Design of a dual pH and temperature responsive hydrogel based on esterified cellulose nanocrystals for potential drug release

Design of Cellulose Nanocrystal-Based Self-Healing Nanocomposite Hydrogels and Application in Motion Sensing and Sweat Detection

Hydrogels, as flexible materials, have been widely used in the field of flexible sensors. Human sweat contains a variety of biomarkers that can reflect the physiological state of the human body. Therefore, it is of great practical significance and application value to realize the detection of sweat composition and combine it with human motion sensing through a hydrogel. Based on mussel-inspired chemistry, polydopamine (PDA) and gold nanoparticles (AuNPs) were coated on the surface of cellulose nanocrystals (CNCs) to obtain CNC-based nanocomposites (CNCs@PDA-Au), which could simultaneously enhance the mechanical, electrochemical, and self-healing properties of hydrogels. The CNCs@PDA-Au was composited with poly(vinyl alcohol) (PVA) hydrogel to obtain the nanocomposite hydrogel (PVA/CNCs@PDA-Au) by freeze-thaw cycles. The PVA/CNCs@PDA-Au has excellent mechanical strength (7.2 MPa) and self-healing properties (88.3%). The motion sensors designed with PVA/CNCs@PDA-Au exhibited a fast response time (122.9 ms), wide strain sensing range (0-600.0%), excellent stability, and fatigue resistance. With the unique electrochemical redox properties of uric acid, the designed hydrogel sensor successfully realized the detection of uric acid in sweat with a wide detection range (1.0-100.0 μmol/L) and low detection limit (0.42 μmol/L). In this study, the dual detection of human motion and uric acid in sweat was successfully realized by the designed PVA/CNCs@PDA-Au nanocomposite hydrogel.

Post-synthetic modification of nano-chitosan using gibberellic acid: Foliar application on sorghum under salt stress conditions and estimation of biochemical parameters

The challenge of desert farming with a high salt level has become an ecological task due to salt stress negatively affecting plant growth and reproduction. The current study deals with the cultivation of sorghum under salt stress conditions to counteract the effect of chitosan and gibberellic acid (GA3). Here, the effects of chitosan, GA3 and nano-composite (GA3@chitosan) on biochemical contents, growth and seed yield of sorghum under salinity stress conditions were studied. The results showed that spraying with GA3@chitosan increased sorghum grain yield by 2.07, 1.81 and 1.64 fold higher than salinity stressed plants, chitosan treatment and GA3 treatment, respectively. Additionally, compared to the control of the same variety, the GA3@chitosan spraying treatment improved the concentration of microelements in the grains of the Shandweel-1 and Dorado by 24.51% and 18.39%, respectively for each variety. Furthermore, spraying GA3@chitosan on sorghum varieties increased the accumulation of the macroelements N, P, and K by 34.03%, 47.61%, and 8.67% higher than salt-stressed plants, respectively. On the other hand, the proline and glycinebetaine content in sorghum leaves sprayed with nano-composite were drop by 51.04% and 11.98% less than stressed plants, respectively. The results showed that, in Ras Sudr, the Shandweel-1 variety produced more grain per feddan than the Dorado variety. These findings suggest that GA3@chitosan improves the chemical and biochemical components leading to a decrease in the negative effect of salt stress on the plant which reflects in the high-yield production of cultivated sorghum plants in salt conditions.

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

A review of recent advances of cellulose-based intelligent-responsive hydrogels as vehicles for controllable drug delivery system

To realize the maximum therapeutic activity of medicine and protect the body from the adverse effects of active ingredients, drug delivery systems (DDS) featured with targeted transportation sites and controllable release have captured extensive attention over the past decades. Hydrogels with unique three-dimensional (3D) porous structures present tunable capacity, controllable degradation, various stimuli sensitivity, therapeutic agents encapsulation, and loaded drugs protection properties, which endow hydrogels with bred-in-the-bone advantages as vehicles for drug delivery. In recent years, with the impressive consciousness of the "back-to-nature" concept, biomass materials are becoming the 'rising star' as the hydrogels building blocks for controlled drug release carriers due to their biodegradability, biocompatibility, and non-toxicity properties. In particular, cellulose and its derivatives are promising candidates for fabricating hydrogels as their rich sources and high availability, and various smart cellulose-based hydrogels as targeted carriers under exogenous such as light, electric field, and magnetic field or endogenous such as pH, temperature, ionic strength, and redox gradients. In this review, we summarized the main synthetic strategies of smart cellulose-based hydrogels including physical and chemical cross-linking, and illustrated the detailed intelligent-responsive mechanism of hydrogels in DDS under external stimulus. Additionally, the ongoing development and challenges of cellulose-based hydrogels in the biomedical field are also presented.

