Synthesis of Biocompatible Cellulose-Coated Nanoceria with pH-Dependent Antioxidant Property

The effect of nanoceria on the alginate-gum arabic crosslinking mechanism and in vitro behavior as a wound dressing

Medical practice has proven that chronic wounds can be treated successfully if the dressing is chosen according to the healing phase of the wound. Correct intervention from the hemostasis and inflammatory phase can prevent oxidative stress and ensure optimal conditions for healing. It is important to design a new wound dressing that does not cause additional injury, has an antioxidant effect, removes dead cells, and promotes wound healing. Considering that the traditional dressings are not moisture-retentive, we proposed an alginate-gum arabic polymeric matrix enhanced with cerium oxide nanoparticles. The cryogels were prepared by cross-linking polysaccharides and cerium oxide nanoparticles via calcium cations to form a sponge-like structure. The blend of micro- and macro-pores provides a suitable environment for nutrient distribution and keeps an adequate moisture level, mimicking the functions of the native cellular matrix. The release of cerium oxide nanoparticles occurs gradually, at the same time as the degradation of the biopolymer, promoting the attachment and viability of keratinocytes and fibroblast cells. It was found that stimulating epithelial regeneration is improved through the antioxidant effect and the adsorption capacity of hemoglobin. The results also indicate good in vitro biocompatibility and recommend them as promising dressings for skin wound treatments.

A comparative study on surface-engineered nanoceria using a catechol copolymer design: colloidal stability vs. antioxidant activity

Nanoceria (NC) are widely studied as potent nanozyme antioxidants, featuring unique multifunctional, self-regenerative, and high-throughput enzymatic functions. However, bare NC are reported to show poor colloidal stability in biological media. Despite this, the nexus between colloidal stability and antioxidant activity has rarely been assessed. Here, a library of three copolymeric stabilising agents was synthesised, each consisting of hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) brushes (P(OEGMA)) and a novel catechol anchoring block, and used for surface engineering of NC. The colloidal stability of the surface-engineered NC was assessed in phosphate buffered saline (PBS) by monitoring their precipitation via UV-Vis spectrophotometry, and their catalase (CAT)- and superoxide dismutase (SOD)-like activities were analysed using fluorospectrophotometry. The obtained results indicate that P(OEGMA) coating improves colloidal stability of NC over 48 h, highlighting the stable attachment of catechol functionalities to the surface of NC. In addition, X-ray photoelectron spectroscopy (XPS) indicates that the catechol functionalities lead to an increase in Ce3+/Ce4+ ratio and the concentration of oxygen vacancies, depending on the number of catechol units. Altogether, surface engineering of NC optimally results in an increase in CAT- and SOD-like activities by, respectively, 41% (=57.7% H2O2 elimination) and 78% (=78.0% O2˙- elimination) relative to bare NC, signifying a positive correlation between colloidal stability and antioxidant activity of the NC nanozymes.

The Dimensionality of Hydrogen Bond Networks Induces Diverse Physical Properties of Peptide Crystals

Short peptides are attractive building blocks for the fabrication of self-assembled materials with significant biological, chemical, and physical properties. The microscopic and macroscopic properties of assemblies are usually closely related to the dimensionality of formed hydrogen bond networks. Here, two completely different supramolecular architectures connected by distinct hydrogen bond networks were obtained by simply adding a hydroxyl group to switch from cyclo-tryptophan-alanine (cyclo-WA) to cyclo-tryptophan-serine (cyclo-WS). While hydroxyl-bearing cyclo-WS molecules provided an additional hydrogen bond donor that links to adjacent molecules, forming a rigid three-dimensional network, cyclo-WA arranged into a water-mediated zipper-like structure with a softer two-dimensional layer template. This subtle alteration resulted in a 14-fold enhancement of Young's modulus values in cyclo-WS compared to cyclo-WA. Both cyclo-dipeptides exhibit biocompatibility, high fluorescence, and piezoelectricity. The demonstrated role of dimensionality of hydrogen bond networks opens new avenues for rational design of materials with precise morphologies and customizable properties for bioelectronic applications.

