Thiol-modified DNA Research Articles

Engineering DNA Nanocube SAM Scaffolds for FRET-Based Biosensing: Interfacial Characterization and Sensor Demonstration.

Decorating a gold surface with molecular-level control over the positioning of DNA probes was demonstrated using a self-assembled monolayer (SAM) of wireframe DNA nanocube structures. The DNA nanocubes were specifically adsorbed and oriented using thiol-modified DNA on one face of the cube. The DNA nanocube SAM had a uniform coverage over the gold single crystal bead electrode with a separation of 20-30 nm measured by AFM. The face of the nanocube furthest from the gold surface was designed to hybridize with two different sequences of a 50 base single-stranded DNA probe that was modified with a fluorophore. The first 20 bases were hybridized with the DNA nanocube. One of a pair of FRET fluorophores was used for each probe strand. The dimensions of the nanocube controlled the relative spacing between these fluorophores. When the DNA probes were single-stranded, a FRET signal was observed. FRET decreased to background levels when a complementary DNA target was hybridized to either probe, resulting in a turn-off sensor with little cross-talk between the individual hybridization events. Hybridization isotherms for one target gave KA = 170 pM and a detection limit <50 pM. In addition, the DNA nanocube SAM was configured to be used as a turn-on NeutrAvidin sensor using biotinylated DNA targets hybridized to each probe resulting in an increase in FRET. We show that the wireframe DNA nanocube can be an effective scaffold for preparing biosensors with controlled separation between surface-bound probes facilitating precise sensor surface design and enabling a wide range of sensing modalities with more than one signal available for correlative confirmation of the target binding.

Comparative Analysis of QCM and Electrochemical Aptasensors for SARS-CoV-2 Detection.

The rapid and accurate detection of SARS-CoV-2, particularly its spike receptor-binding domain (S-RBD), was crucial for managing the COVID-19 pandemic. This study presents the development and optimization of two types of aptasensors: quartz crystal microbalance (QCM) and electrochemical sensors, both employing thiol-modified DNA aptamers for S-RBD detection. The QCM aptasensor demonstrated exceptional sensitivity, achieved by optimizing aptamer concentration, buffer composition, and pre-treatment conditions, with a limit of detection (LOD) of 0.07 pg/mL and a linear range from 1 pg/mL to 0.1 µg/mL, and a significant frequency change was observed upon target binding. The electrochemical aptasensor, designed for rapid and efficient preparation, utilized a one-step modification process that reduced the preparation time to 2 h while maintaining high sensitivity and specificity. Electrochemical impedance spectroscopy (EIS) enabled the detection of S-RBD concentrations as low as 132 ng/mL. Both sensors exhibited high specificity, with negligible non-specific interactions observed in the presence of competing proteins. Additionally, the QCM aptasensor's functionality and stability were verified in biological fluids, indicating its potential for real-world applications. This study highlights the comparative advantages of QCM and electrochemical aptasensors in terms of preparation time, sensitivity, and specificity, offering valuable insights for the development of rapid, sensitive, and specific diagnostic tools for the detection of SARS-CoV-2 and other viruses.

Highly selective detection of deoxyribonucleic acid in living cells using RecA-green fluorescent protein-single-stranded deoxyribonucleic acid filament fluorescence resonance energy transfer probe.

A fluorescence resonance energy transfer (FRET) method was developed for double-stranded deoxyribonucleic acid (dsDNA) detection in living cells using the RecA-GFP (green fluorescent protein) fusion protein filament. In brief, the thiol-modified single-stranded DNA (ssDNA) was attached to gold nanoparticles (AuNPs); on the contrary, the prepared RecA-GFP fusion protein interacted with ssDNA. Due to the FRET between AuNPs and RecA-GFP, fluorescence of RecA-GFP fusion protein was quenched. In the presence of homologous dsDNA, homologous recombination occurred to release RecA-GFP fusion protein. Thus, the fluorescence of RecA-GFP was recovered. The dsDNA concentration was detected using fluorescence intensity of RecA-GFP. Under optimal conditions, this method could detect dsDNA activity as low as 0.015 optical density (OD) Escherichia coli cells, with a wide linear range from 0.05 to 0.9 OD cells, and the regression equation was ΔF = 342.7c + 78.9, with a linear relationship coefficient of 0.9920. Therefore, it provided a promising approach for the selective detection of dsDNA in living cells for early clinical diagnosis of genetic diseases.

