Biocompatibility and membrane strength of C3H10T1/2 cell-loaded alginate-based microcapsules

Hydrogel Microencapsulation Enhances Cryopreservation of Red Blood Cells with Trehalose

Cryopreservation of red blood cells (RBCs) plays a vital role in preserving rare blood and serologic testing, which is essential for clinical transfusion medicine. The main difficulties of the current cryopreservation technique are the high glycerol concentration and the tedious deglycerolization procedure after thawing. In this study, we explored a microencapsulation method for cryopreservation. RBC-hydrogel microcapsules with a diameter of approximately 2.184 ± 0.061 mm were generated by an electrostatic spraying device. Then, 0.7 M trehalose was used as a cryoprotective agent (CPA), and microcapsules were adhered to a stainless steel grid for liquid nitrogen freezing. The results show that compared with the RBCs frozen by cryovials, the recovery of RBCs after microencapsulation is significantly improved, up to a maximum of more than 85%. Additionally, the washing process can be completed using only 0.9% NaCl. After washing, the RBCs maintained their morphology and adenosine 5'-triphosphate (ATP) levels and met clinical transfusion standards. The microencapsulation method provides a promising, referenceable, and more practical strategy for future clinical transfusion medicine.

Multilayer Alginate Microcapsules For Live Cell Microencapsulation; Is There Any Preference For Selecting Cationic Polymers?

Since 1980 after introducing the concept of live cell encapsulation by Lim et al., this technology has received enormous attention. Several studies have been conducted to improve this technique; different polymers, either natural or synthetic, have been used as microcapsules` making materials and different substances as coating layers. Literature review leads us to the conclusion that alginate (Alg) multilayer microcapsules and, in particular, alginate-poly l-lysine (PLL)-alginate (APA) are the most used structures for live cell encapsulation. Although, disadvantages of PLL (e.g., weak mechanical strength and low biocompatibility) made researchers work on other cationic polymers to find an alternative. This review aims to discuss more popularly suggested cationic polymers such as poly l-ornithine (PLO), chitosan, etc. As alternatives for PLL and, more importantly, we want to take a closer look to see which one of these systems are closer to clinical applications.

Bioencapsulation technologies in tissue engineering

Bioencapsulation technologies have played an important role in the developing successes of tissue engineering. Besides offering immunoisolation, they also show promise for cell/tissue banking and the directed differentiation of stem cells, by providing a unique microenvironment. This review describes bioencapsulation technologies and summarizes their recent progress in research into tissue engineering. The review concludes with a brief outlook regarding future research directions in this field.

Potentiated Osteoinductivity via Cotransfection with BMP-2 and VEGF Genes in Microencapsulated C2C12 Cells

Microcapsules with entrapped cells hold great promise for repairing bone defects. Unfortunately, the osteoinductivity of microcapsules has been restricted by many factors, among which the deficiency of functional proteins is a significant priority. We potentiated the osteoinductivity of microencapsulated cells via cotransfection with BMP-2 and VEGF genes. Various tissue-derived mesenchymal stem cells and cell lines were compared for BMP-2 and VEGF cotransfection. Ethidium bromide (EB)/Calcein AM staining revealed that all of the cell categories could survive for 4 weeks after microencapsulation. An ELISA assay indicated that all microencapsulated BMP-2 or VEGF transfected cells could secrete gene products constitutively for 1 month. Particularly, the recombinant microencapsulated C2C12 cells released the most desirable level of BMP-2 and VEGF. Further experiments demonstrated that microencapsulated BMP-2 and VEGF cotransfected C2C12 cells generated both BMP-2 and VEGF for 4 weeks. Additionally, the cotransfection of BMP-2 and VEGF in microencapsulated C2C12 cells showed a stronger osteogenic induction against BMSCs than individual BMP-2-transfected microencapsulated C2C12 cells. These results demonstrated that the cotransfection of BMP-2 and VEGF into microencapsulated C2C12 cells is of potent utility for the potentiation of bone regeneration, which would provide a promising clinical strategy for cellular therapy in bone defects.

Endogenous release of female hormones from co-microencapsulated rat granulosa and theca cells

Deficiency of female hormones is the principal cause of menopausal syndrome. The aim of this study was to establish a co-microencapsulation model of ovarian granulosa cells (GCs) and theca cells (TCs), and to investigate its endogenous release of female hormones. Rat ovarian GCs and TCs were isolated and co-microencapsulated in alginate-chitosan-alginate microcapsules. The effects of cell number ratio of GCs/TCs on syntheses of estradiol (E2) and progesterone (P4) were investigated in vitro. Serum levels of E2 and P4 in ovariectomized rats were measured for 60 days after the co-microencapsulated GCs and TCs were transplanted. It was showed that E2 synthesis in vitro was influenced by cell number ratio of GCs/TCs and the ratio for the maximum synthesis was 1:2. Serum E2 and P4 levels could be maintained normal for 60 days by the co-microencapsulated GCs/TCs. Transplantation of co-microencapsulated GCs/TCs may be a promising approach to provide endogenous female hormones for menopausal syndrome.

