Metal Complexes Research Articles

Synthesis, Characterization, and Resistive Memory Behaviors of Highly Strained Cyclometalated Platinum(II) Nanohoops.

Strained carbon nanohoops exhibit attractive photophysical properties due to their unique π-conjugated structure. However, incorporation of such nanohoops into the pincer ligand of metal complexes has rarely been explored. Herein, a new family of highly strained cyclometalated platinum(II) nanohoops has been synthesized and characterized. Strain-promoted C-H bond activation has been observed during the metal coordination process, and Hückel-Möbius topology and random-columnar packing in the solid state are found. Transient absorption spectroscopy revealed the size-dependent excited state properties of the nanohoops. Moreover, the nanohoops have been successfully employed as active materials in the fabrication of solution-processable resistive memory devices, including the use of the smallest platinum(II) nanohoop for the fabrication of a binary memory, with low switching threshold voltages of ca. 1.5 V, high ON/OFF current ratios, and good stability. These results demonstrate that strain incorporation into the structure can be an effective strategy to fundamentally fine-tune the reactivity, optoelectronic, and resistive memory properties.

Cobalt(II)-Catalyzed Synthesis of γ-Diketones from Aryl Alkenes and Its Utilization in the Synthesis of Various Heterocyclic Compounds.

An earth-abundant Co(II) salt-catalyzed mild and affordable synthetic route has been developed for the synthesis of industrially relevant 1,4-dicarbonyl compounds (or γ-diketones) via oxidative coupling between aryl alkenes and ketones (both cyclic and acyclic) using TBHP and DBU as the oxidant and base, respectively. 1,4-Dicarbonyl compounds are known to be synthesized using expensive metal catalysts, dual catalysts, or low-cost metal complexes combined with an additive or ligand template, which further needs to be synthesized. Herein, we report the synthesis of 1,4-dicarbonyl compounds using cobalt(II) acetate as a catalyst without any expensive co-catalyst or ligand templates. This methodology has a broad substrate scope with significant yields and good functional group tolerance. Generation of unsymmetrical 1,4-dicarbonyls at room temperature and its versatile synthetic expansion to produce synthetically and biologically valuable heterocyclic compounds are salient features of this novel methodology. In addition, various controlled experiments such as primary kinetic isotope effect study, Hammett analysis with variation of the nature of the substituents on the styrene ring, and theoretical calculations (density functional theory) unravel the mechanistic intricacies involved in this new, simple, and atom-economic methodology.

Ciprofloxacin Metal Complexes–Silica Nanoparticles: Characterization, Spectroscopic Study, DNA Interaction and Biological Activity

AbstractCiprofloxacin (CIPH) was classified as one of the most effective quinolone antibiotics, which is commonly used to cure a wide range of infections resulting from Gram-negative and Gram-positive microorganisms. The complexes which formed due to the interaction of Ni(II), Zn(II), Cu(II), Gd(III) and Sm(III) with ciprofloxacin were characterized by CHN% analysis, conductivity, FTIR, electronic spectra, fluorescence measurements, and magnetic susceptibility, besides studying the complex–DNA interaction. Meanwhile, the molar conductance values (0.001 mol·L−1 in DMSO) revealed the electrolytic behavior of the complexes and could be designated with the A−B+ formula. In addition, the geometry of the compounds was confirmed from the electronic transitions as well as the μeff values as octahedral for all complexes. The postulated formula could be generally assigned as [M(CIP)a(CIPH)b(H2O)c](NO3)(H2O)n(C2H5OH)m. Moreover, the interaction between metal complexes and DNA revealed that the Cu complex had the highest binding constant. Nanotechnology was applied to synthesized compounds using silica nanoparticles (SiNPs), which were prepared using a sol–gel process. The silica nanoparticles were chemically functionalized for binding the ligand and its metal complexes; this enables the as-prepared compounds to enhance their features as a drug delivery platform. Meanwhile, the antimicrobial activity was tested for the free complexes and SiNPs composites. Collectively, Sm complex gave the largest zone of inhibition, while the Cu(II)–SiNPs composite showed the strongest potential to reduce the bacterial activity. Furthermore, the fluorescence data of CIPH, ligand–metal mixture and the effect of silica nanoparticles on them were studied.

