Mg- and Mn-MOFs Boost the Antibiotic Activity of Nalidixic Acid

Synthesis and characterisation of antimicrobial metal-organic frameworks as multi-drug carriers

Antibiotic resistance is a significant global concern, necessitating the development of either new antibiotics or advanced delivery methods. With this in mind, we report on the synthesis and characterisation of a new family of Metal-Organic Frameworks (MOFs), OnG6 MOFs, designed to act as multi-drug carriers for bacterial infection treatment. OnG6 is based on the pro-drug 4,4'-azodisalicylic acid (AZDH4), which in vivo produces two equivalents of para-aminosalicylic acid (ASA), a crucial drug for M. tuberculosis treatment. X-ray and computational studies revealed that OnG6 MOFs are mesoporous MOFs with etb topology and an [M2(AZD)] formula (M = Zn, OnG6-Zn; Mg, OnG6-Mg; Cu, OnG6-Cu; and Co, OnG6-Co), featuring 1-dimensional channel type pores of 25 Å diameter. OnG6 MOFs are the first reported MOFs bearing the ligand AZDH4, joining the family of mesoporous MOFs arranged in a honeycomb pattern. They absorb isoniazid (INH) and ciprofloxacin (CIPRO) with the former being a specific antibiotic for M. tuberculosis, and the latter being a broader-spectrum antibiotic. The stability of the MOFs and their capacity for antibiotic uptake depend on the nature of the metal ion, with OnG6-Mg demonstrating the highest drug absorption. The antimicrobial activity of these species was assessed against S. aureus and E. coli, revealing that the carriers containing CIPRO displayed optimal efficacy.

Recent advances and potential applications for metal-organic framework (MOFs) and MOFs-derived materials: Characterizations and antimicrobial activities

Microbial infections, particularly those caused by antibiotic-resistant pathogens, pose a critical global health threat. Metal-Organic Frameworks (MOFs), porous crystalline structures built from metal ions and organic linkers, initially developed for gas adsorption, have emerged as promising alternatives to traditional antibiotics. This review, covering research up to 2023, explores the potential of MOFs and MOF-based materials as broad-spectrum antimicrobial agents against bacteria, viruses, fungi, and even parasites. It delves into the historical context of antimicrobial agents, recent advancements in MOF research, and the diverse synthesis techniques employed for their production. Furthermore, the review comprehensively analyzes the mechanisms of action by which MOFs combat various microbial threats. By highlighting the vast potential of MOFs, their diverse synthesis methods, and their effectiveness against various pathogens, this study underscores their potential as a novel solution to the growing challenge of antibiotic resistance.

Antibiotic Coordination Frameworks against Antibiotic Resistance: How to Involve Students through Experimental Practices in the Search for Solutions to Public Health Problems

For decades, multiple varieties of antibiotics have been successfully used for therapeutic purposes. Nevertheless, antibiotic resistance is currently one of the major threats to global health. This work presents an innovative laboratory practice carried out in an inorganic medicinal chemistry course within the Degrees of Pharmacy and Biochemistry for undergraduate students. This experiment includes three classes of 2 h each. The first class consisted of the mechanochemical synthesis of an antibiotic coordination framework (ACF) using a known antibiotic (nalidixic acid) and zinc as the ligand. The prepared Zn-nalidixic acid ACF (Zn-ACF) was obtained in up to 82% yield with high purity. On the second day, the synthesized Zn-ACF was characterized by Fourier-transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD). Finally, during the last class, the antimicrobial activity was tested against Escherichia coli by the well diffusion method. The students verified the higher antimicrobial activity of Zn-ACF compared to nalidixic acid, proving that small changes in the chemical structure can result in great biological differences. In the end, the students presented their results in a poster format, encouraging the development of their soft skills and scientific results communication and dissemination. In the future, it is expected that such a laboratory experiment at the interface between medicinal chemistry, microbiology, analytical techniques, public health, and pharmacology will lead to the development and implementation of some service-learning practices and will serve as a model to look at for other courses and institutions.

