Human mesenchymal stem cells labelled with dye-loaded amorphous silica nanoparticles: long-term biosafety, stemness preservation and traceability in the beating heart

Treatment of myocardial infarction with mesenchymal stem cells (MSCs) has proven beneficial effects in both animal and clinical studies. Engineered silica nanoparticles (SiO2-NPs) have been extensively used as contrast agents in regenerative medicine, due to their resistance to degradation and ease of functionalization. However, there are still controversies on their effective biosafety on cellular systems. In this perspective, the aims of the present study are: 1) to deeply investigate the impact of amorphous 50 nm SiO2-NPs on viability and function of human bone marrow-derived MSCs (hMSCs); 2) to optimize a protocol of harmless hMSCs labelling and test its feasibility in a beating heart model. Optimal cell labelling is obtained after 16 h exposure of hMSCs to fluorescent 50 nm SiO2-NPs (50 µg mL(-1)); interestingly, lysosomal activation consequent to NPs storage is not associated to oxidative stress. During prolonged culture hMSCs do not undergo cyto- or genotoxicity, preserve their proliferative potential and their stemness/differentiation properties. Finally, the bright fluorescence emitted by internalized SiO2-NPs allows both clear visualization of hMSCs in normal and infarcted rat hearts and ultrastructural analysis of cell engraftment inside myocardial tissue. Overall, 50 nm SiO2-NPs display elevated compatibility with hMSCs in terms of lack of cyto- and genotoxicity and maintenance of important features of these cells. The demonstrated biosafety, combined with proper cell labelling and visualization in histological sections, make these SiO2-NPs optimal candidates for the purpose of stem cell tracking inside heart tissue

Cross-linkable polyion complex micelles from polypept(o)ide-based ABC-triblock copolymers for siRNA delivery

ABC-type triblock copolymers are a rising platform especially for oligonucleotide delivery as they offer an additional functionality besides the anyhow needed functions of shielding and complexation. The authors present a polypept(o)ide-based triblock copolymer synthesized by amine-initiated ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs), comprising a shielding block A of polysarcosine (pSar), a poly(S-ethylsulfonyl-l-cystein) (pCys(SO2 Et)) block B for bioreversible and chemo-selective cross-linking and a poly(l-lysine) (pLys) block C for complexation to construct polyion complex (PIC) micelles as vehicle for small interfering RNA (siRNA) delivery. The self-assembly behavior of ABC-type triblocks is investigated to derive correlations between block lengths of the polymer and PIC micelle structure, showing an enormous effect of the β-sheet forming pCys(SO2 Et) block. Moreover, the block enables the introduction of disulfide cross-links by reaction with multifunctional thiols to increase stability against dilution. The right content of the additional block leads to well-defined cross-linked 50-60 nm PIC micelles purified from production impurities and determinable siRNA loading. These PIC micelles can deliver functional siRNA into Neuro2A and KB cells evaluated by cellular uptake and specific gene knockdown assays.Drug Delivery Technolog

Influence of the Plastic Properties on the Machinability of Aluminium Alloys

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaA presente dissertação tem como objetivo analisar a influência das propriedades plásticas na maquinabilidade de duas ligas de alumínio com composição química e comportamento mecânico distintos. As ligas utilizadas no estudo são uma liga não-tratável termicamente, da série AA 5083 – H111, e uma liga tratável termicamente, da série AA 6082 – T6. Com o objetivo de analisar a maquinabilidade das duas ligas foram efetuados ensaios de corte por arranque de apara recorrendo aos processos de furação, fresagem e torneamento. Em cada tipo de ensaio fizeram-se variar os parâmetros do processo de modo a criar condições severas de corte e melhor poder avaliar a influência do comportamento plástico das ligas na maquinabilidade. As diferenças na maquinabilidade das duas ligas foram avaliadas recorrendo a medições de temperatura e da rugosidade superficial, nos ensaios de torneamento, a medições de força, nos ensaios de furação, e à avaliação das aparas e da qualidade das superfícies maquinadas, nos ensaios de fresagem. A evolução do degaste das ferramentas foi analisada no final de todos os ensaios e relacionada com as condições de corte. O estudo realizado permitiu concluir que as duas ligas apresentam diferenças acentuadas na sensibilidade aos parâmetros de corte. Ou seja, enquanto a temperatura e a força de corte, para a liga AA 5083, variam com a velocidade e a profundidade de corte, para a liga AA 6082, variam apenas em função da profundidade de corte. Este resultado foi atribuído à maior sensibilidade da liga AA 5083 ao encruamento e à velocidade de deformação. Observou-se também que o comportamento plástico das ligas apresenta uma forte influência sobre a degradação das ferramentas de corte. Enquanto para a liga AA 6082 foi observado formação de apara aderente, com forte impacto nas condições de maquinagem, para a liga AA 5083, quase não se observou dano significativo das ferramentas. O estudo mostrou também que, quer a dureza, quer o limite de elasticidade dos materiais a maquinar, podem não ser bons indicadores da propensão do material a formar apara aderente.The main objective of the present dissertation is to analyze the influence of the plastic properties on the machinability of two aluminium alloys with different chemical composition and mechanical behavior. The alloys used in the study are a thermally non-treatable alloy of the AA 5083 – H111 series and a thermally treatable alloy of the AA 6082 – T6 series. For this purpose were used cutting tests procedures such as turning, drilling and milling. In each type of test the process parameters were changed in order to create severe cutting conditions and to evaluate better the influence of the plastic behavior of the alloys in the machinability.Differences in the machinability of the two alloys were evaluated using temperature and surface roughness measurements in turning tests, force measurements in drilling tests, and the evaluation of chips and the quality of machined surfaces in the milling tests. The evolution of the tool detrition was analyzed at the end of all the tests and related to the cutting conditions.In conclusion, this study demonstrated that the two alloys showed marked differences in the sensivity to the cut parameters. While the temperature and shear force vary with the speed and depth of cut for alloy AA 5083, for alloy AA 6082, it only vary with depth of cut. This result was attributed to the higher strain rate and strain hardening sensivity of the AA 5083. It was also observed that the plastic behavior of the alloys has a strong influence on the degradation of the cutting tools. While for the alloy AA 6082 adherent chip formation was observed, with strong impact in the machining conditions, for the alloy AA 5083, no significant tool damage was observed. The study also showed that both the hardness and the elasticity limit of the materials to be machined may not be good indicators of the propensy of the material to form adherent chip