A Review of Recent Developments in Biopolymer Nano-Based Drug Delivery Systems with Antioxidative Properties: Insights into the Last Five Years

In recent years, biopolymer-based nano-drug delivery systems with antioxidative properties have gained significant attention in the field of pharmaceutical research. These systems offer promising strategies for targeted and controlled drug delivery while also providing antioxidant effects that can mitigate oxidative stress-related diseases. Generally, the healthcare landscape is constantly evolving, necessitating the continual development of innovative therapeutic approaches and drug delivery systems (DDSs). DDSs play a pivotal role in enhancing treatment efficacy, minimizing adverse effects, and optimizing patient compliance. Among these, nanotechnology-driven delivery approaches have garnered significant attention due to their unique properties, such as improved solubility, controlled release, and targeted delivery. Nanomaterials, including nanoparticles, nanocapsules, nanotubes, etc., offer versatile platforms for drug delivery and tissue engineering applications. Additionally, biopolymer-based DDSs hold immense promise, leveraging natural or synthetic biopolymers to encapsulate drugs and enable targeted and controlled release. These systems offer numerous advantages, including biocompatibility, biodegradability, and low immunogenicity. The utilization of polysaccharides, polynucleotides, proteins, and polyesters as biopolymer matrices further enhances the versatility and applicability of DDSs. Moreover, substances with antioxidative properties have emerged as key players in combating oxidative stress-related diseases, offering protection against cellular damage and chronic illnesses. The development of biopolymer-based nanoformulations with antioxidative properties represents a burgeoning research area, with a substantial increase in publications in recent years. This review provides a comprehensive overview of the recent developments within this area over the past five years. It discusses various biopolymer materials, fabrication techniques, stabilizers, factors influencing degradation, and drug release. Additionally, it highlights emerging trends, challenges, and prospects in this rapidly evolving field.

Multifunctional 58S Bioactive Glass/Silver/Cerium Oxide-Based Biocomposites with Effective Antibacterial, Cytocompatibility, and Mechanical Properties

58S bioactive glass (BG) has effective biocompatibility and bioresorbable properties for bone tissue engineering; however, it has limitations regarding antibacterial, antioxidant, and mechanical properties. Therefore, we have developed BGAC biocomposites by reinforcing 58S BG with silver and ceria nanoparticles, which showed effective bactericidal properties by forming inhibited zones of 2.13 mm (against Escherichia coli) and 1.96 mm (against Staphylococcus aureus; evidenced by disc diffusion assay) and an increment in the antioxidant properties by 39.9%. Moreover, the elastic modulus, hardness, and fracture toughness were observed to be increased by ∼84.7% (∼51.9 GPa), ∼54.5% (∼3.4 GPa), and ∼160% (∼1.3 MPam1/2), whereas the specific wear rate was decreased by ∼55.2% (∼1.9 × 10-11 m3/Nm). X-ray diffraction, high-resolution transmission electron microscopy, and field emission scanning electron microscopy confirmed the fabrication of biocomposites and the uniform distribution of the nanomaterials in the BG matrix. The addition of silver nanoparticles in the 58S BG matrix (in BGA) increased mechanical properties by composite strengthening and bactericidal properties by damaging the cytoplasmic membrane of bacterial cells. The addition of nanoceria in 58S BG (BGC) increased the antioxidant properties by 44.5% (as evidenced by the 2,2-diphenyl-1-picrylhydrazyl assay). The resazurin reduction assay and MTT assay confirmed the effective cytocompatibility for BGAC biocomposites against mouse embryonic fibroblast cells (NIH3T3) and mouse bone marrow stromal cells. Overall, BGAC resulted in mechanical properties comparable to those of cancellous bone, and its effective antibacterial and cytocompatibility properties make it a good candidate for bone healing.

Antioxidant Polymers with Phenolic Pendants for the Mitigation of Cellular Oxidative Stress

Overproduction of reactive oxygen species (ROS) in cells is a major health concern as it may lead to various diseases through oxidative damage of biomolecules. Commonly used traditional small molecular antioxidants (polyphenols, carotenoids, vitamins, etc.) have inadequate efficacy in lowering excessive levels of ROS due to their poor aqueous solubility and bioavailability. In response to the widespread occurrence of antioxidant polyphenols in various biorenewable resources, we aimed to develop water-soluble antioxidant polymers with side chain phenolic pendants. Four different types of copolymers (P1-P4) containing phenyl rings with different numbers of hydroxy (-OH) substituents (0: phenylalanine, 1: tyrosyl, 2: catechol, or 3: gallol) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization with a desired molar mass (8500-10000 g/mol) and a narrow dispersity (Đ ≤ 1.3). After successful characterizations of P1-P4, their in vitro antioxidant properties were analyzed by different methods, including 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+), 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl (TMB), and β-carotene (βC) assays. Our results revealed that the gallol pendant polymers can effectively scavenge ROS. Furthermore, electron paramagnetic resonance (EPR) spectroscopy with DPPH• also confirmed the radical quenching ability of the synthesized polymers. The gallol pendant polymers, at a well-tolerated concentration, could effectively penetrate the macrophage cells and restore the H2O2-induced ROS to the basal level. Overall, the present approach demonstrates the efficacy of water-soluble antioxidant polymers with gallol pendants toward the mitigation of cellular oxidative stress.