Bode Phase Angle Signaling of a TB Disease Biomarker.

Tuberculosis (TB) is a worldwide burden whose total control and eradication remains a challenge due to factors including false positive/negative diagnoses associated with the poor sensitivity of the current diagnostics in immune-compromised and post-vaccinated individuals. As these factors complicate both diagnosis and treatment, the early diagnosis of TB is of pivotal importance towards reaching the universal vision of a TB-free world. Here, an aptasensor for signaling an interferon gamma (IFN-γ) TB biomarker at low levels is reported. The aptasensor was assembled through gold-thiol interactions between poly(3,4-propylenedioxythiophene), gold nanoparticles, and a thiol-modified DNA aptamer specific to IFN-γ. The aptasensor sensitively detected IFN-γ in spiked pleural fluid samples with a detection limit of 0.09 pg/mL within a linear range from 0.2 pg/mL to 1.2 pg/mL. The good performance of the reported aptasensor indicates that it holds the potential for application in the early diagnosis of, in addition to TB, various diseases associated with IFN-γ release in clinical samples.

Disposable microRNA biosensors based on dual-role polymer-dispersed silver nanowires for diagnosis of viral hemorrhagic septicemia virus infection in olive flounder

Fish farms often suffer from viral infections that can lead to mass mortality. Early detection of these infections can help prevent the spread of the infection. microRNA (miRNA) is a new biomarker for detecting early infections in farmed olive flounder. We developed a disposable miRNA biosensor by utilizing screen-printed carbon electrodes with polymer-dispersed silver nanowires (P-AgNWs). The target miRNA here was miR-15b-5p, which is considered a specific candidate for detecting viral hemorrhagic septicemia virus (VHSV) infection in fish. A capture probe (CP), a thiol-modified DNA oligonucleotide chain complementary to the miR-15b-5p, was immobilized on the surface of P-AgNWs. While the hybridization of miR-15b-5p with the CP is monitored using square wave voltammetry techniques based on the specific binding of methylene blue (MB) to the DNA-RNA hybrid formed between CP and the miR-15b-5p. The miRNA biosensor demonstrated a wide linear response range of 1.0–100 fM under optimum conditions with a low detection limit of 0.70 fM. According to a series of voltammetric experiments, the approach demonstrated acceptable precision and sensitivity for determining the miR-15b-5p levels in olive flounder infected with VHSV.

Label-free electrochemical biosensor with magnetically induced self-assembly for the detection of cancer antigen 125

Magnetically induced self-assembly technology was used to construct a label-free electrochemical biosensor based on magnetic Mg0.5Cu0.5Fe2O4-Au nanocomposites for the sensitive detection of cancer antigen 125 (CA125). To aim for this, Mg0.5Cu0.5Fe2O4 nanoparticles were first prepared via the rapid combustion process. The average diameter of the nanoparticles calcined at 800 °C with the absolute ethanol volume of 20 mL was about 169.3 nm. Then Au was used for the surface modification by NaBH4 reduction reaction approach. The magnetic glassy carbon electrode (MGCE) was modified by Mg0.5Cu0.5Fe2O4-Au via a magnetic induction self-assembly process. The reduced thiol-modified single-stranded DNA was attached to the Mg0.5Cu0.5Fe2O4-Au nanocomposites by Au-S bonds without any coupling agent. CA125 antigen was grabbed directly by its aptamer DNA due to its specific identification with the aptamer. Finally, the modified electrodes were blocked with BSA and then characterized. Finally, DPV analysis was used for CA125 detection, the novel fabricated biosensor demonstrated good detection properties for CA125 with a linear range of 5–125 U/mL and a detection limit of 4.4 U/mL. The results showed that the aptamer sensor had good specificity, repeatability, and stability. The feasibility of our sensor for the determination of CA125 was also demonstrated by measuring CA125 levels in serum using the Roche gold-standard instrument of the People’s Hospital of Danyang as the reference value. The recoveries of real serum samples were 94.65–101.71%, and RSDs were 1.26–4.65%. Moreover, the surface of the electrode could be cleaned and reused by magnetic separation, greatly reducing the cost and providing the possibility for a point-of-care test (POCT). This work demonstrated a new strategy for integrating both nanostructures and biocompatibility to build advanced cancer biomarker sensors with wide applications.

