Primary surface measurement reported
Saline contact angle on titanium discs before and after vacuum plasma treatment, used to evaluate surface hydrophilicity on machined and rough surfaces.
Client Citation Analysis
Plasma Treatment to Remove Titanium Surface Contaminants and Improve Implant Biocompatibility: An In Vitro Study
This in vitro study evaluates vacuum plasma treatment on machined and rough titanium discs, with Dropometer-measured saline contact angle used as the direct hydrophilicity readout alongside contamination, cell-attachment, morphology, and gene-expression analyses.
At-a-Glance Summary
How the paper credits the instrument
The wettability test was conducted using “a tensiometer (Droplet Lab, Droplet Biosciences, Cambridge, MA, USA)” to measure the contact angle of a saline droplet on titanium surfaces.
How the surface-tension / contact-angle data were used in the study
The contact-angle data were used to compare titanium surface hydrophilicity before and after plasma treatment on machined and rough discs. The authors interpreted the lower post-treatment contact angles together with reduced carbon contamination and improved early fibroblast and osteoblast attachment.
Replication / reliability statement
Five machined and five rough-surfaced titanium discs were used for wettability testing, with the same discs measured before and after treatment to ensure consistency.
Paper Details
Title
Plasma Treatment to Remove Titanium Surface Contaminants and Improve Implant Biocompatibility: An In Vitro Study
Authors
Kailing Ho; Takahiko Shiba; Chia-Yu Chen; David M. Kim
Journal
Biomimetics
Year
2025
Volume
10
Pages / Article
571
License
CC BY 4.0
Funding & interests
Authors at Harvard School of Dental Medicine and Institute of Science Tokyo. The authors declare no conflicts of interest. Droplet Lab appears in no funding, acknowledgement, affiliation or conflict statement — the tensiometer was a lab instrument, not a donation. Disclosed commercial relationships: Plasmapp donated the ACTILINK plasma device, and BioHorizons and Hoowon donated the titanium discs.
6.2
Scopus metrics (Elsevier / Scopus rating 2024)
Scopus metrics (Elsevier / Scopus rating 2024)
CiteScore subject ranks (CiteScore 2024)
- Q3 - Engineering, Biomedical Engineering (168/323)
- Q3 - Materials Science, Biomaterials
0.967
Scopus metrics (Elsevier / Scopus rating 2024)
0.647
Scopus metrics (Elsevier / Scopus rating 2024)
4.2
Journal Impact Factor (Clarivate JCR)
4.0
Journal Impact Factor (Clarivate JCR)
Journal Impact Factor (Clarivate JCR)
JCR category rank
- Q1 - Engineering, Multidisciplinary;
- Q3 - Materials Science, Biomaterials
What Was Measured
Primary surface / interfacial measurement
The paper reports titanium-surface hydrophilicity by measuring the contact angle of a saline droplet before and after plasma treatment. Reported values decreased from 83.1° to 24.1° on machined discs and from 77.3° to 15.7° on rough discs.
Supporting measurements
Supporting measurements included SEM surface-topography imaging, EDS-based carbon analysis, cell viability assays for fibroblast and osteoblast adherence, immunohistochemistry staining of actin cytoskeleton and nuclei, SEM imaging of cell morphology, and RNA sequencing for differential gene expression.
Instruments Mentioned
Contact angle / hydrophilicity
tensiometer (Droplet Lab, Droplet Biosciences, Cambridge, MA, USA)
Surface topography
Zeiss Gemini 360 FE-SEM SEC; ZEISS, Oberkochen, Germany
Hydrocarbon contamination / carbon mapping
EDS via the Zeiss Gemini 360 FE-SEM SEC
Cell adherence
CellTiter-Glo Luminescent Cell Viability Assay, Promega
Cytoskeleton / nuclei staining
TRITC-conjugated phalloidin and DAPI stain
RNA library preparation
Zymo-Seq RiboFree Total RNA Library Kit
Plasma treatment (the study's independent variable)
ACTILINK (Plasmapp Co., Ltd., Seoul, Republic of Korea) — vacuum plasma device, capacitively coupled plasma discharged through vacuum pumping; each titanium disc treated 30 s in an enclosed plasma-filled chamber. Donated by the manufacturer.
Statistics
GraphPad Prism 10.4.1 (GraphPad Software Inc., La Jolla, CA, USA). Paired Student's t-test for before/after disc comparisons; unpaired Student's t-test for between-group analyses.
Titanium discs
Grade 4 titanium discs, 10 mm diameter × 2 mm thickness (BioHorizons, Birmingham, AL, USA) for topography, hydrocarbon and hydrophilicity testing; Grade 4 discs 10 mm × 5 mm (Hoowon, EDI Co., Ltd., Busan, Republic of Korea) for cell viability, IHC and RNA sequencing. Both sets donated by the suppliers.
What the paper does and does not report about the wettability protocol
The paper reports the liquid (saline, concentration unspecified), the substrate (Grade 4 titanium discs, 10 mm × 2 mm), the sample size (five machined and five rough discs, the same discs before and after) and the statistical test (paired Student's t-test). It does not report droplet volume, ambient temperature or humidity, the interval between plasma treatment and measurement, the number of droplets per disc, or standard deviations in the text — the four reported means carry no dispersion outside the Figure 5C and 5F graphics. Static angles only; no advancing, receding or hysteresis measurement, and no surface energy model. Saline rather than deionised water means these values are not directly comparable to the water contact angle literature on titanium.
