Synthesis and characterization of pH- and temperature-sensitive materials based on alginate and poly(N-isopropylacrylamide/acrylic acid) for drug delivery

Tailoring cell sheets for biomedical applications

Cell sheet technology has emerged as a novel scaffold-free approach for cell-based therapies in regenerative medicine. Techniques for harvesting cell sheets are essential to preserve the integrity of living cell sheets. This review provides an overview of fundamental technologies to fabricate cell sheets and recent advances in cell sheet-based tissue engineering. In addition to the commonly used temperature-responsive systems, we introduce alternative approaches, such as ROS-induced, magnetic-controlled, and light-induced cell sheet technologies. Moreover, we discuss the modification of the cell sheet to improve its function, including stacking, genetic modification, and vascularization. With the significant advances in cell sheet technology, cell sheets have been widely applied in various tissues and organs, including but not limited to the lung, cornea, cartilage, periodontium, heart, and liver. This review further describes both the preclinical and clinical applications of cell sheets. We believe that the progress in cell sheet technology would further propel its biomedical applications.

Assessment of temperature-sensitive properties of ionically crosslinked sodium alginate/hydroxypropyl cellulose blend microspheres: preparation, characterization, and in vitro release of paracetamol

Today, polymer systems can be formed to respond to single stimuli or multiple stimuli by changing their properties. The use of these systems, which are designed to be sensitive to stimuli, is expanding in a wide range of applications. Herein, microspheres of sodium alginate (NaAlg) and hydroxypropyl cellulose (HPC) sensitive to dual stimuli for the controlled release of model drug paracetamol were produced by the ionotropic gelation method in the presence of Zn²⁺ ions. FTIR, DSC, TGA, SEM, and particle size measurements were used to describe the blend microspheres. Low critical solution temperatures (LCST) of polymer blends at different ratios were determined and the biggest change according to the LCST value of HPC was found to be approximately 1-2 °C lower than 41 °C in microspheres with a NaAlg/HPC ratio of 50/50. In vitro release experiments of paracetamol from microspheres were carried out in a gastrointestinal tract simulation environment at two different temperatures (37 °C and 47 °C). From the release profiles, paracetamol release varied depending on the NaAlg/HPC ratio, the paracetamol content in the microspheres, the exposure time to Zn²⁺ ions, and the pH of the medium. Among the microsphere formulations, the highest entrapment efficiency was 57.86%, obtained for B₇ formulation microspheres with a NaAlg/HPC ratio of 70/30, a paracetamol loading percentage of 20%, and a crosslinking time of 5 min.RESEARCH HIGHLIGHTSMicrospheres of sodium alginate (NaAlg) and hydroxypropyl cellulose (HPC) sensitive to dual stimuli for the controlled release of model drug paracetamol were produced by the ionotropic gelation method in the presence of Zn²⁺ ions.LCST values of the microspheres with a NaAlg/HPC ratio of 50/50 were significantly lower by 1-2 °C than the LCST value of HPC, and the release results supported the temperature sensitivity of the microspheres.Among the microsphere formulations, the highest entrapment efficiency was 57.86% obtained for B₇ formulation microspheres.These microspheres can be used as a temperature-sensitive drug delivery system in the biomedical field and also as an encapsulation system of cancer drugs for cancer treatment modalities such as hyperthermia.

Alginate: Enhancement Strategies for Advanced Applications

Alginate is an excellent biodegradable and renewable material that is already used for a broad range of industrial applications, including advanced fields, such as biomedicine and bioengineering, due to its excellent biodegradable and biocompatible properties. This biopolymer can be produced from brown algae or a microorganism culture. This review presents the principles, chemical structures, gelation properties, chemical interactions, production, sterilization, purification, types, and alginate-based hydrogels developed so far. We present all of the advanced strategies used to remarkably enhance this biopolymer's physicochemical and biological characteristics in various forms, such as injectable gels, fibers, films, hydrogels, and scaffolds. Thus, we present here all of the material engineering enhancement approaches achieved so far in this biopolymer in terms of mechanical reinforcement, thermal and electrical performance, wettability, water sorption and diffusion, antimicrobial activity, in vivo and in vitro biological behavior, including toxicity, cell adhesion, proliferation, and differentiation, immunological response, biodegradation, porosity, and its use as scaffolds for tissue engineering applications. These improvements to overcome the drawbacks of the alginate biopolymer could exponentially increase the significant number of alginate applications that go from the paper industry to the bioprinting of organs.