Microencapsulation of stem cells to study cellular interactions

Microencapsulation is a technique used in both controlled delivery of materials over time as well as preservation of these materials while delivery is occurring. The range of materials able to be encapsulated is variable, from drugs to living cells. The latter is described here. Electrospray microencapsulation applies a high-voltage field, through which a polymeric material is extruded. A gelling bath, comprising a cross-linking material, is used to create a stable hydrogel containing secondary substances intended for delivery. Control of extrusion parameters, such as flow rate and voltage, allows for specification of diameter and pore sizes of the microcapsules.

Silk sericin-alginate-chitosan microcapsules: hepatocytes encapsulation for enhanced cellular functions

The encapsulation based technology permits long-term delivery of desired therapeutic products in local regions of body without the need of immunosuppressant drugs. In this study microcapsules composed of sericin and alginate micro bead as inner core and with an outer chitosan shell are prepared. This work is proposed for live cell encapsulation for potential therapeutic applications. The sericin protein is obtained from cocoons of non-mulberry silkworm Antheraea mylitta. The sericin-alginate micro beads are prepared via ionotropic gelation under high applied voltage. The beads further coated with chitosan and crosslinked with genipin. The microcapsules developed are nearly spherical in shape with smooth surface morphology. Alamar blue assay and confocal microscopy indicate high cell viability and uniform encapsulated cell distribution within the sericin-alginate-chitosan microcapsules indicating that the microcapsules maintain favourable microenvironment for the cells. The functional analysis of encapsulated cells demonstrates that the glucose consumption, urea secretion rate and intracellular albumin content increased in the microcapsules. The study suggests that the developed sericin-alginate-chitosan microcapsule contributes towards the development of cell encapsulation model. It also offers to generate enriched population of metabolically and functionally active cells for the future therapeutics especially for hepatocytes transplantation in acute liver failure.

Female hormone release of microencapsulated Xenopus laevis ovarian cells

Cell microencapsulation has potential for the treatment of endocrine diseases. This study aims to probe the feasibility of Xenopus laevis as an animal model for cell microencapsulation and transplantation and to evaluate the female hormone release of microencapsulated X. laevis ovarian cells. The cells were harvested, cultured and microencapsulated into alginate-chitosan-alginate microcapsules with an electrostatic generator. The estradiol and progesterone releases of the microencapsulated X. laevis ovarian cells were investigated both in vitro and in vivo. The results showed that the microencapsulated cells kept secreting estradiol and progesterone in vitro for 60 days. After transplantation, serum estradiol and progesterone levels in ovariectomized X. laevis remained elevated for 60 days. X. laevis has been proved to be a suitable animal model for cell microencapsulation and transplantation. Microencapsulated ovarian cells may be considered as a promising endogenous drug delivery system for the treatment of deficiency of female hormones.

A novel pulsed drug-delivery system: polyelectrolyte layer-by-layer coating of chitosan-alginate microgels

Purpose

The aim of this report was to introduce a novel “core-membrane” microgel drug-delivery device for spontaneously pulsed release without any external trigger.

Methods

The microgel core was prepared with alginate and chitosan. The semipermeable membrane outside the microgel was made of polyelectrolytes including polycation poly(allylamine hydrochloride) and sodium polystyrene sulfonate. The drug release of this novel system was governed by the swelling pressure of the core and the rupture of the outer membrane.

Results

The size of the core-membrane microgel drug-delivery device was 452.90 ± 2.71 μm. The surface charge depended on the layer-by-layer coating of polyelectrolytes, with zeta potential of 38.6 ± 1.4 mV. The confocal microscope exhibited the layer-by-layer outer membrane and inner core. The in vitro release profile showed that the content release remained low during the first 2.67 hours. After this lag time, the cumulative release increased to 80% in the next 0.95 hours, which suggested a pulsed drug release. The in vivo drug release in mice showed that the outer membrane was ruptured at approximately 3 to 4 hours, as drug was explosively released.

Conclusion

These data suggest that the encapsulated substance in the core-membrane microgel delivery device can achieve a massive drug release after outer membrane rupture. This device was an effective system for pulsed drug delivery.