SERS-fluorescence dual-mode nanoprobe for the detection and imaging of Bax mRNA during apoptosis.

Adual-mode nanoprobe was constructed to detect Bax messenger RNA (mRNA), consisting of gold nanotriangles (AuNTs), a Cy5-modified recognition sequence, and a thiol-modified DNA sequence. Bax mRNA is one of the key pro-apoptotic factors in the apoptosis pathway. Raman enhancement and fluorescence quenching of the signal group Cy5 were performed using AuNTs as substrates. The thiol-modified nucleic acid chain is partially complementary to the Cy5-modified nucleic acid chain to form a double strand and is linked to the AuNTs by the Au-S bond. When Bax mRNA is present, the Cy5-modified strand specifically binds to it to form a more stable duplex, making Cy5 far away from AuNTs, and SERS signal is weakened while fluorescence signal is enhanced. The nanoprobe can be used for the quantitative detection of Bax mRNA in vitro. Combined with the high sensitivity of SERS and the visualization of fluorescence, this method has good specificity and can be used for in situ imaging and dynamic monitoring of Bax mRNA during deoxynivalenol (DON) toxin-induced apoptosis of HepG2 cells. DON plays a pathogenic role mainly by inducing cell apoptosis. Theresults confirmed that the proposed dual-mode nanoprobe has good versatility in various human cell lines.

Design of a new electrochemical aptasensor based on screen printed carbon electrode modified with gold nanoparticles for the detection of fumonisin B1 in maize flour

A new aptasensor for detecting fumonisin B1 (FB1) in the maize samples was developed based on DNA- aptamer recognition and electrochemical technique. A thiol-modified single-stranded DNA (ss-HSDNA) was immobilized on a screen printed carbon electrode (SPCE) electrodeposited by gold nanoparticles (AuNPs). The morphology and structure of SPCE and AuNPs/SPCE were evaluated via scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The SEM results demonstrated that the SPCE had a flat sheet-like structure, and the AuNPs were homogeneously electrodeposited on the SPCE. Cyclic voltammetry (CV) experiments in the [Fe(CN)6]− 3/− 4 solution were conducted to investigate each step of electrode modification as well as aptasensor performance. Aptamer-FB1 interaction prevented the electron transfer permitting the determination of FB1 in the range of 0.5–500 ng/mL with a low detection limit (0.14 ng/mL). The designed aptasensor was also shown high selectivity, acceptable repeatability and reproducibility, good long-term stability, and excellent recovery. Furthermore, there was a strong correlation between the findings achieved via the designed aptasensor and high performance liquid chromatography (HPLC). Therefore, a simple construction process and satisfactory electrochemical performance of the proposed aptasensor have a great potential for the detection of FB1 in maize samples.

Fluorogenic response from DNA templated micrometer range self-assembled gold nanorod.