Role of the Droplet Lab instrument
The paper credits "a tensiometer (Droplet Lab, Droplet Biosciences, Cambridge, MA, USA)" in Section 2.5, used for a wettability test on titanium discs. It does not name a product or model. The authors placed a saline droplet on the surface and measured contact angle before and after 30 s vacuum plasma treatment on both machined and rough-surfaced Grade 4 titanium discs, using the same discs for paired before/after comparison.
In the study workflow, the tensiometer supplied the direct hydrophilicity readout that the authors used to quantify the plasma-induced surface shift and relate that shift to subsequent cell-response findings.
Key Findings
Marked hydrophilicity increase
Plasma treatment produced a strong reduction in saline contact angle on both titanium surface types. Machined discs shifted from 83.1° to 24.1°, and rough discs shifted from 77.3° to 15.7°, with both reductions reported as statistically significant at p < 0.0001.
Cleaner surface with preserved microtopography
EDS analysis showed carbon content decreasing from 2.60% to 1.87%, a 28.1% reduction after plasma treatment. SEM imaging at 10,000× showed the titanium surface architecture was preserved during treatment.
Earlier fibroblast attachment
Fibroblast adherence on machined titanium discs was higher at the 1, 2, and 6 h time points after plasma treatment. Immunohistochemistry and SEM also showed broader cytoskeletal spread and more spread-out pseudopodia morphology at early time points.
Earlier osteoblast attachment
Osteoblast adherence on rough titanium discs was higher at the 1 and 2 h time points after plasma treatment. IHC and SEM images showed more spread-out morphology, and by 24 h osteoblasts in the plasma group displayed a long, spindle-shaped, well-attached morphology.
Fibroblast transcriptional response at 6 h
RNA sequencing identified two genes as significantly upregulated in plasma-treated fibroblasts at 6 h versus the no-plasma group: Apln (log2 fold change = 1.90, FDR = 3.9 × 10−2) and Crabp2 (log2 fold change = 3.13, FDR = 1.4 × 10−4). The paper links these genes to angiogenesis and cell growth differentiation.
Figures & Visuals
What it shows
This figure shows the saline-droplet contact-angle images and before/after distributions for machined and rough titanium surfaces, making it the central visual for the Droplet Lab tensiometer's hydrophilicity result
What it shows
This figure shows EDS-based carbon mapping and the reduction in carbon percentage by weight after plasma treatment, providing chemical context for the hydrophilicity change seen in Figure 5.
What it shows
This figure shows that the plasma-treated machined surfaces had higher fibroblast adherence at early time points, connecting the wettability shift to the soft-tissue-facing cell model used in the study.
What it shows
This figure shows higher early osteoblast adherence on plasma-treated rough surfaces, linking the surface hydrophilicity result to the implant-body-facing cell model.
Why It Matters
In this paper, the contact-angle data — measured with the tensiometer the paper credits as "(Droplet Lab, Droplet Biosciences, Cambridge, MA, USA)" are the study's direct surface-level evidence that vacuum plasma treatment shifts titanium toward a more hydrophilic state. The authors treat hydrophilicity as one of several markers alongside carbon contamination removal, cell attachment, cytoskeletal morphology and gene expression; their Discussion devotes one paragraph to it and draws the hydrophilicity-to-bone-response link from prior literature (Wennerberg et al., reference 24) rather than from their own data.
Within the paper's implant-biomaterials context, the wettability and cell-attachment datasets are independent outputs of the same treatment. The paper does not correlate them or test a mechanism linking them; its hydrophilicity-to-bone-response argument cites prior in vivo and in vitro work: "Improved hydrophilicity has been shown to have a stronger short-term bone response in existing in vivo and in vitro experiments [24]." The authors frame these results around improved implant biocompatibility and early healing-related interactions on implant and abutment surfaces.
The authors do not know how long the hydrophilic state lasts
They state it "remains unclear whether the hydrophilic state induced by plasma treatment persists over time or whether it requires additional surface modifications to maintain its bioactive properties," and call for studies assessing long-term stability. The paper also notes it was "conducted in an in vitro setting" that "does not replicate the complex biological environment present in vivo," acknowledges "the limitations of the disc model used in this study," and calls for in vivo validation and direct comparison against alternative surface modification technologies such as UV irradiation.
Practical Takeaways
Direct hydrophilicity readout
The Droplet Lab tensiometer provided the quantitative surface readout that distinguishes untreated from plasma-treated titanium in this study. The contact-angle shift was large on both machined and rough discs.
Useful paired before/after design
The same discs were measured before and after treatment, which made the wettability comparison tightly matched to the plasma intervention. That design strengthens the study’s surface-level comparison.
Relevant across two implant-facing surface types
The authors used the tensiometer on both machined and rough titanium surfaces, aligning the wettability test with abutment-like and implant-body-like use cases inside the study design.
Best interpreted with complementary assays
In this paper, the contact-angle result gains value when read together with EDS carbon reduction, cell-attachment assays, morphology imaging, and RNA sequencing. The study uses that combined workflow to interpret plasma treatment as a surface-bioactivation step.
Strong fit for early-stage response studies
The most prominent biological differences appeared at early time points, making the tensiometer readout especially relevant as an upstream indicator of the surface state the cells first encounter.