Chemical modification strategies to prepare advanced protein-based biomaterials

Nature is a superb source of inspiration when it comes to the development of biomaterials. Proteins, an exquisite asset virtually involved in all biological functions, are envisioned as a biomaterial due to their ability to be chemically modified. Owing to the rich chemical repertoire provided by the side chains and C-/N-terminus present in their backbone, scientists are pursuing chemical ways to upgrade isolated proteins, while maintaining their biological activity or relevant structural properties. By inserting chemical motifs, the crosslinking capability of proteins and capability to attach biochemical and molecular groups can be controlled yielding nano to macro constructs and hydrogels with improved physicochemical and mechanical properties. These cutting-edge approaches elevate the potential use of proteins as promising biomaterials for biotechnology and biomedicine.publishe

Cell surface engineering to control cellular interactions

Cell surface composition determines all interactions of the cell with its environment, thus cell functions such as adhesion, migration and cell–cell interactions can potentially be controlled by engineering and manipulating the cell membrane. Cell membranes present a rich repertoire of molecules, therefore a versatile ground for modification. However the complex and dynamic nature of the cell surface is also a major challenge for cell surface engineering that should also involve strategies compatible with cell viability. Cell surface engineering by selective chemical reactions or by the introduction of exogenous targeting ligands can be a powerful tool for engineering novel interactions and controlling cell function. In addition to chemical conjugation and modification of functional groups, ligands of interest to modify the surface of cells include recombinant proteins, liposomes or nanoparticles. Here, we review recent efforts to perform changes to cell surface composition. We focus on the engineering of the cell surface with biological, chemical or physical methods to modulate cell functions and control cell–cell and cell–microenvironment interactions. Potential applications of cell surface engineering are also discussed

Layer-by-Layer Deposition of Antibacterial Polyelectrolytes on Cotton Fibres

The introduction of molecules with biological properties on textile materials is essential for a number of biotechnological applications. With the purpose of testing new processes applied to textiles, in this study, we present the first results on the feasibility of using the Layerby-Layer (LbL) deposition process in natural fibers such as cotton, with natural polyelectrolytes like chitosan (CH) and alginic acid sodium salt (ALG), the durability of CH/ALG multilayer on cotton were evaluated. The increase of negative charges to the substrate cotton was made with NaBr and TEMPO, to ensure the success of the process of LbL. Three characterization methods to assess electrostatic LbL deposition were performed: the contact angle between a liquid (water) and the sample surface, in order to characterize the wettability of the samples with the different layers of CH and ALG; dyeing of the CH/ALG assembled cotton fabric with cationic methylene blue that shows regular changes in terms of color depth (K/S value), which indicate that the surface were alternately deposited with CH and ALG layers and, finally, the analysis by infrared spectroscopy using Fourier Transform with Attenuated Total Reflection (ATR-FTIR), to assess the changes in the interaction between CH and ALG deposited on cotton samples.info:eu-repo/semantics/publishedVersio

Layer-by-layer deposition of antimicrobial polymers on cellulosic fibers: a new strategy to develop bioactive textiles

In recent years, there has been an increase of infectious diseases caused by different microorganisms and the development of antibiotic resistance. In this way, the search for new and efficient antibacterial materials is imperative. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan (CH) and alginates (ALG). In this study, a simple technique of Layer by Layer (LbL) of applying polycation CH and polyanion ALG was used to prepare CH/ALG multilayers on cotton samples via the electrostatic assembly with success. The CH/ALG cotton samples (functionalized) were investigated for their antibacterial properties towards Staphylococcus aureus and Klebsiella pneumonia using the international standard method JIS L 1902:2002. The antibacterial activity of the functionalized samples was tested in terms of bacteriostatic and bactericidal activity, and results showed that the samples exhibited a bacteriostatic effect on the two bacteria tested, as expected. In addition, samples with five layers (CH/ALG/CH/ALG/CH) were more effective in inhibiting bacterial growth. This new coating for cellulosic fibers is a new strategy and may open new avenues for the development of antimicrobial polymers with potential application in health-care field.info:eu-repo/semantics/publishedVersio

Micro/nano-structured superhydrophobic surfaces in the biomedical field: part I: basic concepts and biomimetic approaches

Part II is available at: http://hdl.handle.net/1822/44292Inspired by natural structures, great attention has been devoted to the study and development of surfaces with extreme wettable properties. The meticulous study of natural systems revealed that the micro/nano-topography of the surface is critical to obtaining unique wettability features, including superhydrophobicity. However, the surface chemistry also has an important role in such surface characteristics. As the interaction of biomaterials with the biological milieu occurs at the surface of the materials, it is expected that synthetic substrates with extreme and controllable wettability ranging from superhydrophilic to superhydrophobic regimes could bring about the possibility of new investigations of cellâ material interactions on nonconventional surfaces and the development of alternative devices with biomedical utility. This first part of the review will describe in detail how proteins and cells interact with micro/nano-structured surfaces exhibiting extreme wettabilities.AC Lima is grateful for financial support from Portuguese Foundation for Science and Technology (FCT) through the grant SFRH/BD/71395/2010 (under the scope of QRENPOPH – Tipologia 4.1 – Formação Avançada subsidized by European Social Found as well as by national funds of MEC). The authors also acknowledge the national funds from the FCT in the scope of project PTDC/CTM-BIO/1814/2012. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript

Engineering immunomodulatory hydrogels and cell-laden systems towards bone regeneration

The well-known synergetic interplay between the skeletal and immune systems has changed the design of advanced bone tissue engineering strategies. The immune system is essential during the bone lifetime, with macrophages playing multiple roles in bone healing and biomaterial integration. If in the past, the most valuable aspect of implants was to avoid immune responses of the host, nowadays, it is well-established how important are the crosstalks between immune cells and bone-engineered niches for an efficient regenerative process to occur. For that, it is essential to recapitulate the multiphenotypic cellular environment of bone tissue when designing new approaches. Indeed, the lack of osteoimmunomodulatory knowledge may be the explanation for the poor translation of biomaterials into clinical practice. Thus, smarter hydrogels incorporating immunomodulatory bioactive factors, stem cells, and immune cells are being proposed to develop a new generation of bone tissue engineering strategies. This review highlights the power of immune cells to upgrade the development of innovative engineered strategies, mainly focusing on orthopaedic and dental applications.publishe

An immunomodulatory miniaturized 3D screening platform using liquefied capsules

A critical determinant of successful clinical outcomes is the host's response to the biomaterial. Therefore, the prediction of the immunomodulatory bioperformance of biomedical devices following implantation is of utmost importance. Herein, liquefied capsules are proposed as immunomodulatory miniaturized 3D platforms for the high-content combinatorial screening of different polymers that could be used generically in scaffolds. Additionally, the confined and liquefied core of capsules affords a cell-mediated 3D assembly with bioinstructive microplatforms, allowing to study the potential synergistic effect that cells in tissue engineering therapies have on the immunological environment before implantation. As a proof-of-concept, three different polyelectrolytes, ranging in charge density and source, are used. Poly(L-lysine)-, alginate-, and chitosan-ending capsules with or without encapsulated mesenchymal stem/stromal cells (MSCs) are placed on top of a 2D culture of macrophages. Results show that chitosan-ending capsules, as well as the presence of MSCs, favor the balance of macrophage polarization toward a more regenerative profile, through the up-regulation of anti-inflammatory markers, and the release of pro-regenerative cytokines. Overall, the developed system enables the study of the immunomodulatory bioperformance of several polymers in a cost-effective and scalable fashion, while the paracrine signaling between encapsulated cells and the immunological environment can be simultaneously evaluated.publishe

Viscous microcapsules as microbioreactors to study mesenchymal stem/stromal cells osteolineage commitment

It is essential to design a multifunctional well-controlled platform to transfermechanical cues to the cells in different magnitudes. This study introduces aplatform, a miniaturized bioreactor, which enables to study the effect of shearstress in microsized compartmentalized structures. In this system, thewell-established cell encapsulation system of liquefied capsules (LCs) is usedas microbioreactors in which the encapsulated cells are exposed to variablecore viscosities to experience different mechanical forces under a 3D dynamicculture. The LC technology is joined with electrospraying to produce suchmicrobioreactors at high rates, thus allowing the application of microcapsulesfor high-throughput screening. Using this platform for osteogenicdifferentiation as an example, shows that microbioreactors with higher coreviscosity which produce higher shear stress lead to significantly higherosteogenic characteristics. Moreover, in this system the forces experienced bycells in each LC are simulated by computational modeling. The maximum wallshear stress applied to the cells inside the bioreactor with low, and high coreviscosity environment is estimated to be 297 and 1367 mPa, respectively, forthe experimental setup employed. This work outlines the potential of LCmicrobioreactors as a reliable in vitro customizable platform with a wide rangeof applications.publishe

Cell encapsulation in liquified compartments: Protocol optimization and challenges

Cell encapsulation is a widely used technique in the field of Tissue Engineering and Regenerative Medicine (TERM). However, for the particular case of liquefied compartmentalised systems, only a limited number of studies have been reported in the literature. We have been exploring a unique cell encapsulation system composed by liquefied and multilayered capsules. This system transfigured the concept of 3D scaffolds for TERM, and was already successfully applied for bone and cartilage regeneration. Due to a number of appealing features, we envisage that it can be applied in many other fields, including in advanced therapies or as disease models for drug discovery. In this review, we intend to highlight the advantages of this new system, while discussing the methodology, and sharing the protocol optimization and results. The different liquefied systems for cell encapsulation reported in the literature will be also discussed, considering the different encapsulation matrixes as core templates, the types of membranes, and the core liquefaction treatments.publishe

Behaviour of the ferroelectric phase transition of P(VDF/TrFE) (75/25) with increasing deformation

Samples of P(VDF-TrFE) 75/25 with several permanent deformations along the two main directions of the material were investigated by means infrared spectroscopy and calorimetric methods. The evolution of the phase transition temperature and the ferroelectric anomaly with increasing deformation was monitored and correlated with the structural changes occurring in the material.Fundaçãoo para a Ciência e Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação" (POCTI) - POCTI/CTM/33501/99