β-Cyclodextrin Stabilized Nanoceria for Hydrolytic Cleavage of Paraoxon in Aqueous and Cationic Micellar Media

Beta-cyclodextrin (β-CD) stabilized cerium oxide nanoparticles (β-CD@CeO₂ NPs) were synthesized through a hydrothermal route. The electronic properties, surface functional group, surface composition, size, and morphologies of the as-synthesized β-CD@CeO₂ NPs were characterized using UV-visible spectroscopy, FTIR analysis, high resolution X-ray photoelectron spectroscopy (HRXPS), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The pH-dependent variation of the ζ-potential of β-CD@CeO₂ NPs and the catalytic activity of the NPs for the hydrolysis of paraoxon were investigated. The observed pseudo-first-order rate constant (k_obs) for the hydrolysis of paraoxon is increased with increasing pH and the ζ-potential of β-CD@CeO₂ NPs. The kinetics and mechanism of hydrolysis of paraoxon in the aqueous and cationic micellar media have been discussed.

Cationized silica ceria nanocomposites to target biofilms in chronic wounds

Altered wound healing is a major challenge faced by both developed and developing nations. Biofilm formation has been identified as one of the causative factors for the progression of chronic wounds. The spread of biofilm is controlled by inhibiting the biofilm formation or disrupting the mature biofilm. Functional nanomaterials/enzymes with antimicrobial effects, such as metal oxides, rare earth metals, and carbon nanoparticles have been investigated to treat biofilm and overcome the drawbacks associated with the antibiotic therapy. Cerium oxide nanoparticles (CNPs) have drawn significant attention as a promising antimicrobial agent owing to their antibacterial, enzyme-mimetic, and crystalline properties but they suffer from poor colloidal stability and dispersity in an aqueous environment and size-dependent function. In this work, we have developed a functionalized silica ceria nanocomposite (FSC), as an antibiotic-free system, to treat biofilms. The FSC possesses a high surface area of mesoporous silica nanoparticles (MSNs) combined with the intrinsic antibacterial activity of cerium oxide for biofilm inhibition. The nanocomposite was fabricated using silica and ceria precursors, and it exhibited a high surface area of 436 m²/g and an average particle size of around 450 nm. The physical and chemical properties of nanocomposite were characterized using FTIR, XRD, UV-Vis, BET, EDX, and XPS analysis. It exhibited a potent antioxidant activity (86%), positive haloperoxidase mimetic property, and broad-spectrum antibacterial activities. It showed 99.9% inhibition against S. aureus (Gram-positive) and 81% inhibition against E. coli (Gram-negative) within 12 and 24 h along with the significant inhibition of biofilm formation (80%) as well as the disruptive effect against the established biofilm (77%) of S. aureus. Cell viability assays indicated the proliferative nature of composite in normal basal conditions and increased cell viability (97%) in the presence of oxidative stress. Despite being a cationic nanomaterial, it showed a good hemocompatibility against human blood and caused complete wound closure in mouse fibroblast cell line within 24 h. The functionalized silica ceria nanocomposite developed has a strong potential in chronic wound healing applications.

Synthesis and defect characterization of hybrid ceria nanostructures as a possible novel therapeutic material towards COVID-19 mitigation

This study reports the synthesis of hybrid nanostructures composed of cerium dioxide and microcrystalline cellulose prepared by the microwave-assisted hydrothermal route under distinct temperature and pH values. Their structural, morphological and spectroscopic behaviors were investigated by X-Rays Diffraction, Field Emission Gun Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, and Fourier-Transform Infrared, Ultraviolet-Visible, Raman and Positron Annihilation Lifetime spectroscopies to evaluate the presence of structural defects and their correlation with the underlying mechanism regarding the biocide activity of the studied material. The samples showed mean crystallite sizes around 10 nm, characterizing the formation of quantum dots unevenly distributed along the cellulose surface with a certain agglomeration degree. The samples presented the characteristic Ce-O vibration close to 450 cm-1 and a second-order mode around 1050 cm-1, which is indicative of distribution of localized energetic levels originated from defective species, essential in the scavenging of reactive oxygen species. Positron spectroscopic studies showed first and second lifetime components ranging between 202-223 ps and 360-373 ps, respectively, revealing the presence of two distinct defective oxygen species, in addition to an increment in the concentration of Ce3+-oxygen vacancy associates as a function of temperature. Therefore, we have successfully synthesized hybrid nanoceria structures with potential multifunctional therapeutic properties to be further evaluated against the COVID-19.

