Aptamer-Based Carboxyl-Terminated Nanocrystalline Diamond Sensing Arrays for Adenosine Triphosphate Detection

At a Glance

Metadata	Details
Publication Date	2017-07-21
Journal	Sensors
Authors	Evi Suaebah, Takuro Naramura, Miho Myodo, Masataka Hasegawa, Shuichi Shoji
Institutions	Waseda University, Photonics Electronics Technology Research Association
Citations	8
Analysis	Full AI Review Included

6CCVD Technical Analysis & Product Documentation: Aptamer-Based Nanocrystalline Diamond Biosensors

This documentation analyzes the key technical findings of the paper “Aptamer-Based Carboxyl-Terminated Nanocrystalline Diamond Sensing Arrays for Adenosine Triphosphate Detection” and maps experimental requirements to 6CCVD’s advanced Material-Process-Device (MPD) capabilities, positioning 6CCVD as the premier supplier for researchers targeting high-stability diamond biosensing platforms.

Executive Summary

The research successfully demonstrates a high-sensitivity, reusable, label-free biosensor for Adenosine Triphosphate (ATP) detection leveraging Nanocrystalline Diamond (NCD) functionalization.

Core Achievement: Successful fabrication of NCD-based aptasensors detecting ATP via dual fluorescence signal decrease and field-effect transistor (FET) threshold voltage shift.
Key Functionalization: Direct carboxyl (-COOH) termination achieved on the NCD surface using Vacuum Ultraviolet (VUV) excimer laser irradiation in an oxygen atmosphere.
Performance Metrics: Fluorescence detection showed a clear signal decrease (up to 66%) upon ATP binding and aptamer release. FET characteristics measured a 7.28 mV negative shift in threshold voltage.
Material Stability: The carboxyl-modified NCD provided sufficient stability for supporting DNA covalent immobilization, maintaining activity and reusability over seven cycles across two weeks.
Passivation Strategy: Fluorine (F) termination using C₃F₈ plasma was effectively used as a low-noise background passivation layer to minimize non-specific adsorption outside the sensing dots.
Applicable Range: The sensor reliably detected ATP across a concentration range from 10 µM (lower limit) to 1 mM (upper limit).

Technical Specifications

The critical parameters and performance metrics extracted from the biosensor fabrication and testing process are summarized below.

Parameter	Value	Unit	Context
Material Substrate	Nanocrystalline Diamond (NCD)	N/A	Grown on Silicon (Si) substrate
CVD Growth Temp	~700	°C	For initial CH₃ termination (30 min)
CVD Power	1.2	kW	Microwave Plasma CVD system
CVD Pressure	50	Torr	During CH₃ termination step
CH₄ Concentration	3	%	3 sccm CH₄ diluted in 297 sccm H₂
VUV Wavelength	172	nm	Xenon excimer lamp for COOH termination
VUV O₂ Pressure	3 x 10⁴	Pa	During VUV irradiation (45 min)
Carboxyl Coverage	>1	% Area	Determined by C 1s XPS analysis
Pattern Geometry	20 µm Diameter Dots	µm	Separated by 20 µm gaps
Channel Gate Width	500	µm	For Solution Gate FET (SGFET) device
Metalization Layer	150	nm	Gold (Au) film deposited by evaporation
ATP Detection Range	10 µM to 1	mM	Effective concentration range
Fluorescence Signal Decrease	66	%	Measured relative to hybridization intensity
Threshold Voltage Shift	7.28	mV	Negative shift indicating ATP detection
Sensor Reusability	7	Cycles	Stable performance over two weeks

Key Methodologies

The following ordered sequence outlines the critical synthesis and functionalization steps required to replicate or advance this diamond-based biosensor platform.

NCD Synthesis and Initial Termination: NCD films were grown on silicon using MPCVD. An initial 30-minute exposure to 3% CH₄ in H₂ plasma at 50 Torr and 1.2 kW power resulted in partial methyl (CH₃) termination.
Carboxyl Termination (Patterned Area): The CH₃-terminated NCD surface underwent direct functionalization via exposure to a Xenon excimer laser (172 nm, 20 W) for 45 minutes in a pure oxygen atmosphere (3 x 10⁴ Pa). This produced the carboxyl (-COOH) groups necessary for subsequent DNA immobilization.
Gold Metalization: A 150 nm thick Gold (Au) layer was deposited onto the NCD surface via a metal mask (for FET) or blanket deposition (for patterning).
Photolithographic Patterning: Standard photolithography was used to create the 20 µm dot patterns, followed by gold etching using KI/I₂ solution to define the dot areas.
Fluorine Passivation (Background Area): The regions outside the active dot patterns were exposed to C₃F₈ plasma (Reactive Ion Etching, RIE) for 15 seconds to create a fluorine-terminated background, serving as a non-specific adsorption passivation layer.
Biomolecule Activation and Immobilization: The carboxyl-terminated regions were activated using N-HydroxySuccinimide/carbodiimide hydrochloride (NHS/EDC) chemistry. Amine-modified supporting DNA (21-mer) was covalently immobilized at 38 °C for 2 hours.
Aptamer Hybridization and Detection: Fluorescently labeled DNA aptamers (Cy-5) were hybridized to the supporting DNA at 25 °C. ATP detection was performed by observing the aptamer release (indicated by fluorescence signal decrease and FET threshold shift).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and precision engineering services necessary to replicate, scale, and optimize this high-performance biosensing platform.

