In Situ Measurement of Intracellular Thermal Conductivity Using Diamond Nanoparticle

At a Glance

Metadata	Details
Publication Date	2022-01-01
Journal	Seibutsu Butsuri
Authors	Shingo Sotoma
Institutions	The University of Osaka
Analysis	Full AI Review Included

Technical Documentation & Analysis: Intracellular Thermal Conductivity Measurement Using Diamond Nanoparticles

This document analyzes the research detailing the use of Fluorescent Nanodiamonds (FND) containing Nitrogen-Vacancy (NV) centers for high-resolution, in situ measurement of intracellular thermal conductivity. This application highlights the critical role of high-quality CVD diamond materials in advanced quantum sensing and bio-thermal research.

Executive Summary

The following points summarize the core technical achievements and commercial relevance of the research:

Novel Hybrid Sensor: Development of a FND-Polydopamine (PDA) hybrid nanosystem, where the PDA acts as a photo-thermal nano-heater and the FND NV center functions as a robust quantum temperature sensor.
Quantum Sensing Precision: Achieved high-resolution temperature measurement (0.1 °C) using the Optically Detected Magnetic Resonance (ODMR) technique, leveraging the temperature-dependent shift of the NV center’s zero-field splitting.
Intracellular Measurement: Successfully introduced the FND-PDA system into HeLa and MCF-7 cells to measure localized thermal conductivity in situ.
Significant Finding: Measured intracellular thermal conductivity was approximately 0.11 W/mK, roughly six times lower than water, and comparable to lipids or proteins (0.1-0.2 W/mK).
Thermal Heterogeneity: The results demonstrated significant spatial variability (large standard deviation) in local thermal conductivity within the cell, suggesting thermal heterogeneity impacts biological function.
Material Robustness: The diamond NV center proved highly resistant to the complex cellular environment (pH, viscosity, molecular interactions), validating its suitability for biological quantum sensing.

Technical Specifications

The following hard data points were extracted from the research paper, detailing the performance and results of the FND-PDA system.

Parameter	Value	Unit	Context
Temperature Sensing Resolution (ODMR)	0.1	°C	High-precision quantum sensing method
Temperature Sensing Resolution (All-optical)	0.5	°C	Based on Zero Phonon Line (ZPL) shift
ZPL Shift Sensitivity	0.015	nm/K^-1	Required for all-optical temperature measurement
Intracellular Thermal Conductivity (HeLa/MCF-7)	0.11	W/mK	Average measured value, significantly lower than water
Measured Temperature Rise (HeLa)	3.0 ± 1.0	°C	Local heating induced by PDA nano-heater
Measured Temperature Rise (MCF-7)	2.9 ± 0.8	°C	Local heating induced by PDA nano-heater
Validation Medium: Water Thermal Conductivity	0.61	W/mK	Confirmed accuracy of the measurement principle
Validation Medium: Air Thermal Conductivity	0.026	W/mK	Confirmed accuracy of the measurement principle
Validation Medium: Mineral Oil Thermal Conductivity	0.135	W/mK	Confirmed accuracy of the measurement principle

Key Methodologies

The experiment relied on advanced material synthesis and quantum measurement techniques to achieve localized thermal sensing:

Hybrid Nanosystem Synthesis: Fluorescent Nanodiamonds (FND) containing NV centers were synthesized and subsequently coated with Polydopamine (PDA) to create the FND-PDA hybrid sensor.
Dual Functionality: The PDA coating acts as a photo-thermal conversion material (nano-heater) when irradiated, while the NV center within the FND acts as the temperature sensor.
Thermal Measurement Principle: The temperature rise of the FND-PDA system is inversely proportional to the thermal conductivity of the surrounding medium. Faster heat dissipation (high conductivity) results in a smaller temperature rise.
High-Resolution Readout: The Optically Detected Magnetic Resonance (ODMR) technique was employed to monitor the temperature-dependent shift of the NV center’s zero-field splitting (D), providing 0.1 °C resolution.
Cellular Integration: FND-PDA nanoparticles were successfully introduced into HeLa and MCF-7 cells, and their location was confirmed using confocal microscopy.
Validation: The system was rigorously validated by measuring the known thermal conductivities of reference media (air, water, mineral oil) before application in biological systems.

6CCVD Solutions & Capabilities

This research demonstrates the immense potential of diamond-based quantum sensors. While the paper focused on nanodiamonds, scaling this technology for integrated quantum devices, high-throughput screening, or advanced microfluidic platforms requires high-quality, bulk CVD diamond, a core specialty of 6CCVD.

Applicable Materials

To replicate or extend this research into integrated quantum devices, 6CCVD recommends the following materials:

Optical Grade Single Crystal Diamond (SCD): Essential for creating high-coherence NV centers. 6CCVD provides high-purity SCD wafers with extremely low background nitrogen, crucial for maximizing NV center stability and coherence time required for high-precision quantum sensing (ODMR).
High-Purity Polycrystalline Diamond (PCD): For applications requiring large area coverage or integration into complex microfluidic systems, 6CCVD offers PCD plates up to 125 mm in diameter, providing a robust, thermally stable platform.
Boron-Doped Diamond (BDD): For related electrochemical or heating applications, BDD substrates offer tunable conductivity and excellent chemical inertness, potentially serving as integrated resistive heaters or electrodes in future thermal sensing setups.

Customization Potential

6CCVD’s advanced manufacturing capabilities directly address the needs of quantum and bio-sensing engineers:

Research Requirement / Scaling Need	6CCVD Customization Capability
Integrated Quantum Chips	Custom Dimensions & Thickness: We supply SCD and PCD plates up to 125 mm (PCD) and custom SCD sizes up to 10x10 mm, with precise thickness control from 0.1 µm to 500 µm, ideal for micro-machining and integration.
Microwave Delivery for ODMR	Precision Metalization Services: ODMR requires efficient microwave delivery. 6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for depositing high-quality microwave striplines or contact pads directly onto the diamond surface.
Surface Functionalization (e.g., PDA Coating)	Ultra-Low Roughness Polishing: Our SCD wafers are polished to achieve surface roughness Ra < 1 nm, ensuring an atomically smooth surface critical for reproducible surface chemistry, functionalization (like the PDA coating), and minimizing optical scattering.
Substrate Integration	Thick Substrates: We provide diamond substrates up to 10 mm thick for robust mechanical support in high-pressure or high-power experimental setups.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing diamond material parameters for quantum applications. We can assist researchers in:

Material Selection: Determining the optimal crystal orientation, nitrogen concentration, and defect engineering strategy to maximize NV center yield and coherence for similar Bio-thermal Quantum Sensing projects.
Device Integration: Providing consultation on metalization schemes and laser cutting services necessary to integrate diamond wafers into complex ODMR or microfluidic systems.
Global Logistics: Offering reliable global shipping (DDU default, DDP available) to ensure rapid delivery of custom materials worldwide.

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

View Original Abstract

ナノ温度計として機能する蛍光性ナノダイヤモンドとナノヒーターとして機能するポリドーパミンを融合させることによって，ナノ領域の熱伝導率を計測可能なナノシステムを新開発した．細胞の熱伝導率を計測した結果，従来考えられてきた水よりも著しく低く，細胞内構造に由来する大きなばらつきを持つことが示唆された．

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Original Source

DOI: https://doi.org/10.2142/biophys.62.122