Muhammad Usman Khalid

The increasing prevalence of multidrug-resistant bacterial infections has created an urgent need for antibacterial biomaterials that combine effective antimicrobial activity with good biocompatibility. In this study, niobium pentoxide (Nb₂O₅)-loaded chitosan–gelatin (CG-Nb) hybrid hydrogels containing 1.1% (G1), 1.6% (G2), and 2.0% (G3) (w/w) Nb₂O₅ were evaluated for their antibacterial activity, photo-induced singlet oxygen generation, and cytocompatibility. Antibacterial performance against Staphylococcus aureus and Escherichia coli was assessed using agar diffusion, direct-contact colony reduction, and scanning electron microscopy, while singlet oxygen generation was investigated using the 9,10-diphenylanthracene (DPA) bleaching assay. Cytocompatibility was evaluated using L929 fibroblasts according to ISO 10993-5. The CG-Nb hydrogels exhibited concentration-dependent antibacterial activity, with G3 showing the highest antibacterial activity among the investigated formulations. G3 produced estimated bacterial reductions of 95.7% against S. aureus and 93.3% against E. coli in the direct-contact assay, while maintaining 87.3 ± 4.8% L929 fibroblast viability after 24 h. SEM analysis revealed progressive morphological changes in bacterial cells with increasing Nb₂O₅ content. The DPA bleaching assay demonstrated that G3 generated photo-induced singlet oxygen under blue-light irradiation. Because the antibacterial assays were performed without blue-light irradiation, the present results do not allow the photo-induced singlet oxygen generation observed in the DPA assay to be directly associated with the antibacterial activity of the hydrogels. Overall, the Nb₂O₅-containing chitosan–gelatin hydrogels exhibited enhanced antibacterial activity across the evaluated concentration range while maintaining favorable cytocompatibility under the tested conditions. These findings provide a biological evaluation of the previously developed hydrogel platform and support further investigation of CG-Nb hydrogels for antibacterial biomaterial applications.

The increasing prevalence of multidrug-resistant bacterial infections necessitates the development of novel antibacterial biomaterials that combine potent antimicrobial activity with excellent cytocompatibility. This study aimed to fabricate and evaluate niobium pentoxide (Nb₂O₅)-loaded chitosan-gelatin (CG-Nb) hybrid hydrogels as a functional antibacterial platform. CG-Nb hydrogels containing 1.1% (G1), 1.6% (G2), and 2.0% (G3) w/w Nb₂O₅ nanoparticles were synthesized via citric acid-assisted dissolution and glutaraldehyde crosslinking. Antibacterial activity against Staphylococcus aureus and Escherichia coli was assessed using agar well diffusion, direct contact colony reduction, and scanning electron microscopy (SEM). Singlet oxygen (¹O₂) generation was evaluated via the 9,10-diphenylanthracene (DPA) bleaching assay. Cytocompatibility was determined using the XTT assay with L929 fibroblasts, in accordance with ISO 10993-5. The CG-Nb hydrogels exhibited concentration-dependent antibacterial activity. G3 (2.0% w/w Nb₂O₅) produced the largest inhibition zones (24.2 ± 1.1 mm against S. aureus; 21.3 ± 1.0 mm against E. coli) and achieved colony reductions of 95.7% and 93.3%, respectively. SEM revealed progressive morphological damage from sparse intact cells in G1 to complete membrane collapse in G3. The DPA assay confirmed Nb₂O₅'s capacity to generate singlet oxygen upon photoexcitation (11.2 ± 2.2% bleaching at 30 min), supporting a ROS-mediated antibacterial mechanism that operates alongside chitosan's membrane-disrupting activity. All formulations remained non-cytotoxic, with G3 maintaining 87.3 ± 4.8% fibroblast viability, well above the 70% ISO 10993-5 threshold. These findings suggest that CG-Nb hydrogels, particularly the G3 formulation, are promising candidates for infection-resistant biomedical applications in vitro, including potential use in wound dressings and implant coatings, pending further in vivo validation.

