Animal protein-based soft materials for tissue engineering applications

Proteins have long been used in coatings for cell culture plates and to supplement cell culture media. Due to their unmatched biocompatibility, biodegradability, bioactivity and immune-privilege, the interest in proteins rapidly advanced for the design and engineering of more complex substrates for biomedical applications. In this chapter, the proteins typically used in the design and fabrication of biomedical devices are presented and discussed, with particular focus in human-based platforms. However, restrictions in the use of protein-derived materials are associated with their limited processability and stability, but to overcome this, multiple bioconjugation techniques have been described and are herein presented. An overview of current protein-based materials that have found clinical application and that have been commercialized is also provided.publishe

Supercritical fluids: an emerging technology for the preparation of scaffolds for tissue engineering

[Excerpt] The field of tissue engineering has evolved greatly since the idea of combining active compounds and scaffolds to create artificial tissues. Small molecular weight drugs that control proliferation differentiation of cells can be incorporated into biodegradable scaffolds to induce cellular differentiation and tissue remodeling. The scaffold plays, therefore an important role not only as a physical support but also in the cell proliferation and differentiation. One of the most important stages of tissue engineering is the design and processing of a porous 3D structure, with high porosity, high interconnectivity between the porous and uniform distribution. A variety of processing techniques have been developed and include solvent casting and particles leaching, compression moulding and particle leaching, thermally induced phase separation, gas-foaming processes, among others. The main disadvantages of these methods are the use of organic solvents and the high temperatures required. The presence of residual organic solvents is being rigorously controlled by international safety regulations, it is necessary to warrant the complete removal and absence of these substances, without exposing bioactive compounds to high temperatures, which may degrade them. Supercritical fluid technology appears, therefore as an interesting alternative to the traditional processing methods.[...]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.The authors would like to thank Fundacao para a Ciencia e Tecnologia (FCT) for the funding granted concerning the project - PTDC/EBB-BIO/113671/2009 (FCOMP-01-0124-FEDER-014752) Skin2Tex. Also, we would like to thank Fundo Europeu de Desenvolvimento Regional (FEDER) through COMPETE - Programa Operacional Factores de Competitividade (POFC) for the co-funding

Psychological Impact of Coronavirus Disease 2019 Among Italians During the First Week of Lockdown

Pandemics and government-mandated quarantining measures have a substantial impact on mental health. This study investigated the psychological impact of the coronavirus disease 2019 (COVID-19) crisis on Italian residents during the first week of government-imposed lockdown and the role of defense mechanisms as protective factors against distress. In this cross-sectional study, 5,683 Italians responded to an online survey assessing socio-demographics, overall psychological distress, post-traumatic symptoms, and defense mechanisms using validated measures as the Symptom Checklist-90 (SCL-90), the Impact of Event Scale-Revised (IES-R), and the Defense Mechanisms Rating Scale-Self-Report-30 (DMRS-SR-30). Data were collected from March 13 to March 18, within the first week of lockdown in Italy. Results showed that younger age and female gender were associated with increased psychological distress. Having positive cases nearby, more days on lockdown, and having to relocate were also associated with greater distress. Higher overall defensive functioning (ODF) was associated with lower levels of depression (r = −.44, 95% CI −0.48, −0.40), anxiety (r = −.38, 95% CI −0.42, −0.35), and post-traumatic stress symptoms (PTSS) (r = −.34, 95% CI −0.38, −0.30). Conversely, less adaptive defensive functioning was related to greater affective distress across all domains. Each increased unit of ODF decreased the chances of developing post-traumatic stress symptoms (PTSS) by 71% (odds ratio = 0.29, p < 0.001, 95% CI.026,.032). The psychological impact of COVID-19 among Italians during the early weeks of government lockdown has been significant. The pandemic continues to have extraordinary mental health impact as it moves across the globe. Given the salience of defensive functioning in psychological distress, consideration of interventions that foster the use of more adaptive defenses may be an important component of building resilience amidst a pandemic

Selective cell recruitment and spatially controlled cell attachment on instructive chitosan surfaces functionalized with antibodies

Bioactive constructs to guide cellular mobilization and function have been proposed as an approach for a new generation of biomaterials in functional tissue engineering. Adult mesenchymal stem cells have been widely used as a source for cell based therapeutic strategies, namely tissue engineering. This is a heterogeneous cell population containing many subpopulations with distinct regenerative capacity. Thus, one of the issues for the effective clinical use of stem cells in tissue engineering is the isolation of a highly purified, expandable specific subpopulation of stem cells. Antibody functionalized biomaterials could be promising candidates to isolate and recruit specific cell types. Here we propose a new concept of instructive biomaterials that are able to recruit and purify specific cell types from a mixed cell population. This biomimetic concept uses a target-specific chitosan substrate to capture specific adipose derived stem cells. Specific antibodies were covalently immobilized onto chitosan membranes using bis[sulfosuccinimidyl] suberate (BS3). Quartz crystal microbalance (QCM) was used to monitor antibody immobilization/adsorption onto the chitosan films. Specific antibodies covalently immobilized kept their bioactivity and captured specific cell types from a mixed cell population. Microcontact printing allowed to covalently immobilize antibodies in patterns and simultaneously a spatial control in cell attachmentThe authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for the fellowships SFRH/BD/61390/2009 (C.A.C) and SFRH/BPD/45206/2008 (A.M.F), and also to the International Max-Planck-Research School (C.A.C) for the financial support. We are grateful to Hospital da Prelada for the donations. This work was carried out under the scope of the EU 7th Framework Programme (FP7/2007-2013) under grant agreement no. NMP4-SL-2009-229292 (Find&Bind)

