The results of experimental investigations into foaming process of poly(ε-caprolactone) using supercritical CO2 are presented. The objective of the study was to explore the aspects of fabrication of biodegradable and biocompatible scaffolds that can be applied as a temporary three-dimensional extracellular matrix analog for cells to grow into a new tissue. The influence of foaming process parameters, which have been proven previously to affect significantly scaffold bioactivity, such as pressure (8-18 MPa), temperature (323-373 K) and time of saturation (1-6 h) on microstructure and mechanical properties of produced polymer porous structures is presented. The morphology and mechanical properties of considered materials were analyzed using a scanning electron microscope (SEM), x-ray microtomography (μ-CT) and a static compression test. A precise control over porosity and morphology of obtained polymer porous structures by adjusting the foaming process parameters has been proved. The obtained poly(ε-caprolactone) solid foams prepared using scCO2 have demonstrated sufficient mechanical strength to be applied as scaffolds in tissue engineering.
The process of cognitive aging in global sense can be characterised by changes of the fluid and crystallised intelligence. In the context of this explanation the basic question is which cognitive functions and regulatory mechanisms play the basic role of the determinants for cognitive aging. Probable, mechanism of associative memory play a central role in top-down direction of cognitive processing. This type of memory connect the resources/networks of long term memory with the current processing in working memory. Another set of mechanisms concerns with bottom-up direction based on procedural memory, which is fundamental for the functioning of the mind as whole (Tulving theory,1985). Unfortunately, our knowledge about associative memory and its relations to working and procedural memory is incomplete and unclear. The importance of associative memory are partly, empirically supported by classic research on decreasing the cognitive components of intelligence aging, since the fluid and crystallized intelligence where discovered (Horn, Cattell, 1967). Changes of the mind functioning and its cognitive growth/aging can be characterised as a complex chain from primary, biologically determined mind, through Piagetian and Vygotsky’s type of mind to relatively balanced mind.
One of the actual challenges in tissue engineering applications is to efficiently produce as high of number of cells as it is only possible, in the shortest time. In static cultures, the production of animal cell biomass in integrated forms (i.e. aggregates, inoculated scaffolds) is limited due to inefficient diffusion of culture medium components observed in such non-mixed culture systems, especially in the case of cell-inoculated fiber-based dense 3D scaffolds, inside which the intensification of mass transfer is particularly important. The applicability of a prototyped, small-scale, continuously wave-induced agitated system for intensification of anchorage-dependent CP5 chondrocytes proliferation outside and inside three-dimensional poly(lactic acid) (PLA) scaffolds has been discussed. Fibrous PLA-based constructs have been inoculated with CP5 cells and then maintained in two independent incubation systems: (i) non-agitated conditions and (ii) culture with wave-induced agitation. Significantly higher values of the volumetric glucose consumption rate have been noted for the system with the wave-induced agitation. The advantage of the presented wave-induced agitation culture system has been confirmed by lower activity of lactate dehydrogenase (LDH) released from the cells in the samples of culture medium harvested from the agitated cultures, in contrast to rather high values of LDH activity measured for static conditions. Results of the proceeded experiments and their analysis clearly exhibited the feasibility of the culture system supported with continuously wave-induced agitation for robust proliferation of the CP5 chondrocytes on PLA-based structures. Aside from the practicability of the prototyped system, we believe that it could also be applied as a standard method offering advantages for all types of the daily routine laboratory-scale animal cell cultures utilizing various fiber-based biomaterials, with the use of only regular laboratory devices.
The article analyses the issue of the potential development of theoretical thinking in young children. The context for this discussion is found in the cultural and historical development theory of L.S. Vygotsky which constitutes the basis for assumptions regarding the thinking about development and education of children. It highlights the elementary education stage as a very important area of designing „developmental teaching” as understood by Vygotsky. The article emphasizes the role of an adult who builds the scaffolding for the child’s thinking and acting, and establishes the conditions and teaching environment necessary for the performance of a cognitive process directed at the development of theoretical thinking. In the author’s opinion building the foundation for theoretical thinking will be possible when teachers set „the right developmental and educational tasks” for a child who is constructing knowledge.