The green synthesis and applications of biological metal-organic frameworks for targeted drug delivery and tumor treatments

Biological metal-organic frameworks (bio-MOFs) constitute a growing subclass of MOFs composed of metals and bio-ligands derived from biology, such as nucleobases, peptides, saccharides, and amino acids. Bio-ligands are more abundant than other traditional organic ligands, providing multiple coordination sites for MOFs. However, bio-MOFs are typically prepared using hazardous or harmful solvents or reagents, as well as laborious processes that do not conform to environmentally friendly standards. To improve biocompatibility and biosafety, eco-friendly synthesis and functionalization techniques should be employed with mild conditions and safer materials, aiming to reduce or avoid the use of toxic and hazardous chemical agents. Recently, bio-MOF applications have gained importance in some research areas, including imaging, tumor therapy, and targeted drug delivery, owing to their flexibility, low steric hindrances, low toxicity, remarkable biocompatibility, surface property refining, and degradability. This has led to an exponential increase in research on these materials. This paper provides a comprehensive review of updated strategies for the synthesis of environmentally friendly bio-MOFs, as well as an examination of the current progress and accomplishments in green-synthesized bio-MOFs for drug delivery aims and tumor treatments. In conclusion, we consider the challenges of applying bio-MOFs for biomedical applications and clarify the possible research orientation that can lead to highly efficient therapeutic outcomes.

Innovative Metal-Organic Frameworks for Targeted Oral Cancer Therapy: A Review

Metal-organic frameworks (MOFs) have proven to be very effective carriers for drug delivery in various biological applications. In recent years, the development of hybrid nanostructures has made significant progress, including developing an innovative MOF-loaded nanocomposite with a highly porous structure and low toxicity that can be used to fabricate core-shell nanocomposites by combining complementary materials. This review study discusses using MOF materials in cancer treatment, imaging, and antibacterial effects, focusing on oral cancer cells. For patients with oral cancer, we offer a regular program for accurately designing and producing various anticancer and antibacterial agents to achieve maximum effectiveness and the lowest side effects. Also, we want to ensure that the anticancer agent works optimally and has as few side effects as possible before it is tested in vitro and in vivo. It is also essential that new anticancer drugs for cancer treatment are tested for efficacy and safety before they go into further research.

Synthesis, Spectral Characterization and Potential Fluorescent Properties of Three Lanthanide(III) Ions Complexes with Nalidixic Acid

Three new solid lanthanide complexes with nalidixic acid (HNal) with the stoichiometry [Ln(Nal)₃]·5·.5H₂O (Ln = Tb, Dy and Ho) were synthesized applying the green synthesis method from the aqueous solutions without the organic solvent addition and fully characterized by the elemental analysis, XRF, complexometric titration, gravimetric analysis, molar conductivity and solubility measurements, powder X-Ray diffraction, UV-Vis and infrared (FT-IR) spectroscopies. Moreover, the luminescent properties of the Tb(III), Dy(III), and Ho(III) complexes in the solid state and in the solutions were investigated. On the basis of the detailed spectral analysis, it was concluded that the nalidixate ligands bind to the lanthanide ions by the bidentate carboxylate and carbonyl groups while water molecules belong to the outer coordination sphere. At the excitation of UV light, the complexes exhibited characteristic emission of central lanthanide ions, the intensity of which depends significantly on the excitation wavelength and/or the solvent. Thus, the application of nalidixic acid (apart from biological activity) for the synthesis of luminescent lanthanide complexes was confirmed which can find potential applications in the field of photonic devices and/or bioimaging agents.

