In this study, we present a promising approach for the rapid development of porous polydimethylsiloxane (PDMS) scaffold prototypes, with outer geometry defined from the design stage, according to the form of conventional implants or adapted to patients' biostructures. The manufacture method is based on phase separation processes using materials obtained by casting within additive rapid prototyped molds. We include a comparative study of PDMS sponges obtained by different simple processes. Final in vitro assessment is carried out using hMSCs (bone marrow-derived human mesenchymal stem cells), cultured onto porous PDMS scaffolds functionalized with aminopropyltriethoxysilane (APTS) and equilibrated with a trophic factors medium produced by the cells. Results show that porous PDMS scaffold prototypes are excellent 3D platforms for hMSCs adhesion. Furthermore, this PDMS-3D niche, seeded with hMSCs and chondrogenic incubation medium during three weeks, showed a successful chondrogenesis determined by collagen type II expression. Thus, results show a versatile method to produce a 3D niche to address questions about cartilage and endochondral bone formation or skeleton tissues clinical approaches.
A b s t r a c tArticular repair is a relevant and challenging area for the emerging fields of tissue engineering and biofabrication. The need of significant gradients of properties, for the promotion of osteochondral repair, has led to the develop ment of several families of composite biomaterials and scaffolds, using different effective approaches, although a perfect solution has not yet been found. In this study we present the design, modeling, rapid manufacturing and in vitro testing of a composite scaffold aimed at osteochondral repair. The presented composite scaffold stands out for having a functional gradient of density and stiffness in the bony phase, obtained in titanium by means of computer aided design combined with additive manufacture using selective laser sintering. The chondral phase is obtained by sugar leaching, using a PDMS matrix and sugar as porogen, and is joined to the bony phase during the polymerization of PDMS, therefore avoiding the use of supporting adhesives or additional intermediate layers. The mechanical performance of the construct is biomimetic and the stiffness values of the bony and chondral phases can be tuned to the desired applications, by means of controlled modifications of different parameters. A human mesenchymal stem cell (h MSC) conditioned medium (CM) is used for improving scaffold response. Cell culture results provide relevant information regarding the viability of the composite scaffolds used.
Gold nanotriangles (AuNTs) functionalized with dithiolated oligonucleotides have been employed to develop an amplification-free electrochemical biosensor for SARS-CoV-2 in patient samples. Gold nanotriangles, prepared through a seed-mediated growth method and exhaustively characterized by different techniques, serve as an improved electrochemical platform and for DNA probe immobilization. Azure A is used as an electrochemical indicator of the hybridization event. The biosensor detects either single stranded DNA or RNA sequences of SARS-CoV-2 of different lengths, with a low detection limit of 22.2 fM. In addition, it allows to detect point mutations in SARS-CoV-2 genome with the aim to detect more infective SARS-CoV-2 variants such as Alpha, Beta, Gamma, Delta, and Omicron. Results obtained with the biosensor in nasopharyngeal swab samples from COVID-19 patients show the possibility to clearly discriminate between non-infected and infected patient samples as well as patient samples with different viral load. Furthermore, the results correlate well with those obtained by the gold standard technique RT-qPCR, with the advantage of avoiding the amplification process and the need of sophisticated equipment.
Graphical abstract
This paper presents the complete development and experimental validation of a microsystem designed to systematically assess the impact of surface topography on cell adhesion and dynamics. The microsystem includes two pools for culturing cells and for including chemicals. These pools are connected by several channels that have different microtextures, along which the cells crawl from one well to another. The impact of channel surface topography on cell performance, as well as the influence of other relevant factors, can therefore be assessed. The microsystem stands out for its being able to precisely define the surface topographies from the design stage and also has the advantage of including the different textures under study in a single device. Validation has been carried out by culturing human mesenchymal stem cells (hMSCs) on the microsystem pre-treated with a coating of hMSC conditioned medium (CM) produced by these cells. The impact of surface topography on cell adhesion, motility, and velocity has been quantified, and the relevance of using a coating of hMSC-CM for these kinds of studies has been analyzed. Main results, current challenges, and future proposals based on the use of the proposed microsystem as an experimental resource for studying cell mechanobiology are also presented.
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