Synthesis, characterization, and application of composite alginate microspheres with magnetic and fluorescent functionalities

The synthesis and evaluation of thiolated alginate as the barrier to block nutrient absorption on small intestine for body-weight control

Obesity is the most common health concern all over the world. However, till now, there is no promising way to manage obesity or body-weight control. The aim of the study is to develop an edible gel as a health supplement that temporarily attaches to the mucus of the intestines, forming an absorption barrier to block the nutrients. We modify the alginate with the thiol group as thiolated alginate (TA) that may stay on the mucosa layer for a much longer time to reduce nutrient absorption. In this study, the TA is synthesized successfully and proved a good mucosal adhesion to serve as a barrier for nutrient absorption both in vitro and in vivo. The results of in vivo imaging system (IVIS) show that the synthesized TA can be exiled from the gastrointestinal tract within 24 h. The animal study shows that the TA by daily oral administration can effectively reduce body weight and fat deposition. The biosafety is evaluated in vitro at the cellular level, based on ISO-10993, and further checked by animal study. We do believe that the TA could have a greater potential to be developed into a safe health supplement to manage obesity and for body-weight control.

Polydopamine-coated nanocomposite theranostic implants for localized chemotherapy and MRI imaging

Sustained and localized delivery of chemotherapeutics in postoperative cancer treatment leads to a radical improvement in prognosis and a much decreased risk of tumor recurrence. In this work, polydopamine (PDA)-coated superparamagnetic iron oxide nanoparticle (SPION)-loaded polycaprolactone and poly (lactic-co-glycolic acid) fibers were developed as a potential implant to ensure safe and sustained release of the chemotherapeutic drug methotrexate (MTX), as well as provide local contrast for magnetic resonance imaging (MRI). Fibres were prepared by co-axial electrospinning and loaded with MTX-layered double hydroxide (LDH) nanocomposites in the core, yielding organic-inorganic hybrids ranging from 1.23 to 1.48 µm in diameter. After surface coating with PDA, SPIONs were subsequently loaded on the fibre surface and found to be evenly distributed, providing high MRI contrast. In vitro drug release studies showed the PDA coated fibres gave sustained release of MTX over 18 days, and the release profile is responsive to conditions representative of the tumor microenvironment such as slightly acidic pH values or elevated concentrations of the reducing agent glutathione (GSH). In vitro studies with Caco-2 and A549 cells showed highly effective killing with the PDA coated formulations, which was further enhanced at higher levels of GSH. The fibres hence have the potential to act as an implantable drug-eluting platform for the sustained release of cytotoxic agents within a tumor site, providing a novel treatment option for post-operative cancer patients.

Single-Step Synthesis of Alginate Microgels Enveloped with a Covalent Polymeric Shell: A Simple Way to Protect Encapsulated Cells

Microgels of biopolymers such as alginate are widely used to encapsulate cells and other biological payloads. Alginate is an attractive material for cell encapsulation because it is nontoxic and convenient: spherical alginate gels are easily created by contacting aqueous droplets of sodium alginate with divalent cations such as Ca²⁺. Alginate chains in the gel become cross-linked by Ca²⁺ cations into a 3-D network. When alginate gels are placed in a buffer, however, the Ca²⁺ cross-links are eliminated by exchange with Na⁺, thereby weakening and degrading the gels. With time, encapsulated cells are released into the external solution. Here, we describe a simple solution to the above problem, which involves forming alginate gels enveloped by a thin shell of a covalently cross-linked gel. The shell is formed via free-radical polymerization using conventional monomers such as acrylamide (AAm) or acrylate derivatives, including polyethylene glycol diacrylate (PEGDA). The entire process is performed in a single step at room temperature (or 37 °C) under mild, aqueous conditions. It involves combining the alginate solution with a radical initiator, which is then introduced as droplets into a reservoir containing Ca²⁺ and monomers. Within minutes of either simple incubation or exposure to ultraviolet (UV) light, the droplets are converted into alginate-polymer microcapsules with a core of alginate and a shell of the polymer (AAm or PEGDA). The microcapsules are mechanically more robust than conventional alginate/Ca²⁺ microgels, and while the latter swell and degrade when placed in buffers or in chelators like sodium citrate, the former remain stable under all conditions. We encapsulate both bacteria and mammalian cells in these microcapsules and find that the cells remain viable and functional over time. Lastly, a variation of the synthesis technique is shown to generate multilayered microcapsules with a liquid core surrounded by concentric layers of alginate and AAm gels. We anticipate that the approaches presented here will find application in a variety of areas including cell therapies, artificial cells, drug delivery, and tissue engineering.