Hybrid photocatalyst constructed using polymerized metal complexes and semiconductor powders for photocatalytic carbon dioxide reduction

Abstract Hybrid photocatalysts prepared by the adsorption of metal complexes on semiconductors via anchoring groups are among notable photocatalysts for selective CO2 reduction using abundant electron donors. However, their photocatalytic activities are limited by their low adsorption amounts and strength. In this study, we demonstrate the reductive polymerization of vinyl groups in metal complexes triggered by excited electrons on semiconductors as a new immobilization method. This approach significantly enhanced the adsorption amount and durability, thus increasing the photocatalytic performance.

Synthesis and Characterization of Novel Schiff Base Complexes of Cu (II), Cd (II), Ni (II), and Co (II) Ions with N'-(4-Nitrobenzylidene) Isonicotinohydrazide

The Schiff base complexes of Cu (II), Cd (II), Ni (II), and Co (II) ions were synthesized utilizing Schiff base ligand. The Schiff base ligand was produced through the reaction of isoniazid with equimolar quantities of p-nitrobenzaldehyde yielding final product of N'-(4-nitrobenzylidene) isonicotinohydrazide (L). The ligand and its metal complexes were assessed by TLC, melting point determination, conductivity measurement, FTIR spectroscopy, magnetic moment analysis, and UV-Vis spectroscopy. The FTIR spectra revealed that the Schiff base ligand established coordination bonds with the metal ion by utilizing the nitrogen (N) atom of the azomethine group and the oxygen (O) atom of the carbonyl group. All synthesized compounds exhibited cytotoxicity against brine shrimp nauplii, thereby confirming their biological activity. [Ni(L)2] and [Cd(L)2] complexes displayed greater cytotoxic or anticancer efficacy. In addition, the antibacterial efficacy of both ligand and its complexes was investigated against several harmful bacteria. In comparison with the ligand (L), the antibacterial activity of the complexes of [Cu(L)2], [Cd(L)2], and [Ni(L)2] is higher, whereas that of [Co(L)2] is lower.

Organometallic ruthenium complexes derived from anthracene and pyrene chromophores: Synthesis and photophysical properties

AbstractTwo new monopyridyl‐based Anthracene and Pyrene ligands were synthesized and employed to design Ruthenium‐coordinated organometallic complexes, RuAnthra and RuPyrene, respectively. The ligands and their metal complexes were fully characterized by different analytical techniques, including multinuclear 1D‐ and 2D‐NMR, electrospray ionization‐mass spectrometry, UV–Vis, fluorescence spectroscopy, and elemental analysis. Furthermore, their photophysical properties were studied in different solvents with increasing polarity using UV–Vis and fluorescence spectroscopy, showing less or no significant solvolysis effect. The average emission lifetimes of the complexes were further determined using time‐resolved emission spectroscopy. Additionally, the ligands and their metal complexes showed excellent ability to generate singlet oxygen and can be useful for several important potential applications.

Bimetallic Ag125Cu8 Nanocluster, Structure Determination, and Nonlinear Optical Properties.

The atomic precision of the subnanometer nanoclusters has provided sound proof on the structural correlation of metal complexes and larger-sized metal nanoparticles. Herein, we report the synthesis, crystallography, structural characterization, electrochemistry, and optical properties of a 133-atom intermetallic nanocluster protected by 57 thiolates (3-methylbenzenethiol, abbreviated as m-MBTH) and 3 chlorides, with the formula of Ag125Cu8(m-MBT)57Cl3. This is the largest Ag-Cu bimetallic cluster ever reported. Crystallographic analysis revealed that the nanocluster has a three-layer concentric core-shell structure, Ag7@Ag47@Ag71Cu8S57Cl3, and the Ag54 metal kernel adopts a D5h symmetry. The nuclei number is between that of the previously reported large silver cluster [Ag136(SR)64Cl3Ag0.45]- and the large silver-rich cluster Au130-xAgx(SR)55 (x = 98). All these three clusters bear a similar metallic core structure, while the main structural difference lies in the shell motif structures. Electron counting revealed an open electron shell with 73 delocalized electrons, which was verified by the electron paramagnetic resonance analysis. The DPV electrochemical measurement indicates a multielectron state quantization double-layer charging shape and single-electron sequential charging and discharging characteristic of the AgCu alloy cluster. In addition, the open-hole Z-scan test reveals the nonlinear optical absorption (2-3 optical absorption in the NIR-II/III region) of Ag125Cu8 nanoclusters.

