Differential size‐exclusion chromatography for the analysis of gelatin–polyelectrolyte complexes

Differential size‐exclusion chromatography (SEC) is used to characterize complexes formed between gelatin and two synthetic polyelectrolytes, sodium poly(styrenesulfonate) and sodium poly(2‐acrylamido‐2‐methylpropanesulfonate). The analysis is performed under aqueous, low‐salt conditions where maximum complexation between gelatin and the polyelectrolytes occurs. The adsorption effects that are commonly encountered in conventional SEC for gelatin and other charged polymers chromatographed under these solution conditions are minimized, because the columns are constantly equilibrated with the analytes in the mobile phase. Analyte solutions of identical composition, but of higher or lower concentration than that contained in the mobile phase, are injected, resulting in positive or negative detector responses, respectively. This method can separate the complexes from individual components, and can be used to determine relative sizes and stoichiometries of the complexes as a function of both the input ratio of gelatin to polyelectrolyte and the molecular weight of the polyelectrolyte. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 275–280, 1999     

Thermoreversible gelation on cooling and on heating of an aqueous gelatin–poly(N-isopropylacrylamide) conjugate

A polymer conjugate composed of 43 wt% gelatin and 57 wt% poly(N-isopropylacrylamide) (PNIPAAm) was prepared. The dynamic viscoelastic properties of an aqueous solution of the conjugate at the concentration of 5 wt% were examined. The solution was viscous fluid at 30°C and turned into an elastic homogeneous hydrogel upon heating above 34°C or upon cooling below 10°C. The resultant hydrogels turned back into a solution at the opposite temperature cycles of the gelation. It is considered that the driving force of the gelation is the intermolecular hydrophobic interaction of PNIPAAm blocks or the intermolecular helix association of gelatin blocks, respectively, on heating or on cooling. © 1998 John Wiley & Sons, Ltd.     

Photoinduced Charge Separation in an Aqueous Phase Using Nanoporous TiO2 Film and a Quasi‐Solid Made of Natural Products

Solar cells comprised of nanoparticulate TiO₂ porous film photosensitized with an adsorbing dye have been utilized as photoinduced charge separation systems in aqueous media with the view to forming future artificial photosynthetic systems able to create fuels from solar energy and water. The photoinduced charge separation of the sensitized TiO₂ cell in a quasi‐solid, made from agarose or κ‐carrageenan, was investigated.

I–V curves under 98 mW · cm⁻² irradiation of ITO/TiO₂/Ru(dcbpy)₂(NCS)₂. Electrolyte: 0.1 M LiI/0.01 M I₂ in a quasi‐solid of 0.2 wt.‐% gelatin containing a large excess of water.     

Self-Forming Norbornene-Tetrazine Hydrogels with Independently Tunable Properties

Although photopolymerization reactions are commonly used to form hydrogels, these strategies rely on light and may not be suitable for delivering therapeutics in a minimally invasive manner. Here, hyaluronic acid (HA) macromers are modified with norbornene (Nor) or tetrazine (Tet) and upon mixing click into covalently crosslinked Nor-Tet hydrogels via a Diels–Alder reaction. By incorporating a high degree of Nor and Tet substitution, Nor-Tet hydrogels with a broad range in elastic moduli (5 to 30 kPa) and fast gelation times (1 to 5 min) are achieved. By pre-coupling methacrylated HANor macromers with thiolated peptides via a Michael addition reaction, Nor-Tet hydrogels are peptide-functionalized without affecting their physical properties. Mesenchymal stem cells (MSCs) on RGD-functionalized Nor-Tet hydrogels adhere and exhibit stiffness-dependent differences in matrix mechanosensing. Fluid properties of Nor-Tet hydrogel solutions allow for injections through narrow syringe needles and can locally deliver viable cells and peptides. Substituting HA with enzymatically degradable gelatin also results in cell-responsive Nor-Tet hydrogels, and MSCs encapsulated in Nor-Tet hydrogels preferentially differentiate into adipocytes or osteoblasts, based on 3D cellular spreading regulated by stable (HA) and degradable (gelatin) macromers.     