Utilization of Functionalized Metal–Organic Framework Nanoparticle as Targeted Drug Delivery System for Cancer Therapy

Cancer is a multifaceted disease that results from the complex interaction between genetic and environmental factors. Cancer is a mortal disease with the biggest clinical, societal, and economic burden. Research on better methods of the detection, diagnosis, and treatment of cancer is crucial. Recent advancements in material science have led to the development of metal–organic frameworks, also known as MOFs. MOFs have recently been established as promising and adaptable delivery platforms and target vehicles for cancer therapy. These MOFs have been constructed in a fashion that offers them the capability of drug release that is stimuli-responsive. This feature has the potential to be exploited for cancer therapy that is externally led. This review presents an in-depth summary of the research that has been conducted to date in the field of MOF-based nanoplatforms for cancer therapeutics.

BioMOF-Based Anti-Cancer Drug Delivery Systems

A variety of nanomaterials have been developed specifically for biomedical applications, such as drug delivery in cancer treatment. These materials involve both synthetic and natural nanoparticles and nanofibers of varying dimensions. The efficacy of a drug delivery system (DDS) depends on its biocompatibility, intrinsic high surface area, high interconnected porosity, and chemical functionality. Recent advances in metal-organic framework (MOF) nanostructures have led to the achievement of these desirable features. MOFs consist of metal ions and organic linkers that are assembled in different geometries and can be produced in 0, 1, 2, or 3 dimensions. The defining features of MOFs are their outstanding surface area, interconnected porosity, and variable chemical functionality, which enable an endless range of modalities for loading drugs into their hierarchical structures. MOFs, coupled with biocompatibility requisites, are now regarded as highly successful DDSs for the treatment of diverse diseases. This review aims to present the development and applications of DDSs based on chemically-functionalized MOF nanostructures in the context of cancer treatment. A concise overview of the structure, synthesis, and mode of action of MOF-DDS is provided.

Metal-Organic Frameworks and Their Biodegradable Composites for Controlled Delivery of Antimicrobial Drugs

Antimicrobial resistance (AMR) is a growing global crisis with an increasing number of untreatable or exceedingly difficult-to-treat bacterial infections, due to their growing resistance to existing drugs. It is predicted that AMR will be the leading cause of death by 2050. In addition to ongoing efforts on preventive strategies and infection control, there is ongoing research towards the development of novel vaccines, antimicrobial agents, and optimised diagnostic practices to address AMR. However, developing new therapeutic agents and medicines can be a lengthy process. Therefore, there is a parallel ongoing worldwide effort to develop materials for optimised drug delivery to improve efficacy and minimise AMR. Examples of such materials include functionalisation of surfaces so that they can become self-disinfecting or non-fouling, and the development of nanoparticles with promising antimicrobial properties attributed to their ability to damage numerous essential components of pathogens. A relatively new class of materials, metal-organic frameworks (MOFs), is also being investigated for their ability to act as carriers of antimicrobial agents, because of their ultrahigh porosity and modular structures, which can be engineered to control the delivery mechanism of loaded drugs. Biodegradable polymers have also been found to show promising applications as antimicrobial carriers; and, recently, several studies have been reported on delivery of antimicrobial drugs using composites of MOF and biodegradable polymers. This review article reflects on MOFs and polymer-MOF composites, as carriers and delivery agents of antimicrobial drugs, that have been studied recently, and provides an overview of the state of the art in this highly topical area of research.

Combination Strategies of Different Antimicrobials: An Efficient and Alternative Tool for Pathogen Inactivation

Despite the discovery and development of an array of antimicrobial agents, multidrug resistance poses a major threat to public health and progressively increases mortality. Recently, several studies have focused on developing promising solutions to overcome these problems. This has led to the development of effective alternative methods of controlling antibiotic-resistant pathogens. The use of antimicrobial agents in combination can produce synergistic effects if each drug invades a different target or signaling pathway with a different mechanism of action. Therefore, drug combinations can achieve a higher probability and selectivity of therapeutic responses than single drugs. In this systematic review, we discuss the combined effects of different antimicrobial agents, such as plant extracts, essential oils, and nanomaterials. Furthermore, we review their synergistic interactions and antimicrobial activities with the mechanism of action, toxicity, and future directions of different antimicrobial agents in combination. Upon combination at an optimum synergistic ratio, two or more drugs can have a significantly enhanced therapeutic effect at lower concentrations. Hence, using drug combinations could be a new, simple, and effective alternative to solve the problem of antibiotic resistance and reduce susceptibility.