Mitochondria-targeting metallodrugs for cancer therapy: perspectives from cell death modes.

Mitochondria, recognized as the cellular powerhouses, are indispensable organelles responsible for crucial cellular processes, such as energy metabolism, material synthesis, and signaling transduction. Their intricate involvement in a broad spectrum of diseases, particularly cancer, has propelled the exploration of mitochondria-targeting treatment as a promising strategy for cancer therapy. Since the groundbreaking discovery of cisplatin, the trajectory of research on the development of metal complexes have been marked by continuous advancement, giving rise to a diverse array of metallodrugs characterized by variations in ligand types, metal center properties, and oxidation states. By specifically targeting mitochondria, these metallodrugs exhibit the remarkable ability to elicit various programmed cell death pathways, encompassing apoptosis, autophagy, and ferroptosis. This review primarily focuses on recent developments in transition metal-based mitochondria-targeting agents, offering a comprehensive exploration of their capacity to induce distinct cell death modes. The aim is not only to disseminate knowledge but also to stimulate an active field of research toward new clinical applications and novel anticancer mechanisms.

Synthesis and characterization of indazole derived Schiff base ligands and their metal complexes: Biological and computational studies

Indazoles represent one of the most important heterocycles in drug molecules. Therefore, in the pursuit of potent biological agents, a series of ligands (HL1-HL4) and their corresponding transition metal complexes [M(L1-L4)2(H2O)2] were synthesized by the condensation reaction of 6-aminoindazole with various derivatives of salicylaldehyde. Further, the compounds underwent characterization through several physicochemical (TGA, powder XRD, SEM, EDAX) and spectroscopic techniques (FT-IR, UV–Vis, NMR, mass spectrometry, ESR). These techniques suggested hexacoordinated stereochemistry of the metal complexes, where ligands chelate via oxygen atom of phenolic ring, azomethine nitrogen and oxygen atom of water molecules in 1:2 (M:L) molar ratio. The thermal stability of the complexes was demonstrated by thermal analysis revealing three step decompositions leaving behind metal oxide as an end residue. The surface morphology of the ligands was distinct from metal complexes as revealed by SEM analysis, while mapping images demonstrated the simultaneously existence of the elements. While, to ascertain the nature of the obtained compounds (crystalline or amorphous), powder X-ray investigation was conducted by utilizing a wavelength of 1.54 Å. The compound’s antioxidant potential was assessed through DPPH assays and anti-inflammatory activity was evaluated using BSA denaturation inhibition assay, while their antimicrobial potential was evaluated against six microbial strains (E. coli, S. aureus, P. aeruginosa, B. subtilis, C. albicans, A. niger) by serial dilution approach. The performed biological evaluations revealed that the complexes are more efficient in controlling infectious ailment in comparison of ligands. HL2 (2) and its Cu(II), Zn(II) complexes (11, 12) exhibited potent antimicrobial activity (MIC value: 0.0047, 0.0048 µmol/mL against B. subtilis) and potent anti-inflammatory efficacy (IC50 value: 6.7 ± 0.044, 6.9 ± 0.036 µM). All the complexes exhibited potent antioxidant activity and their is enhancement in the activity of Schiff base ligands upon complexation, complex (19) demonstrated the greatest activity with IC50 value 2.1 ± 0.059. Additionally, the ADMET score provided a robust indication of the compounds’ drug-like behaviour. Furthermore, the biological effectiveness of the highly microbial potent ligand HL2 (2) and its complexes (9–12) was demonstrated through computational studies. The binding studies exposed that complexes (11, 12) exhibited lowest binding energy at −7.8, −7.9 kcal/mol. While, DFT study emphasized that complex (12) exhibits the highest electrophilicity index value (6.359), suggesting its affinity for binding with biological molecules and also revealed that complexes exhibit greater potency compared to the ligands and could potentially be utilized as drugs for combatting pathogen-induced malformations.

