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

Smart Polymer Microspheres: Preparation, Microstructures, Stimuli-Responsive Properties, and Applications

Smart polymer microspheres (SPMs) are a class of stimulus-responsive materials that undergo physical, chemical, or property changes in response to external stimuli, such as temperature, pH, light, and magnetic fields. In recent years, their diverse responsiveness and tunable structures have enabled broad applications in biomedicine, environmental protection, information encryption, and other fields. This study provides a detailed review of recent preparation methods of SPMs, focusing on physical methods such as emulsification-solvent evaporation, microfluidics, and electrostatic spraying as well as chemical approaches such as emulsion and precipitation polymerization. Meanwhile, different types of stimulus-responsive behaviors, such as temperature-, pH-, light-, and magnetic-responsiveness, are thoroughly examined. This study also explores the applications of SPMs in drug delivery, tissue engineering, and environmental monitoring, while discussing future technological challenges and development directions in this field.

Dual responsive phase behavior of nonionic cellulose-based polymer brushes by visible-light-driven organocatalyzed atom transfer radical polymerization

Hydroxypropyl cellulose (HPC) is a nonionic, thermo-responsive polymer with temperature-dependent phase behavior. This behavior can be modified by grafting molecular units and polymer brushes onto the cellulose backbone. However, the thermo-response of such modified celluloses under biological and environmental conditions, such as pH, has been scarcely reported. This study details the synthesis and characterization of dual-temperature- and pH-responsive poly(vinyl pyrrolidone)-graft-hydroxypropyl cellulose (PVP-g-HPC) by organocatalyzed visible-light-driven atom transfer radical polymerization (O-ATRP). Employing a "grafting-from" approach, we synthesized a series of PVP-g-HPCs with controlled molecular weight and narrow dispersity. By precisely adjusting the molar ratios of HPC and N-vinyl pyrrolidone, we investigated the changes in the lower critical solution temperature (LCST) under various pH conditions. Our results revealed that the thermo-responsive PVP side chains exhibited a reverse dependence on pH. Additionally, the LCST window of HPC thermo-responsive derivatives was expanded to 37 °C within the physiological pH range.

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.

Design and assembly of biodegradable capsules based on alginate hydrogel composite for the encapsulation of blue dye

The encapsulation of bluing agents in biodegradable polymeric capsules is an emerging option in laundry detergents sector to substitute formaldehyde-based polymers, because they are non-biodegradable, carcinogenic and toxic. In this work, we present for the first time the successful encapsulation of a blue dye in biodegradable capsules which shell was formed by an alginate hydrogel and a polyethylene glycol network. Different types of capsules were synthesized (addition or not of the diacrylate monomer) and irradiation of the crosslinking solution at different times. Furthermore, a deep characterization of each type of capsules was performed (chemical and morphological characterization, assessment of their mechanical and thermal properties, evaluation of their biodegradability), noting that the incorporation of the diacrylate monomer (PEGDMA) and the two different irradiation times selected substantially affected the final properties of the capsules. The obtained results will serve to comprehend how the dye can be released from the capsules.

Microcarriers in application for cartilage tissue engineering: Recent progress and challenges

Successful regeneration of cartilage tissue at a clinical scale has been a tremendous challenge in the past decades. Microcarriers (MCs), usually used for cell and drug delivery, have been studied broadly across a wide range of medical fields, especially the cartilage tissue engineering (TE). Notably, microcarrier systems provide an attractive method for regulating cell phenotype and microtissue maturations, they also serve as powerful injectable carriers and are combined with new technologies for cartilage regeneration. In this review, we introduced the typical methods to fabricate various types of microcarriers and discussed the appropriate materials for microcarriers. Furthermore, we highlighted recent progress of applications and general design principle for microcarriers. Finally, we summarized the current challenges and promising prospects of microcarrier-based systems for medical applications. Overall, this review provides comprehensive and systematic guidelines for the rational design and applications of microcarriers in cartilage TE.