Synthesis of temperature-responsive Dextran-MA/PNIPAAm particles for controlled drug delivery using superhydrophobic surfaces

Purpose: To implement a bioinspired methodology using superhydrophobic surfaces suitable for producing smart hydro- gel beads in which the bioactive substance is introduced in the particles during their formation. Methods: Several superhydrophobic surfaces, including polystyrene, aluminum and copper, were prepared. Polymeric solutions composed by photo-crosslinked dextran-methacrylated and thermal responsive poly(N-isopropylacrylamide) mixed with a protein (insulin or albumin) were dropped on the superhydrophobic surfaces, and the obtained millimetric spheres were hardened in a dry environment under UV light. Results: Spherical and non-sticky hydrogels particles were formed in few minutes on the superhydrophobic surfaces. The proteins included in the liquid formulation were homogeneously distributed in the particle network. The particles exhibited temperature-sensitive swelling, porosity and protein release rate, with the responsiveness tunable by the dextran-MA/PNIPAAm weight ratio.Conclusions: The proposed method permitted the preparation of smart hydrogel particles in one step with almost 100% encapsulation yield. The temperature-sensitive release profiles suggest that the obtained spherical-shaped biomaterials are suitable as protein carriers. These stimuli-responsive beads could have potential to be used in pharmaceutical or other biomedical applications, including tissue engineering and regenerative medicine.The authors acknowledge funding from the project: PTDC/QUI/68804/2006 (FCT), IBEROMARE-Procept, FEDER and MICINN (SAF2008-01679). The research leading to these results has also received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement #NMP4-SL-2009-229292. The authors are grateful to project DISC REGENERATION, Collaborative Project-Large-scale integrating project, NMP3-LA-2008-213904 for the use of the UV lamp

Novel methodology based on biomimetic superhydrophobic substrates to immobilize cells and proteins in hydrogel spheres for applications in bone regeneration

Cell-based therapies for regenerative medicine have been characterized by the low retention and integration of injected cells into host structures. Cell immobilization in hydrogels for target cell delivery has been developed to circumvent this issue. In this work mesenchymal stem cells isolated from Wistar rats bone marrow (rMSCs) were immobilized in alginate beads fabricated using an innovative approach involving the gellification of the liquid precursor droplets onto biomimetic superhydrophobic surfaces without the need of any precipitation bath. The process occurred in mild conditions preventing the loss of cell viability. Furthermore, fibronectin (FN) was also immobilized inside alginate beads with high efficiency in order to mimic the composition of the extracellular matrix. This process occurred in a very fast way (around 5 min), at room temperature, without aggressive mechanical strengths or particle aggregation. The methodology employed allowed the production of alginate beads exhibiting a homogenous rMSCs and FN distribution. Encapsulated rMSCs remained viable and were released from the alginate for more than 20 days. In vivo assays were also performed, by implanting these particles in a calvarial bone defect to evaluate their potential for bone tissue regeneration. Microcomputed tomography and histological analysis results showed that this hybrid system accelerated bone regeneration process. The methodology employed had a dual role by preventing cell and FN loss and avoiding any contamination of the beads or exchange of molecules with the surrounding environment. In principle, the method used for cell encapsulation could be extended to other systems aimed to be used in tissue regeneration strategies.The authors acknowledge the financial support of the Portuguese Foundation for Science and Technology (PTDC/EME-TME/103375/2008 and PTDC/EBB-BIO/114320/2009) for the PhD fellowship to Ana Catarina Lima (SFRH/BD/71395/2010), A. Sofia Silva (SFRH/BD/51584/2011), and Patricia Batista (SFRH/BD/45511/2008)

Association between Choroidal Characteristics and Systemic Severity in Amyloidosis

PURPOSE: This study aimed to describe the choroidal features of ocular amyloidosis using multimodal imaging, to correlate these findings with systemic involvement, and to propose a choroidal grading system. METHODS: Eleven patients with systemic amyloidosis were reviewed retrospectively. Each case was assigned a grade according to the severity of choroidal findings as determined by both enhanced depth imaging optical coherence tomography and indocyanine green angiography. The severity of systemic amyloidosis was then correlated with the choroidal involvement. RESULTS: On indocyanine green angiography, all patients exhibited hyperfluorescent spots in the late stage and were classified according to preexisting criteria. On enhanced depth imaging optical coherence tomography, hyperreflective foci were seen in the choriocapillaris and Sattler's layer in Grade 1, partial loss of Sattler's layer was additionally seen in Grade 2, and a dense hyperreflective Haller's layer was seen in Grade 3. Choroidal grading scores were significantly correlated with the systemic severity score (P = 0.0014, Pearson's correlation coefficient; ρ = 0.83). CONCLUSION: With ocular amyloidosis, evaluation of choroidal characteristics using multimodal imaging may serve as a biomarker for systemic involvement

Impact of heavy hole-light hole coupling on optical selection rules in GaAs quantum dots

We report strong heavy hole-light mixing in GaAs quantum dots grown by droplet epitaxy. Using the neutral and charged exciton emission as a monitor we observe the direct consequence of quantum dot symmetry reduction in this strain free system. By fitting the polar diagram of the emission with simple analytical expressions obtained from k$\cdot$p theory we are able to extract the mixing that arises from the heavy-light hole coupling due to the geometrical asymmetry of the quantum dot.Comment: 4 pages, 2 figure