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- Molecular imprinting and surface grafting of glycoprotein fragments in polymeric nanosystems: from cancer diagnosis to virus targetingPublication . Bzainia, Amir; Gomes, Catarina P.; Dias, Rolando; Costa, Mário RuiGlycoproteins and glycans are widely found in eukaryotes, prokaryotes, archaea, and viruses. Many fundamental biological mechanisms, such as molecular recognition, signal transduction, cell adhesion, and immune response are regulated with the intervention of glycoproteins, glycans, and monosaccharides. Several diseases are a result of anomalous changes affecting the structure of these molecules or their abnormal expression. Therefore, glycoproteins, glycans, and monosaccharides are often considered biomarkers for diagnosis purposes and therapeutic agents in cancer treatment. The development of vaccines and antibodies for infection diseases also relies on these kinds of molecular structures. The mimic of glycoproteins or their molecular recognition with tailored synthetic polymers can be used to develop tools aiding in the diagnosis and treatment of different kinds of diseases, through sensing, imaging, controlled drug delivery, virus inhibition, and so on. This chapter describes the use of molecular imprinting techniques and grafting mechanisms with glycoproteins, glycans, and saccharides aiming at the development of such kinds of synthetic polymers. Due to their practical relevance, a special emphasis is given to systems involving sialic acid or derivatives, boronic acid-based polymers (e.g., with surface-oriented molecular imprinting of glycoproteins) and glycopolymers synthesis through grafting of saccharide moieties in polymer backbones or nano-surfaces (e.g., for the generation of macromolecules/surfaces with polyvalent interactions). Along the text, the use of “controlled” (or rather reversibly deactivated) radical polymerization is highlighted to show new opportunities arising in this field with these synthetic routes. Improved precision in the design of special molecular architectures, functionalization, hybridization, surface modification, and size control of macromolecular-based devices (e.g., nanofabrication) are some important goals in the development of tailored synthetic materials that can be achieved with controlled radical polymerization. Specific examples involving these special kinds of synthetic polymers with their application in cancer and virus targeting are provided.
- Purification of stilbenes from grape stems in a continuous process based on photo-molecularly imprinted adsorbents and hydroalcoholic solventsPublication . Bzainia, Amir; Igrejas, Getúlio; Pereira, Maria João; Costa, Mário Rui; Dias, RolandoThis study presents a sustainable method to purify stilbenes from residual grape stem biomass. This approach was experimentally validated through the use of a pilot size fixed-bed adsorption prototype for the automation of the purification process. Molecularly imprinted polymers, synthesized through photopolymerization at room temperature and incorporating the 4-vinylpyridine monomer, serve as adsorbents. The purification procedure leads to a significant enrichment, with a more than 22-fold increase in (E)-ε-viniferin and a 9-fold increase in (E)-resveratrol. High recoveries of 80.3% and 62.1% for (E)-ε-viniferin and (E)-resveratrol, respectively, were achieved. Notably, the use of eco-friendly water and ethanol mixtures distinguishes this method from others focused on stilbenes purification. This study further explores the variability of the stilbenes in the residual grape stems by analysing different varieties, emphasizing the complexity of the starting material of the purification process. The range of purities achieved for the fractions enriched with stilbenes (e.g., 12.8% for (E)-ε-viniferin and 3.4% for (E)-resveratrol) are suitable for direct use in controlling of Plasmopara viticola, the agent causing grapevine downy mildew. Furthermore, through compositional combination of these fractions, it is possible to conceive new stilbene-containing phytochemicals with improved anti-fungal activity. Therefore, the developed adsorbents and purification process, enabling the steady enrichment of stilbenes regardless of the unavoidable variability in the initial vine biomass, is a contribution towards the quest for more environmentally friendly and sustainable phytochemicals.
