218 research outputs found
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
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
Photopolymerizable platelet lysate hydrogels for customizable 3D cell culture platforms
3D cell culture platforms have emerged as a setting that resembles in vivo environments replacing the traditional 2D platforms. Over the recent years, an extensive effort has been made on the development of more physiologically relevant 3D cell culture platforms. Extracellular matrix-based materials have been reported as a bioactive and biocompatible support for cell culture. For example, human plasma derivatives have been extensively used in cell culture. Despite all the promising results, in most cases these types of materials have poor mechanical properties and poor stability in vitro. Here plasma-based hydrogels with increased stability are proposed. Platelet lysates are modified by addition of methacryloyl groups (PLMA) that polymerize in controlled geometries upon UV light exposure. The hydrogels could also generate porous scaffolds after lyophilization. The results show that PLMA materials have increased mechanical properties that can be easily adjusted by changing PLMA concentration or modification degree. Cells readily adhere, proliferate, and migrate, exhibiting high viability when encapsulated in PLMA hydrogels. The innovation potential of PLMA materials is based on the fact that it is a complete xeno-free solution for human cell culture, thus an effective alternative to the current gold standards for 3D cell culture based on animal products.publishe
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
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
Close-to-native bone repair via tissue-engineered endochondral ossification approaches
In order to solve the clinical challenges related to bone grafting, several tissue engineering (TE) strategies have been proposed to repair critical-sized defects. Generally, the classical TE approaches are designed to promote bone repair via intramembranous ossification. Although promising, strategies that direct the osteogenic differentiation of mesenchymal stem/stromal cells are usually characterized by a lack of functional vascular supply, often resulting in necrotic cores. A less explored alternative is engineering bone constructs through a cartilage-mediated approach, resembling the embryological process of endochondral ossification. The remodeling of an intermediary hypertrophic cartilaginous template triggers vascular invasion and bone tissue deposition. Thus, employing this knowledge can be a promising direction for the next generation of bone TE constructs. This review highlights the most recent biomimetic strategies for applying endochondral ossification in bone TE while discussing the plethora of cell types, culture conditions, and biomaterials essential to promote a successful bone regeneration process.publishe
Effect of the mechanical stretching on the ferroelectric properties of a (VDF/TrFE) (75/25) copolymer film
The transition phase behaviour of a vinylidene fluoride–trifluoroethylene (VDF–TrFE) copolymer film was studied after
being subjected to different mechanical stretching levels in both longitudinal (L) and transversal (T) directions relatively to the
initial extrusion direction. Both ferroelectric–paraelectric (FE–PE) and melting transitions were detected in the films by
differential scanning calorimetry, that were not affected by L stretching. This suggests that sliding mechanism along the c-axis
of such films during plastic deformation influences slightly the all-trans chain conformations and the CF2 dipole orientation. On the other hand, the FE–PE peak decreases in area and temperature upon T stretching, indicating a damage of the ferroelectric phase. However, the melting peak maintains unchanged. This fact provides evidence that the mechanical stretching do not change the total degree of crystallinity. The results suggest that the stretching induces a FE–PE phase transformation, without affecting the degree of crystallinity.Fundação para a Ciência e Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação" (POCTI) - POCTI/CTM/33501/99.Hamburger Synchrotronstrahlungslabor (HASYLAB) - Project II-01-006 EC
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