## 4 Conclusions  
The separation of polysomes is crucial to assess the physiological or pathological state of a cell, since the mRNA associated with polysomes is the actively translated, as such representing a proxy for proteomes. The isolation of mRNA associated to polysomes is traditionally obtained by time-consuming and laborious protocols. Prompted by the idea of providing the scientific community with a rapid, miniaturized and simple device, alternative strategies were explored in this work.  
Different materials, i.e., gold and silicon, and different functionalizations were tested in order to set up biofunctional surfaces for the purification of mammalian/human polysomes. A panel of either positively or negatively charged and polar or apolar molecules were used to modulate the surface properties of flat substrates, screening their ability to entrap polysomes. Charged surfaces were the best surfaces able to capture an high amount of intact polysomes. Negatively-charged surfaces were selected for preparing a proof-of-concept microdevice, successfully tested for the adsorption of polysomes and extraction of polysomal RNA in an integrated analysis. Leveraging on simple preparation and use, biofunctional surfaces are envisaged as promising tools for the future development of protocols and devices able to speed up and optimize the separation and analysis of polysomes, with possible diagnostic purposes.  
**Supplementary Materials:** The following are available online at [[https://www.mdpi.com/2076-31/11/2/776/s1](https://www.mdpi.com/2076-31/11/2/776/s1)]([https://www.mdpi.com/2076-31/11/2/776/s1](https://www.mdpi.com/2076-31/11/2/776/s1)), Figure S1: Typical polysome sedimentation profile of a MCF-7 cell lysate after sucrose gradient centrifugation and fractionation, Figure S2: Scheme with dimensions, CAD rendering and actual microdevice employed for polysome purification, Figure S3: Human ribosome structure, Figure S4: AFM images of ribosomes adsorbed on bare gold, on MCOOH, MOH and MNH\({}_{2}\) functionalized gold surfaces, Figure S5: Height, minimum and maximum lateral size distributions obtained by grain-analysis on surfaces obtained depositing ribosomes on bare gold and MCOOH, MNH\({}_{2}\), and MOH functionalized gold, Figure S6: AFM image of M11 CH\({}_{3}\) functionalized gold surfaces treated with ribosomes, Figure S7: Height, minimum and maximum lateral size distributions obtained by grain-analysis on surfaces obtained depositing polysomes on bare gold, MCOOH, MNH\({}_{2}\), and MOH functionalized gold, Figure S8: AFM image of M11 CH\({}_{3}\) functionalized gold surfaces treated with polysomes, Figure S9: Height, minimum and maximum lateral size distributions obtained by grain-analysis on surfaces obtained depositing polysomes on plasma-treated TG-SO, triCAS treated silicon surfaces and CST treated TG-SO, Figure S10: Electrophograms of RNA eluted from microdevices after incubation of cell lysate. Table S1: List of undecanethiols used to functionalize gold substrates and of carboxysilanes used to functionalize silicon oxide surfaces, Table S2: Chemical composition of bare and functionalized TG-SO surfaces, measured by XPS at 60\({}^{\circ}\)take off angle.  
**Author Contributions:** Conceptualization, L.L. and C.P. ([PERSON]); Data curation, L.L., L.M., L.P., L.V. and C.P. ([PERSON]); Funding acquisition, C.P. ([PERSON]); Investigation, L.M., L.P., L.V., G.V. and C.P. ([PERSON]); Methodology, G.V.; Supervision, L.L. and C.P. ([PERSON]); Writing--original draft, C.P. ([PERSON]); Writing--review and editing, L.L., L.P., G.V. and C.P. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.