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    • Silk which is a mixture of mainly SF and sericin

    2024-03-25

    Silk, which is a mixture of mainly SF and sericin, has an extensive history in clinical application as a suture material. Unwanted immune reactions to silk sutures observed early on in their application were assigned to the presence of sericin. However, in vitro and in vivo evaluations of pure SF films, scaffolds, or fibers demonstrated excellent biocompatibility, while maintaining the distinguishing mechanical features of silks as compared to most synthetic and all biopolymers known [18], [19], [20], [21], [22]. The performance of SF might be improved by the addition of cell-binding domains, such as the RGD domain, to increase the release of bioengineered products from terminally differentiated cells, such as interferon-beta release from fibroblasts [23]. However, the use of unmodified SF, which does not contain cell-binding domains and after methanol treatment predominantly forms beta-sheets, might be advantageous for the maintenance of defined differentiation pathways of stem cells or precursor cells. Therefore, unmodified SF should be a particularly suitable substrate for cells in which differentiation needs to be tightly controlled by exogenous cues. In addition to the biocompatibility of SF and its robust mechanical stability, the slow and complete biodegradation of the material in vivo is an important characteristic. This is relevant in light of the estimated time frame for function of bioincubators (release matrices) in epilepsy of 6–12 months, and based on previous findings detailing biodegradation at other anatomic sites than the cccp mitochondria [20], [24], [25].
    Materials and methods
    Results
    Discussion Local cell-mediated adenosine release has been demonstrated to represent an effective strategy to suppress seizures in the rat-kindling model of epilepsy [5], [6], [27]. In these previous studies, cells were engineered to release adenosine based on a genetic disruption of Adk−/−. The cells were encapsulated into a semipermeable, synthetic polyethersulfone membrane and implanted into the lateral brain ventricle of kindled rats. While this approach proved that paracrine cell-mediated adenosine release into the lateral ventricle was an efficacious treatment of epilepsy, the therapeutic effect did not persist because of limited cell viability within the polymer capsules. Furthermore, the system faced limitations due to the persistent nature of polysulfone, demanding a second surgical intervention if the bioreactor had to be replaced. New approaches in cell therapy must consider the long-term maintenance of cells on a biopolymeric substrate, which exhibits mechanical strength, biocompatibility, slow degradation, little or no immune or inflammatory response from the host tissue, and allow for cell adherence to the biomaterial matrix. Collagens have already proven their compatibility in nervous tissue [10], [11], [12], [13], [14]. However, they exhibit weak mechanical stability, fast biodegradation and may not be stable enough to maintain cell cultures in vivo. SF may offer an alternative to fill the niche due to its distinguished mechanical properties and optimal biodegradation times, adjustable between 6 and 12 months or more [24]. In addition, cells adhere directly to SF matrices and inflammatory reactions were less as compared to collagens or synthetic polymers [19], [20], [25], [26], [28]. Here we compared SF and fast degrading Col-1 with PO-coated tissue culture plastic as substrates for Adk−/− ESC-derived glial precursor cell culture in an effort to determine the feasibility of such substrates for clinically relevant epilepsy treatment. While the hydrophobicity of PO-coated tissue culture plastic appeared to be significantly lower than non-coated plastic, it was comparable to that of SF and Col-1 (Fig. 1). Therefore, in terms of hydrophilic interactions with the cells, SF and Col-1 appear equally capable compared to the traditional substrate used for cell culture, PO. Corroborating these findings, we observed that both Adk−/− and control (wt) ESC-derived glial precursor cells cultured on SF and Col-1 appeared to adhere and spread on the substrate to a similar degree as that observed on PO (Fig. 2). Therefore, SF and Col-1 are able to support the initial adherence and culture of ESC-derived glial precursor cells.