BioMOF-Mn: An Antimicrobial Agent and an Efficient Nanocatalyst for Domino One-Pot Preparation of Xanthene Derivatives

In this paper, a new Mn-based metal-organic framework [UoB-6] was obtained via a one-step ultrasonic irradiation method with the ligand (H₂bdda: 4,4'-(1,4-phenylenebis(azaneylylidene))bis(methaneylylidene))dibenzoic acid. The structural integrity of the synthesized BioMOF-Mn was corroborated by FT-IR, EDX, ICP, XRD, TEM, DLS, FESEM, and BET-BJH analyses. The aerobic oxidative domino reaction of benzyl alcohols or aldehydes with dimedone derivatives was performed in the presence of the UoB-6 catalyst to produce xanthene derivatives in good yields. Hot filtration and Hg poisoning tests proved the heterogeneous nature of the catalyst. Novel synthesized xanthene-based bis-aldehydes were introduced as potent HDAC1 inhibitors according to molecular docking calculations. Finally, the inhibitory activities of Mn-MOF nanoparticles were evaluated on Escherichia coli and Candida albicans. The MIC, MBC, and MFC values were determined from 2048 to 4096 μg·mL^-1 according to antimicrobial susceptibility testing methods. The inhibitory effects of antimicrobial agents can be exacerbated when loaded on BioMOFs.

Silver(I)-Tazobactam Frameworks with Improved Antimicrobial Activity

Tazobactam (TazoH) is a penicillinate sulfone β-lactamase inhibitor with negligible antimicrobial activity, commonly used with other antibiotics to provide an effective combination against many susceptible organisms expressing β-lactamases. Two novel Ag(I)-tazobactam frameworks ([Ag(I)-Tazo] and [Ag(I)-Tazo₂]) prepared by mechanochemistry are presented herein as alternative forms to improve the antimicrobial activity of tazobactam by exploring synergistic effects with silver, being the first crystal structures reported of tazobactam coordinating to a metal site. The topological analysis of the 3D ([Ag(I)-Tazo]) and 2D+1D ([Ag(I)-Tazo₂]) frameworks revealed underlying nets with the cbs (CrB self-dual) and decorated sql topologies, respectively. These novel frameworks are stable and show an enhanced antimicrobial activity when compared to tazobactam alone. Amongst the tested microorganisms, Pseudomonas aeruginosa is the most sensitive to tazobactam and the new compounds. This study thus unveils novel facets of tazobactam chemistry and opens up its application as a multifunctional linker for the design of antibiotic coordination frameworks and related materials.

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

This review summarizes recent progress in the development and applications of metal–organic gels (MOGs) and their hybrids and derivatives dividing them into subclasses and discussing their synthesis, design and structure–property relationship.

Mechanochemistry in Portugal-A Step towards Sustainable Chemical Synthesis

In Portugal, publications with mechanochemical methods date back to 2009, with the report on mechanochemical strategies for the synthesis of metallopharmaceuticals. Since then, mechanochemical applications have grown in Portugal, spanning several fields, mainly crystal engineering and supramolecular chemistry, catalysis, and organic and inorganic chemistry. The area with the most increased development is the synthesis of multicomponent crystal forms, with several groups synthesizing solvates, salts, and cocrystals in which the main objective was to improve physical properties of the active pharmaceutical ingredients. Recently, non-crystalline materials, such as ionic liquids and amorphous solid dispersions, have also been studied using mechanochemical methods. An area that is in expansion is the use of mechanochemical synthesis of bioinspired metal-organic frameworks with an emphasis in antibiotic coordination frameworks. The use of mechanochemistry for catalysis and organic and inorganic synthesis has also grown due to the synthetic advantages, ease of synthesis, scalability, sustainability, and, in the majority of cases, the superior properties of the synthesized materials. It can be easily concluded that mechanochemistry is expanding in Portugal in diverse research areas.