High-Strength, High-Swelling-Resistant, High-Sensitivity Hydrogel Sensor Prepared with Wood That Retains Lignin

Wood-derived hydrogels possess satisfactory longitudinal strength but lack excellent swelling resistance and dry shrinkage resistance when achieving high anisotropy. In this study, we displayed the preparation of highly dimensional stable wood/polyacrylamide hydrogels (wood/PAM-Al3+). The alkali-treated wood retains lignin as the skeleton of the hydrogel. Second, Al ions were added to the metal coordination with lignin. Finally, by employing free radical polymerization, we construct a conductive electronic network using polyaniline within the wood/PAM-Al3+ matrix to create the flexible sensor. This approach leverages lignin's integrated structure within the middle lamella to provide enhanced swelling resistance and stronger binding strength in the transverse direction. Furthermore, coordination between lignin and Al ions improves the mechanical strength of the wood hydrogel. Polyaniline provides stable linear pressure and temperature responses. The wood/PAM-Al3+ exhibits a transverse swelling ratio of 3.90% while achieving a longitudinal tensile strength of 20.5 MPa. This high-strength and high-stability sensor is capable of monitoring macroscale human behavior. Therefore, this study presents a simple yet innovative strategy for constructing tough hydrogels while also establishing an alternative pathway for exploring lignin networks in new functional materials development.

Nano/Micro-Structural Supramolecular Biopolymers: Innovative Networks with the Boundless Potential in Sustainable Agriculture

Sustainable agriculture plays a crucial role in meeting the growing global demand for food while minimizing adverse environmental impacts from the overuse of synthetic pesticides and conventional fertilizers. In this context, renewable biopolymers being more sustainable offer a viable solution to improve agricultural sustainability and production. Nano/micro-structural supramolecular biopolymers are among these innovative biopolymers that are much sought after for their unique features. These biomaterials have complex hierarchical structures, great stability, adjustable mechanical strength, stimuli-responsiveness, and self-healing attributes. Functional molecules may be added to their flexible structure, for enabling novel agricultural uses. This overview scrutinizes how nano/micro-structural supramolecular biopolymers may radically alter farming practices and solve lingering problems in agricultural sector namely improve agricultural production, soil health, and resource efficiency. Controlled bioactive ingredient released from biopolymers allows the tailored administration of agrochemicals, bioactive agents, and biostimulators as they enhance nutrient absorption, moisture retention, and root growth. Nano/micro-structural supramolecular biopolymers may protect crops by appending antimicrobials and biosensing entities while their eco-friendliness supports sustainable agriculture. Despite their potential, further studies are warranted to understand and optimize their usage in agricultural domain. This effort seeks to bridge the knowledge gap by investigating their applications, challenges, and future prospects in the agricultural sector. Through experimental investigations and theoretical modeling, this overview aims to provide valuable insights into the practical implementation and optimization of supramolecular biopolymers in sustainable agriculture, ultimately contributing to the development of innovative and eco-friendly solutions to enhance agricultural productivity while minimizing environmental impact.

Enhanced the treatment of ischemic stroke through intranasal temperature-sensitive hydrogels of edaravone and borneol inclusion complex

Since ischemic stroke occurs by a combination of multiple mechanisms, therapies that modulate multiple mechanisms are required for its treatment. The combination of edaravone (EDA) and borneol can significantly ameliorate the symptoms of neurological deficits in cerebral ischemia-reperfusion model in rats. In this study, the solubility of borneol and edaravone was improved by hydroxypropyl-β-cyclodextrin and PEG400. Furthermore, a nasal temperature-sensitive hydrogel containing both edaravone and borneol inclusion complex (EDA-BP TSGS) was developed to overcome the obstacles of ischemic stroke treatment including the obstruction of the blood-brain barrier (BBB) and the unavailability and untimely of intravenous injection. The effectiveness of the thermosensitive hydrogel was investigated in transient middle cerebral artery occlusion/reperfusion model rats (MCAO/R). The results showed that EDA-BP TSGS could significantly alleviate the symptoms of neurological deficits and decrease the cerebral infarct area and the degree of brain damage. In summary, nasal EDA-BP TSGS is a secure and effective brain-targeting formulation that may provide a viable option for the clinical prophylaxis and treatment of ischemic stroke.

High-yield and scalable cellulose nanomesh preparation via dilute acid vapor and enzymatic hydrolysis-mediated nanofabrication

Nanocellulose has received considerable attention in diverse research fields owing to its unique nanostructure-mediated physicochemical properties. However, classical acid hydrolysis usually destroys the microstructural integrity of cellulose, leading to the violent dissociation of cellulose into low-dimensional nanofibers and limiting the formation of intact structures with high specific surface areas. Herein, we have optimized the methodology of dilute acid vapor hydrolysis combined with the enzymatic hydrolysis (DAVE) method and investigated the pore formation mechanism of cellulose nanomesh (CNM). Benefiting from the selective nano-engraving effect of hydrochloric acid vapor on the amorphous region of cellulose followed by widening of the three-dimensional nanopores using enzymatic hydrolysis, confirmed by topographic, spectroscopic, and crystallographic tests, the as-prepared CNM, significantly different from the existing nanocellulose, exhibited improved specific surface area (98.37 m2/g), high yield (88.5 %), high crystallinity (73.4 %), and excellent thermal stability (375.4 °C). The proposed DAVE approach may open a new avenue for nanocellulose manufacturing.

