Control of Biohazards: A High Performance Energetic Polycyclized Iodine-Containing Biocide

Polyiodo Azole-Based Metal-Organic Framework Energetic Biocidal Material for Synergetic Sterilization Applications

Biological hazards caused by bacteria, viruses, and toxins have become a major survival and development issue facing the international community. However, the traditional method of disinfection and sterilization is helpless in dealing with viruses that spread quickly and are highly infectious. Metal-organic framework (MOF) biocidal materials hold promise as superior alternatives to traditional sterilization materials because of their stable framework structures and unique properties. Now, we demonstrate for the first time the synthesis of a MOF (TIBT-Cu) containing Cu metal centers and tetraiodo-4,4'-bi-1,2,4-triazole as the main ligand. This novel MOF biocidal material has good thermal stability (Td = 278 °C), excellent mechanical sensitivity, and a high bacteriostatic efficiency (>99.90%). Additionally, the particles produced by the combustion of TIBT-Cu are composed of active iodine substances and CuO particles, which can act synergistically against harmful microorganisms such as bacteria and viruses. This study provides a new perspective for the preparation of highly effective bactericidal materials.

Asymmetrical Methylene-Bridge Linked Fully Iodinated Azoles as Energetic Biocidal Materials with Improved Thermal Stability

The instability and volatility of iodine is high, however, effective iodine biocidal species can be readily stored in iodinated azoles and then be released upon decomposition or detonation. Iodine azoles with high iodine content and high thermal stability are highly desired. In this work, the strategy of methylene bridging with asymmetric structures of 3,4,5-triiodo-1-H-pyrazole (TIP), 2,4,5-triiodo-1H-imidazol (TIM), and tetraiodo-1H-pyrrole (TIPL) are proposed. Two highly stable fully iodinated methylene-bridged azole compounds 3,4,5-triiodo-1-((2,4,5-triiodo-1H-imidazol-1-yl)methyl)-1H-pyrazole (3) and 3,4,5-triiodo-1-((tetraiodo-1H-pyrrol-1-yl)methyl)-1H-pyrazole (4) were obtained with high iodine content and excellent thermal stability (iodine content: 84.27% for compound 3 and 86.48% for compound 4; T_d: 3: 285 °C, 4: 260 °C). Furthermore, their composites with high-energy oxidant ammonium perchlorate (AP) were designed. The combustion behavior and thermal decomposition properties of the formulations were tested and evaluated. This work may open a new avenue to develop advanced energetic biocidal materials with well-balanced energetic and biocidal properties and versatile functionality.

Periodate-based molecular perovskites as promising energetic biocidal agents

Epidemics caused by pathogens in recent years have created an urgent need for energetic biocidal agents with the capacity of detonation and releasing bactericides. Herein we present a new type of energetic biocidal agents based on a series of iodine-rich molecular perovskites, (H₂dabco)M(IO₄)₃ (dabco = 1,4-diazabicyclo[2.2.2]octane, M = Na⁺/K⁺/Rb⁺/NH₄ ⁺ for DAI-1/2/3/4) and (H₂dabco)Na(H₄IO₆)₃ (DAI-X1). These compounds possess a cubic perovskite structure, and notably have not only high iodine contents (49-54 wt%), but also high performance in detonation velocity (6.331-6.558 km s^-1) and detonation pressure (30.69-30.88 GPa). In particular, DAI-4 has a very high iodine content of 54.0 wt% and simultaneously an exceptional detonation velocity up to 6.558 km s^-1. As disclosed by laser scanning confocal microscopy observation and a standard micro-broth dilution method, the detonation products of DAI-4 exhibit a broad-spectrum bactericidal effect against bacteria (E. coli, S. aureus, and P. aeruginosa). The advantages of easy scale-up synthesis, low cost, high detonation performance, and high iodine contents enable these periodate-based molecular perovskites to be highly promising candidates for energetic biocidal agents.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s40843-022-2257-6.