Plasmonic gold nanorod (AuNR) on a macromolecular matrix exhibits an end-to-end (ETE) long-range self-assembly (AuNR)n with n > 100. In the case of small molecules as a template, the pre-synthesized macromolecular matrix is missing and this brings a synthetic challenge in directed long-range assembly of AuNR. Self-assembly with thiol-modified small DNA and AuNR shows a much short-range ETE assembly with n < 25 via a simple evaporation technique on a solid surface. In this study, the introduction of two short amine modified probe DNAs (∼2.5 nm) and one 22-mer complementary single strand (ss)-DNA template (∼7 nm) show the long-range ETE self-assembly of (AuNR)n with n > 130. In the solution state, the zigzag arrangement within the assembled structure controls the typical change in the absorption behavior for (AuNR)n ETE assembly. The formation of this long-range ETE self-assembly in a solution state was verified from the combined effect of fluorescence resonance energy transfer (FRET) and hotspot-induced fluorescence enhancement. The probe DNAs and templated DNA concentration on fluorescence enhancement have been varied to monitor the effect of (AuNR)n with n = ∼5-130 in ETE self-assembly. Primarily quenched FRET acceptor in the presence of AuNR decisively exhibits remarkable fluorogenic response in ETE self-assembly with maximum n value. Although the FRET efficiencies among the fluorophores are comparable, the fluorogenic boost in ETE AuNR is due to the increased number of intrinsic navigated hotspots in these assemblies.

Rapid and sensitive detection of box turtles using an electrochemical DNA biosensor based on a gold/graphene nanocomposite.

The Southeast Asian box turtle, Cuora amboinensis, is an ecologically important endangered species which needs an onsite monitoring device to protect it from extinction. An electrochemical DNA biosensor was developed to detect the C. amboinensis mitochondrial cytochrome b gene based on an in silico designed probe using bioinformatics tools, and it was also validated in wet-lab experiments. As a detection platform, a screen-printed carbon electrode (SPCE) enhanced with a nanocomposite containing gold nanoparticles and graphene was used. The morphology of the nanoparticles was analysed by field-emission scanning electron microscopy and structural characteristics were analysed by using energy-dispersive X-ray, UV-vis, and Fourier-transform infrared spectroscopy. The electrochemical characteristics of the modified electrodes were studied by cyclic voltammetry, differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy. The thiol-modified synthetic DNA probe was immobilised on modified SPCEs to facilitate hybridisation with the reverse complementary DNA. The turtle DNA was distinguished based on hybridisation-induced electrochemical change in the presence of methylene blue compared to their mismatches, noncomplementary, and nontarget species DNA measured by DPV. The developed biosensor exhibited a selective response towards reverse complementary DNAs and was able to discriminate turtles from other species. The modified electrode displayed good linearity for reverse complementary DNAs in the range of 1 × 10-11-5 × 10-6 M with a limit of detection of 0.85 × 10-12 M. This indicates that the proposed biosensor has the potential to be applied for the detection of real turtle species.

DNA Nanostructure-Guided Plasmon Coupling Architectures

DNA Nanostructure-Guided Plasmon Coupling Architectures

Noncanonical DNA Cleavage by BamHI Endonuclease in Laterally Confined DNA Monolayers Is a Step Function of DNA Density and Sequence.

Cleavage of DNA at noncanonical recognition sequences by restriction endonucleases (star activity) in bulk solution can be promoted by global experimental parameters, including enzyme or substrate concentration, temperature, pH, or buffer composition. To study the effect of nanoscale confinement on the noncanonical behaviour of BamHI, which cleaves a single unique sequence of 6 bp, we used AFM nanografting to generate laterally confined DNA monolayers (LCDM) at different densities, either in the form of small patches, several microns in width, or complete monolayers of thiol-modified DNA on a gold surface. We focused on two 44-bp DNAs, each containing a noncanonical BamHI site differing by 2 bp from the cognate recognition sequence. Topographic AFM imaging was used to monitor end-point reactions by measuring the decrease in the LCDM height with respect to the surrounding reference surface. At low DNA densities, BamHI efficiently cleaves only its cognate sequence while at intermediate DNA densities, noncanonical sequence cleavage occurs, and can be controlled in a stepwise (on/off) fashion by varying the DNA density and restriction site sequence. This study shows that endonuclease action on noncanonical sites in confined nanoarchitectures can be modulated by varying local physical parameters, independent of global chemical parameters.