Preparation and characterization of slow-release fertilizers loaded guar gum-g-poly methylmethacrylate-cl-polylactic acid (Gg-g-PMMA-cl-PLA) hydrogel and its effect on wheat growth

In order to reduce the harmful effects of synthetic non-biodegradable hydrogel, biopolymers have attracted attention, particularly for use in slow-release fertilizers. The current attempt intends to develop a hydrogel from biopolymers for sustainable release of water and nutrients in soil. Here, guar gum is used as a polysaccharide, MMA as a monomer, KPS as an initiator, and Polylactic acid as a cross-linker. Further investigation is done to study synthesized hydrogel in the development of wheat crop. Biodegradation study shows that it's environmentally favorable and degradable, contributing nutrients to the soil as it decomposes. Fertilizer release studies in soil and water show that the timing of the nutrient release is delayed, improving soil water holding capacity and retention studies. The agronomic parameters show that fertilizers-loaded hydrogel has a positive effect on physiological, morphological characteristics like shoot length, root length, number of shoots and roots, shoot weight and root weight, chlorophyll content, and most notably, fruiting efficiency is enhanced as compared with commercially available hydrogel. ATR-FTIR, SEM-EDX, TGA-DTA, and XRD analysis used to confirm successful loading of fertilizers and biodegradation of hydrogel. The encouraging findings suggested that this hydrogel could be used as a multifunctional, fertilizers-loaded hydrogel in crop production.

Bacterial cellulose composite hydrogel for pre-concentration and mass spectrometric detection of thiol-containing biomarker

Simple soaking of bacterial cellulose (BC) membrane in carboxymethyl cellulose (CMC) solution yielded BC/CMC hydrogel having re-swellable property. Then, gold nanoparticles (AuNPs) were embedded in the BC/CMC hydrogel via in situ chemical reduction to form BC/CMC/AuNPs composite hydrogel. It was found that the composite hydrogel exhibited physical/chemical characteristics similar to those of BC. The AuNPs with an average diameter of 13 nm distributed uniformly within the BC/CMC matrix as verified by transmission electron microscopy. The novelty of this work is the application of the BC/CMC/AuNPs composite hydrogel for selective adsorption of an important thiol-containing biomarker of Alzheimer's disease, glutathione (GSH), prior to direct laser desorption/ionization mass spectrometric (LDI-MS) detection. GSH adsorbed in the BC/CMC/AuNPs composite hydrogel showed the high ionization signal in LDI-MS providing a linear range of 50-10,000 nM with a limit of detection as low as 54.1 nM, which is a cut-off level for distinguishing between normal individuals and Alzheimer's patients. It should be emphasized that an additional matrix was not necessary as AuNPs can act as self-matrix for LDI-MS analysis. Furthermore, the BC/CMC/AuNPs composite hydrogel can effectively preconcentrate GSH approximately 10 times upon adsorption allowing for ultrasensitive detection of GSH required for disease diagnosis.

Graphene Oxide-Functionalized Bacterial Cellulose-Gelatin Hydrogel with Curcumin Release and Kinetics: In Vitro Biological Evaluation

Biopolymer-based bioactive hydrogels are excellent wound dressing materials for wound healing applications. They have excellent properties, including hydrophilicity, tunable mechanical and morphological properties, controllable functionality, biodegradability, and desirable biocompatibility. The bioactive hydrogels were fabricated from bacterial cellulose (BC), gelatin, and graphene oxide (GO). The GO-functionalized-BC (GO-f-BC) was synthesized by a hydrothermal method and chemically crosslinked with bacterial cellulose and gelatin using tetraethyl orthosilicate (TEOS) as a crosslinker. The structural, morphological, and wettability properties were studied using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a universal testing machine (UTM), respectively. The swelling analysis was conducted in different media, and aqueous medium exhibited maximum hydrogel swelling compared to other media. The Franz diffusion method was used to study curcumin (Cur) release (Max = 69.32%, Min = 49.32%), and Cur release kinetics followed the Hixson-Crowell model. Fibroblast (3T3) cell lines were employed to determine the cell viability and proliferation to bioactive hydrogels. Antibacterial activities of bioactive hydrogels were evaluated against infection-causing bacterial strains. Bioactive hydrogels are hemocompatible due to their less than 0.5% hemolysis against fresh human blood. The results show that bioactive hydrogels can be potential wound dressing materials for wound healing applications.

Tailoring the Swelling-Shrinkable Behavior of Hydrogels for Biomedical Applications

Hydrogels with tailor-made swelling-shrinkable properties have aroused considerable interest in numerous biomedical domains. For example, as swelling is a key issue for blood and wound extrudates absorption, the transference of nutrients and metabolites, as well as drug diffusion and release, hydrogels with high swelling capacity have been widely applicated in full-thickness skin wound healing and tissue regeneration, and drug delivery. Nevertheless, in the fields of tissue adhesives and internal soft-tissue wound healing, and bioelectronics, non-swelling hydrogels play very important functions owing to their stable macroscopic dimension and physical performance in physiological environment. Moreover, the negative swelling behavior (i.e., shrinkage) of hydrogels can be exploited to drive noninvasive wound closure, and achieve resolution enhancement of hydrogel scaffolds. In addition, it can help push out the entrapped drugs, thus promote drug release. However, there still has not been a general review of the constructions and biomedical applications of hydrogels from the viewpoint of swelling-shrinkable properties. Therefore, this review summarizes the tactics employed so far in tailoring the swelling-shrinkable properties of hydrogels and their biomedical applications. And a relatively comprehensive understanding of the current progress and future challenge of the hydrogels with different swelling-shrinkable features is provided for potential clinical translations.

