Preparation and characterization of novel biocompatible cryogels of poly (vinyl alcohol) and egg-albumin and their water sorption study

Advanced Particle Size Analysis in High-Solid-Content Polymer Dispersions Using Photon Density Wave Spectroscopy

High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12-55% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both systems have been analyzed with common particle-size-measuring techniques like dynamic light scattering (DLS) and static light scattering (SLS) and compared to inline particle size distribution (PSD) measurements via photon density wave (PDW) spectroscopy in undiluted samples. It is shown that particle size measurements of undiluted polystyrene dispersions are in good agreement between analysis methods. However, for polyvinyl acetate particles, size determination is challenging due to bound water in the produced polymer. For the first time, water-swelling factors were determined via an iterative approach of PDW spectroscopy error (Χ2) minimization. It is shown that water-swollen particles can be analyzed in high-solid-content solutions and their physical properties can be assumed to determine the refractive index, density, and volume fraction in dispersion. It was found that assumed water swelling improved the reduced scattering coefficient fit by PDW spectroscopy by up to ten times and particle size determination was refined and enabled. Particle size analysis of the water-swollen particles agreed well with offline-based state-of-the-art techniques.

Cryogels: Advancing Biomaterials for Transformative Biomedical Applications

Cryogels, composed of synthetic and natural materials, have emerged as versatile biomaterials with applications in tissue engineering, controlled drug delivery, regenerative medicine, and therapeutics. However, optimizing cryogel properties, such as mechanical strength and release profiles, remains challenging. To advance the field, researchers are exploring advanced manufacturing techniques, biomimetic design, and addressing long-term stability. Combination therapies and drug delivery systems using cryogels show promise. In vivo evaluation and clinical trials are crucial for safety and efficacy. Overcoming practical challenges, including scalability, structural integrity, mass transfer constraints, biocompatibility, seamless integration, and cost-effectiveness, is essential. By addressing these challenges, cryogels can transform biomedical applications with innovative biomaterials.

Amino acid-based hydrophobic affinity cryogel for protein purification from ora-pro-nobis (Pereskia aculeata Miller) leaves

The surfaces of the polyacrylamide cryogels were coated with L-tryptophan (cryogel-Trp) or L-phenylalanine (cryogel-Phe) to enhance crude leaf extract-derived ora-pro-nobis (OPN) protein binding via pseudo-specific hydrophobic interactions. Cryogels functionalized with amino acids were prepared and characterized through morphological, hydrodynamic, and thermal analyses. The adsorption capacities of cryogel-Phe and cryogel-Trp were evaluated in terms of type (sodium sulfate or sodium phosphate) and concentration (0.02 or 0.10 mol∙L^-1) of saline solution, pH (4.0, 5.5, or 7.0), and NaCl concentration (0.0 or 0.5 mol∙L^-1). The cryogel-Phe presented a higher adsorptive capacity, achieving its maximum value (q = 92.53 mg∙g^-1) when the crude OPN crude leaf extract was diluted in sodium sulfate 0.02 mol∙L^-1 + NaCl 0.50 mol∙L^-1, at pH = 7.0. The dilution rate significantly (p < 0.05) affected the recovered protein amount after the adsorption and elution processes, reaching 94.45% when the feedstock solution was prepared with a crude extract 5 times. The zeta potential for the eluted OPN proteins was 5.76 mV (pH = 3.23) for both dilution rates. The secondary structure composition mainly included β-sheets (46.50%) and α-helices (13.93%). The cryogel-Phe exhibited interconnected pores ranging 20-300 μm in size, with a Young modulus of 1.51 MPa, and thermal degradation started at 230 °C. These results indicate that the cryogel-Phe exhibited satisfactory properties as promising chromatography support for use in high-throughput purification of crude leaf extract-derived OPN proteins.

Microfluidic generation of egg-derived protein microcarriers for 3D cell culture and drug delivery

Microcarriers have a demonstrated value for biomedical applications, in particular for drug delivery and three-dimensional cell culture. Attempts to develop this technique tend to focus on the fabrication of functional microparticles by using convenient methods with innovative but accessible materials. Inspired by the process of boiling eggs in everyday life, which causes the solidification of egg proteins, we present a new microfluidic "cooking" approach for the generation of egg-derived microcarriers for cell culture and drug delivery. As the egg emulsion droplets are formed with exquisite precision during the microfluidic emulsification, the resultant egg microcarriers present highly monodisperse and uniform morphologies at the size range of hundred microns to one millimeter. Benefiting from the excellent biocompatibility of the egg protein components, the obtained microcarriers showed good performances of cell adherence and growth. In addition, after a freezing treatment, the egg microcarriers were shown to have interconnected porous structures throughout their whole sphere, could absorb and load different kinds of drugs or other active molecules, and work as microcarrier-based delivery systems. These features point to the potential value of the microfluidic egg microcarriers in biomedicine.