A new ratiometric electrochemical aptasensor for the sensitive detection of carcinoembryonic antigen based on exonuclease I-assisted target recycling and hybridization chain reaction amplification strategy

In this work, a novel ratiometric electrochemical aptasensor was designed on the basis of dual-amplification mechanism by using exonuclease I (Exo I)-assisted target recycling and hybridization chain reaction (HCR). The thiol-modified capture DNA (Cp-DNA) was fixed on the surface of the gold electrode (AuE) modified with gold nanoparticles (AuNPs) through Au-S bonds. The ferrocene (Fc)-labeled DNA (Fc-DNA) hybridized with Cp-DNA to form Fc-DNA/Cp-DNA duplex. The presence of carcinoembryonic antigen (CEA) led to the dissociation of Fc-DNA from Fc-DNA/Cp-DNA duplex and initiated Exo Ⅰ-assisted target recycling to digest Fc-DNA, so numerous Fc left away from the electrode surface and resulting in the “signal off” of Fc. Moreover, Cp-DNA was exposed to bind trigger DNA and initiate HCR with the presence of H1 and H2 probes, resulting in the intercalating of numerous methylene blue (MB) molecules and the “signal-on” of MB. This dual signal strategy significantly amplified the decrease of Fc signal and the increase of MB signal, achieving a linear range of 1 pg mL−1 to 100 ng mL−1 with a detection limit of 0.479 pg mL−1 (S/N = 3). Besides, the developed aptasensor exhibited high specificity, good stability and reproducibility. More importantly, the aptasensor had been applied in detection of CEA in diluted human serum and displayed satisfactory anti-interference property. By changing the corresponding aptamer sequences, the designed strategy can be employed to detect other targets, which holds promising application in clinical diagnosis.

A pretreatment-free electrical capacitance biosensor for exosome detection in undiluted serum

The exosome is considered a useful biomarker for the early diagnosis of cancer. However, pretreatment of samples used in diagnosis is time-consuming. Herein, we fabricated a capacitance-based electrical biosensor that requires no pretreatment of the sample; it is composed of a DNA aptamer/molybdenum disulfide (MoS2) heterolayer on an interdigitated micro-gap electrode (IDMGE)/printed circuit board (PCB) system for detecting exosomes in an undiluted serum sample. The DNA aptamer detects the CD63 protein on the exosome as the biomarker, while the MoS2 nanoparticle enhances electrical sensitivity. In this study, for the first time, the IDMGE system was used to amplify the electrical signal efficiently for exosome detection. The IDMGE amplifies the capacitance signal as the gap between electrodes decreases, making it easy to detect the target by utilizing the heightened sensitivity. Moreover, it is possible to immobilize a bio-probe more efficiently than with an electrical sensitivity–enhancing electrode with the same area. The thiol-modified (SH-) CD63 DNA aptamer was introduced as the bio-probe that selectively binds to the CD63 protein on the exosome surface. The capacitance signal from the IDMGE electrical sensor increased linearly with the increase in the concentration of exosomes in human serum expressed on a logarithmic scale, the detection limit being 2192.6 exosomes/mL. The proposed biosensor can detect exosomes in undiluted human serum with high selectivity and sensitivity. A blind test was also carried out to test the reliability of the biosensor. The capacitance-based electrical biosensor thus offers a new platform for cancer diagnosis in the future.

Redox Buffering Effects in Potentiometric Detection of DNA Using Thiol-Modified Gold Electrodes.