Novel Co(II), Cu(II) and Fe(II) Pentadentate Schiff base complexes: Synthesis, characterization, antimicrobial, antioxidant, and molecular docking studies

The compound H2L, which is a ligand with five coordinating atoms, consisting of three nitrogen atoms and two sulfur atoms (N3S2), was reacted with Fe(OAc)2, Cu(OAc)2.H2O, and Co(OAc)2·4H2O to form the corresponding metal complexes ([FeL], [CuL], [CoL]). Many techniques, including NMR (for ligand), FT-IR, UV–Vis, elemental analysis, and molar conductivity, were used to characterize the synthesized compounds. According to the spectrum of data, complex molecule structures have a distorted triangular bipyramidal geometry with five coordination locations. The compounds that exhibit non-electrolyte behavior in solution do not possess any conductivity features. Evaluation was performed to determine the antioxidant activity of the synthesized compounds in comparison to the stable free radical DPPH. The ligand and its metal complexes were evaluated for antibacterial activity against several Gram-positive and Gram-negative bacteria, as well as a yeast strain. In comparison to the common antibiotic Amoxycillin/Clavulanic Acid (AMC-30), the Schiff base ligand (H2L) and its Cu(II) metal complex showed noticeably larger inhibitory zones against S. aureus. All the compounds showed a high negative binding affinity for S. aureus amino acid molecules when they were docked. The results indicated that the metal complexes, particularly the cobalt complex, exhibited a higher affinity for binding compared to the free ligand.

Metal complexes with thiosemicarbazone derivative and isatine: A promising new class of materials for biomedical and environmental applications

Metal complexes with thiosemicarbazones and isatine have been shown to exhibit a wide range of biological activities, including antibacterial, antifungal, and anticancer activity. These complexes have also been shown to be effective photocatalysts for degrading dyes, making them a subject of significant interest. This article presents the synthesis and characterization of mixed ligand complexes of isatine-thiosemicarbazones to explore their biological activity and potential for photocatalytic applications. In this study, we synthesized mixed ligand complexes of isatine-thiosemicarbazones with various metal ions, including Cu(II), Cd(II), and Fe(III). Characterization techniques such as elemental analysis, infrared (IR), mass spectrometry (MS), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) were utilized to understand their structural composition and morphological properties. The complexes exhibited remarkable antibacterial activity against Escherichia coli, Staphylococcus aureus, Streptococcus mutants, and antifungal effects on Candida albicans. Notably, the Fe-complex demonstrated the highest activity, followed by the Cu-complex and Cd-complex. Strong anticancer effects were observed against human liver HepG2 and breast MDA cancer cells, with the Fe-complex displaying the highest activity. Additionally, the complexes displayed significant photocatalytic activity in the decomposition of rose bengal dye using ultraviolet light irradiation, with the Cu-complex showing the highest degradation efficiency. The results indicate that these mixed ligand metal complexes have potential therapeutic applications as antibacterial, antifungal, and anticancer agents. Moreover, they suggest their prospective utility as photocatalysts for the remediation of dye-contaminated wastewater.

