Monitoring of Carbonated Hydroxyapatite Growth on Modified Polycrystalline CVD-Diamond Coatings on Titanium Substrates

At a Glance

Metadata	Details
Publication Date	2024-01-06
Journal	Crystals
Authors	Rocco Carcione, Valeria Guglielmotti, Francesco Mura, Silvia Orlanducci, Emanuela Tamburri
Institutions	National Agency for New Technologies, Energy and Sustainable Economic Development, Sapienza University of Rome
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: Bioactive PCD for Tissue Engineering

Executive Summary

This documentation analyzes the research on monitoring Carbonated Hydroxyapatite (C-HA) growth on modified Polycrystalline CVD Diamond (PCD) coatings, highlighting 6CCVD’s capability to supply materials for advanced hard tissue engineering applications.

Core Achievement: Successful demonstration that controlled surface chemistry modification of PCD significantly enhances bioactivity and promotes the growth of bone-like C-HA.
Methodology: PCD films were synthesized on titanium substrates via HF-CVD and subsequently modified by oxidative annealing in air at 350 °C.
Surface Functionalization: The annealing process increased the surface concentration of C-O polar groups to approximately 10%, which acted as nucleation sites for C-HA precipitation.
Enhanced Bioactivity: The modified PCD (D_A sample) exhibited faster and more continuous C-HA growth compared to pristine PCD or bare titanium.
Biomimetic Results: The resulting C-HA crystals displayed a desirable needle-like morphology and chemical composition closely matching human bone mineral, specifically achieving a Ca/P ratio of 2.11 and a carbonate weight percent of 5.5%.
Market Relevance: These findings confirm MPCVD diamond as a highly tunable, bioactive platform, positioning 6CCVD materials as ideal scaffolds for implantable prostheses and regenerative medicine.

Technical Specifications

The following table extracts key parameters and results relevant to the synthesis and characterization of the PCD films and the resulting C-HA deposits.

Parameter	Value	Unit	Context
Substrate Material	Polycrystalline Titanium	N/A	Thickness: 0.5 mm
CVD Method Used	HF-CVD	N/A	Hot Filament Chemical Vapor Deposition
Gas Mixture Ratio (CH₄:H₂)	1.25:100	N/A	Diamond Synthesis
Filament Temperature	2130 ± 10	°C	CVD Growth Condition
Chamber Pressure	36 ± 1	torr	CVD Growth Condition
Oxidative Annealing Temperature	350	°C	Surface Modification (D_A sample)
Annealing Duration	20	min	Surface Modification
SBF Concentration	1.5x	N/A	Simulated Body Fluid
Average Surface Roughness (Ra)	~350	nm	Pristine (D) and Annealed (D_A) PCD
Diamond Volume Fraction (D_A)	96	%	Calculated from Raman spectroscopy
C-O Surface Content (D_A)	~10	%	XPS analysis after annealing
Final Ca/P Ratio (D_A, 20 days)	2.11	N/A	Closely matching human bone mineral (2.0)
Final Carbonate Weight Percent (D_A, 20 days)	5.5	%	Closely matching human bone mineral (5-7%)
C-HA Morphology (D_A)	Continuous, needle-like texture	N/A	Fundamental for osteogenic activity

Key Methodologies

The experiment successfully tailored the PCD surface for enhanced bioactivity through precise synthesis and post-treatment steps:

Substrate Preparation: Polycrystalline titanium sheets (1 cm x 1 cm, 0.5 mm thick) were electropolished at -30 °C (20 V, 15 min) to achieve a mirror-like surface.
Seeding: Substrates were subjected to a 15 min sonication cycle in a “seeding” solution of 50 mg nanodiamond powder in ethanol to ensure homogeneous nucleation.
PCD Synthesis (HF-CVD): Diamond films were grown for 3 hours using a 1.25:100 CH₄/H₂ mixture, maintaining a filament temperature of 2130 ± 10 °C and a chamber pressure of 36 ± 1 torr.
Surface Modification: Pristine diamond films (D) were oxidatively annealed in air at 350 °C for 20 minutes to produce the modified D_A samples, increasing C-O surface moieties.
Hydroxyapatite Precipitation: Samples were immersed in 1.5x Simulated Body Fluid (SBF) at 37 °C, buffered to pH 7.40, for monitoring periods ranging from 3 to 20 days.
Structural Monitoring: C-HA growth and structural quality were monitored primarily using Raman spectroscopy (960 cm^-1 phosphate mode and 1070 cm^-1 carbonate mode) and confirmed by SEM-EDX and XPS analysis.