Label-free potentiometric detection of DNA molecules using a field-effect transistor (FET) with a gold gate offers an electrical sensing platform for rapid, straightforward, and inexpensive analyses of nucleic acid samples. To induce DNA hybridization on the FET sensor surface to enable potentiometric detection, probe DNA that is complementary to the target DNA has to be immobilized on the FET gate surface. A common method for probe DNA functionalization is based on thiol–gold chemistry, immobilizing thiol-modified probe DNA on a gold gate with thiol–gold bonds. A self-assembled monolayer (SAM), based on the same thiol–gold chemistry, is also needed to passivate the rest of the gold gate surface to prevent non-specific adsorption and to enable favorable steric configuration of the probe DNA. Herein, the applicability of such FET-based potentiometric DNA sensing was carefully investigated, using a silicon nanoribbon FET with a gold-sensing gate modified with thiol–gold chemistry. We discover that the potential of the gold-sensing electrode is determined by the mixed potential of the gold–thiol and gold–oxygen redox interactions. This mixed potential gives rise to a redox buffer effect which buffers the change in the surface charge induced by the DNA hybridization, thus suppressing the potentiometric signal. Analogous redox buffer effects may also be present for other types of potentiometric detections of biomarkers based on thiol–gold chemistry.

Electrochemical Impedimetric Study of Non-Watson-Crick Base Pairs of DNA.

Electrochemical impedance spectroscopy (EIS) was used to detect non-Watson-Crick base pairs of DNA. Thiol-modified DNA as a probe and mercaptohexanol (MCH) were co-immobilized to form a DNA/MCH mixed self-assembled monolayer on a gold electrode surface and then hybridized with complementary DNAs. The DNA layers were measured by the EIS method and interpreted by equivalent circuits. Every terminal base mismatch of the DNA duplex brought about an increase in the charge-transfer resistance (Rct), unlike the case with a fully matched DNA duplex. The value of Rct was highly sensitive to the number of base mismatches for both unpaired and overhang DNA at the terminal. For internal base mismatches, however, no significant increase in Rct was observed. These experimental results proved that the charge transfer of redox molecules to the electrode surface is largely hindered by an end fraying motion due to base unpairing and dangling overhang. EIS was able to detect these steric properties of DNA strands. Furthermore, an electrode modified with G-quadruplex (G4) DNA demonstrated the influences of bulkiness and loop structure on the accessibility of the redox probe to the electrode.

Evanescent wave cavity ring-down spectroscopy based interfacial sensing of prostate-specific antigen

Evanescent wave cavity ring-down spectroscopy (EW-CRDS) is implemented as a sensitive probe for the detection of prostate-specific antigen (PSA) with a sub-femtomolar limit of detection (LOD). PSA, a glycoprotein, is an essential biomarker for scrutinizing prostate cancer. Gold nanoparticles (Au NPs) were synthesized to serve as a sensitive reporter which are strongly bound to the thiol-modified target DNA. While Au NPs/target DNA flowed via a microfluidic channel, the target DNA may hybridize with aptamer DNA immobilized on the silica surface. Thus, the adsorption kinetics of hybridization between the Au NPs/target and aptamer was measured with interfacial optical absorbance using Langmuir fit of adsorption equilibrium. The LOD of Au NPs/PSA sensor reaches 0.54 fM signifying tremendous detecting proficiency of EW-CRDS. The evanescent wave is highly sensitive for small changes in absorption of material leading to a significant variation of the ring-down time constant. Moreover, Au NPs possess inherent excellent surface plasmonic properties that made them a promising probe material for the interfacial sensing process. To assess the significance of probe material, 5-carboxytetramethylrhodamine was substituted as a reporter to determine sensing kinetics, showing LOD of 99.1 fM. EW-CRDS approach could be used as an efficient sensing technique for the examination of malignant diseases and many biological reactions.

