Conformal nano-thin modified polyelectrolyte coatings for encapsulation of cells.

Encapsulation of cells in polymeric shells allows for separation of biological material from produced factors, which may find biotechnological and biomedical applications. Human T-lymphocyte cell line Jurkat as well as rat pancreatic islets were encapsulated using LbL technique within shells of polyelectrolyte modified by incorporation of biotin complexed with avidin to improve cell coating and to create the potential ability to elicit specific biochemical responses. The coating with nano-thin modified shells allowed for maintenance of the evaluated cells' integrity and viability during the 8-day culture. The different PE impact may be observed on different biological materials. The islets exhibited lower mitochondrial activity than the Jurkat cells. Nevertheless, coating of cells with polyelectrolyte modified membrane allowed for functioning of both model cell types: 10 µm leukemia cells or 150 µm islets during the culture. Applied membranes maintained the molecular structure during the culture period. The conclusion is that applied modified membrane conformation may be recommended for coating shells for biomedical purposes.

The influence of porcine pancreas digestion parameters and islet histomorphology on islet isolation outcome.

Transplantation of the pig islets of Langerhans is considered as the future treatment for patients suffering from type I diabetes mellitus. Despite the adaptation of modified Ricordi method and highly purified collagenase, the results of pancreas digestions are precarious. Selection of proper donor and optimal digestion procedure are fundamental. The aim of this study was to assess the impact of pancreas procuring parameters on pig islets yield. The pancreata were harvested from 69 market sows weighting over 150 kg. After intraductal injection of cold collagenase solution pancreata were transported in UW solution or under conditions of two layer method (TLM). In laboratory pancreata were digested at 37 degrees C according to Ricordi isolation method or stationary in the bottle. The particular parameters of isolation procedure were considered as substantial. Pig weight, volume of infused collagenase solution, TLM application and pancreas dividing before digestion positively affected islet yield. Additionally, the influence of pancreatic islet tissue histomorphology on isolation outcome was studied. Proper donor selection as well as adequate digestion parameters could improve pig islet recovery during islet isolation.

The experimental study of polyelectrolyte coatings suitability for encapsulation of cells.

Living cells encapsulated in polymeric shells are receiving increasing attention because of their possible biotechnological and biomedical applications. The aim of this work is to evaluate how different polyelectrolyte coatings, characterized by different numbers of polyelectrolyte layers and by different polyelectrolyte conformations, affect the viability of encapsulated biological material. We demonstrate the ability to individually encapsulate HL-60 cells as well as rat pancreatic islets within polymeric shells consisting of different PE layers using the layer-by-layer process. Coating of HL-60 cells allows for surviving and functioning of cells for all applied PE as well as for different numbers of layers. The islets encapsulated in applied polyelectrolytes exhibited the lower level of mitochondrial activity as compared to non-encapsulated islets. Nevertheless, encapsulated islets exhibited comparable absorbance values during the whole period of culture. Polyelectrolyte coating seems to be a promising way of allowing capsule void volume minimization in a model of encapsulated biological material for local production of biologically active substances.

Suitability of polyelectrolyte shells modified with fullerene derivate for immunoisolation of cells. Experimental study.

The polymeric permiselective membranes application for immunoisolation of cells separating the transplanted cells from the host immunological system may eliminate immunosuppressive therapy during transplantation. The suitability of polyelectrolyte modified nanocoatings for immunoisolation of cells was assessed. The polymeric shells modified with incorporated fullerene derivate were applied for encapsulation of human T-lymphocyte cell line Jurkat or rat pancreatic islets of Langerhans using layer-by-layer technique. Hydroxylated fullerene was incorporated to the polyelectrolyte shell for hydrophility increase as well as for layer stability improvement. Evaluation with AFM, FTIR, fluorescence microscopy confirmed the nanocoating presence on the encapsulated cells. It was observed that polylysine-polyethyleneimine membrane with incorporated fullerenol allowed for encapsulated cells functioning in vitro. Membrane conformation applied for encapsulation of pancreatic rat islets allowed for glucose level decline during xenotransplantation into mice. The elaborated nanocoating may be recommended as the possible alternative to the space consuming microencapsulation for biomedical purposes.

Histomorphometrical analysis of porcine islets of Langerhans.

Xenotransplantation of pig islets of Langerhans may be an efficient method for treatment of type I diabetic patients. Considering the shortage of human pancreas donors, pigs offer readily available islet source. Unfortunately, their morphologic characteristics makes isolation of pig islets of Langerhans extremely difficult. The selection of a suitable donor may favorably affect the success of isolation. Therefore, we examined pig breeds and weights for their influence histomorphometric features of Langerhans islets. Pancreatic tissue biopsy specimens were obtained from Polish Large White pigs (n=5), Polish Landrace pigs (n=8), Pietrain pigs (n=4), and marked-weight pigs of 100 kg (n=8) or more than 200 kg (n=10). Biopsy specimens were fixed and stored in 4% formaldehyde. Tissue sections were stained with polyclonal guinea pig anti-insulin antibody. The number of islets per 1 cm2 was counted in each section. Mean diameters and areas of the islets were measured to calculate the percentage volume density. Differences were observed among the groups of pigs weighing 200 kg and 100 kg in islet mean diameter and area. The number of islets/cm2 was higher among Pietrain than Polish Landrace pigs (425.45±111.7 versus 315.33±36.59 islet/cm2, P<.05). Furthermore, Pietrain pigs showed the largest volume density (1.44%). Histological analysis revealed that Pietrain pigs of 100 kg and market-weight pigs of 200 kg were the best donors for islets of Langerhans.