Andrada Serafim

One-pot synthesis of superabsorbent hybrid hydrogels based on methacrylamide gelatin and polyacrylamide. Effortless control of hydrogel properties through composition design

BiocompatibLe methacryLamide-modified geLatin (GELMA) hydrogeLs with tuned characteristics, obtained through network-forming photopoLymerization, have recenty attracted increasing attention due to their wide range of possibLe appLications such as drug reLease, tissue regeneration and generation of bioartificiaL impLants. Due to the controlled number of C=C bonds, GELMA may simuLtaneousLy act as macromonomer and crossLinker Leading through poLymerization to hydrogeLs with rationally designed performances. This study provides effortess one-pot synthesis of hybrid hydrogeLs based on covaLenty Linked GELMA and poLyacryLamide (PM), using photo-induced network-forming poLymerization. ConventionaL synthesis of simiLar hydrogeLs Leads to interpenetrating geLatin and PAA networks, usually invoLving muLtistep crossLinking of the components and the use of toxic crossLinkers. Through the described one-pot chemistry, the synthetic water superabsorbent PM with its well-recognized advantages can rationally benefit from the high biocompatibiLity and cell-adherence of GELMA in a simpLe covaLent way. This work provides a correLation between the composition and the corresponding hydrogeL properties (incLuding swelling, pH influence, mechanicaL behaviour, abiLity to generate porous scaffoLds, enzymatic degradation). The addition of PM moduLated the network density and the water affinity allowing the controL of eLasticity and degradabiLity. SuppLementary crossLinking of the synthetic component provided additionaL controL over hydrophiLicity. The capacity of such hydrogeLs to generate porous scaffoLds was proved; interesting morphoLogies were deveLoped onLy by varying the composition. In vitro ceLLuLar studies indicated that the presence of GELMA conferred controlled cell-affinity properties to the bicomponent hydrogeLs. NevertheLess, the drug reLease potentiaL of such hydrogeLs was preLiminarlly investigated using sodium nafcillin. GELMA PM hydrogeLs may be usefuL for tissue regeneration due to effortess synthesis, compositionaL flexibiLity and variabLe properties.

Osteoblast-Like Cell Behavior on Porous Scaffolds Based on Poly(styrene) Fibers

Scaffolds of nonresorbable biomaterials can represent an interesting alternative for replacing large bone defects in some particular clinical cases with massive bone loss. Poly(styrene) microfibers were prepared by a dry spinning method. They were partially melted to provide 3D porous scaffolds. The quality of the material was assessed by Raman spectroscopy. Surface roughness was determined by atomic force microscopy and vertical interference microscopy. Saos-2 osteoblast-like cells were seeded on the surface of the fibers and left to proliferate. Cell morphology, evaluated by scanning electron microscopy, revealed that they can spread and elongate on the rough microfiber surface. Porous 3D scaffolds made of nonresorbable poly(styrene) fibers are cytocompatible biomaterials mimicking allogenic bone trabeculae and allowing the growth and development of osteoblast-like cells in vitro.

Apatite formation on active nanostructured coating based on functionalized gold nanoparticles

In this work, we developed a simple method of surface functionalization of polymer substrates to provide them with the ability to form biomimetic hydroxyapatite (HA) when incubated in synthetic body fluids (SBF). In a first step, gold nanoparticles (AuNPs) were used as surface nanostructuring units for a biocompatible polymer, poly(2-hydroxyethyl methacrylate), known to not promote biomineralization in SBF, and under physiological conditions. The treatment of AuNPs-modified substrate with mercaptosuccinic acid leads to brushes of carboxyl-ended chains self-assembled onto the gold-polymer hybrid nanosurface. The main aim of this work was to demonstrate that these multianionic nanosurfaces would induce HA formation when incubated in solutions mimicking physiologic conditions. The formation of apatite and its morphology and composition were successfully investigated by means of high resolution scanning and transmission electron microscopy with energy dispersive X-ray microanalysis, infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Emphasis was put on the nucleation of HA in areas with agglomerated carboxyl-ended functionalized nanoparticles. The results obtained in this study may unlock new applications for smart active coatings based on functionalized AuNPs, such as the induction of biomineralization.

Electrospun fish gelatin fibrous scaffolds with improved bio-interactions due to carboxylated nanodiamond loading

Nanotechnology and biomimicry represent appealing but still underexploited techniques to develop innovative scaffolds with ECM-inspired features for tissue engineering. In the present work we have investigated the potential of a combination of two designed elements to trigger enhanced bio-interactions with bone regeneration potential: COOH-functionalized nanodiamond particles (COOH-NDPs) have been loaded for the first time into electrospun fish gelatin hydrogel fibers thus generating nanocomposite fibrous scaffolds with interconnected porosity. When compared to control fish gelatin fibers, no significant modification of the mineralization capacity in acellular simulated body fluid has been evidenced by micro-structural and spectroscopic investigations, for fibers with COOH-NDPs content ranging from 0.25% to 1%. It is important to mention that, following Ca/P alternate incubation, nano-apatite crystals were preferentially developed and firmly adhered on the fiber regions in the proximity of COOH-NDPs, as proven by transmission electron microscopy (TEM). Significant mineralization occurred in the culture media in the presence of MG63 osteoblast-like cells and seems to be directly stimulated by the presence of the nanoparticles. Altogether, these findings emphasize the ability of NDPs to enhance, when immobilized in gelatin fibers and exposed to specific media, the formation of apatite. It was also noticed that the number of adherent MG63 cells, their morphology and spreading were improved by increasing the amount of NDPs in the fibers (fluorescence and scanning electron microscopy). This work successfully proves the potential of such nanocomposite fibers to find applications in bone regeneration.