Chitosan–gelatin (CG) hybrid hydrogels are widely recognized for their biocompatibility and suitability for soft tissue engineering, wound dressings, and biomedical coatings. Despite this promise, conventional CG systems often exhibit limited mechanical strength, restricted durability, and uncontrolled swelling, which can reduce their clinical relevance. In this study, we introduce an enhanced soft hydrogel platform reinforced with niobium pentoxide (Nb₂O₅) nanoparticles and chemically crosslinked using glutaraldehyde, with citric acid serving as a dissolution medium and processing aid. Three hydrogel variants (G1, G2 and G3) were prepared by adjusting nanoparticle concentration and subsequently evaluated through structural, morphological, swelling, gel-fraction, and rheological analyses. SEM imaging revealed that increasing Nb₂O₅ content produced notable architectural transitions—from smooth porous matrices to nanoparticle-distributed, heterogenous pore structures. XRD, FTIR, and Raman spectroscopy confirmed the structural retention of Nb₂O₅ and its effective interaction with the polymer network. Swelling and gel-fraction measurements demonstrated improved network stability in nanoparticle-loaded systems, with G2 providing the most desirable balance between swelling capacity (298%) and gel fraction (91%). Rheological studies further identified G2 as the most stable and elastic composition, exhibiting strong shear-thinning behavior and high structural recovery. Overall, G2 emerges as the optimal formulation for future biomedical development.

Niobium pentoxide (Nb ₂ O ₅ ) nanoparticles (NPs) hold promise for biomedical applications owing to their tunable physicochemical properties. Here, Nb ₂ O ₅ NPs were synthesized via two chemical routes: (i) direct dissolution of Nb ₂ O ₅ in hydrofluoric acid (HF), and (ii) reaction of ammonium niobate (V) oxalate hydrate with hydrogen peroxide (H ₂ O ₂ ). Characterization by x-ray diffraction, electron microscopy, and dynamic light scattering confirmed route-dependent differences in crystallinity, size, and dispersion. Antibacterial assays against E. coli revealed highest efficacy for H ₂ O ₂ -derived NPs (12 g l ⁻¹ ), attributed to their ultra-small crystallites (∼4.5 nm), monodispersity (PDI = 0.118), and good colloidal stability. In the HF route, the 5 g l ⁻¹ sample also showed strong antibacterial activity, likely due to increased particle concentration despite larger size distribution. Mechanistic studies demonstrated that bactericidal effects correlated with enhanced reactive oxygen species (ROS) generation, particularly in H ₂ O ₂ -synthesized NPs with oxygen-defect structures. Inductively coupled plasma mass spectrometry confirmed low but detectable Nb ion release, indicating that ROS production, rather than ion leaching, was the dominant antibacterial mechanism. These findings highlight the importance of synthesis route and precursor concentration in tailoring the antibacterial performance of Nb ₂ O ₅ NPs, supporting their potential as effective nanomaterials for biomedical applications.

Niobium nanoparticles (NbNPs) have gained attention as promising materials in biomedical applications due to their exceptional biocompatibility, corrosion resistance, and versatility. These nanoparticles offer potential in drug delivery, imaging, and tissue engineering, where their nanoscale properties allow precise interactions with biological systems. Among niobium-based nanomaterials, niobium pentoxide (Nb₂O₅) is the most extensively studied due to its chemical stability, bioactivity, and optical properties. Nb₂O₅ nanoparticles have shown significant potential in catalysis, biosensing, and photodynamic therapy, as their stability and reactivity make them ideal for functionalization in advanced biomedical applications. Despite these advantages, challenges remain regarding the biodegradability and long-term retention of NbNPs in biological systems. Their accumulation in tissues can lead to risks such as chronic inflammation or toxicity, emphasizing the importance of designing nanoparticles with controlled clearance and biodegradability. Surface modifications, such as coatings with biocompatible polymers, have demonstrated the ability to mitigate these risks while enhancing therapeutic efficacy. This review provides a comprehensive overview of NbNPs, with a focus on Nb₂O₅, highlighting their unique properties, current biomedical applications, and limitations. By addressing the remaining challenges, this work aims to guide the development of safer and more effective niobium-based nanomaterials for future medical innovations.