- Functionalization of polymer networks to target trans-resveratrol in winemaking residues supported by statistical design of experimentsPublication . Bzainia, Amir; Dias, Rolando; Costa, Mário RuiThe present work aims to produce functionalized polymer networks to target the bioactive molecule trans-resveratrol found in winemaking residues, specifically at grape stems. The synergistic choice of photoinitiation, polymerization composition, and molecular imprinting approach allows the functionalization of these materials. Experimental design is applied to methodically perform the syntheses. The amount of crosslinker, the total monomer's concentration, and the ratio of trans-resveratrol to the functional monomer 4-vinylpyridine (4VP) are the factors selected for this experimental design. The binding capacities and the selectivity of the synthesized materials are assessed through sorption experiments in acetonitrile and hydroalcoholic media. Consequently, a multivariate linear regression analysis leads to describe the uptake of trans-resveratrol by the materials in both media. The crosslinker content and the ratio of trans-resveratrol to 4VP are found to be impactful parameters while designing such materials. These studies allow the identification of working conditions for sorption/desorption processes combining a high retention capability of the adsorbents with selectivity. Furthermore, four materials are selected to enrich trans-resveratrol from grape stems extracts in a continuous process of solid-phase extraction. The results show that the functionalized materials are able to enrich 12-fold the content of trans-resveratrol in some fractions demonstrating the interest of such polymers.
- Preparation and ionic transport properties of conductive polymers for dye-sensitized solar cellsPublication . Bzainia, Amir; Dias, Rolando; Mezni, MohamedThis work aims to improve the components of the dye-sensitized solar cells (DSSCs) which are a type of photovoltaics that consist mainly of a photoanode, a counter electrode, a light sensitive molecule (sensitizer) and an electrolyte solution that regenerates the solar cell through a redox system. The improvement of the DSSC focuses on the material used for the counter electrode. Usually, it is made out from platinum sputtered on a conductive glass. However, platinum is an expensive metal that is hard to manipulate and can be corroded by the mediator. In this perspective, an alternative material for the expensive platinum is investigated which is the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT). This polymer has a structure that promotes high ionic and electronic conductivities, and it can be doped with different anions (e.g. PSS, perchlorate). PEDOT was synthesized chemically and electrochemically. Its chemical structure was characterized by FTIR. The electrochemical behavior of PEDOT was assessed by cyclic voltammetry (CV). The catalytic activity of PEDOT towards the redox system proved to be higher than the activity of the platinum. In addition to the experimental approach, modelling of the ionic-electronic conductivity of PEDOT was performed based on the Nernst-Planck-Poisson and the Butler-Volmer formalisms, and the simulation outputs were fitted to the experimental data. In the last step, the conductive polymer PEDOT was used as a counter electrode to fabricate DSSCs. The cells were characterized through electrochemical impedance spectroscopy (EIS) and through current-voltage (J-V) curves. The based PEDOT cells demonstrated an efficiency of 8.1%, which was higher than the based-platinum solar cells (6.3%).
- Polymersomes as versatile drug delivery vesicular carriersPublication . Gomes, Catarina; Bzainia, Amir; Dias, Rolando; Costa, Mário RuiStable artificial vesicles with a tiny membrane enclosing a liquid solution are generically defined as polymersomes. They are produced using amphiphilic synthetic polymers, usually block copolymers. Often, polymersomes assume a spherical geometry and their size can range from tens of nanometers up to a few microns (e.g., 50 nm!5 μm). The thickness of the membrane is generally of the order of a few nanometers (e.g., 5!20 nm) and the most common polymersomes contain in the core an aqueous solution. Fig. 11.1 depicts a typical polymersome showing a hollow sphere containing an aqueous solution in the core enclosed by a bi-layer membrane.1 The bi-layer membrane (internal/external hydrophilic coronas with a hydrophobic separating layer) is formed due to the self-assembly of an amphiphilic copolymer. The aqueous core can be used to encapsulate hydrophilic therapeutic molecules (e.g., drugs, enzymes, proteins, DNA, and RNA) while hydrophobic drugs can be loaded in the middle-layer. Homing devices, such as antibodies, can also be incorporated in the external surface of the polymersomes in order to enhance local drug release.1 Besides surface functionalization, the membrane of polymersomes can also be tailored through polymerization mechanisms such as crosslinking to enhance its hardness, if desired.