Applicable Materials

To achieve the high stability and specific functionalization required for this aptasensor, 6CCVD recommends highly uniform Polycrystalline Diamond (PCD) films suitable for Nanocrystalline Diamond (NCD) synthesis.

Research Requirement	6CCVD Solution	Material Specification
NCD Precursor Film	Fine-Grained Polycrystalline Diamond (PCD)	High-uniformity, low internal stress films optimized for post-growth etching/functionalization (up to 125mm).
Enhanced Sensitivity	Optical Grade SCD (0.1µm - 500µm)	For applications requiring superior crystallinity and lower surface defect density compared to NCD for optimized electrical performance in SGFETs.
Electrochemical Devices	Heavy Boron-Doped Diamond (BDD)	Provides the robust, stable, and wide potential window required for electrochemical detection methods (alternatives to fluorescence/FET).

Customization Potential

The success of this research hinges on precise dimensional control, selective metalization, and specific surface terminations—all areas of core expertise for 6CCVD.

Precision Metalization Services: The paper utilized 150 nm of Gold (Au) for electrodes. 6CCVD provides in-house thin-film deposition and patterning using: Au, Pt, Pd, Ti, W, and Cu. We can deposit high-purity metal stacks (e.g., Ti/Pt/Au adhesion layers) tailored for optimal electrical contact and biocompatibility in FET devices.
Patterning and Dimensions: The study used 20 µm dot arrays. 6CCVD offers precision laser cutting, dicing, and custom patterning for features down to the micron scale, enabling scalable array fabrication on wafers up to 125 mm.
Surface Preparation Expertise: While the paper used VUV/RIE for functionalization (COOH/F termination), 6CCVD can supply materials pre-processed with specific H- or O-terminations, or consult on advanced methods to ensure optimal surface chemistry for downstream VUV treatment and biomolecule immobilization.
Surface Quality: 6CCVD guarantees ultra-low roughness polishing, offering Ra < 1nm for SCD and Ra < 5nm for inch-size PCD materials, ensuring minimal non-specific adsorption and high stability essential for sensitive biosensors.

Engineering Support

6CCVD’s in-house team of PhD material scientists and technical engineers specialize in optimizing CVD diamond properties for cutting-edge applications. We provide expert consultation on:

Process Transfer: Assisting researchers in translating lab-scale functionalization techniques (VUV, RIE) onto high-quality, large-area 6CCVD substrates.
SGFET Optimization: Material selection and thickness control (SCD or PCD thickness 0.1 µm to 500 µm) to maximize carrier mobility and signal-to-noise ratio in ATP detection biosensors and general SGFET designs.
Packaging Solutions: Guidance on electrode integration, epoxy masking, and overall device packaging stability, crucial for long-term reusability demonstrated in this Nanocrystalline Diamond Aptasensor.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Here, we propose simple diamond functionalization by carboxyl termination for adenosine triphosphate (ATP) detection by an aptamer. The high-sensitivity label-free aptamer sensor for ATP detection was fabricated on nanocrystalline diamond (NCD). Carboxyl termination of the NCD surface by vacuum ultraviolet excimer laser and fluorine termination of the background region as a passivated layer were investigated by X-ray photoelectron spectroscopy. Single strand DNA (amide modification) was used as the supporting biomolecule to immobilize into the diamond surface via carboxyl termination and become a double strand with aptamer. ATP detection by aptamer was observed as a 66% fluorescence signal intensity decrease of the hybridization intensity signal. The sensor operation was also investigated by the field-effect characteristics. The shift of the drain current-drain voltage characteristics was used as the indicator for detection of ATP. From the field-effect characteristics, the shift of the drain current-drain voltage was observed in the negative direction. The negative charge direction shows that the aptamer is capable of detecting ATP. The ability of the sensor to detect ATP was investigated by fabricating a field-effect transistor on the modified NCD surface.

Tech Support

Original Source

DOI: https://doi.org/10.3390/s17071686

References

2005 - FluMag-SELEX as an advantageous method for DNA aptamer selection [Crossref]
2011 - Aptamer based Fluorescent Biosensor [Crossref]
2013 - Nucleic acid aptamers as high affinity ligands in biotechnology and biosensorics
2011 - Aptamer modules as sensors and detectors [Crossref]
2014 - Aptamer-based biosensors for biomedical diagnostics [Crossref]
2008 - ATP detection using a label-free DNA aptamer and a cationic tetrahedralfluorene [Crossref]
2011 - Diamond electrolyte solution gate FETs for DNA and protein sensors using DNA/RNA aptamers [Crossref]
2017 - Diamond nanostructures for drug delivery, bioimaging, and biosensing [Crossref]
2007 - Diamond for bio-sensor applications [Crossref]