Exploring the versatility of sulfur-containing heterocyclic metal complexes: Application in medical and prospects of visible-light-driven photocatalysis

Numerous heterocyclic moieties serve as the foundational structure for clinically employed drugs, underscoring the significance of heterocycles in the innovation of pharmacologically active compounds. In the present investigation, a heterocyclic skeleton of thiophene-clubbed benzimidazole (tmb) was developed and utilized to synthesize seven novel series of metal (M(II) = Co, Ni, Cu, and Zn) complexes to explore diverse applications including pharmacological and photocatalytic performance. A sharp singlet peak appeared at 5.72 ppm (tmb) and 5.94 ppm for the Zn(II)-tmb complex corresponding to -CH2 protons, as evidenced by 1H NMR results, confirming the formation of targeted compounds. Antimicrobial assay and docking studies confirmed that the mixed metal complex; [Cu(tmb)2(1,10-phen)Cl2] possesses the highest activity and displayed significant biofilm inhibition, achieving 86.35 and 89.8% at concentrations of 1 and 0.020 mg/mL, respectively against E. coli. Furthermore, the photocatalytic activity was monitored by the degradation of methylene blue dye under direct sunlight and [Cu(tmb)2Cl2] exhibited a maximum degradation efficiency of 96.15% in 45 min. These findings could serve as inspiration for the development of benzimidazole-based metal complexes as effective anti-biofilm and photocatalytic agents.

Chemical Compatibility of Energetic Metal Complexes with Polymers by Thermal Analytical Techniques

Energetic metal complexes have been established to be effective combustion catalyst for energetic composites and propellants with improved performance. Chemical compatibility is an important aspect in the development of novel energetic composites which are related to safe processing, handling, and storage. In the present paper, the compatibility of energetic metal complexes [Zn(atrz)(DNBA)2(H2O)2]n (complex 1) and [Cd(atrz)(DNBA)2(H2O)2]n (complex 2) with Viton A and epoxy resin as polymer binder are studied by thermal analytical techniques. The compatibility was studied through vacuum stability test (VST) and differential scanning calorimetry (DSC) according to standardization agreement (STANAG) 4147 method. Furthermore, physicochemical methods including powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR) were used to support the thermal analytical methods. The VST results indicate that the volume of gases evolved for complex 1/Viton A, complex 1/epoxy resin, complex 2/Viton A, and complex 2/epoxy resin is found to be 0.545, 0.86, 0.403, and 0.884 mLg-1, respectively, indicating high compatibility with one another. According to the STANAG 4147 criteria, the DSC/DTG data demonstrate that the difference in Tmax is less than 2°C for all the admixtures, suggesting that the polymer binders under investigation are compatible with complexes. TG results demonstrate that the mass loss difference is less than 4% for all admixtures, indicating good compatibility. The essential additional information offered by the supplementary non-thermal FTIR and PXRD techniques confirm that no reaction occurs between metal complex and polymer. SEM micrographs exhibit that metal complex crystals are embedded in the polymer matrix.

Synthesis, Molecular Docking, and antibacterial evaluation of Quinoline-Derived Ni(II), Cu(II) and Zn(II) complexes

We hereby report the synthesis of novel Ni(II), Cu(II) and Zn(II) complexes of (E)-2-(((7-chloro-2-hydroxyquinolin-3-yl)methylene)amino)-3-methylbutanoic acid ligand obtained by reacting 2,7-dichloroquinoline-3-carboaldehyde and amino acid, valine for antibacterial applications. The ligand and the metal complexes were characterized using FT-IR, UV–Vis, TGA/DTA, pXRD spectroscopic techniques and density functional theory (DFT) calculations. The Schiff base ligand was tridentate with ONO active binding sites as confirmed from its FT-IR spectral analysis. Disc diffusion method was used to assess the antibacterial potential of the Schiff base ligand and its metal complexes. The Schiff base ligand shows antibacterial activities of 8.33 ± 0.471 mm at concentration of 100 µg/ml and 9.33 ± 0.471 mm at concentration of 200 µg/ml against S. aureus. However, the copper complex exhibited zone of inhibition of 11.50 ± 0.408 mm at concentration of 100 µg/ml and 12.67 ± 0.471 mm at concentration of 200 µg/ml against S. aureus. This indicates that the copper complex has better antibacterial activity than the free Schiff base ligand. The overall result revealed the promising potential of the metal complexes for application as antibacterial agents. The DFT calculated absorption spectra agree with the corresponding experimental results. The molecular docking analyses also provided important insights on the interaction of the synthesized complexes with the target proteins.