Thermo-Responsive Hydrogels Encapsulating Targeted Core-Shell Nanoparticles as Injectable Drug Delivery Systems

As therapeutic agents that allow for minimally invasive administration, injectable biomaterials stand out as effective tools with tunable properties. Furthermore, hydrogels with responsive features present potential platforms for delivering therapeutics to desired sites in the body. Herein, temperature-responsive hydrogel scaffolds with embedded targeted nanoparticles were utilized to achieve controlled drug delivery via local drug administration. Poly(N-isopropylacrylamide) (pNIPAM) hydrogels, prepared with an ethylene-glycol-based cross-linker, demonstrated thermo-sensitive gelation ability upon injection into environments at body temperature. This hydrogel network was engineered to provide a slow and controlled drug release profile by being incorporated with curcumin-loaded nanoparticles bearing high encapsulation efficiency. A core (alginate)-shell (chitosan) nanoparticle design was preferred to ensure the stability of the drug molecules encapsulated in the core and to provide slower drug release. Nanoparticle-embedded hydrogels were shown to release curcumin at least four times slower compared to the free nanoparticle itself and to possess high water uptake capacity and more mechanically stable viscoelastic behavior. Moreover, this therapy has the potential to specifically address tumor tissues over-expressing folate receptors like ovaries, as the nanoparticles target the receptors by folic acid conjugation to the periphery. Together with its temperature-driven injectability, it can be concluded that this hydrogel scaffold with drug-loaded and embedded folate-targeting nanoparticles would provide effective therapy for tumor tissues accessible via minimally invasive routes and be beneficial for post-operative drug administration after tumor resection.

Multi-Physically Cross-Linked Hydrogels for Flexible Sensors with High Strength and Self-Healing Properties

Excellent mechanical properties and self-healing properties are very important for the practical application of hydrogel flexible sensors. In this study, acrylic acid and stearyl methyl acrylate were selected as monomers to synthesize hydrophobic association hydrogels, and multi-physically cross-linked hydrogels were synthesized by adding ferric chloride and polyvinyl alcohol to introduce ion interaction and a hydrogen bond cross-linking network. The hydrogels were characterized by FTIR, XRD and SEM, and the mechanical properties and self-healing properties were tested using a universal testing machine. It was confirmed that the strength of the hydrogel was significantly improved with the addition of ferric chloride and polyvinyl alcohol, and the hydrogel still showed good self-healing properties. Further testing of its application as a conductive sensor has demonstrated sensitive and stable motion sensing capabilities. This provides an important reference for high-performance hydrogel sensors with both high strength and self-healing properties.

Dual pH- and Thermo-Sensitive Poly(N-isopropylacrylamide-co-allylamine) Nanogels for Curcumin Delivery: Swelling-Deswelling Behavior and Phase Transition Mechanism

Curcumin (Cur) is a beneficial ingredient with numerous bioactivities. However, due to its low solubility and poor bioavailability, its therapeutic application is limited. In this work, we prepared poly-N-isopropylacrylamide p(NIPAm) and polyallylamine p(Am)-based nanogel (p(NIPAm-co-Am)) NG for a dual pH- and temperature-sensitive copolymer system for drug delivery application. In this copolymer system, the p(NIPAm) segment was incorporated to introduce thermoresponsive behavior and the p(Am) segment was incorporated to introduce drug binding sites (amine groups) in the resulting (p(NIPAm-co-Am)) NG system. Various instrumental characterizations including ¹H nuclear magnetic resonance (¹H NMR) spectroscopy, Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM), zeta potential, and particle size analysis were performed to confirm the copolymer synthesis. Curcumin (Cur), an anticancer bioactive substance, was employed to assess the in vitro drug loading and release performance of the resulting copolymer nanogels system at varied pH levels (pH 7.2, 6.5, and 4.0) and temperatures (25 °C, 37 °C, and 42 °C). The cytocompatibility of the p(NIPAm-co-Am) NG sample was also tested on MDA-MB-231 cells at various sample concentrations. All the study results indicate that the p(NIPAm-co-Am) NG produced might be effective for drug loading and release under pH and temperature dual-stimuli conditions. As a result, the p(NIPAm-co-Am) NG system has the potential to be beneficial in the use of drug delivery applications in cancer therapy.

Insight into the Latest Medical Applications of Nanocellulose

Nanocelluloses (NCs) are appealing nanomaterials that have experienced rapid development in recent years, with great potential in the biomedical field. This trend aligns with the increasing demand for sustainable materials, which will contribute both to an improvement in wellbeing and an extension of human life, and with the demand to keep up with advances in medical technology. In recent years, due to the diversity of their physical and biological properties and the possibility of tuning them according to the desired goal, these nanomaterials represent a point of maximum interest in the medical field. Applications such as tissue engineering, drug delivery, wound dressing, medical implants or those in cardiovascular health are some of the applications in which NCs have been successfully used. This review presents insight into the latest medical applications of NCs, in the forms of cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs) and bacterial nanocellulose (BNC), with an emphasis on the domains that have recently experienced remarkable growth, namely wound dressing, tissue engineering and drug delivery. In order to highlight only the most recent achievements, the presented information is focused on studies from the last 3 years. Approaches to the preparation of NCs are discussed either by top-down (chemical or mechanical degradation) or by bottom-up (biosynthesis) techniques, along with their morphological characterization and unique properties, such as mechanical and biological properties. Finally, the main challenges, limitations and future research directions of NCs are identified in a sustained effort to identify their effective use in biomedical fields.

k-Carrageenan based magnetic@polyelectrolyte complex composite hydrogel for pH and temperature-responsive curcumin delivery

