Human Blood Platelets Adsorption on Polymeric Materials for Liquid Biopsy

Abstract

Platelets are emerging as a promising source of blood biomarkers for several pathologies, including cancer. New automated techniques for easier manipulation of platelets in the context of lab-on-a-chips could be of great support for liquid biopsy. Here, several polymeric materials were investigated for their behavior in terms of adhesion and activation of human platelets. Polymeric materials were selected among the most used in microfabrication (PDMS, PMMA and COC) and commercial and home-made resins for 3D printing technology with the aim to identify the most suitable for the realization of microdevices for human platelets isolation and analysis. To visualize adherent platelets and their activation state scanning, electron microscopy was used, while confocal microscopy was used for evaluating platelets' features. In addition, atomic force microscopy was employed to further study platelets adherent to the polymeric materials. Polymers were divided in two main groups: the most prone to platelet adhesion and materials that cause few or no platelets to adhere. Therefore, different polymeric materials could be identified as suitable for the realization of microdevices aimed at capturing human platelets, while other materials could be employed for the fabrication of microdevices or parts of microdevices for the processing of platelets, without loss on surfaces during the process.

Keywords: biomarker content; liquid biopsy; platelets isolation and analysis; polymeric microdevices.

Figure 1

Platelets density on different materials measured with SEM. Data are means of at least four images and standard deviations are shown.

Figure 2

Example of SEM images of platelets adherent to: (a) COC; (b) PMMA; (c) NOA81; (d) PDMS; (e) PEGDA; (f) SpotGP and (g) TG. Insets are magnifications of each material (scale bar 2 µm).

Figure 3

Correlation between platelet adhesions measured with SEM (density as platelets/cm²) and wettability (CA) of polymeric materials.

Figure 4

Platelets density measured by confocal microscopy. Data are means of at least three images and standard deviations are shown.

Figure 5

Confocal images of platelets adherent to polymeric materials. In the first column, the signal of CD41 is reported (panels (a,d,g,j)), while, in the second, the signal of CD62P is shown (panels (b,e,h,k)). The last column refers to merged signal (co-localization, (c,f,i,l)). Scale bars: 5 µm for COC and SpotGP, 15 µm for NOA81 and PDMS.

Figure 5

Confocal images of platelets adherent to polymeric materials. In the first column, the signal of CD41 is reported (panels (a,d,g,j)), while, in the second, the signal of CD62P is shown (panels (b,e,h,k)). The last column refers to merged signal (co-localization, (c,f,i,l)). Scale bars: 5 µm for COC and SpotGP, 15 µm for NOA81 and PDMS.

Figure 6

Representative AFM analysis of platelets adherent to: (a) PMMA (z false-color scale from −50 to 250 nm), (b) NOA81 (z false-color scale from −10 to 80 nm), and (c) COC (z false-color scale: −50 to 450 nm). The height profiles traced along the yellow lines are shown respectively in (d–f).

Figure 7

Comparison among platelets density per unit area measured with the different imaging techniques. In (a) platelets adherent to PMMA are shown, in (b) to NOA81 and in (c) to the COC polymer.