Gelatin-PVP Hydrogels with Potential Skin Grafts Applications

This work presents the synthesis and characterization of natural-synthetic hydrogels based on gelatin (Gel) and polyvinylpyrrolidone (PVP), with potential for skin grafts applications. The natural component, Gel insures the biocompatibility and biodegradability of the bicomponent system [1], while the synthetic counterpart, PVP, is a physiologic inert component, extensively used in medicine due to its water affinity and due to its capacity of confer elasticity to films and membranes with potential applications in skin grafts [2]. The obtained hydrogels were subjected to morpho-structural analysis and rheological and mechanical tests (traction). The water affinity of the systems was estimated and their capacity to generate porous substrates through freeze-drying was evaluated.

Nanocomposite particles with improved microstructure for 3D culture systems and bone regeneration

Nano-apatite and gelatin-alginate hydrogel microparticles have been prepared by a one-step synthesis combined with electrostatic bead generation, for the reconstruction of bone defects. Based on the analysis of bone composition, architecture and embryonic intramembranous ossification, a bio-inspired fabrication has been developed. Accordingly, the mineral phase has been in situ synthesized, calcifying the hydrogel matrix while the latter was crosslinked, finally generating microparticles that can assemble into a bone defect to ensure interconnected pores. Although nano-apatite—biopolymer composites have been widely investigated, microstructural optimization to provide improved distribution and stability of the mineral is rarely achieved. The optimization of the developed method progressively resulted in two types of formulations (15P and 7.5P), with 15 and 7.5 (wt%) phosphate content in the initial precursor. The osteolytic potential was investigated using differentiated macrophages. A commercially available calcium phosphate bone graft substitute (Eurocer 400) was incorporated into the hydrogel, and the obtained composites were in vitro tested for comparison. The cytocompatibility of the microparticles was studied with mouse osteoblast-like cell line MC3T3-E1. Results indicated the best in vitro performance have been obtained for the sample loaded with 7.5P. Preliminary evaluation of biocompatibility into a critical size (3 mm) defect in rabbits showed that 7.5P nanocomposite is associated with newly formed bone in the proximity of the microparticles, after 28 days.Graphical abstract

Design of cellulose–alginate films using PEG/NaOH aqueous solution as co-solvent

In this work, a novel poly(ethylene glycol) (PEG)/NaOH system was successfully applied as a co-solvent for two naturally occurring polysaccharides, cellulose (Cel) and sodium alginate (Alg), to obtain biopolymeric films. Different amounts of Cel and Alg were dissolved in aqueous mixtures of PEG and NaOH, cast onto a glass plate, and cross-linked using a combination of physical and chemical cross-linking via a well-controlled experimental procedure. The resultant films were further characterized to investigate the influence of both the PEG chain and the Cel/Alg feed ratio on their swelling kinetics and their spectral, thermal and morphological features. The Cel/Alg hydrogels were characterized by rheological measurement to evaluate their mechanical strength in the fully hydrated state. The experimental results show that the synthesized films exhibit interesting properties in both the water-swollen condition and dried state. The features are highly reliant on the PEG molecular weight used and on the Cel/Alg ratio. Considering the flexibility, stability and mechanical strength in the wet state, Cel/Alg-derived films could serve as suitable substrates for various engineering applications.

The Potential of NDPs-Loaded Fish Gelatin Fibers as Reinforcing Agent for Fish Gelatin Hydrogels

In this work we report the potential of nanostructured fibers consisting of nanodiamond particles (NDPs) and fish gelatin (FG) to modulate the mechanical properties of fish gelatin hydrogels, in the aim of developing bioinspired ECM analogues. NDPS-loaded FG fibers were obtained by electrospinning. The biocomposites were obtained through the enzymatic crosslinking of gelatin in the presence of NDPs-loaded FG fibers. The mechanical behavior was assessed at different preparative stages (precursors, fibrous mesh, biocomposite scaffolds).

Hybrid Hydrogels Intended as Scaffolds for Soft Tissue Repair

This work describes the investigation of the properties of hydrogels based on methacrylamide-modified gelatin (GelMA) and polyvinylpyrrolidone (PVP) with potential applications in wound treatment. While the semi-natural polymer insures the biocompatibility and biodegradability of the synthesized materials, the synthetic polymer was selected due to its water affinity and interesting mechanical properties. The efficiency of the polymerization process and the stability of the PVP within the semi interpenetrated polymer network (semiIPN) were verified through gel fraction study. The water affinity, tensile strength and rheological properties of the hydrogels were also investigated.