The dual stimuli-responsive drug delivery system has attracted a lot of interest in controlled drug delivery to specific sites. The magnetic iron oxide nanoparticles integrated polyelectrolyte complex-based hydrogel (MPEC HG) system was developed in this work. First, magnetic nanoparticles were produced in situ in the synthetic polymer polyhexamethylene guanidine (PHMG). Furthermore, the natural biopolymer k-carrageenan (kCG) was employed to form the polyelectrolyte complex (PEC) through charge-balancing interaction between positively charged guanidine units and negatively charged sulfonate groups. Various characterization approaches were used to characterize the developed magnetic polyelectrolyte complex hydrogel (MPEC HG) system. Curcumin (Cur) was employed as a model bioactive agent to examine the drug loading and stimuli-responsive drug release efficiency of the MPEC HG system. Under the combined pH and temperature stimuli conditions (pH 5.0/42 °C), the developed hydrogel system demonstrated great drug loading efficiency (~ 68 %) and enhanced drug release. Furthermore, the MPEC HG system's in vitro cytotoxicity behavior was investigated on a human liver cancer (HepG2) cell line, and the results revealed that the MPEC HG system is biocompatible. As a result, the MPEC HG system might be used for dual pH and temperature stimuli-responsive drug delivery applications in cancer therapy.

Facile fabrication of a broad-spectrum starch/poly(α-l-lysine) hydrogel adsorbent with thermal/pH-sensitive IPN structure through simultaneous dual-click strategy

A thermal/pH-sensitive interpenetrating network (IPN) hydrogel was prepared facilely from starch and poly(α-l-lysine) through amino-anhydride and azide-alkyne double-click reactions in one pot. The synthesized polymers and hydrogels were systematically characterized using different analytical techniques such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and rheometer. The preparation conditions of the IPN hydrogel were optimized via one-factor experiments. Experimental results indicated the IPN hydrogel possessed pH and temperature sensitivity. Effect of different parameters (pH, contact time, adsorbent dosage, initial concentration, ionic strength, and temperature) on adsorption behavior were investigated in monocomponent system with cationic methylene blue (MB) and anionic Eosin Y (EY) as model pollutants. The results indicated that the adsorption process of the IPN hydrogel for MB and EY followed pseudo-second-order kinetics. The adsorption data for MB and EY fitted well with the Langmuir isotherm model, indicating monolayer chemisorption. The good adsorption performance was due to various active functional groups (-COOH, -OH, -NH₂, etc.) in the IPN hydrogel. The strategy described here opens up a new way for preparing IPN hydrogel. The as-prepared hydrogel exhibits potential application and bright prospects as an adsorbent in wastewater treatment.

Application of Nanocellulose-Based Aerogels in Bone Tissue Engineering: Current Trends and Outlooks

The complex or compromised bone defects caused by osteomyelitis, malignant tumors, metastatic tumors, skeletal abnormalities, and systemic diseases are difficult to be self-repaired, leading to a non-union fracture. With the increasing demands of bone transplantation, more and more attention has been paid to artificial bone substitutes. As biopolymer-based aerogel materials, nanocellulose aerogels have been widely utilized in bone tissue engineering. More importantly, nanocellulose aerogels not only mimic the structure of the extracellular matrix but could also deliver drugs and bioactive molecules to promote tissue healing and growth. Here, we reviewed the most recent literature about nanocellulose-based aerogels, summarized the preparation, modification, composite fabrication, and applications of nanocellulose-based aerogels in bone tissue engineering, as well as giving special focus to the current limitations and future opportunities of nanocellulose aerogels for bone tissue engineering.

Preparation, thermal response mechanisms and biomedical applications of thermosensitive hydrogels for drug delivery

INTRODUCTION

Drug treatment is one of the main ways of coping with disease today. For the disadvantages of drug management, thermosensitive hydrogel is used as a countermeasure, which can realize the simple sustained release of drugs and the controlled release of drugs in complex physiological environments.

AREAS COVERED

This paper talks about thermosensitive hydrogels that can be used as drug carriers. The common preparation materials, material forms, thermal response mechanisms, characteristics of thermosensitive hydrogels for drug release and main disease treatment applications are reviewed.

EXPERT OPINION

When thermosensitive hydrogels are used as drug loading and delivery platforms, desired drug release patterns and release profiles can be tailored by selecting raw materials, thermal response mechanisms, and material forms. The properties of hydrogels prepared from synthetic polymers will be more stable than natural polymers. Integrating multiple thermosensitive mechanisms or different kinds of thermosensitive mechanisms on the same hydrogel is expected to realize the spatiotemporal differential delivery of multiple drugs under temperature stimulation. The industrial transformation of thermosensitive hydrogels as drug delivery platforms needs to meet some important conditions.