Poly(tannic acid) nanocoating based surface modification for construction of multifunctional composite CeO2NZs to enhance cell proliferation and antioxidative viability of preosteoblasts

Ceria (CeO₂) based materials possess many antioxidant enzyme-like activities and unique properties for bone repair, but their free radical scavenging function is still insufficient. In order to deal with the complex oxidative stress environment in bone repair, multifunctional composite CeO₂ nanozymes (CeO₂NZs), featuring multiple antioxidative properties, were constructed via surface modification on CeO₂NZs with nanoscale poly(tannic acid) (PTA) coatings. Moreover, we adjusted pH conditions (ranging from 4 to 9) to effectively control the formation and antioxidative properties of PTA coatings on CeO₂NZ surfaces. Here, the physical properties of this novel inorganic and organic composite antioxidant, such as surface morphology, particle size, crystal structure, surface charge and element composition, were thoroughly characterized. The PTA/CeO₂NZs showed obvious coating morphology under weak acid conditions (pH = 5-6), and the PTA layer at pH = 5 is about 1 nm in thickness. Compared with untreated CeO₂NZs, the PTA/CeO₂NZs showed stronger SOD-like activity and obviously higher free radical scavenging rate (for both ABTS⁺˙ and DPPH˙).Notably, this composite antioxidative nanozyme not only exhibited favorable cell proliferation of preosteoblasts (MC3T3-E1) but also provided strong antioxidative property to maintain cell vitality against H₂O₂ induced oxidative damage. In particular, this study provides new insights into the designing of surface polyphenolic coatings at the nanoscale, and these multiple antioxidative properties shown by PTA coated CeO₂NZs make them suitable for protecting cells under the oxidative stress environment.

Production of Oligoalginate via Solution Plasma Process and Its Capability of Biological Growth Enhancement

The objective of the study was to depolymerize alginate into short-length oligoalginates, adopting the simple solution plasma process (SPP) technique, for successful use in free radical scavenging and growth promotion in cell culture and agricultural practices. Alginate at various concentrations was depolymerized to oligoalginates using SPP by discharging for various times. The depolymerization into oligoalginates was proved by DNS, TLC, FT-IR, and HPAEC analyses and caused decrease in viscosity. Oligoalginates derived from 0.5% alginate (100 mg∙mL^-1) showed the highest antioxidant activities in vitro. The oligoalginates enhanced growth of the human embryonic kidney (HEK293) cells to significant levels in a concentration-dependent manner without any extent of toxicity. The oligoalginates also promoted growth of lettuce. Thus, SPP is a powerful technique to break down alginate into oligoalginates that can be utilized as a free radical scavenger and as a growth promoter of animal cells and agricultural plants.

CeO2 Nanoparticle-Containing Polymers for Biomedical Applications: A Review

The development of advanced composite biomaterials combining the versatility and biodegradability of polymers and the unique characteristics of metal oxide nanoparticles unveils new horizons in emerging biomedical applications, including tissue regeneration, drug delivery and gene therapy, theranostics and medical imaging. Nanocrystalline cerium(IV) oxide, or nanoceria, stands out from a crowd of other metal oxides as being a truly unique material, showing great potential in biomedicine due to its low systemic toxicity and numerous beneficial effects on living systems. The combination of nanoceria with new generations of biomedical polymers, such as PolyHEMA (poly(2-hydroxyethyl methacrylate)-based hydrogels, electrospun nanofibrous polycaprolactone or natural-based chitosan or cellulose, helps to expand the prospective area of applications by facilitating their bioavailability and averting potential negative effects. This review describes recent advances in biomedical polymeric material practices, highlights up-to-the-minute cerium oxide nanoparticle applications, as well as polymer-nanoceria composites, and aims to address the question: how can nanoceria enhance the biomedical potential of modern polymeric materials?