Improved Swelling Property of Tissue Adhesive Hydrogels Based on α-Cyclodextrin/Decyl Group-Modified Alaska Pollock Gelatin Inclusion Complexes

Adhesives/sealants are used after suturing to prevent leakage of cerebrospinal fluid from an anastomotic site. Commercial adhesives/sealants have been used to close the cerebral dura. However, swelling of the cured adhesives/sealants induces increased intracranial pressure and decreases the strength of the seal. In the present study, tissue adhesive hydrogels with improved swelling property using inclusion complex composed of α-cyclodextrin (αCD) and decyl group (C10)-modified Alaska pollock-derived gelatin (C10-ApGltn) with a high degree of substitution (DS) (>20 mol%) are developed. Viscosity of C10-ApGltn with a high DS solution remarkably decreased by the addition of αCD. The resulting αCD/C10-ApGltn adhesive hydrogel composed of αCD/C10-ApGltn inclusion complexes and poly(ethylene glycol) (PEG)-based crosslinker showed improved swelling property after immersion in saline. Also, the resulting adhesive has a significantly higher burst strength than fibrin-based adhesives and is as strong as a PEG-based adhesive. Quantitative analysis of αCD revealed that the improved swelling property of the resulting adhesive hydrogels is induced by the release of αCD from cured adhesive, and the subsequent assembly of decyl groups in the saline. These results suggest that adhesives developed using the αCD/C10-ApGltn inclusion complex can be useful for closing the cerebral dura mater.     

Ionically Modified Gelatin Hydrogels Maintain Murine Myogenic Cell Viability and Fusion Capacity

For tissue engineering of skeletal muscles, there is a need for biomaterials which do not only allow cell attachment, proliferation, and differentiation, but also support the physiological conditions of the tissue. Next to the chemical nature and structure of the biomaterial, its response to the application of biophysical stimuli, such as mechanical deformation or application of electrical pulses, can impact in vitro tissue culture. In this study, gelatin methacryloyl (GelMA) is modified with hydrophilic 2-acryloxyethyltrimethylammonium chloride (AETA) and 3-sulfopropyl acrylate potassium (SPA) ionic comonomers to obtain a piezoionic hydrogel. Rheology, mass swelling, gel fraction, and mechanical characteristics are determined. The piezoionic properties of the SPA and AETA-modified GelMA are confirmed by a significant increase in ionic conductivity and an electrical response as a function of mechanical stress. Murine myoblasts display a viability of >95% after 1 week on the piezoionic hydrogels, confirming their biocompatibility. The GelMA modifications do not influence the fusion capacity of the seeded myoblasts or myotube width after myotube formation. These results describe a novel functionalization providing new possibilities to exploit piezo-effects in the tissue engineering field.     

Laponite–Gelatin Nanofibrous Microsphere Promoting Human Dental Follicle Stem Cells Attachment and Osteogenic Differentiation for Noninvasive Stem Cell Transplantation

Nanofibrous microspheres (NFM) are emerging as prominent next-generation biomimetic injectable scaffold system for stem cell delivery and different tissue regeneration where nanofibrous topography facilitates ECM-like stem cells niches. Addition of osteogenic bioactive nanosilicate platelets within NFM can provide osteoconductive cues to facilitate matrix mediated osteogenic differentiation of stem cells and enhance the efficiency of bone tissue regeneration. In this study, gelatin nanofibrous microspheres are prepared containing fluoride-doped laponite XL21 (LP) using the emulsion mediated thermal induce phase separation (TIPS) technique. Systematic studies are performed to understand the effect of physicochemical properties of biomimicking NFM alone and with different concentrations of LP on human dental follicle stem cells (hDFSCs), their cellular attachment, proliferation, and osteogenic differentiation. The study highlights the effect of LP nanosilicate with biomimicking nanofibrous injectable scaffold system aiding in enhancing stem cell differentiation under normal physiological conditions compared to NFM without LP. The laponite–NFM shows suitability as excellent injectable biomaterials system for stem cell attachment, proliferation and osteogenic differentiation for stem cell transplantation and bone tissue regeneration.