Synthesis, characterization, thermal, theoretical studies, antimicrobial, antioxidant activity, superoxide dismutase-like activity and catalase mimetics of metal(II) complexes derived from sugar and Schiff base

Abstract Scientists are searching for reactive oxygen species, which have been associated with various health issues like heart problems, neurological disorders, inflammation, and aging. Salen complexes have proven to be effective in multiple oxidative stress situations and have been used as catalase and superoxide mimetics. To explore this further, three mixed complexes were synthesized using a Schiff base (salen) and a sugar (d-glucose) with Co(II), Ni(II), and Cu(II) ions. These complexes were then diagnosed by different analytical and spectral techniques. Stoichiometry, stereochemistry, some physical properties, and the method of bonding complexes were measured. Comparisons of the IR and 1HNMR spectra of the ligands with the complexes demonstrated the involvement of the azomethine group of the ligand in the chelation process. The mass spectra and TGA agree with the proposed formula of the complexes, and the conductivity and UV–Vis data supported the octahedral geometry of the complexes, and information was obtained from partial parameter calculations by molecular modeling. The metal complexes exhibited strong antimicrobial and antioxidant properties when compared to standard drugs. The like-superoxide and catalyst mimetic complexes were screened using DPPH ABTS, revealing their effectiveness.

Tuning the sensing properties of isophthalic dihydrazide-based receptor via formation of organic–inorganic hybrid and metal complex: An enhanced sensing activity for Hg2+ and CN− detection in semi-aqueous medium

A Schiff base receptor H2L has been synthesized through a condensation reaction between 2-hydroxy-3-methoxybenzaldehyde and isophthalic dihydrazide. The compound has been characterized by various characterization techniques such as 1H, FT-IR, CHNS and single crystal X-ray crystallography. Despite its limited solubility in water, a strategy was employed to enhance its effectiveness in aqueous environment by forming fluorescent nanoaggregates of H2L through a re-precipitation method. The fluorescent nanoaggregates of H2L show strong recognition ability towards Hg2+ ions through a fluorescence turn-on mechanism in H2O–DMSO (90 %, v/v). The study has been extended by developing a hybrid nano-assembly of H2L as Ag@H2L which exhibits higher sensitivity for Hg2+ ions with an improved detection limit 9.3 × 10−9 M as compared to that of organic nanoaggregates having 7.9 × 10−8 M in H2O–DMSO (90 %, v/v). Further Hg2+ complex of H2L has also been synthesized and characterized using elemental analysis, mass spectrometry and IR, UV–Vis spectroscopic techniques. The findings have been complimented by density functional theory (DFT) computations. The synthesized H2L-Hg complex is able to detect CN− ion using UV–Vis spectroscopy in H2O–DMSO (80 %, v/v) with a detection limits of 1.04 × 10−6 M.

Cobalt-Mediated Photochemical C-H Arylation of Pyrroles.

Precious metal complexes remain ubiquitous in photoredox catalysis (PRC) despite concerted efforts to find more earth-abundant catalysts and replacements based on 3d metals in particular. Most otherwise plausible 3d metal complexes are assumed to be unsuitable due to short-lived excited states, which has led researchers to prioritize the pursuit of longer excited-state lifetimes through careful molecular design. However, we report herein that the C-H arylation of pyrroles and related substrates (which are benchmark reactions for assessing the efficacy of photoredox catalysts) can be achieved using a simple and readily accessible octahedral bis(diiminopyridine) cobalt complex, [1‑Co](PF6)2. Notably, [1‑Co]2+ efficiently functionalizes both chloro- and bromoarene substrates despite the short excited-state lifetime of the key photoexcited intermediate *[1‑Co]2+ (8ps). We present herein the scope of this C-H arylation protocol and provide mechanistic insights derived from detailed spectroscopic and computational studies. These indicate that, despite its transient existence, reduction of *[1‑Co]2+ is facilitated via pre-assembly with the NEt3 reductant, highlighting an alternative strategy for the future development of 3d metal-catalyzed PRC.