Design and fabrication of hybrid triple-responsive κ-carrageenan-based nanospheres for controlled drug delivery

In the last two decades, the utilization of magnetic nanospheres in intelligent polymeric structures have received increased attention of researchers in numerous biomedical applications. Here, hybrid nanostructured triple-responsive magnetic nanospheres (κ-Car-g-P(AA/DMA)@Fe₃O₄) containing inorganic iron oxide core (Fe₃O₄) and organic graft copolymeric shell based on κ-carrageenan (κ-Car) and poly(acrylic acid/dimethylaminoethyl methacrylate) (P(AA/DMA)) were synthesized by microwave induced co-precipitation technique. The structure, size, surface morphology, magnetic property and stability of synthesized κ-Car-g-P(AA/DMA)@Fe₃O₄ magnetic nanospheres were characterized using FTIR, UV, XRD, TEM, Zeta-sizer, and VSM. κ-Car-g-P(AA/DMA)@Fe₃O₄ nanospheres were loaded with 5-Fluorouracil (5-FU) as an antineoplastic drug, and their 5-FU release behavior was explored in diverse graft yields, pH values, temperatures and in the existence of an alternating magnetic field. The κ-Car-g-P(AA/DMA)@Fe₃O₄ nanospheres demonstrated pH-, thermo-, and magnetic field-responsive 5-FU release with good biocompatibility and excellent anticancer activity. In addition, 5-FU release under 50 mT magnetic field reached to 100% within 4 h. This work exhibits that hybrid nanospheres have a triple stimuli-responsive influence, which is of principal importance for the future design and application of multi-functional responsive platforms to develop externally stimulated release of active agents and their healthcare capability.

Synthesis and characterization of temperature-sensitive microspheres based on acrylamide grafted hydroxypropyl cellulose and chitosan for the controlled release of amoxicillin trihydrate

This study deals with the preparation of temperature-sensitive chitosan/hydroxypropyl cellulose-graft-polyacrylamide (CS/HPC-g-PAAm) blend microspheres as a controlled drug release system. For this purpose, HPC-g-PAAm copolymers of hydroxypropyl cellulose (HPC) with acrylamide (AAm) were synthesized using cerium (IV) ammonium nitrate as initiator. The HPC-g-PAAm copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR), elemental analysis, and differential scanning calorimetry (DSC). Lower critical solution temperatures (LCST) of the synthesized copolymers were determined. Temperature-sensitive blend microspheres of HPC-g-PAAm and chitosan were prepared by emulsion cross-linking method using glutaraldehyde (GA) as a cross-linker in the hydrochloric acid catalyst (HCl) and they were used to achieve controlled release of amoxicillin trihydrate (AMX), an antibiotic drug. The microspheres were characterized by DSC, X-ray diffraction (X-RD), and FTIR spectroscopy. In addition, surfaces of empty and drug-loaded microspheres were examined by scanning electron microscopy (SEM). The effects of variables such as CS/HPC-g-PAAm ratio, drug/polymer ratio, amount of cross-linker, and reaction time of grafting on AMX release were investigated at three different pH environments (1.2, 6.8, 7.4) at 25 °C, 37 °C, and 50 °C. The release results showed that the microspheres had temperature sensitivity and the AMX release was slightly more controlled by especially increasing graft yield (%).

Development and optimization of Fe3+-crosslinked sodium alginate-methylcellulose semi-interpenetrating polymer network beads for controlled release of ibuprofen

In this study, ionically crosslinked beads of sodium alginate (NaAlg) and methylcellulose (MC) were prepared as semi-interpenetrating polymer networks (semi-IPN) in the size range of 1.97 ± 0.09-1.22 ± 0.13 mm by crosslinking with FeCl₃ and loaded with ibuprofen (IBU), which is a nonsteroidal anti-inflammatory drug. The highest 93.33% entrapment efficiency of IBU was achieved, and the drug release behaviors, mean particle size, and entrapment efficiency of beads were investigated in terms of the polymer composition, a ratio of ibuprofen to polymer, exposure time to crosslinker, and concentration of the crosslinking agent. Semi-IPN formulations prepared were also characterized using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), X-ray Diffraction (X-RD), and scanning electron microscopy (SEM). It was observed that IBU-loaded beads displayed better release performance with an increase amount of NaAlg in the structure. Finally, the optimum IBU release was obtained as 93.9% for beads containing 66.7% (w/w) NaAlg, 33.3% (w/w) MC, IBU/polymer ratio of 1/4, FeCl₃ concentration of 0.1 M, and crosslinking time of 90 min. The in vitro release rate was fitted to five empirical equations, and the diffusion exponent n, which indicated that the release mechanism of IBU from beads followed the Anomalous and Case II transport mechanism.