Amperometric aptasensor for carcinoembryonic antigen based on a reduced graphene oxide/gold nanoparticles modified electrode

Abstract We report the construction of a novel amperometric aptasensor for the highly specific detection of carcinoembryonic antigen (CEA). The sensing interface was assembled by electrodeposition of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) on a carbon screen-printed electrode (SPE) and further functionalization with a biotin and thiol-modified anti-CEA DNA hairpin aptamer. The sensing approach relies on the specific recognition of CEA by the folded aptamer, causing unfolding of the DNA hairpin structure and unmasking the biotin residues at the aptamer chain. Further incubation with a sptreptavidin-peroxidase conjugate allows the amperometric detection of the cancer biomarker. This aptasensor was able to detect CEA in the broad range from 20 pg mL−1 to 2 μg mL−1 (112 fM–11 μM) with a detection limit of 16 pg mL−1 (90 fM). The aptasensor also showed high reproducibility, specificity and stability, and was successfully validated in diluted human serum samples.

Graphene Templated DNA Arrays and Biotin-Streptavidin Sensitive Bio-Transistors Patterned by Dynamic Self-Assembly of Polymeric Films Confined within a Roll-on-Plate Geometry.

Patterning of surfaces with a simple strategy provides insights into the functional interfaces by suitable modification of the surface by novel techniques. Especially, highly ordered structural topographies and chemical features from the wide range of interfaces have been considered as important characteristics to understand the complex relationship between the surface chemistries and biological systems. Here, we report a simple fabrication method to create patterned surfaces over large areas using evaporative self-assembly that is designed to produce a sacrificial template and lithographic etch masks of polymeric stripe patterns, ranging from micrometer to nanoscale. By facilitating a roll-on-plate geometry, the periodically patterned surface structures formed by repetitive slip-stick motions were thoroughly examined to be used for the deposition of the Au nanoparticles decorated graphene oxide (i.e., AuNPs, ~21 nm) and the formation of conductive graphene channels. The fluorescently labeled thiol-modified DNA was applied on the patterned arrays of graphene oxide (GO)/AuNPs, and biotin-streptavidin sensitive devices built with graphene-based transistors (GFETs, effective mobility of ~320 cm2 V−1 s−1) were demonstrated as examples of the platform for the next-generation biosensors with the high sensing response up to ~1 nM of target analyte (i.e., streptavidin). Our strategy suggests that the stripe patterned arrays of polymer films as sacrificial templates can be a simple route to creating highly sensitive biointerfaces and highlighting the development of new chemically patterned surfaces composed of graphene-based nanomaterials.

DNA-Biofunctionalization of CTAC-Capped Gold Nanocubes.

Clinical diagnostics and disease control are fields that strongly depend on technologies for rapid, sensitive, and selective detection of biological or chemical analytes. Nanoparticles have become an integral part in various biomedical detection devices and nanotherapeutics. An increasing focus is laid on gold nanoparticles as they express less cytotoxicity, high stability, and hold unique optical properties with the ability of signal transduction of biological recognition events with enhanced analytical performance. Strong electromagnetic field enhancements can be found in close proximity to the nanoparticle that can be exploited to enhance signals for e.g., metal-enhanced fluorescence or Raman spectroscopy. Even stronger field enhancements can be achieved with sharp-edged nanoparticles, which are synthesized with the help of facet blocking agents, such as cetyltrimethylammonium bromide/chloride (CTAB/CTAC). However, chemical modification of the nanoparticle surface is necessary to reduce the particle’s cytotoxicity, stabilize it against aggregation, and to bioconjugate it with biomolecules to increase its biocompatibility and/or specificity for analytical applications. Here, a reliable two-step protocol following a ligand exchange with bis (p-sulfonatophenyl) phenyl phosphine (BSPP) as the intermediate capping-agent is demonstrated, which results in the reliable biofunctionalization of CTAC-capped gold nanocubes with thiol-modified DNA. The functionalized nanocubes have been characterized regarding their electric potential, plasmonic properties, and stability against high concentrations of NaCl and MgCl2.