Characterization of polymeric microcapsules containing a low molecular weight peptide for controlled release

A need exists to prolong the release of rapidly metabolized peptides of a low molecular weight, while delivering this peptide without environmental interference. Previous studies have used bovine serum albumin (BSA) as a model peptide to study release characteristics from alginate microcapsules. BSA is 66 kDa in size, while the peptide of interest here, connexin-43 carboxyl-terminus mimetic peptide (αCT1), is only 3.4 kDa. Such a change in size results in a much different set of release parameters. Our overall goal is a sustained release over a 24+ h period. Prolonged application of the peptide to a wound site to investigate therapeutic effects is ideal. As a result, a diffusion method using alginate microcapsules, along with the addition of poly-l-lysine and poly-l-ornithine, has been explored. We first aimed to establish and characterize our parameters through a set of parametric tests. Variations in polymer coating, change in pH, and changes in loading ratio have previously been shown to effect release using model compounds. Here we test specific changes in these parameters to show effects on the release of αCT1. Additionally, the microcapsules were attached to several biomaterials and surgical implants by ultraviolet cross-linking to study the effectiveness of attachment and delivery. Analysis and measurements using phase contrast microscopy, scanning electron microscopy, and atomic force microscopy were used to characterize changes in microcapsule morphology.

A Novel Core-Shell Microcapsule for Encapsulation and 3D Culture of Embryonic Stem Cells

In this study, we report the preparation of a novel microcapsule of ~ 100 μm with a liquid (as compared to solid-like alginate hydrogel) core and an alginate-chitosan-alginate (ACA) shell for encapsulation and culture of embryonic stem (ES) cells in the miniaturized 3D space of the liquid core. Murine R1 ES cells cultured in the microcapsules were found to survive (> 90%) well and proliferate to form either a single aggregate of pluripotent cells or embryoid body (EB) of more differentiated cells in each microcapsule within 7 days, dependent on the culture medium used. This novel microcapsule technology allows massive production of the cell aggregates or EBs of uniform size and controllable pluripotency, which is important for the practical application of stem cell based therapy. Moreover, the semipermeable ACA shell was found to significantly reduce immunoglobulin G (IgG) binding to the encapsulated cells by up to 8.2 times, compared to non-encapsulated cardiac fibroblasts, mesenchymal stem cells, and ES cells. This reduction should minimize inflammatory and immune responses induced damage to the cells implanted in vivo becasue IgG binding is an important first step of the undesired host responses. Therefore, the ACA microcapsule with selective shell permeability should be of importance to advance the emerging cell-based medicine.

Enhancement of surface graft density of MPEG on alginate/chitosan hydrogel microcapsules for protein repellency

Alginate/chitosan/alginate (ACA) hydrogel microcapsules were modified with methoxy poly(ethylene glycol) (MPEG) to improve protein repellency and biocompatibility. Increased MPEG surface graft density (n(S)) on hydrogel microcapsules was achieved by controlling the grafting parameters including the buffer layer substrate, membrane thickness, and grafting method. X-ray photoelectron spectroscopy (XPS) model was employed to quantitatively analyze n(S) on this three-dimensional (3D) hydrogel network structure. Our results indicated that neutralizing with alginate, increasing membrane thickness, and in situ covalent grafting could increase n(S) effectively. ACAC(PEG) was more promising than ACC(PEG) in protein repellency because alginate supplied more -COO(-) negative binding sites and prevented MPEG from diffusing. The n(S) increased with membrane thickness, showing better protein repellency. Moreover, the in situ covalent grafting provided an effective way to enhance n(S), and 1.00 ± 0.03 chains/nm(2) was achieved, exhibiting almost complete immunity to protein adsorption. This antifouling hydrogel biomaterial is expected to be useful in transplantation in vivo.

Microencapsulating and Banking Living Cells for Cell-Based Medicine

A major challenge to the eventual success of the emerging cell-based medicine such as tissue engineering, regenerative medicine, and cell transplantation is the limited availability of the desired cell sources. This challenge can be addressed by cell microencapsulation to overcome the undesired immune response (i.e., to achieve immunoisolation) so that non-autologous cells can be used to treat human diseases, and by cell/tissue preservation to bank living cells for wide distribution to end users so that they are readily available when needed in the future. This review summarizes the status quo of research in both cell microencapsulation and banking the microencapsulated cells. It is concluded with a brief outlook of future research directions in this important field.

Encapsulation of Living Cells in Small (∼100 μm) Alginate Microcapsules by Electrostatic Spraying: A Parametric Study

A parametric study was performed to understand the effect of preparation parameters on size, morphology, and encapsulation efficiency (i.e., cells/microcapsule) of alginate microcapsules prepared using the electrostatic spray method. The preparation parameters studied include sodium alginate concentration, spray voltage, flow rate, and cell density. It was found that both the flow rate and spray voltage have a significant impact on microcapsule size while the microcapsule morphology is greatly influenced by both the sodium alginate concentration and spray voltage. To obtain small (∼100 μm) cell-loaded microcapsules with good morphology (i.e., round in shape and uniform in size) and high encapsulation efficiency (>5 cells/microcapsule), the optimal ranges of spray voltage, flow rate, alginate concentration, and cell density are from 1.6–1.8 kV, 1.5–3 ml/h, >1.5% (w/v), and (3–5)×106 cells/ml, respectively. Under optimal preparation conditions, cells were found to survive the microencapsulation process well.