Cobalt‐Mediated Photochemical C−H Arylation of Pyrroles

Precious metal complexes remain ubiquitous in photoredox catalysis (PRC) despite concerted efforts to find more earth‐abundant catalysts and replacements based on 3d metals in particular. Most otherwise plausible 3d metal complexes are assumed to be unsuitable due to short‐lived excited states, which has led researchers to prioritize the pursuit of longer excited‐state lifetimes through careful molecular design. However, we report herein that the C−H arylation of pyrroles and related substrates (which are benchmark reactions for assessing the efficacy of photoredox catalysts) can be achieved using a simple and readily accessible octahedral bis(diiminopyridine) cobalt complex, [1‑Co](PF6)2. Notably, [1‑Co]2+ efficiently functionalizes both chloro‐ and bromoarene substrates despite the short excited‐state lifetime of the key photoexcited intermediate *[1‑Co]2+ (8 ps). We present herein the scope of this C−H arylation protocol and provide mechanistic insights derived from detailed spectroscopic and computational studies. These indicate that, despite its transient existence, reduction of *[1‑Co]2+ is facilitated via pre‐assembly with the NEt3 reductant, highlighting an alternative strategy for the future development of 3d metal‐catalyzed PRC.

Stretchable hydrogels of chitosan/hyaluronic acid induced by polyelectrolyte complexation around neutral pH

In this work, we propose the formation of stretchable hydrogels at neutral pH from the physical crosslinking of chitosan (CS) and hyaluronic acid (HA) by polyelectrolyte complexation. A mixture of CS (Mw ≈ 600 kg/mol, degree of acetylation ≈ 50 %) solution and HA (Mw ≈ 77 kg/mol) solution was prepared with an excess of salts screening the electrostatic interactions CS/HA. In a controlled manner, the polyelectrolyte complexation was induced through the progressive dialysis of the salted polymer mixture against a sodium acetate solution (AcONa, 0.01 M) for 7 days. Depending on [HA], various materials were obtained: viscous solutions at [HA] = 0.75 % (w/v); hydrogels at [HA] = 1.50–2.24 % w/v with Young modulus of 14 kPa and stretchable to 200 %. The small angle X-ray scattering characterization of the hydrogels revealed a multiscale organization related to the conformation of the polymers induced by the physical interactions. The dialysis process with AcONa was optimized by adding a dialysis step against a zinc acetate solution containing Zn2+. The combination of polyelectrolyte complexation between CS/HA and metallic complexation between Zn2+ and the polymers led to an enhancement of the hydrogel stretchability up to 400 %.

A review of recent advances in the use of complex metal nanostructures for biomedical applications from diagnosis to treatment.

Complex metal nanostructures represent an exceptional category of materials characterized by distinct morphologies and physicochemical properties. Nanostructures with shape anisotropies, such as nanorods, nanostars, nanocages, and nanoprisms, are particularly appealing due to their tunable surface plasmon resonances, controllable surface chemistries, and effective targeting capabilities. These complex nanostructures can absorb light in the near-infrared, enabling noteworthy applications in nanomedicine, molecular imaging, and biology. The engineering of targeting abilities through surface modifications involving ligands, antibodies, peptides, and other agents potentiates their effects. Recent years have witnessed the development of innovative structures with diverse compositions, expanding their applications in biomedicine. These applications encompass targeted imaging, surface-enhanced Raman spectroscopy, near-infrared II imaging, catalytic therapy, photothermal therapy, and cancer treatment. This review seeks to provide the nanomedicine community with a thorough and informative overview of the evolving landscape of complex metal nanoparticle research, with a specific emphasis on their roles in imaging, cancer therapy, infectious diseases, and biofilm treatment. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Diagnostic Tools > Diagnostic Nanodevices.