Preparation of esterified biomass waste hydrogels and their removal of Pb2+, Cu2+ and Cd2+ from aqueous solution

The treatment of polluted water is a serious environmental problem in the world. Biomass is easily modified and can be prepared into adsorbent materials, which is expected to solve the problem of heavy metal ion adsorption in sewage. In this paper, esterified tobacco straw based hydrogels (ETS-PAA) were synthesized from waste tobacco straw biomass. The structure and thermal stability of these hydrogels were characterized by FTIR, SEM, EDS, XPS and TG. The adsorption of metal ions by the hydrogel was measured by ICP-MS. The effects of initial ion concentration, adsorption time, pH, and temperature on the heavy metal adsorption were investigated. The results showed that ETS-PAA possessed more pores, which led to a better adsorption capacity. The maximum adsorption amounts of Pb²⁺, Cu²⁺ and Cd²⁺ were 2.41 mmol·g^-1, 1.93 mmol·g^-1 and 1.77 mmol·g^-1, respectively. Finally, the adsorption mechanism and kinetics were analyzed. The adsorption was mainly accomplished by ion exchange of -COOK on the monomer chain with heavy metal ions, coordination of -OH and -CONH with heavy metal ions and interaction of ester bond, -COOH with heavy metal ions. The adsorption process was in accordance with the pseudo-second-order kinetic model and Freundlich model. The adsorption process belonged to multilayer chemisorption. This work shows that ETS-PAA was a promising material for the removal of heavy metal pollutants from aqueous solution.

Temperature-responsive hydrogel prepared from carboxymethyl cellulose-stabilized N-vinylcaprolactam with potential for fertilizer delivery

The growth of plants is highly dependent on sufficient water and suitable fertilizer nutrients, but the soil often loses moisture and the fertilizers are low efficiency. To address this issue, the temperature-responsive hydrogels were developed using the N-vinylcaprolactam (NVCL) dispersed in water through the emulsification of carboxymethyl cellulose (CMC) and acrylamide (AM), and urea was loaded into the hydrogel as a fertilizer. The amount of CMC and monomer have an effect on the structure, mechanical properties, swelling ability, and temperature sensitivity of the hydrogel. Therefore, the maximum swelling ratio of the hydrogel can reach 2056 % with the increasing hydrophilic groups, and the hydrogel exhibits a deswelling behavior as the temperature rises to higher than LCST due to the temperature responsiveness. Moreover, the fertilizer can rapidly release when the temperature is higher than LSCT, and exhibits similar release behavior in water and soil. Thus, the temperature-responsive hydrogel shows a great potential application for the controlled release of water and fertilizer in agriculture and forestry.

High-performance carboxymethyl cellulose-based composite film tailored by versatile zeolitic imidazolate framework

Robust biopolymer-based composite film with multifunctional performances significantly contributes to the packaging field. Herein, we proposed a sort of carboxymethyl cellulose (CMC) based composite film via incorporating versatile zeolitic imidazolate framework (ZIF) materials. Compared to pristine CMC film, the OTR, WVTR, and tensile strength of CMC/ZIF composite film with 1 wt ‰ Zn/Co-ZIF were improved from 64.89 cm³*μm/(m²*d*kPa), 1579.21 g/(m²*24h) and 16.9 MPa to 20.79 cm³*μm/(m²*d*kPa), 1209.58 g/(m²*24h) and 70.1 MPa, respectively. Notably, owing to the reduced band gap and intrinsic chemical and thermal stability of Zn/Co-ZIF, the fabricated Zn/Co-ZIF/CMC composite film presented well UV protection capability within the whole UV region and excellent UV-blocking durability after being exposed to UV-light at 365 nm for 12 h. In practice, the photocatalytic degradation of RhB solutions under UV light could be effectively suppressed when using Zn/Co-ZIF/CMC film as UV protection layer. Our findings proposed the potential application of these versatile ZIF materials as functional nanofiller within biopolymer substances for UV protection and transparent packaging area.

Hydrogels based on gelatin, xanthan gum, and cellulose obtained by reactive extrusion and thermopressing processes

Polysaccharides and proteins are compatible macromolecules that can be used to obtain biopolymeric hydrogels through physical interactions. In this study, an environmentally friendly strategy is being proposed to produce gelatin-xanthan gum- cellulose hydrogels, without the addition of chemical synthetic crosslinkers. Xanthan gum was employed as an alternative crosslinking agent, and cellulose was used as a potential reinforcing agent in the polymeric matrix. Firstly, the biopolymers were mixed by the extrusion process, and glycerol was used as a plasticizer. Then, the polymeric mixture was molded by thermopressing to obtain hydrogels as laminated films. All hydrogels formulations resulted in films with smooth surfaces, without pores or cracks, resulting in amorphous polymeric matrices. The obtained hydrogels had a pH-dependent degree of swelling, the highest swelling values were obtained at pH 4 (5.3-7.9 g/g) after 24 h of immersion. Cellulose acted as a reinforcing agent for hydrogels, increasing thermal stability, tensile strength, and Young's modulus of films when employed at the higher level (7%). The strategy employed in this study to obtain nontoxic hydrogels without synthetic crosslinkers was effective, resulting in materials with promising properties to be used as pharmaceutical forms to deliver active compounds in cosmetic or pharmaceutical products.

pH and Thermoresponsive PNIPAm-co-Polyacrylamide Hydrogel for Dual Stimuli-Responsive Controlled Drug Delivery