- A simple process to purify (E)-resveratrol from grape stems with a photo-molecularly imprinted sorbentPublication . Bzainia, Amir; Dias, Rolando; Costa, Mário RuiThe present work focused on the development of a process of sorption-desorption to purify (E)-resveratrol found in winemaking residues, specifically from the crude extract of grape stems. The core element of this process is a photo-molecularly imprinted sorbent (MIS) synthesized by means of the molecular imprinting technique (MIT). This sorbent is a 4-vinylpyridine rich polymer network which binds (E)-resveratrol at stereospecific sites. Comparison of sorption isotherms of the MIS and its counterpart non-imprinted sorbent (NIS) shows the higher capability of the MIS to bind (E)-resveratrol. It is noteworthy that the size of MIS particles was larger than to those of the NIS (as found by scanning electron microscopy analysis) facilitating its use in sorption-desorption processes without reaching a high backpressure. The MIS was then used to purify (E)-resveratrol from grape stems extract in a two-step purification procedure through a simple device. The initial purification step permitted to increase the purity of (E)-resveratrol from 29% to 78% (34% of recovery), whereas a further one took it to 87% (70% of recovery). The purified fractions were obtained in hydroalcoholic medium and contained other bioactive stilbenes such as (E)-Ɛ-viniferin. The results of this research provide a compelling proof of concept for room-temperature photopolymerization, enabling the development of highly efficient imprinted polymers as sorbents for purifying bioactive compounds from agricultural residues. This significant advancement paves the way for its large-scale implementation in a circular bioeconomy approach.
- Carbon-based hydrogelsPublication . Bzainia, Amir; Gomes, Catarina P.; Dias, Rolando; Costa, Mário RuiThis chapter intends to give insight into the use of carbon-based hydrogels for energy storage and/or conversion, which are becoming critical, given the ongoing need for decarbonization and growing renewable energy production. The ability to use sustainable materials and the added advantage to incorporate tailor-made, nontoxic, cheap, and electrochemically active functional moieties during their synthesis make them frontrunner materials in the field of green chemistry and energy applications. Here, after a brief introduction of graphene-, synthetic polymer-, and natural polymer-based hydrogels and many possibilities for their hybrid combination, a particular emphasis is given to their application to energy storage, energy conversion, and energy efficiency enhancement systems. Application examples concerning metal-air batteries, fuel cells, water electrolyzers, microbial fuel cells, photoelectrochemical water splitting, supercapacitors, lithium-ion batteries, and other metal-ion batteries, desalination, and water purification through solar vapor generation are highlighted.
- Enrichment of Quercetin from Winemaking Residual Diatomaceous Earth via a Tailor-Made Imprinted AdsorbentPublication . Bzainia, Amir; Dias, Rolando; Costa, Mário RuiResidual diatomaceous earth (RDE) from winemaking activities is a rich and currently underexploited source of phenolic compounds which ought to be recycled from the perspective of circular bioeconomy. In this work, we demonstrate the feasibility of molecularly imprinted polymers (MIPs) for the enrichment of quercetin, a flavonoid at a fairly high content in residual diatomaceous earth. These MIPs were synthesized through free radical polymerization. FTIR confirmed the integration of the functional monomers into the polymeric chains. Batch adsorption experiments were used to assess the retention and selectivity of those MIPs towards quercetin. Commercial resins were compared with the synthesized materials using the same procedures. These adsorption experiments allowed the selection of the best performing MIP for the valorization of RDE extract. This treatment consisted of saturating the selected MIP with the extract and then desorbing the retained compounds using solvents of selected compositions. The desorbed fractions were analyzed using liquid chromatography, and the results demonstrated an increase in quercetin’s fractional area from 5% in the RDE extract to more than 40% in some fractions, which is roughly an eightfold enrichment of quercetin. Moreover, other flavonoids of close chemical structure to quercetin have been rather retained and enriched by the MIP.