The Experimental Study of Polyelectrolyte Coatings Suitability for Encapsulation of Cells

A Functionalized Membrane Layer as Part of a Dressing to Aid Wound Healing

PURPOSE

This study is an approach to a dressing platform based on support functionalized with oxygenating factors within an alginate layer, constituting a safe and even contact surface for interface with a wound.

METHODS

An alginate layer with incorporated oxygenating elements deposited on the support patch was assessed. As an oxygenating factor, perfluorooctyl was applied, and the layer coatings in two options, cross-linked and not, were evaluated. The function of human dermal fibroblast cells cultured in the presence of these constructs was analyzed, as well as their morphology using flow cytometry, fluorescence microscopy, and scanning electron microscopy. In addition, the membrane coating material was assessed using FTIR, AFM, and SEM-EDX characterization.

RESULTS

The applied membrane coatings adsorbed on the patch ensured the viability of the human fibroblasts cultured on the membranes during 10 days of culture. However, on the sixth day of culture, the percentage of live cells grown in the presence of cross-linked alginate with oxygenating factor ((ALG-PFC)net) was significantly higher than that of the cells cultured in the presence of the alginate coatings alone. SEM-EDX analysis of the (ALG-PFC)_net confirmed the presence of oxygenating and cross-linking factors. In addition, the regular granular branched structure of the layer coating material involving the oxygenating and cross-linking factors was observed using the AFM technique.

CONCLUSION

The topography of the layer coating material involving the oxygenating and cross-linking factors ensures an even contact surface for interface with the wound. Considering 5-day intervals between dressing replacements, the platform with an oxygenating configuration ensuring the growth and morphology of the human fibroblasts can be recommended at this time as an element of a dressing system.

A Composite Membrane System with Gold Nanoparticles, Hydroxyapatite, and Fullerenol for Dual Interaction for Biomedical Purposes

Background: Wound dressing plays a vital role in post-operative aftercare. There is the necessity to develop dressings for application on the border of soft and hard tissue. This study aimed to develop multifunctional polyelectrolyte layers enhanced by hydroxyapatite nanoparticles, gold nanoparticles (AuNPs), and/or fullerenol nanocomposites to achieve a wound dressing that could be applied on the bone-skin interface. Methods: Constructed shells were examined using TEM, STEM, and EDX techniques. The human osteoblasts or fibroblasts were immobilized within the shells. The systems morphology was assessed using SEM. The functioning of cells was determined by flow cytomery. Moreover, the internalization of AuNPs was assessed. Results: Involvement of fullerenol and/or hydroxyapatite nanoparticles influenced the immobilized cell systems morphology. Membranes with fullerenol and hydroxyapatite nanoparticles were observed to block the internalization of AuNPs by immobilized hFOB cells. Conclusions: The designed bilayer membranes incorporating fullerenol, and bacteriostatic elements, prevented the internalization of AuNPs by hFOB cells and ensured the proper counts and morphology of eukaryotic cells. The developed material can be recommended for dressings at the bone-skin interface.

Polyelectrolyte membrane scaffold sustains growth of neuronal cells

Cell immobilization within nano‐thin polymeric shells can provide an optimal concentration of biological material in a defined space and facilitate its directional growth. Herein, polyelectrolyte membrane scaffolds were constructed using a layer‐by‐layer approach to determine the possibility of promoting improved growth of rat cortical neuronal cells. Membrane presence was confirmed by Fourier transform infrared spectroscopy, Zeta potential, and atomic force and scanning electron microscopy. Scaffold performance toward neuronal cell growth was assessed in vitro during a 14‐day culture. Cell conditions were analyzed immunocytochemically. Furthermore, western blot and real‐time PCR analyses were used to validate the presence of neuronal and glial cells on the scaffolds. We observed that alginate/chitosan, alginate/polylysine, and polyethyleneimine/chitosan scaffolds promote neuronal growth similarly to the control, poly‐d‐lysine/laminin. We conclude that membranes maintaining cell viability, integrity and immobilization in systems supporting neuronal regeneration can be applied in neurological disease or wound healing treatment. © 2018 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 839–850, 2019.