Effects of Magnesium, Calcium, and Aluminum Chelation on Fluoroquinolone Absorption Rate and Bioavailability: A Computational Study

Fluoroquinolones (FQs) are a widespread class of broad-spectrum antibiotics prescribed as a first line of defense, and, in some cases, as the only treatment against bacterial infection. However, when administered orally, reduced absorption and bioavailability can occur due to chelation in the gastrointestinal tract (GIT) with multivalent metal cations acquired from diet, coadministered compounds (sucralfate, didanosine), or drug formulation. Predicting the extent to which this interaction reduces in vivo antibiotic absorption and systemic exposure remains desirable yet challenging. In this study, we focus on quinolone interactions with magnesium, calcium and aluminum as found in dietary supplements, antacids (Maalox) orally administered therapies (sucralfate, didanosine). The effect of FQ-metal complexation on absorption rate was investigated through a combined molecular and pharmacokinetic (PK) modeling study. Quantum mechanical calculations elucidated FQ-metal binding energies, which were leveraged to predict the magnitude of reduced bioavailability via a quantitative structure-property relationship (QSPR). This work will help inform clinical FQ formulation design, alert to possible dietary effects, and shed light on drug-drug interactions resulting from coadministration at an earlier stage in the drug development pipeline.

Antimicrobial Activity of Pyrazinamide Coordination Frameworks Synthesized by Mechanochemistry

The urge for the development of a more efficient antibiotic crystalline forms led us to the disclosure of new antibiotic coordination frameworks of pyrazinamide, a well-known drug used for the treatment of tuberculosis, with some of the novel compounds unravelling improved antimycobacterial activity. Mechanochemistry was the preferred synthetic technique to yield novel compounds, allowing the reproduction of a 1D zinc framework, the synthesis of a novel hydrogen bonding manganese framework, and three new compounds with silver. The structural characterization of the novel forms is presented along with stability studies. The increased antimicrobial activity of the new silver-based frameworks against Escherichia coli, Staphylococcus aureus, and Mycobacterium smegmatis is particularly relevant.

Multimetallic Nanoparticles as Alternative Antimicrobial Agents: Challenges and Perspectives

Recently, infectious diseases caused by bacterial pathogens have become a major cause of morbidity and mortality globally due to their resistance to multiple antibiotics. This has triggered initiatives to develop novel, alternative antimicrobial materials, which solve the issue of infection with multidrug-resistant bacteria. Nanotechnology using nanoscale materials, especially multimetallic nanoparticles (NPs), has attracted interest because of the favorable physicochemical properties of these materials, including antibacterial properties and excellent biocompatibility. Multimetallic NPs, particularly those formed by more than two metals, exhibit rich electronic, optical, and magnetic properties. Multimetallic NP properties, including size and shape, zeta potential, and large surface area, facilitate their efficient interaction with bacterial cell membranes, thereby inducing disruption, reactive oxygen species production, protein dysfunction, DNA damage, and killing potentiated by the host's immune system. In this review, we summarize research progress on the synergistic effect of multimetallic NPs as alternative antimicrobial agents for treating severe bacterial infections. We highlight recent promising innovations of multimetallic NPs that help overcome antimicrobial resistance. These include insights into their properties, mode of action, the development of synthetic methods, and combinatorial therapies using bi- and trimetallic NPs with other existing antimicrobial agents.

From pipemidic acid molecular salts to metal complexes and BioMOFs using mechanochemistry

Mechanochemistry has proven to be an excellent sustainable, efficient and fast tool for the discovery of new crystal forms of old drugs.