Facile synthesis of AA'B- and ABC-type polypept(o)ide miktoarm star polymers utilizing polysarcosine end group functionalization for core introduction

Drug Delivery Technolog

Secondary-Structure-Driven Self-Assembly of Reactive Polypept(o)ides: Controlling Size, Shape, and Function of Core Cross-Linked Nanostructures

Achieving precise control over the morphology and function of polymeric nanostructures during self-assembly remains a challenge in materials as well as biomedical science, especially when independent control over particle properties is desired. Herein, we report on nanostructures derived from amphiphilic block copolypept(o)ides by secondary-structure-directed self-assembly, presenting a strategy to adjust core polarity and function separately from particle preparation in a bioreversible manner. The peptide-inherent process of secondary-structure formation allows for the synthesis of spherical and worm-like core-cross-linked architectures from the same block copolymer, introducing a simple yet powerful approach to versatile peptide-based core-shell nanostructures.FWN – Publicaties zonder aanstelling Universiteit Leide

Ketogenic diets slow melanoma growth in vivo regardless of tumor genetics and metabolic plasticity

Abstract Background Growing evidence supports the use of low-carbohydrate/high-fat ketogenic diets as an adjunctive cancer therapy. However, it is unclear which genetic, metabolic, or immunological factors contribute to the beneficial effect of ketogenic diets. Therefore, we investigated the effect of ketogenic diets on the progression and metabolism of genetically and metabolically heterogeneous melanoma xenografts, as well as on the development of melanoma metastases in mice with a functional immune system. Methods Mice bearing BRAF mutant, NRAS mutant, and wild-type melanoma xenografts as well as mice bearing highly metastatic melanoma allografts were fed with a control diet or ketogenic diets, differing in their triglyceride composition, to evaluate the effect of ketogenic diets on tumor growth and metastasis. We performed an in-depth targeted metabolomics analysis in plasma and xenografts to elucidate potential antitumor mechanisms in vivo. Results We show that ketogenic diets effectively reduced tumor growth in immunocompromised mice bearing genetically and metabolically heterogeneous human melanoma xenografts. Furthermore, the ketogenic diets exerted a metastasis-reducing effect in the immunocompetent syngeneic melanoma mouse model. Targeted analysis of plasma and tumor metabolomes revealed that ketogenic diets induced distinct changes in amino acid metabolism. Interestingly, ketogenic diets reduced the levels of alpha-amino adipic acid, a biomarker of cancer, in circulation to levels observed in tumor-free mice. Additionally, alpha-amino adipic acid was reduced in xenografts by ketogenic diets. Moreover, the ketogenic diets increased sphingomyelin levels in plasma and the hydroxylation of sphingomyelins and acylcarnitines in tumors. Conclusions Ketogenic diets induced antitumor effects toward melanoma regardless of the tumors´ genetic background, its metabolic signature, and the host immune status. Moreover, ketogenic diets simultaneously affected multiple metabolic pathways to create an unfavorable environment for melanoma cell proliferation, supporting their potential as a complementary nutritional approach to melanoma therapy