Antimicrobial Hexaaquacopper(II) Complexes with Novel Polyiodide Chains

The non-toxic inorganic antimicrobial agents iodine (I2) and copper (Cu) are interesting alternatives for biocidal applications. Iodine is broad-spectrum antimicrobial agent but its use is overshadowed by compound instability, uncontrolled iodine release and short-term effectiveness. These disadvantages can be reduced by forming complex-stabilized, polymeric polyiodides. In a facile, in-vitro synthesis we prepared the copper-pentaiodide complex [Cu(H2O)6(12-crown-4)5]I6 · 2I2, investigated its structure and antimicrobial properties. The chemical structure of the compound has been verified. We used agar well and disc-diffusion method assays against nine microbial reference strains in comparison to common antibiotics. The stable complex revealed excellent inhibition zones against C. albicans WDCM 00054, and strong antibacterial activities against several pathogens. [Cu(H2O)6(12-crown-4)5]I6 · 2I2 is a strong antimicrobial agent with an interesting crystal structure consisting of complexes located on an inversion center and surrounded by six 12-crown-4 molecules forming a cationic substructure. The six 12-crown-4 molecules form hydrogen bonds with the central Cu(H2O)6. The anionic substructure is a halogen bonded polymer which is formed by formal I5- repetition units. The topology of this chain-type polyiodide is unique. The I5- repetition units can be understood as a triodide anion connected to two iodine molecules.

New Promises from an Old Friend: Iodine-Rich Compounds as Prospective Energetic Biocidal Agents

For a very long time, frequent occurrences of biocrises have wreaked havoc on human beings, animals, and the environment. As a result, it is necessary to develop biocidal agents to destroy or neutralize active agents by releasing large amounts of strong biocides which are obtained upon detonation. Iodine is an efficient biocidal agent for bacteria, fungi, yeasts, viruses, spores, and protozoan parasites, and it is the sole element in the periodic table that can destroy microbes without contaminating the environment. Based on chemical biology, the mechanism of iodine as a bactericide may arise from oxidation and iodination reactions of cellular proteins and nucleic acids. However, because of the high vapor pressure causing elemental iodine to sublime readily at room temperature, it is inconvenient to use this material in its normal solid state directly as a biocidal agent under ambient conditions. Iodine-rich compounds where iodine is firmly bonded in molecules as a C-I or I-O moiety have been observed to be among the most promising energetic biocidal compounds. Gaseous products comprised of large amounts of iodine or iodine-containing components as strong biocides are released in the decomposition or explosion of iodine-rich compounds. Because of the detonation pressure, the iodine species are distributed over a large area greatly improving the efficacy of the system and requiring considerably less effort compared to traditional biocidal methods. The commercially available tetraiodomethane and tetraiodoethene, which possess superb iodine content also have the disadvantages of volatility, light sensitivity, and chemically reactivity, and therefore, are not suitable for use directly as biocidal agents. It is absolutely critical to synthesize new iodine-rich compounds with good thermal and chemical stabilities.In this Account, we describe our strategies for the syntheses of energetic iodine-rich compounds while maintaining the maximum iodine content with concomitant stability and routes for the synthesis of oxygen-containing iodine-rich compounds to improve the oxygen balance and achieve both high-energy and high-iodine content. In the other work, which involves cocrystals, iodine-containing polymers were also summarized. It is hoped that this Account will provide guidelines for the design and syntheses of new iodine-rich compounds and a route for the development of inexpensive, more efficient, and safer iodine-rich antibiological warfare agents of the future.

Facile Synthesis of Antimicrobial Aloe Vera-"Smart" Triiodide-PVP Biomaterials

Antibiotic resistance is an eminent threat for the survival of mankind. Nosocomial infections caused by multidrug resistant microorganisms are a reason for morbidity and mortality worldwide. Plant-based antimicrobial agents are based on synergistic mechanisms which prevent resistance and have been used for centuries against ailments. We suggest the use of cost-effective, eco-friendly Aloe Vera Barbadensis Miller (AV)-iodine biomaterials as a new generation of antimicrobial agents. In a facile, one-pot synthesis, we encapsulated fresh AV gel with polyvinylpyrrolidone (PVP) as a stabilizing agent and incorporated iodine moieties in the form of iodine (I2) and sodium iodide (NaI) into the polymer matrix. Ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), microstructural analysis by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) verified the composition of AV-PVP-I2, AV-PVP-I2-NaI. AV, AV-PVP, AV-PVP-I2, AV-PVP-I2-NaI, and AV-PVP-NaI were tested in-vitro by disc diffusion assay and dip-coated on polyglycolic acid (PGA) sutures against ten microbial reference strains. All the tested pathogens were more susceptible towards AV-PVP-I2 due to the inclusion of "smart" triiodides with halogen bonding in vitro and on dip-coated sutures. The biocomplexes AV-PVP-I2, AV-PVP-I2-NaI showed remarkable antimicrobial properties. "Smart" biohybrids with triiodide inclusions have excellent antifungal and promising antimicrobial activities, with potential use against surgical site infections (SSI) and as disinfecting agents.