Fluorescein-Metal Hybrid Surfactant Conjugates as a Smart Material for Antimicrobial Photodynamic Therapy against Staphylococcus aureus

Photodynamic therapy (PDT) has been extensively used as an effective alternative for the treatment of bacterial infection using photosensitizers (PSs) in the presence of appropriate light. However, the limitation in the effectiveness of PDT is because of the low yield of singlet oxygen from existing PSs because of their low solubility. Thus, we have developed a platform to enhance the solubility and the photodynamic activity of PSs against bacterial cells using metallosurfactants. Herein, we have used manganese metal-containing single- (MnC I) and double-chain metallosurfactants (MnC II) which show an interplay of electrostatic/hydrophobic interactions with fluorescein (FL) dye (as a PS) and when used in the presence of light enhances the PDT. These interactions play a significant role in enhancing the singlet oxygen generation efficiency of FL. MnC I and MnC II have shown good antimicrobial activity against Gram-positive Staphylococcus aureus (S. aureus) bacteria. More interestingly, these metallosurfactants when combined with FL significantly enhanced the affectivity against S. aureus, wherein 100% killing was achieved. As compared to experiments performed in the dark, the metallosurfactant, by enhancing the solubility of FL, increases the formation of singlet oxygen upon light irradiation and thus increases cell death. Therefore, the synergistic effect of FL (light toxicity) and metallosurfactants (dark toxicity) defined excellent reduction in the colony formation of bacteria. These results were corroborated through field-emission scanning electron microscopy and optical microscopy, where the rupturing of the cell wall of bacterial cells was observed during this therapy. Moreover, the binding of metallosurfactants to the genomic DNA of S. aureus was also evaluated by gel retardation analysis and UV-visible spectroscopy. The outcomes from this study will deliver formulations for PDT which can be used in clinical medical applications and cancer therapy in the future.

M. Antunes A, André V. Bioactivity of Isostructural Hydrogen Bonding Frameworks Built from Pipemidic Acid Metal Complexes

We report herein three novel complexes whose design was based on the approach that consists of combining commercially available antibiotics with metals to attain different physicochemical properties and promote antimicrobial activity. Thus, new isostructural three-dimensional (3D) hydrogen bonding frameworks of pipemidic acid with manganese (II), zinc (II) and calcium (II) have been synthesised by mechanochemistry and are stable under shelf conditions. Notably, the antimicrobial activity of the compounds is maintained or even increased; in particular, the activity of the complexes is augmented against Escherichia coli, a representative of Gram-negative bacteria that have emerged as a major concern in drug resistance. Moreover, the synthesised compounds display similar general toxicity (Artemia salina model) levels to the original antibiotic, pipemidic acid. The increased antibacterial activity of the synthesised compounds, together with their appropriate toxicity levels, are promising outcomes.

Recent Bio-Advances in Metal-Organic Frameworks

Metal-organic frameworks (MOFs) have found uses in adsorption, catalysis, gas storage and other industrial applications. Metal Biomolecule Frameworks (bioMOFs) represent an overlap between inorganic, material and medicinal sciences, utilising the porous frameworks for biologically relevant purposes. This review details advances in bioMOFs, looking at the synthesis, properties and applications of both bioinspired materials and MOFs used for bioapplications, such as drug delivery, imaging and catalysis, with a focus on examples from the last five years.

An NIF-doped ZIF-8 hybrid membrane for continuous antimicrobial treatment

Sodium alginate (ALG) composites with ZIF-8 and niflumic acid (NIF) were prepared by a one-pot method at room temperature and characterized by FTIR, SEM and XRD studies. In the composite, ZIF-8 was used as a highly connected node in a supercrosslinked polymer network. In addition, the material exhibits good antibacterial activity against Staphylococcus aureus and Escherichia coli in vitro. Compared to the original ALG membrane and ZIF-8, the ZIF–NIF–ALG membrane has the following advantages: stronger antibacterial properties; slow release of Zn(ii); high drug loading; and longer sustained release time. This research introduces new concepts for the design and manufacture of various antimicrobial membranes and broadens the range of applications of MOFs.

A ZIF-8 hybrid film has shows continuous medical effects, with including antibacterial and anti-inflammatory effects.