The therapeutic delivery system with dual stimuli-responsiveness has attracted attention for drug delivery to target sites. In this study, we used free radical polymerization to develop a temperature and pH-responsive poly(N-isopropyl acrylamide)-co-poly(acrylamide) (PNIPAM-co-PAAm). PNIPAm-co-PAAm copolymer by reacting with N-isopropyl acrylamide (NIPAm) and acrylamide (Am) monomers. In addition, the synthesized melamine-glutaraldehyde (Mela-Glu) precursor was used as a cross-linker in the production of the melamine cross-linked PNIPAm-co-PAAm copolymer hydrogel (PNIPAm-co-PAAm-Mela HG) system. The temperature-responsive phase transition characteristics of the resulting PNIPAM-co-PAAm-Mela HG systems were determined. Furthermore, the pH-responsive drug release efficiency of curcumin was investigated under various pH and temperature circumstances. Under the combined pH and temperature stimuli (pH 5.0/45 °C), the PNIPAm-co-PAAm-Mela HG demonstrated substantial drug loading (74%), and nearly complete release of the loaded drug was accomplished in 8 h. Furthermore, the cytocompatibility of the PNIPAm-co-PAAm-Mela HG was evaluated on a human liver cancer cell line (HepG2), and the findings demonstrated that the prepared PNIPAm-co-PAAm-Mela HG is biocompatible. As a result, the PNIPAm-co-PAAm-Mela HG system might be used for both pH and temperature-stimuli-responsive drug delivery.

Preparation of biomass-based hydrogels and their efficient heavy metal removal from aqueous solution

In this work, a porous tobacco straw-based polyacrylic acid hydrogel STS-PAA with high adsorption performance was prepared by polymerizing pretreated waste tobacco straw (TS) with acrylic acid/potassium acrylate by UV radiation initiation. The adsorption performance of metal ions was investigated. The effects of different temperatures (25°C, 35°C, and 45°C), adsorption times (1-420 min), pH values (2.0-6.0) and initial concentrations (0.25-4.0 mmol L^-1) of metal ions on the adsorption amount of heavy metal ions were investigated. The results showed that the hydrogel had a high removal rate of Pb²⁺, Cd²⁺ and Hg²⁺ in aqueous solution. The adsorption of Pb²⁺ was particularly effective. When C₀ = 4.0 mmol L^-1, pH = 6, the equilibrium adsorption amount of Pb²⁺, Cd²⁺ and Hg²⁺ reached 1.49 mmol g^-1, 1.02 mmol L^-1 and 0.94 mmol g^-1, respectively. The chemical structure and morphology of the hydrogels were characterized by FT-IR, EDS, SEM and XPS. The Langmuir model fits well with the adsorption system. The kinetic data suggest the adsorption of Pb²⁺, Cd²⁺ and Hg²⁺ follow the pseudo-first-order model. This indicates that STS-PAA adsorption of three heavy metal ions is monolayer physical adsorption. Thermodynamic analysis shows that the adsorption of Pb²⁺, Cd²⁺ and Hg²⁺ by STS-PAA is an endothermic (ΔH>0) entropy increase (ΔS>0) non-spontaneous reaction.

Nanocellulose-based drug carriers: Functional design, controllable synthesis, and therapeutic applications

With rising living standards and environmental awareness, materials-oriented chemical engineering has increasingly transitioned from traditional rough models to more resource-saving and eco-friendly models, providing an avenue for bio-based materials in the drug carrier field. Because of its excellent physical and chemical properties, including high specific surface area, abundant accessible hydroxyl groups, biocompatibility, and degradability, nanocellulose (NC) is an emerging bio-based material that has been widely exploited as biomedical materials. The modification techniques of NC, as well as advancements in the design and applications of drug carriers, were primarily discussed in this study. First, the NC modification methods are described; second, the applications of NC and its derivatives as drug carriers are summarized, focusing on NC-based carrier models, types of loaded therapeutic agents, and controlled release stimulators; and finally, the current challenges of NC in the drug carrier field and the directions of future research are also discussed.

Encapsulation and sustained release of curcumin by hawthorn pectin and Tenebrio Molitor protein composite hydrogel

In this study, the effects of pH value, mixing ratio and the Ca²⁺ concentration on the complex gelation of hawthorn pectin (HP) and Tenebrio Molitor protein (TMP) were investigated. The turbidity results showed that the composite gel had the maximum polymer concentration when the mixing ratio was 2:1 and the pH value was 3.35. The rheological measurement results showed that TMP/HP (15 mmol/L) hydrogel (THIH) had the highest storage modulus and loss modulus, indicating that the properties of the hydrogel at this Ca²⁺ concentration had been significantly improved. The results of scanning electron microscope and pore size also proved that the network structure prepared under this condition was compact and uniform, the pore size was small, which was beneficial to the entrapment of active components. Subsequently, in order to explore the storage stability and antioxidant activity of THIH-loaded curcumin in simulated gastrointestinal environment, in vitro simulated digestion experiment was carried out and satisfactory results were obtained. To sum up, THIH was a promising delivery system with broad application prospects, which was expected to provide a novel idea for the entrapment and delivery of active components.

