Bioactive Hydrogel Marbles

Tissue engineered periosteum: Fabrication of a gelatin basedtrilayer composite scaffold with biomimetic properties for enhanced bone healing

The periosteum, a vascularized tissue membrane, is essential in bone regeneration following fractures and bone loss due to some other reasons, yet there exist several research gaps concerning its regeneration. These gaps encompass reduced cellular proliferation and bioactivity, potential toxicity, heightened stiffness of scaffold materials, unfavorable porosity, expensive materials and procedures, and suboptimal survivability or inappropriate degradation rates of the implanted materials. This research used an interdisciplinary approach by forming a new material fabricated through electrospinning for the proposed application as a layer-by-layer tissue-engineered periosteum (TEP). TEP comprises poly(ε-caprolactone) (PCL), PCL/gelatin/magnesium-doped zinc oxide (vascular layer), and gelatin/bioactive glass/COD liver oil (osteoconductive layer). These materials were selected for their diverse properties, when integrated into the scaffold formation, successfully mimic the characteristics of native periosteum. Scanning electron microscopy (SEM) was employed to confirm the trilayer structure of the scaffold and determine the average fiber diameter. In-vitro degradation and swelling studies demonstrated a uniform degradation rate that matches the typical recovery time of periosteum. The scaffold exhibited excellent mechanical properties comparable to natural periosteum. Furthermore, the sustained release kinetics of COD liver oil were observed in the trilayer scaffold. Cell culture results indicated that the three-dimensional topography of the scaffold promoted cell growth, proliferation, and attachment, confirming its non-toxicity, biocompatibility, and bioactivity. This study suggests that the fabricated scaffold holds promise as a potential artificial periosteum for treating periostitis and bone fractures.

Biocompatible Hydrogel-Based Liquid Marbles with Magnetosomes

Liquid marbles are widely known for their potential biomedical applications, especially due to their versatility and ease of preparation. In the present work, we prepared liquid marbles with various cores composed of water, agar-based hydrogels, magnetic fluids, or non-aqueous substances. As a coating material, we used biocompatible particles of plant origin, such as turmeric grains and Lycopodium pollen. Additionally, we provided marbles with magnetic properties by incorporating either magnetosomes or iron oxide nanoparticles as a powder or by injecting another magnetic fluid. Structures obtained in this way were stable and susceptible to manipulation by an external magnetic field. The properties of the magnetic components of our marbles were verified using electron paramagnetic resonance (EPR) spectroscopy and vibrating sample magnetometry (VSM). Our approach to encapsulation of active substances such as antibiotics within a protective hydrogel core opens up new perspectives for the delivery of hydrophobic payloads to the inherently hydrophilic biological environment. Additionally, hydrogel marbles enriched with magnetic materials showed promise as biocompatible heating agents under alternating magnetic fields. A significant innovation of our research was also the fabrication of composite structures in which the gel-like core was surrounded without mixing by a magnetic fluid covered on the outside by the particle shell. Our liquid marbles, especially those with a hydrogel core and magnetic content, due to the ease of preparation and favorable properties, have great potential for biomedical use. The fact that we were able to simultaneously produce, functionalize (by filling with predefined cargo), and manipulate (by means of an external magnetic field) several marbles also seems to be important from an application point of view.

Robust cellulose-based hydrogel marbles with excellent stability for gas sensing

Liquid marbles, as particle-armored droplets, have potential applications in microreactors, biomedicine, controlled release and gas detection. To improve the stability and biocompatibility of marble, biocompatible cellulose acetate particles and 3-allyloxy-2-hydroxy-propyl-cellulose (AHP-cellulose) were used to fabricate robust cellulose-based liquid marbles with excellent stability. Liquid marble was gelled into hydrogel marble via blue-light-irradiated polymerization of AHP-cellulose. The mechanical properties of cellulose-based hydrogel marble are superior to those of liquid marble. The rupture height of liquid marble is 10.5 m, which is 420 times greater than that of water marble (0.025 m). Surprisingly, the hydrogel marble with a 3 % AHP-cellulose concentration remained intact even after being dropped from a height of 50 m, which is comparable with the ability of a leather ball to withstand larger impact. When released from a height of 60 mm, hydrogel marble bounced to approximately 25.5 mm, 881 % higher than liquid marble (2.6 mm). Hydrogel marble exhibited long-lasting stability and was capable of monitoring ammonia with a detection limit of 365.2 mg/m³. The biocompatible cellulose-based hydrogel marble with excellent mechanical stability and reusability detection has great potential in chemical and environmental engineering as gas sensors.