6CCVD Solutions & Capabilities

The successful modulation of PCD bioactivity demonstrated in this research is directly supported and scalable by 6CCVD’s advanced MPCVD capabilities. We offer the precision and scale necessary to transition this promising research into industrial biomedical applications.

Research Requirement	6CCVD Solution & Advantage	Technical Specification
High-Purity PCD Films	Polycrystalline CVD Diamond (PCD) grown via MPCVD, offering superior structural quality and purity control compared to the HF-CVD method used in the paper.	PCD thickness range: 0.1 µm - 500 µm.
Scalable Substrate Dimensions	While the paper used 1 cm x 1 cm samples, 6CCVD provides diamond plates/wafers up to 125 mm in diameter, enabling industrial scaling for large-area implant scaffolds.	Custom Dimensions: Plates/wafers up to 125 mm.
Precise Surface Chemistry Control	6CCVD offers precise, in-situ control over surface termination (H-terminated or O-terminated) during growth, providing a more reliable and homogeneous functionalization than post-synthesis annealing.	Applicable Materials: Optical Grade SCD, Polycrystalline PCD, and Boron-Doped Diamond (BDD).
Tailored Roughness for Bioactivity	The paper utilized rough PCD (Ra ~350 nm). 6CCVD can supply PCD with controlled roughness profiles, or highly polished surfaces (Ra < 5 nm for inch-size PCD) for specific applications like heart valves or blood-contacting devices.	Polishing: Ra < 5 nm (Inch-size PCD).
Integrated Device Fabrication	If the final implant requires electrical contacts (e.g., biosensors or stimulation devices), 6CCVD offers internal metalization services.	Metalization: Au, Pt, Pd, Ti, W, Cu (Internal capability).
Advanced Material Selection	The paper notes the potential of incorporating foreign species (e.g., N, Ti). 6CCVD specializes in custom doping, including Boron-Doped Diamond (BDD), which provides the necessary electroconductivity for enhanced electrochemical deposition of hydroxyapatite, as referenced in related literature.	Substrates: Custom substrates up to 10 mm thick.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of CVD diamond and can assist researchers and engineers in selecting the optimal diamond material (SCD, PCD, or BDD) and surface preparation strategy (H-terminated, O-terminated, or custom metalization) required to replicate or extend this research into specific hard tissue engineering or implantable biosensor projects. We ensure global delivery with DDU default shipping, and DDP available upon request.

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

View Original Abstract

Production of diamond coatings on titanium substrates has demonstrated as a promising strategy for applications ranging from biosensing to hard tissue engineering. The present study focuses on monitoring the nucleation and growth of bone-like carbonated-hydroxyapatite (C-HA) on polycrystalline diamond (PCD) synthetized on titanium substrate by means of a hot filament chemical vapor deposition (HF-CVD) method. The surface terminations of diamond coatings were selectively modified by oxidative treatments. The process of the C-HA deposition, accomplished by precipitation from simulated body fluid (SBF), was monitored from 3 to 20 days by Raman spectroscopy analysis. The coupling of morphological and structural investigations suggests that the modulation of the PCD surface chemistry enhances the bioactivity of the produced materials, allowing for the formation of continuous C-HA coatings with needle-like texture and chemical composition typical of those of the bone mineral. Specifically, after 20 days of immersion in SBF the calculated carbonate weight percent and the Ca/P ratio are 5.5% and 2.1, respectively. Based on these results, this study brings a novelty in tailoring the CVD-diamond properties for advanced biomedical and technological applications.

Tech Support

Original Source

DOI: https://doi.org/10.3390/cryst14010066

References

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