Cryogels are a type of hydrogel material which are fabricated by cryopolymerization at subzero temperature. Due to their unique macroporous structure, shape memory properties and injectability, cryogels have gained significant interest in the fields of tissue engineering for encouraging the repair and regeneration of injured tissues. In this review, the basic concepts relevant to cryogels are introduced, and then the fabrication principle, the process parameters and the unique properties of cryogel are discussed. Next, the latest advances of cryogels as three-dimensional scaffold for various tissue engineering applications are given. Finally, this review summarizes the current limitations of cryogels, and strategies to further improve their properties for tissue engineering. The purpose of this article is to provide a reference guide for the researchers in related fields.
Cryogels ; Porosity ; Tissue Engineering ; Tissue Scaffolds

Plasmid DNA (pDNA) is used as an important vector for gene therapy, and its wide application is restricted by the purity and yield. To obtain high-purity pDNA, a chromatographic method based on anion-exchange supermacroporous cryogel was explored. The anion-exchange cryogel was prepared by grafting diethylaminoethyl-dextran to the epoxide groups of polyacrylamide-based matrix and pUC19 plasmid was used as a target to test the method. The plasmid was transferred into Escherichia coli DH5alpha, cultivated, harvested and lysed. The obtained culture was centrifuged and the supernatant was used as the plasmid feedstock, which was loaded into the anion-exchange cryogel bed for chromatographic separation. By optimizing the pH of running buffer and the elution conditions, high-purity pDNA was obtained by elution with 0.5 mol/L sodium chloride solution at pH 6.6. Compared to the traditional methods for purification of pDNA, animal source enzymes and toxic reagents were not involved in the present separation process, ensuring the safety of both the purification operations and the obtained pDNA.
Anions ; Chromatography, Ion Exchange ; methods ; Cryogels ; chemical synthesis ; DNA ; isolation & purification ; Genetic Vectors ; isolation & purification ; Plasmids ; isolation & purification ; Porosity

BACKGROUND: Reconstruction of large eyelid defects remains challenging due to the lack of suitable eyelid tarsus tissue substitutes. We aimed to evaluate a novel bioengineered chitosan scaffold for use as an eyelid tarsus substitute.METHODS: Three-dimensional macroporous chitosan hydrogel scaffold were produced via cryogelation with specific biomechanical properties designed to directly match characteristics of native eyelid tarsus tissue. Scaffolds were characterized by confocal microscopy and tensile mechanical testing. To optimise biocompatibility, human eyelid skin fibroblasts were cultured from biopsy-sized samples of fresh eyelid skin. Immunological and gene expression analysis including specific fibroblast-specific markers were used to determine the rate of fibroblast de-differentiation in vitro and characterize cells cultured. Eyelid skin fibroblasts were then cultured over the chitosan scaffolds and the resultant adhesion and growth of cells were characterized using immunocytochemical staining.RESULTS: The chitosan scaffolds were shown to support the attachment and proliferation of NIH 3T3 mouse fibroblasts and human orbital skin fibroblasts in vitro. Our novel bioengineered chitosan scaffold has demonstrated biomechanical compatibility and has the ability to support human eyelid skin fibroblast growth and proliferation.CONCLUSIONS: This bioengineered tissue has the potential to be used as a tarsus substitute during eyelid reconstruction, offering the opportunity to pre-seed the patient's own cells and represents a truly personalised approach to tissue engineering.
Animals ; Ankle ; Chitosan ; Cryogels ; Eyelids ; Fibroblasts ; Gene Expression ; Humans ; Hydrogel ; In Vitro Techniques ; Mice ; Microscopy, Confocal ; Orbit ; Skin ; Tissue Engineering

BACKGROUNDChronic kidney disease (CKD) has become a public health problem. New interventions to slow or prevent disease progression are urgently needed. In this setting, cell therapies associated with regenerative effects are attracting increasing interest. We evaluated the effect of embryonic stem cells (ESCs) on the progression of CKD.

METHODSAdult male Sprague-Dawley rats were subjected to 5/6 nephrectomy. We used pedicled greater omentum flaps packing ESC-loaded gelatin microcryogels (GMs) on the 5/6 nephrectomized kidney. The viability of ESCs within the GMs was detected using in vitro two-photon fluorescence confocal imaging. Rats were sacrificed after 12 weeks. Renal injury was evaluated using serum creatinine, urea nitrogen, 24 h protein, renal pathology, and tubular injury score results. Structural damage was evaluated by periodic acid-Schiff and Masson trichrome staining.

RESULTSIn vitro, ESCs could be automatically loaded into the GMs. Uniform cell distribution, good cell attachment, and viability were achieved from day 1 to 7 in vitro. After 12 weeks, in the pedicled greater omentum flaps packing ESC-loaded GMs on 5/6 nephrectomized rats group, the plasma urea nitrogen levels were 26% lower than in the right nephrectomy group, glomerulosclerosis index was 62% lower and tubular injury index was 40% lower than in the 5/6 nephrectomized rats group without GMs.

CONCLUSIONSIn a rat model of established CKD, we demonstrated that the pedicled greater omentum flaps packing ESC-loaded GMs on the 5/6 nephrectomized kidney have a long-lasting therapeutic rescue function, as shown by the decreased progression of CKD and reduced glomerular injury.

Animals ; Cell Proliferation ; Cryogels ; Disease Progression ; Embryonic Stem Cells ; transplantation ; Gelatin ; administration & dosage ; Kidney ; pathology ; Male ; Mice ; Mice, Inbred C57BL ; Rats ; Rats, Sprague-Dawley ; Renal Insufficiency, Chronic ; pathology ; therapy