Synthesis and characteristics of a novel dust suppressant with good weatherability for controlling dust in open coal yards

This study aims to synthesize a dust suppressant for controlling coal dust pollution in open yards using natural polymers. Guided by graft copolymerization theory, potassium persulfate acts as an initiator to excite the free radicals of collagen and sodium alginate, allowing them to combine with acrylic acid and acrylamide to form a new polymer. The TG curve indicates that the thermal stability of the polymer is superior to that of the raw material. Scanning electron microscope (SEM) images show that the product can reduce the generation of dust by bonding the pulverized coal. With CCD method, when the monomer concentration increases in a certain range, the cohesive ability of the product to coal increases first and then decreases. Initiators and crosslinkers showed the same pattern. A series of performance experiments show that the product has a dust suppression rate of 98.7% at a wind speed of 14 m/s, and maintain one of 94.5% at a wind speed of 8 m/s after a rainstorm. In addition, there was no significant loss in dust suppression performance and compressive strength of the solidified layer after wind and rain. Sunlight, low temperature, and high temperature have little influence on the dust suppression effect of the product, which indicates that the product has better weather resistance and helps to suppress dust for a longer time in open air conditions.

Controlled drug delivery of ciprofloxacin from ultrasonic hydrogel

Ciprofloxacin is an antibacterial fluoroquinolone that stops the DNA synthesis, after penetration into the bacterial cells. This drug is applied in the curing of bacterial infections, as well as in antibiotics to treat urinary infections in women, infectious diarrhea and typhoid fever. The objective of the present work is to study controlled release of ciprofloxacin by hydrogel prepared by ultrasound. For this, first the swelling properties of hydrogel and then the absorption of drug were evaluated. The swollen hydrogel was dried in oven (50°C) and was ready for release experiments. During release, the loaded powder of the hydrogel was added to a buffer solution of pH 7.4, similar to human body condition. Then drug concentration was measured using a UV-visible (UV-Vis) spectrophotometer and a calibration curve. The results showed that the hydrogel is sensitive to pH, which makes it a good candidate for ciprofloxacin delivery in intestine. In addition, it was shown that the drug absorption is proportional with the swelling content of the hydrogel and the drug concentration in the loading process. The chemical structure and morphology of the hydrogels and loaded drug were characterized using Fourier transform infrared, UV-Vis, scanning electronic microscopy and thermal gravimetric analysis spectroscopy. According to the results presented here, acrylic-based hydrogels can be used in biomedical fields, especially for controlled drug release.

Angle-independent pH-sensitive composites with natural gyroid structure

pH sensor is an important and practical device with a wide application in environmental protection field and biomedical industries. An efficient way to enhance the practicability of intelligent polymer composed pH sensor is to subtilize the three-dimensional microstructure of the materials, adding measurable features to visualize the output signal. In this work, C. rubi wing scales were combined with pH-responsive smart polymer polymethylacrylic acid (PMAA) through polymerization to achieve a colour-tunable pH sensor with nature gyroid structure. Morphology and reflection characteristics of the novel composites, named G-PMAA, are carefully investigated and compared with the original biotemplate, C. rubi wing scales. The most remarkable property of G-PMAA is a single-value corresponding relationship between pH value and the reflection peak wavelength (λmax), with a colour distinction degree of 18 nm/pH, ensuring the accuracy and authenticity of the output. The pH sensor reported here is totally reversible, which is able to show the same results after several detection circles. Besides, G-PMAA is proved to be not influenced by the detection angle, which makes it a promising pH sensor with superb sensitivity, stability, and angle-independence.

Acid and base dual-controlled cargo molecule release from polyaniline gated-hollow mesoporous silica nanoparticles

Polyaniline chains grafted onto the surface of hollow mesoporous silica served as the gate to realize drug dual-controlled release.