Copolymer-Functionalized Cellulose Nanocrystals as a pH- and NIR-Triggered Drug Carrier for Simultaneous Photothermal Therapy and Chemotherapy of Cancer Cells

As a class of biocompatible and biodegradable naturally derived nanomaterials, cellulose nanocrystals (CNCs) with diverse surface functionalization have aroused considerable attention for a range of biomedical applications in drug or gene delivery, as a fluorescent nanoprobe, in cancer targeting, and in photothermal cancer therapy, among others. Herein, we construct the copolymer-functionalized CNCs as a pH- and near-infrared (NIR)-triggered drug carrier for simultaneous photothermal therapy and chemotherapy of cancer cells. Poly(ε-caprolactone)-b-poly(2-(dimethylamino)ethyl methacrylate) (PCL-b-PDMAEMA) was conjugated onto the surface of CNCs through ring-opening polymerization, followed by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The resultant CNC-based drug carrier can encapsulate doxorubicin (DOX) as a therapeutic agent and indocyanine green (ICG) as an NIR dye in the PCL core and the PDMAEMA shell, respectively, via hydrophobic and electrostatic interactions. In addition to the intrinsic pH response, the release profile of DOX can also be controlled by the duration of laser irradiation due to collapse of the crystal structure of the PCL domain with the increase of temperature induced by photothermal conversion. The drug carrier can exhibit enhanced cytotoxicity toward HepG2, human hepatocyte carcinoma, cells upon laser irradiation, which can be attributed to the synergistic effect arising from NIR-triggered burst release of DOX and photothermal heating. The rod-like morphology of the CNC-based drug carrier may help accelerate the endocytosis in cell membranes compared with its common spherical counterpart. Based on the abovementioned advantages, copolymer-functionalized CNCs can serve as a promising candidate for effective cancer treatment.

Formulation, Characterization, and In Vitro Drug Release Study of β-Cyclodextrin-Based Smart Hydrogels

In this study, novel pH-responsive polymeric β-cyclodextrin-graft-poly(acrylic acid/itaconic acid) hydrogels were fabricated by the free radical polymerization technique. Various concentrations of β-cyclodextrin, acrylic acid, and itaconic acid were crosslinked by ethylene glycol dimethacrylate in the presence of ammonium persulfate. The crosslinked hydrogels were used for the controlled delivery of theophylline. Loading of theophylline was conducted by the absorption and diffusion method. The fabricated network of hydrogel was evaluated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The crosslinking among hydrogel contents and drug loading by the fabricated hydrogel were confirmed by FTIR analysis, while TGA indicated a high thermal stability of the prepared hydrogel as compared to pure β-cyclodextrin and itaconic acid. The high thermal stability of the developed hydrogel indicated an increase in the thermal stability of β-cyclodextrin and itaconic acid after crosslinking. Similarly, a decrease in crystallinity of β-cyclodextrin and itaconic acid was observed after crosslinking, as evaluated by XRD analysis. SEM revealed an irregular and hard surface of the prepared hydrogel, which may be correlated with strong crosslinking among hydrogel contents. Crosslinked insoluble and uncrosslinked soluble fractions of hydrogel were evaluated by sol–gel analysis. An increase in gel fraction was seen with the increase in compositions of hydrogel contents, while a decrease in sol fraction was observed. Dynamic swelling and dissolution studies were performed in three various buffer solutions of pH 1.2, 4.6, and 7.4, respectively. Maximum swelling and drug release were observed at higher pH values as compared to the lower pH value due to the deprotonation and protonation of functional groups of the hydrogel contents; thus, the pH-sensitive nature of the fabricated hydrogel was demonstrated. Likewise, water penetration capability and polymer volume were evaluated by porosity and polymer volume studies. Increased incorporation of β-cyclodextrin, acrylic acid, and itaconic acid led to an increase in swelling, drug release, drug loading, and porosity of the fabricated hydrogel, whereas a decrease was detected with the increasing concentration of ethylene glycol dimethacrylate. Conclusively, the prepared hydrogel could be employed as a suitable and promising carrier for the controlled release of theophylline.

A bioinspired stimuli-responsive amino acid-based antibacterial drug delivery system in cancer therapy

Design of tyrosine based stimuli responsive antibacterial drug delivery system with potential application in cancer therapy.

Synthesis and Characterization of Slow-Release Fertilizer Hydrogel Based on Hydroxy Propyl Methyl Cellulose, Polyvinyl Alcohol, Glycerol and Blended Paper

In this study, biodegradable slow-release fertilizer (SRF) hydrogels were synthesized from hydroxyl propyl methyl cellulose (HPMC), polyvinyl alcohol (PVA), glycerol and urea (SRF1) and HPMC, PVA, glycerol, urea and blended paper (SRF2). The fertilizer hydrogels were characterized by SEM, XRD and FTIR. The swelling capacity of the hydrogels in both distilled and tap water as well as their water retention capacity in sandy soil were evaluated. The hydrogels had good swelling capacity with maximum swelling ratio of 17.2 g/g and 15.6 g/g for SRF1 and SRF2 in distilled, and 14.4 g/g and 15.2 g/g in tap water, respectively. The water retention capacity of the hydrogels in sandy soil exhibited higher water retention when compared with soil without the (SRFs). The soil with the hydrogels was found to have higher water retention than the soil without the hydrogels. The slow-release profile of the hydrogels was also evaluated. The result suggested that the prepared fertilizer hydrogels has a good controlled release capacity. The blended paper component in SRF2 was observed to aid effective release of urea, with about 87.01% release in soil at 44 days compared to the pure urea which was about 97% release within 4 days. The addition of blended paper as a second layer matrix was found to help improve the release properties of the fertilizer. The swelling kinetic of the hydrogel followed Schott's second order model. The release kinetics of urea in water was best described by Kormeye Peppas, suggesting urea release to be by diffusion via the pores and channels of the SRF, which can be controlled by changing the swelling of the SRF. However, the release mechanism in soil is best described by first order kinetic model, suggesting that the release rate in soil is depended on concentration and probably on diffusion rate via the pores and channels of the SRF.