization were investigated: 1) the pH of the aqueous solution and 2) number of potential pulses for obtaining the polymer on the electrode. The pH values of the aqueous solutions were as follows: pH 1.0, pH 3.0 and...

Three-dimensional (3D) cell cultivation systems in vitro are promising biomodels to study the metabolic processes of healthy and diseased human heart cells. Cardiac 3D-spheroids are mimicking cell living conditions and, therefore, they can be employed to investigate processes that occur in both extra-cellular and intra-cellular environments. In thi...

In this work, a novel reagent-less amperometric glucose biosensor based on nanobiocomposite consisting of poly(1,10-phenanthroline-5,6-dione), poly(pyrrole-2-carboxylic acid) (PPCA), gold nanoparticles (AuNP) and glucose oxidase (GOx) was designed. To achieve this, the graphite rod electrode with adsorbed 1,10-phenanthroline-5,6-dione (PD) was imme...

In this study the redox activity of human myocardium‐derived mesenchymal stem cells (hmMSC) were investigated by redox‐competition (RC‐SECM) and generation‐collection (GC‐SECM) modes of scanning electrochemical microscopy (SECM), using 2‐methylnaphthalene‐1,4‐dione (menadione, MD) as a redox mediator. The redox activity of human healthy and dilated...

The modelling of protein-protein binding kinetics is important for the development of affinity-sensors and the prediction of signaling protein based drug efficiency. Therefore, in this research we have evaluated the binding kinetics of several genetically designed protein models: (i) three different ligands based on granulocyte colony-stimulating f...