Core-Shell Beads as Microreactors for Phylogrouping of E. coli Strains

Multiplex polymerase chain reaction (PCR) is an effective tool for simultaneous detection of target genes. Nevertheless, their use has been restricted due to the intrinsic interference between primer pairs. Performing several single PCRs in an array format instead of a multiplex PCR is a simple way to overcome this obstacle. However, there are still major technical challenges in designing a new generation of single PCR microreactors with a small sample volume, rapid thermal cycling, and no evaporation during amplification. We report a simple and robust core-shell bead array for a series of single amplifications. Four core-shell beads with a polymer coating and PCR mixture were synthesized using liquid marble formation and subsequent photo polymerization. Each bead can detect one target gene. We constructed a customised system for thermal cycling of these core-shell beads. Phylogrouping of the E. coli strains was carried out based on the fluorescent signal of the core-shell beads. This platform can be a promising alternative for multiplex nucleic acid analyses due to its simplicity and high throughput. The platform reported here also reduces the cycling time and avoids evaporation as well as contamination of the sample during the amplification process.

Self-mineralizing Ca-enriched methacrylated gellan gum beads for bone tissue engineering

In this study, methacrylated gellan-gum (GG-MA) heteropolysaccharide is proposed as a hydrogel for drug delivery and bone tissue engineering applications. Calcium-enriched beads obtained from the crosslinking of 1% (w/v) GG-MA solutions with 0.1 MCaCl₂ were investigated, considering their intrinsic capacity to promote self-mineralization by ion binding and deposition. Indeed, when immersed in a physiological environment, the Ca-enriched beads promoted the development of a bone-like apatite layer, as confirmed by EDS and XRD chemical analysis. Additionally, the mild production process is compatible with drugs incorporation and release. After encapsulation, Dextran with different molecular weights as well as Dexamethasone 21-phosphate were efficiently released to the surrounding environment. The engineered system was also evaluated considering its biocompatibility, by means of qualitative determination of total complement activation, macrophage proliferation, cytokine release and in vitro cell culture. These experiments showed that the developed hydrogels may not stimulate a disproportionate pro-inflammatory reaction once transplanted. At last, when implanted subcutaneously in CD1 male mice up to 8 weeks, the beads were completely calcified, and no inflammatory reaction was observed. Summing up, these results show that calcium-enriched GG-MA hydrogel beads hold great potential as news tools for bone tissue regeneration and local drug delivery applications. STATEMENT OF SIGNIFICANCE: This work describes a low-cost and straightforward strategy to prepare bioactive methacrylated gellan gum (GG-MA) hydrogels, which can be used as drug delivery systems. GG-MA is a highly anionic polymer, that can be crosslinked with divalent ions, as calcium. Taking advantage of this feature, it was possible to prepare Ca-enriched GG-MA hydrogel beads. These beads display a bioactive behavior, since they promote apatite deposition when placed in physiological conditions. Studies on the immune response suggest that the developed beads do not trigger severe immune responses. Importantly, the mild processing method render these beads compliant with drug delivery strategies, paving the way for the application of dual-functional materials on bone tissue engineering.

On-Demand Coalescence and Splitting of Liquid Marbles and Their Bioapplications

Coalescence and splitting of liquid marbles (LMs) are critical for the mixture of precise amount precursors and removal of the wastes in the microliter range. Here, the coalescence and splitting of LMs are realized by a simple gravity-driven impact method and the two processes are systematically investigated to obtain the optimal parameters. The formation, coalescence, and splitting of LMs can be realized on-demand with a designed channel box. By selecting the functional channels on the device, gravity-based fusion and splitting of LMs are performed to mix medium/drugs and remove spent culture medium in a precise manner, thus ensuring that the microenvironment of the cells is maintained under optimal conditions. The LM-based 3D stem cell spheroids are demonstrated to possess an approximately threefold of cell viability compared with the conventional spheroid obtained from nonadhesive plates. Delivery of the cell spheroid to a hydrophilic surface results in the in situ respreading of cells and gradual formation of typical 2D cell morphology, which offers the possibility for such spheroid-based stem cell delivery in regenerative medicine.