Superior High-Energy-Density Biocidal Agent Achieved with a 3D Metal-Organic Framework

A significant number of challenges are encountered when developing biocidal agents with high throwing capacity for biosafety applications. Now a three-dimensional metal-organic framework (3D MOF) {MOF (2), [Cu(atrz)(IO₃)₂]_n (atrz = 4,4'-azo-1,2,4-triazole)} was obtained using a postsynthetic method from MOF (1) {[Cu(atrz)₃(NO₃)₂]_n}. Benefitting from the oxygen-rich and small volume of the iodate (IO₃) ligands (2.73 Å) in MOF (2) compared to the atrz ligand (7.70 Å) in MOF (1), the density of MOF (2) is 3.168 g cm^-3, nearly twice that of its precursor. Its detonation velocity of 7271 ms^-1 exceeds that of TNT (trinitrotoluene) and its detonation pressure of 40.6 GPa is superior to that of HMX (cyclotetramethylenetetranitramine) (1,3,5,7-tetranitro-1,3,5,7-tetrazoctane, 39.2 Gpa), which are the highest detonation properties for a biocidal agent. Its superior detonation performance results in its main product, I₂, being distributed over a wide area, markedly reducing the diffusion of harmful microorganisms. This study offers novel insight not only for high-energy-density materials but also for huge potential applications as biocidal agents.

"Smart" Antimicrobial Nanocomplexes with Potential to Decrease Surgical Site Infections (SSI)

The emergence of resistant pathogens is a burden on mankind and threatens the existence of our species. Natural and plant-derived antimicrobial agents need to be developed in the race against antibiotic resistance. Nanotechnology is a promising approach with a variety of products. Biosynthesized silver nanoparticles (AgNP) have good antimicrobial activity. We prepared AgNPs with trans-cinnamic acid (TCA) and povidone-iodine (PI) with increased antimicrobial activity. We synthesized also AgNPs with natural cinnamon bark extract (Cinn) in combination with PI and coated biodegradable Polyglycolic Acid (PGA) sutures with the new materials separately. These compounds (TCA-AgNP, TCA-AgNP-PI, Cinn-AgNP, and Cinn-AgNP-PI) and their dip-coated PGA sutures were tested against 10 reference strains of microorganisms and five antibiotics by zone inhibition with disc- and agar-well-diffusion methods. The new compounds TCA-AgNP-PI and Cinn-AgNP-PI are broad spectrum microbicidal agents and therefore potential coating materials for sutures to prevent Surgical Site Infections (SSI). TCA-AgNP-PI inhibits the studied pathogens stronger than Cinn-AgNP-PI in-vitro and on coated sutures. Dynamic light scattering (DLS), ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform infrared spectroscopy (FT-IR), Raman, x-ray diffraction (XRD), microstructural analysis by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the composition of TCA-AgNP-PI and Cinn-AgNP-PI. Smart solutions involving hybrid materials based on synergistic antimicrobial action have promising future perspectives to combat resistant microorganisms.

"Smart" Triiodide Compounds: Does Halogen Bonding Influence Antimicrobial Activities?

Antimicrobial agents containing symmetrical triiodides complexes with halogen bonding may release free iodine molecules in a controlled manner. This happens due to interactions with the plasma membrane of microorganisms which lead to changes in the structure of the triiodide anion. To verify this hypothesis, the triiodide complex [Na(12-crown-4)2]I3 was prepared by an optimized one-pot synthesis and tested against 18 clinical isolates, 10 reference strains of pathogens and five antibiotics. The antimicrobial activities of this symmetrical triiodide complex were determined by zone of inhibition plate studies through disc- and agar-well-diffusion methods. The triiodide complex proved to be a broad spectrum microbicidal agent. The biological activities were related to the calculated partition coefficient (octanol/water). The microstructural analysis of SEM and EDS undermined the purity of the triiodide complex. The anionic structure consists of isolated, symmetrical triiodide anions [I-I-I]- with halogen bonding. Computational methods were used to calculate the energy required to release iodine from [I-I-I]- and [I-I···I]-. The halogen bonding in the triiodide ion reduces the antibacterial activities in comparison to the inhibitory actions of pure iodine but increases the long term stability of [Na(12-crown-4)2]I3.