Encapsulation of E. coli in biomimetic and Fe3O4-doped hydrogel: structural and viability analyses

The current study reports the modification of prokaryotic microorganism through a single-layer technique by using different polyanions/cations and doping with magnetic (Fe₃O₄) nanoparticles. Briefly, individual Escherichia coli cells were encapsulated through deposition of 1% sodium alginate as first layer followed by depositing precipitate layers of calcium chloride, disodium hydrogen phosphate, and Fe₃O₄ nanoparticles. Surface and cross sectional analysis of modified E. coli cells by field emission scanning electron microscope (FE-SEM) confirmed the synthesis of varying sizes of artificial shells around the microbial cells while the deposition of Fe₃O₄ nanoparticles was confirmed by transmission electron microscope (TEM). Thermogravimetric analysis (TGA) showed the deposition of 58 wt% of Fe₃O₄ nanoparticles on E. coli cell surface. Chemical structure analysis by Fourier transform infrared (FTIR) spectroscopy confirmed the presence of characteristic functional groups of deposited reagents in the hydrogel capsule. Zeta potential analysis of hydrogel capsule showed moderate stability with a surface charge of - 21 mV. Growth and viability analysis by Alamar Blue assay indicated marked increase in the reduction of resazurin blue (> 100%) by the modified E. coli indicating their viability. The movement and control of magnetized E. coli cells were manipulated using external permanent magnetic field as observed with optical microscope images. The surface-modified cells can find potential applications in bioremediation, biodegradation, and catalysis and can be used as biosorbents.

Bioresorbable polyelectrolytes for smuggling drugs into cells

There is ample evidence that biodegradable polyelectrolyte nanocapsules are multifunctional vehicles which can smuggle drugs into cells, and release them upon endogenous activation. A large number of endogenous stimuli have already been tested in vitro, and in vivo research is escalating. Thus, the interest in the design of intelligent polyelectrolyte multilayer (PEM) drug delivery systems is clear. The need of the hour is a systematic translation of PEM-based drug delivery systems from the lab to clinical studies. Reviews on multifarious stimuli that can trigger the release of drugs from such systems already exist. This review summarizes the available literature, with emphasis on the recent progress in PEM-based drug delivery systems that are receptive in the presence of endogenous stimuli, including enzymes, glucose, glutathione, pH, and temperature, and addresses different active and passive drug targeting strategies. Insights into the current knowledge on the diversified endogenous approaches and methodological challenges may bring inspiration to resolve issues that currently bottleneck the successful implementation of polyelectrolytes into the catalog of third-generation drug delivery systems.

Nanocoating of single cells: from maintenance of cell viability to manipulation of cellular activities

The chronological progresses in single-cell nanocoating are described. The historical developments in the field are divided into biotemplating, cytocompatible nanocoating, and cells in nano-nutshells, depending on the main research focuses. Each subfield is discussed in conjunction with the others, regarding how and why to manipulate living cells by nanocoating at the single-cell level.

Encapsulation of pancreatic islets within nano-thin functional polyethylene glycol coatings for enhanced insulin secretion

Covalent attachment of polymers to cells and tissues could be used to solve a variety of problems associated with cellular therapies. Insulin-dependent diabetes mellitus is a disease resulting from the autoimmune destruction of the beta cells of the islets of Langerhans in the pancreas. Transplantation of islets into diabetic patients is an attractive form of treatment, provided that the islets could be protected from the host's immune system to prevent graft rejection, and smaller numbers of islets transplanted in smaller volumes could be sufficient to reverse diabetes. Therefore, a need exists to develop islet encapsulation strategies that minimize transplant volume. In this study, we demonstrate the formation of nano-thin, poly(ethylene glycol) (PEG)-rich functional conformal coatings on individual islets via layer-by-layer assembly technique. The surface of the islets is modified with biotin-PEG-N-hydroxysuccinimide (NHS), and the islets are further covered by streptavidin (SA) and biotin-PEG-peptide conjugates using the layer-by-layer method. An insulinotropic ligand, glucagon-like peptide-1 (GLP-1), is conjugated to biotin-PEG-NHS. The insulinotropic effect of GLP-1 is investigated through layer-by-layer encapsulation of islets using the biotin-PEG-GLP-1 conjugate. The effect of islet surface modification using the biotin-PEG-GLP-1 conjugate on insulin secretion in response to glucose challenge is compared via static incubation and dynamic perifusion assays. The results show that islets coated with the functional PEG conjugate are capable of secreting more insulin in response to high glucose levels compared to control islets. Finally, the presence of SA is confirmed by indirect fluorescent staining with SA-Cy3, and the presence of PEG-peptide on the surface of the islets after treatment with biotin-PEG-GLP-1 is confirmed by indirect fluorescent staining with biotin-PEG-fluorescein isothiocyanate (FITC) and separately with an anti-GLP-1 antibody. This work demonstrates the feasibility of treating pancreatic islets with reactive polymeric segments and provides the foundation for a novel means of potential immunoisolation. With this technique, it may be possible to encapsulate and/or modify islets before portal vein transplantation and reduce transplantation volume significantly, and promote islet viability and insulin secretion due to the presence of insulinotropic peptides on the islet surface. Layer-by-layer self-assembly of PEG-GLP-1 offers a unique approach to islet encapsulation to stimulate insulin secretion in response to high glucose levels.