Super-paramagnetic responsive nanofibrous scaffolds under static magnetic field enhance osteogenesis for bone repair in vivo

A novel nanofibrous composite scaffold composed of super-paramagnetic γ-Fe₂O₃ nanoparticles (MNP), hydroxyapatite nanoparticles (nHA) and poly lactide acid (PLA) was prepared using electrospinning technique. The scaffold well responds extern static magnetic field with typical saturation magnetization value of 0.049 emu/g as well as possesses nanofibrous architecture. The scaffolds were implanted in white rabbit model of lumbar transverse defects. Permanent magnets are fixed in the rabbit cages to provide static magnetic field for the rabbits post surgery. Results show that MNP incorporated in the nanofibers endows the scaffolds super-paramagnetic responsive under the applied static magnetic field, which accelerates new bone tissue formation and remodeling in the rabbit defect. The scaffold also exhibits good compatibility of CK, Cr, ALT and ALP within normal limits in the serum within 110 days post implantation. In conclusion, the super-paramagnetic responding scaffold with applying of external magnetic field provides a novel strategy for scaffold-guided bone repair.

Nanoparticle-DNA-polymer composites for hepatocellular carcinoma cell labeling, sensing, and magnetic resonance imaging

This paper describes comparative studies and protocols in (1) self-assembling of ultrasmall superparamagnetic iron oxide nanoparticle (NP), circular plasmid DNA, and branched polyethylenimine (PEI) composites; (2) magnetofection; (3) gene delivery, (4) magnetic resonance imaging (MRI), and (5) cytotoxicity of the composites toward hepatocellular carcinoma HepG2 cells.

Comparative diffusivity measurements for alginate-based atomized and inkjet-bioprinted artificial cells using fluorescence microscopy

Radial diffusivity profiles of atomized (MC, d = 1800 ± 200 µm) and inkjet-printed (MI, d = 40 ± 5 µm) alginate-based artificial cells have been generated using 2D Fluorescence Microscopy. The passive outward diffusion of FITC-Dextrans from MIs (0.5% LV alginate/15% CaCl2 coated with 0.5% Chitosan) and MCs (1.5% MV alginate/1.5% CaCl2) was measured and quantified using a Fickian model. As an expected outcome of miniaturization, the ratios of the outer layer diffusivities defined as D(MIout)/D(MCout) were 4.25 and 5.07 respectively for the 4 and 70 kDa markers, indicative of the enhanced diffusive potential of the miniaturized capsules.

Synthesis of superparamagnetic bare Fe₃O₄ nanostructures and core/shell (Fe₃O₄/alginate) nanocomposites

In this article we report about the synthesis of superparamagnetic bare Fe3O4 nanostructures and core/shell (Fe3O4/alginate) nanocomposites by simple low-temperature based method at pH values 5, 9, and 14. The structural morphology and magnetic behavior of Fe3O4 nanostructures and core/shell (Fe3O4/alginate) nanocomposites (Fe3O4/alg NCs) have been investigated by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). The particle size was calculated by TEM measurements and it turns out to be ∼10 nm and ∼14 nm for bare Fe3O4 nanoparticle and Fe3O4/alg NCs with core/shell structure, respectively. The magnetic properties of the synthesized products were found to be function of pH at which the synthesis has been done. The synthesized Fe3O4 nanoparticle and Fe3O4/alg NCs were found to be superparmagnetic in nature at room temperature. We observed that the value of saturation magnetization in case of Fe3O4/alg NCs decreases by increasing the pH value.

Multifunctional alginate microspheres for biosensing, drug delivery and magnetic resonance imaging

This research aims to develop and investigate a multifunctional implantable system capable of biosensing, drug delivery and magnetic resonance imaging (MRI) for continuous monitoring, controlled anti-inflammatory drug delivery and imaging, respectively. A glucose biosensor, diclofenac sodium (Diclo) and magnetic nanoparticles (MNP) were used as the biosensor component, anti-inflammatory agent and MRI contrast agent, respectively. MNP were synthesized by the co-precipitation technique and loaded with the sensor and drug components into alginate microspheres using a commercial droplet generator. The multifunctional system was then characterized using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry (VSM) and MRI. The MNP were found to be in the size range of 5-15 nm. The final system, comprising the biosensor, drug and MNP loaded inside alginate microspheres, was found to be in the size range of 10-60 μm. Biosensing studies indicated an excellent glucose response curve, with a regression coefficient of 0.974 (0-10mM of glucose, response time: 4 min). In vitro Diclo release shows that MNP loading in alginate microspheres increases the burst release percentage by 11-12% in both 60 and 10 μm particles. However, the duration of release for 85% drug release decreases with MNP loading by 7 and 6 days for 39 the 60 and 10 μm particles, respectively. Super-paramagnetism was confirmed by VSM, with 2.09 and 1.368 emu g(-1), respectively, for the 60 and 10 μm particles, with no hysteresis. MRI showed significant contrast for both sizes. The particles showed an excellent biocompatibility (>80%) for all combinations of formulations. The system shows a great potential for biosensing with concurrent drug delivery and visualization for biomedical applications.