Applied Sciences  
Hototunctional Surfaces for Smart Entrapment of Polysomes  
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the microarray technology [9]. Compared to the other techniques, polysome profiling is unique and it can be used to monitor in parallel the cosedimentation of mRNAs and ribosome associated proteins to the translation machinery [10; 11; 12]. Polysome profiling is based on a differential centrifugation through density sucrose gradients [6; 13; 14]. Although widely employed, polysomal profiling presents several drawbacks, such as the long time of processing, the need of expensive equipment, the fairly high amount of starting material and the presence in the resulting polysomes of sucrose, which could impede their direct use for the following analyses. The progress of sequencing techniques allowed the recent development of alternative methods, in particular ribosome profiling [7; 15]. In this method, the RNA fragments protected from nuclease digestion by ribosomes, are sequenced on large-scale. Ribosome profiling has been validated for translatome studies in several biological models, from cell lines to tissues in various organisms. However, this method also has several disadvantages, for example, it is labor intensive and requires a large amount of starting material. The need to study the translatome in vivo and in specific cell types pushed the development of the ribosome affinity purification techniques [8; 16]. Ribosome affinity purification relies on the development of genetically modified cells/organisms, which express an affinity-tagged ribosome subunit. Thanks to these tagged subunits, the translatome analyses become possible in individual cell types. The major drawback is, of course, that this method could be applied only with samples with genetically tagged ribosomes. Recently, alternative methods of polysomes purification have been proposed. [PERSON] et al. developed a polysome fractionation method based on an ultraHPLC size exclusion chromatography [17]. Although this efficient and reproducible methodology can facilitate the isolation of polysomes from mammalian cells and tissues, it employs expensive instrumentation to be used by skilled personnel. [PERSON] et al. introduced instead a different approach based on the study of interaction of puromycin derived molecules to trap polysomes and the associated RNA [15]. Therefore, the need for new devices and protocols able to specifically purify polysomes in their native state to isolate the associated transcripts is evident. This possibility could give access to information on protein synthesis both for basic research studies and for enabling a deeper comprehension of pathologies where the protein synthesis is affected, like cancer or neurodegenerative diseases [11]. In this context, the setup of bifunctional surfaces able to selectively capture polysomes could be of great value especially in a microdevice perspective. We already demonstrated that biofunctional surfaces prepared on flat substrates [18; 19] can be easily integrated in microdevices [20; 21; 22], if the preparation and the working principle of surfaces is deeply characterized and studied. The aim of the present work is the development and the analysis of functional surfaces enabled to isolate and separate polysomes, with the ultimate goal to provide ideal material for the purification of actively translated mRNAs (both in healthy and in diseased conditions). The surface functionalization is based on the formation of Self-Assembled Monolayers (SAM) of organic molecules, which expose a convenient functional group able to modify polarity and surface charge of the starting substrate.