Biocompatibility of Antifogging SiO-doped Diamond-Like Carbon Laparoscope Coatings

Abstract

Laparoscopes can suffer from fogging and contamination difficulties, resulting in a reduced field of view during surgery. A series of diamond-like carbon films, doped with SiO, were produced by pulsed laser deposition for evaluation as biocompatible, antifogging coatings. DLC films doped with SiO demonstrated hydrophilic properties with water contact angles under 40°. Samples subjected to plasma cleaning had improved contact angle results, with values under 5°. Doping the DLC films with SiO led to an average 40% decrease in modulus and 60% decrease in hardness. Hardness of the doped films, 12.0 - 13.2 GPa, was greater than that of the uncoated fused silica substrate, 9.2 GPa. The biocompatibility was assessed through CellTiter-Glo assays, with the films demonstrating statistically similar levels of cell viability when compared to the control media. The absence of ATP released by blood platelets in contact with the DLC coatings suggests in vivo hemocompatibility. The SiO doped films displayed improved transparency levels in comparison to undoped films, achieving up to an average of 80% transmission over the visible spectrum and an attenuation coefficient of 1.1 × 10⁴ cm^-1 at the 450 nm wavelength. The SiO doped DLC films show promise as a method of fog prevention for laparoscopes.

Keywords: antifogging; biocompatibility; hydrophilic; laparoscope.

Figure 1.

Undoped and SiO doped DLC samples. Note: Witness marks associated with the mounting hardware used during deposition can be seen in the upper left and bottom right of the samples. For each sample, identifying text can be seen through the film and substrate.

Figure 2.

Transmission spectra of DLC films composed of varying amounts of SiO dopant: (a) 100% carbon, (b) 10% dopant, (c) 15% dopant, (d) 20% dopant, (e) 25% dopant, and (f) 30% dopant.

Figure 3.

Attenuation coefficient of the DLC films calculated at a wavelength of 450 nm.

Figure 4.

The effect of silicon monoxide dopant on average water contact angle. Note: Error bars are present but difficult to observe for each sample.

Figure 5.

The effect of SiO dopant on average surface energy. Note: Error bars are present but difficult to observe for each sample.

Figure 6.

Profile of water drops on 30% SiO doped samples: (a) an as-made film and (b) 60 minutes after treatment. Note: The baseline for each measurement is indicated with a yellow, dashed line.

Figure 7.

Results of average contact angle measurements of plasma cleaned vs. as-made films over 14-days: (a) as-made and (b) plasma cleaned. Note: Error bars are present but are not always visible for each measurement.

Figure 8.

Raman spectra of DLC films with varying amounts of laser pulses on SiO dopant: (a) 100% carbon, (b) 10% dopant, (c) 15% dopant, (d) 20% dopant, (e) 25% dopant, and (f) 30% dopant. Note: This data has been normalized.

Figure 9.

Representative AFM images of DLC with varied dopant amounts and an uncoated substrate: (a) uncoated substrate; (b) 100% carbon; (c) 30% SiO dopant; (d) plasma cleaned 30% SiO dopant.

Figure 10.

RMS roughness results for an uncoated substrate, DLC with varied SiO dopant amounts, and a plasma cleaned film.

Figure 11.

Modulus as a function of pulses on SiO dopant.

Figure 12.

Hardness as a function of pulses on SiO dopant.

Figure 13.

Photographs of a 15% SiO doped DLC sample: (A) before soaking and B) after soaking in SBF for 48 weeks.

Figure 14.

Average viability normalized to media controls of NIH 3T3 cells incubated for 24 hours with various SiO doped DLC films (n = 5 technical replicates). The significance of the data was evaluated via ordinary one-way ANOVA with Dunnett's Multiple Comparison Test (*p<0.05).

Figure 15.

Low dose, 100 nM γ-thrombin (orange) induces biphasic, but extensive, platelet aggregation (a) and delayed, but considerable, ATP release (b). High dose, 300 nM γ-thrombin induces rapid, monophasic, extensive platelet aggregation (c) and early, substantial ATP release (d). These controls confirm the potential for platelet aggregation and ATP release that is absent in PRP samples exposed to DLC coated samples or DLC control samples.