Preparation and Property Evaluation of Conductive Hydrogel Using Poly (Vinyl Alcohol)/Polyethylene Glycol/Graphene Oxide for Human Electrocardiogram Acquisition

Conductive hydrogel combined with Ag/AgCl electrode is widely used in the acquisition of bio-signals. However, the high adhesiveness of current commercial hydrogel causes human skin allergies and pruritus easily after wearing hydrogel for electrodes for a long time. In this paper, a novel conductive hydrogel with good mechanical and conductive performance was prepared using polyvinyl alcohol (PVA), polyethylene glycol (PEG), and graphene oxide (GO) nanoparticles. A cyclic freezing⁻thawing method was employed under processing conditions of -40 °C (8 h) and 20 °C (4 h) separately for three cycles in sequence until a strong conductive hydrogel, namely, PVA/PEG/GO gel, was obtained. Characterization (Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy) results indicated that the assembled hydrogel was successfully prepared with a three-dimensional network structure and, thereafter, the high strength and elasticity due to the complete polymeric net formed by dense hydrogen bonds in the freezing process. The as-made PVA/PEG/GO hydrogel was then composited with nonwoven fabric for electrocardiogram (ECG) electrodes. The ECG acquisition data indicated that the prepared hydrogel has good electro-conductivity and can obtain stable ECG signals for humans in a static state and in motion (with a small amount of drift). A comparison of results indicated that the prepared PVA/PEG/GO gel obtained the same quality of ECG signals with commercial conductive gel with fewer cases of allergies and pruritus in volunteer after six hours of wear.

Facile fabrication of egg white macroporous sponges for tissue regeneration

The availability of 3D sponges combining proper biochemical, biophysical, and biomechanical properties with enhanced capacity of in vivo engraftment and vascularization is crucial in regenerative medicine. A simple process is developed to generate macroporous scaffolds with a well-defined architecture of interconnected pores from chicken egg white (EW), a material with protein- and growth factor-binding features which has not yet been employed in regenerative medicine. The physicomechanical properties and degradation rates of the scaffold are finely tuned by using varying concentrations of the cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, without alteration of the biochemical traits. In vitro, EW scaffolds supported active metabolism, proliferation, and migration of human dermal fibroblasts, thereby generating uniform cellular constructs. In vivo, subcutaneous implantation in mice reveals negligible immune reaction and efficient cell and tissue ingrowth. Angiogenesis into EW scaffolds is enhanced as compared to standard collagen type I sponges used as reference material, likely due to significantly higher adsorption of the proangiogenic factor vascular endothelial growth factor. In summary, a material is presented derived by facile processing of a highly abundant natural product. Due to the efficient subcutaneous engraftment capacity, the sponges can find utilization for soft tissue regeneration.

Designing polysaccharide-based antibacterial biomaterials for wound healing applications

In this study, the development and characterization of novel polymer blends based on chitosan-poly (vinyl alcohol) and physically cross-linked by freeze-thaw method for possible use in a variety of biomedical application is reported. The present investigation deals with designing savlon-loaded blend hydrogels (coined as cryogels) of poly (vinyl alcohol) (PVA) and chitosan by repeated freeze-thaw method and their characterization by SEM and FTIR techniques. The FTIR spectra clearly reveal that savlon-loaded chitosan and PVA blends are bonded together through hydrogen bonding. The SEM analysis suggests that cryogels show a well-defined porous morphology. The prepared cryogels were also investigated for swelling and deswelling behaviors. The results reveal that both the swelling and deswelling behaviors greatly depend on factors like chemical composition of the cryogels, number of freeze-thaw cycles, pH and temperature of the swelling bath. The savlon-loaded blends were also investigated for their in vitro blood compatibility and antibacterial activity.

Biopolymer-based hydrogels as scaffolds for tissue engineering applications: a review

Hydrogels are physically or chemically cross-linked polymer networks that are able to absorb large amounts of water. They can be classified into different categories depending on various parameters including the preparation method, the charge, and the mechanical and structural characteristics. The present review aims to give an overview of hydrogels based on natural polymers and their various applications in the field of tissue engineering. In a first part, relevant parameters describing different hydrogel properties and the strategies applied to finetune these characteristics will be described. In a second part, an important class of biopolymers that possess thermosensitive properties (UCST or LCST behavior) will be discussed. Another part of the review will be devoted to the application of cryogels. Finally, the most relevant biopolymer-based hydrogel systems, the different methods of preparation, as well as an in depth overview of the applications in the field of tissue engineering will be given.

Hydrogels for tissue engineering and delivery of tissue-inducing substances

This manuscript presents hydrogels (HGs) from a tissue engineering perspective being especially written for those who are approaching this field by offering a concise but inclusive review of hydrogel synthesis, properties, characterization methods, and applications.