Controllable Construction of Temperature-Sensitive Supramolecular Hydrogel Based on Cellulose and Cyclodextrin

In temperature sensitive hydrogels, the swelling degree or light transmittance of the gel itself changes with variations in ambient temperature, prompting its wide application in controlled drug release, tissue engineering, and material separation. Considering the amphiphilic structure of β-cyclodextrin (β-CD), a cellulose-based supramolecular hydrogel with superior temperature sensitivity was synthesized based on a combination of cellulose and β-CD as well as the host–guest interaction between β-CD and polypropylene glycol (PPG). In the one-pot tandem reaction process, chemical grafting of β-CD on cellulose and the inclusion complexation of β-CD with PPG were performed simultaneously in a NaOH/urea/water system. The obtained supramolecular hydrogel had a lower critical solution temperature (LCST) of 34 °C. There existed covalent bonding between the cellulose and β-CD, host–guest complexation between the β-CD and PPG, and hydrogen bonding and hydrophobic interactions between the components in the network structure of the supramolecular hydrogel. The combination of various covalent and non-covalent bonds endowed the resulting supramolecular hydrogel with good internal network structure stability and thermal stability, as well as sensitive temperature responsiveness within a certain range—implying its potential as a smart material in the fields of medicine, biology, and textiles. This work is expected to bring new strategies for the fabrication of cellulose-based thermosensitive materials, benefitting the high-value utilization of cellulose.

Molecular Dynamics-Assisted Design of High Temperature-Resistant Polyacrylamide/Poloxamer Interpenetrating Network Hydrogels

Polyacrylamide has promising applications in a wide variety of fields. However, conventional polyacrylamide is prone to hydrolysis and thermal degradation under high temperature conditions, resulting in a decrease in solution viscosity with increasing temperature, which limits its practical effect. Herein, combining molecular dynamics and practical experiments, we explored a facile and fast mixing strategy to enhance the thermal stability of polyacrylamide by adding common poloxamers to form the interpenetrating network hydrogel. The blending model of three synthetic polyacrylamides (cationic, anionic, and nonionic) and poloxamers was first established, and then the interaction process between them was simulated by all-atom molecular dynamics. In the results, it was found that the hydrogen bonding between the amide groups on all polymers and the oxygen-containing groups (ether and hydroxyl groups) on poloxamers is very strong, which may be the key to improve the high temperature resistance of the hydrogel. Subsequent rheological tests also showed that poloxamers can indeed significantly improve the stability and viscosity of nonionic polyacrylamide containing only amide groups at high temperatures and can maintain a high viscosity of 3550 mPa·S at 80 °C. Transmission electron microscopy further showed that the nonionic polyacrylamide/poloxamer mixture further formed an interpenetrating network structure. In addition, the Fourier transform infrared test also proved the existence of strong hydrogen bonding between the two polymers. This work provides a useful idea for improving the properties of polyacrylamide, especially for the design of high temperature materials for physical blending.

Ultrasound in cellulose-based hydrogel for biomedical use: From extraction to preparation

As the most abundant natural polymer on the pl anet, cellulose has a wide range of applications in the biomedical field. Cellulose-based hydrogels further expand the applications of this class of biomaterials. However, a number of publications and technical reports are mainly about traditional preparation methods. Sonochemistry offers a simple and green route to material synthesis with the biomedical application of ultrasound. The tiny acoustic bubbles, produced by the propagating sound wave, enclose an incredible facility where matter interact among at energy as high as 13 eV to spark extraordinary chemical reactions. Ultrasonication not only improves the efficiency of cellulose extraction from raw materials, but also influences the hydrogel preparation process. The primary objective of this article is to review the literature concerning the biomedical cellulose-based hydrogel prepared via sonochemistry and application of ultrasound for hydrogel. An innovated category of recent generations of hydrogel materials prepared via ultrasound was also presented in some details.