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Fulltext Antimicrobial and antibiofilm activities of Cu(II) Schiff base complexes against methicillin-susceptible and resistant Staphylococcus aureus

Chung PY, Khoo REY, Liew HS, Low ML

Ann Clin Microbiol Antimicrob, 2021 Sep 24;20(1):67.
PMID: 34560892 DOI: 10.1186/s12941-021-00473-4

BACKGROUND: Methicillin-resistance S. aureus (MRSA) possesses the ability to resist multiple antibiotics and form biofilm. Currently, vancomycin remains the last drug of choice for treatment of MRSA infection. The emergence of vancomycin-resistant S. aureus (VRSA) has necessitated the development of new therapeutic agents against MRSA. In this study, the antimicrobial and antibiofilm activities of two copper-complexes derived from Schiff base (SBDs) were tested individually, and in combination with oxacillin (OXA) and vancomycin (VAN) against reference strains methicillin-susceptible and methicillin-resistant Staphylococcus aureus. The toxicity of the SBDs was also evaluated on a non-cancerous mammalian cell line.
METHODS: The antimicrobial activity was tested against the planktonic S. aureus cells using the microdilution broth assay, while the antibiofilm activity were evaluated using the crystal violet and resazurin assays. The cytotoxicity of the SBDs was assessed on MRC5 (normal lung tissue), using the MTT assay.
RESULTS: The individual SBDs showed significant reduction of biomass and metabolic activity in both S. aureus strains. Combinations of the SBDs with OXA and VAN were mainly additive against the planktonic cells and cells in the biofilm. Both the compounds showed moderate toxicity against the MRC5 cell line. The selectivity index suggested that the compounds were more cytotoxic to S. aureus than the normal cells.
CONCLUSION: Both the SBD compounds demonstrated promising antimicrobial and antibiofilm activities and have the potential to be further developed as an antimicrobial agent against infections caused by MRSA.
Fulltext Crystal structure of 2-{[2-(3-phenyl-allyl-idene)hydrazin-1-yl]thio-carbonyl-sulfanylmeth-yl}pyridinium chloride

Low ML, Ravoof TB, Tahir MI, Crouse KA, Tiekink ER

Acta Crystallogr Sect E Struct Rep Online, 2014 Nov 1;70(Pt 11):o1207-8.
PMID: 25484832 DOI: 10.1107/S1600536814023228

In the title salt of an S-substituted di-thio-carbazate, C16H16N3S2 (+)·Cl(-), the dihedral angles between the almost planar (r.m.s deviation = 0.005 Å) central CN2S2 residue and the terminal pyridinium and phenyl rings are 80.09 (11) and 3.82 (11)°, respectively, indicating the cation has an L-shape; the amine H and thione S atoms are syn. The conformation about each of the imine [1.376 (3) Å] and ethene [1.333 (4) Å] bonds is E. The shortened C-C bond [1.444 (4) Å] linking the double bonds is consistent with conjugation in this part of the mol-ecule. In the crystal, supra-molecular layers with a jagged topology are formed by charged-assisted amine-H⋯Cl(-) and pyridinium-N(+)-H⋯Cl(-) hydrogen bonds. The layers stack along the a axis with no specific directional inter-actions between them.
Fulltext (Pyridin-4-yl)methyl N'-(3-phenyl-allyl-idene)hydrazinecarbodithio-ate

Low ML, Ravoof TB, Tahir MI, Crouse KA, Tiekink ER

Acta Crystallogr Sect E Struct Rep Online, 2013 Feb 1;69(Pt 2):o167-8.
PMID: 23424455 DOI: 10.1107/S1600536812051537

In the title compound, C(16)H(15)N(3)S(2), the central C(2)N(2)S(2) residue is planar (r.m.s. deviation = 0.045 Å) and the pyridyl and benzene rings are inclined and approximately coplanar to this plane, respectively [dihedral angles = 72.85 (9) and 10.73 (9)°], so that, overall, the mol-ecule adopts an L-shape. The conformation about each of the N=C [1.290 (3) Å] and C=C [1.340 (3) Å] bonds is E. Supra-molecular chains along [1-10] are stabilized by N-H⋯N(pyridine) hydrogen bonding and these are connected into a double layer that stacks along the c-axis direction by C-H⋯π(pyridine) inter-actions.
Fulltext Recent Emergence of Rhenium(I) Tricarbonyl Complexes as Photosensitisers for Cancer Therapy

Liew HS, Mai CW, Zulkefeli M, Madheswaran T, Kiew LV, Delsuc N, et al.

Molecules, 2020 Sep 12;25(18).
PMID: 32932573 DOI: 10.3390/molecules25184176

Photodynamic therapy (PDT) is emerging as a significant complementary or alternative approach for cancer treatment. PDT drugs act as photosensitisers, which upon using appropriate wavelength light and in the presence of molecular oxygen, can lead to cell death. Herein, we reviewed the general characteristics of the different generation of photosensitisers. We also outlined the emergence of rhenium (Re) and more specifically, Re(I) tricarbonyl complexes as a new generation of metal-based photosensitisers for photodynamic therapy that are of great interest in multidisciplinary research. The photophysical properties and structures of Re(I) complexes discussed in this review are summarised to determine basic features and similarities among the structures that are important for their phototoxic activity and future investigations. We further examined the in vitro and in vivo efficacies of the Re(I) complexes that have been synthesised for anticancer purposes. We also discussed Re(I) complexes in conjunction with the advancement of two-photon PDT, drug combination study, nanomedicine, and photothermal therapy to overcome the limitation of such complexes, which generally absorb short wavelengths.
Fulltext Pioneering Annual Colorectal Cancer Screening and Treatment Targeting Low Income Communities in Malaysia (20102015)

Tze CN, Fitzgerald H, Qureshi A, Tan HJ, Low ML

Asian Pac J Cancer Prev, 2016;17(7):3179-83.
PMID: 27509948

The aim of this study was to assess the rate of uptake of a customised annual Colorectal Cancer Awareness, Screening and Treatment Project (CCASTP) using faecal immunohistochemical test (FIT) kits in low income communities in Malaysia. The immediate objectives were (1) to evaluate the level of adherence of CRC screening among lowincome groups, (2) to assess the knowledge and awareness of the screened population and (3) to assess the accuracy of FIT kits. A total of 1,581 FIT kits were distributed between years 2010 to 2015 to healthy asymptomatic participants of the annual CCASTP organized by Empowered the Cancer Advocacy Society of Malaysia. Data for sociodemographic characteristics, critical health and lifestyle information of the registered subjects were collected. Findings for use of the FIT kits were collected when they were returned for stool analyses. Those testingd positive were invited to undergo a colonoscopy examination. A total of 1,436 (90.8%) of the subjects retuned the FITkits, showing high compliance. Among the 129 subjects with positive FIT results, 92 (71.3%) underwent colonoscopy. Six cases (6.5%) of CRC were found. Based on the data collected, the level of awareness of stool examination and knowledge about CRC was poor amongst the participants. Gender, age group, ethnicity and risk factors (i.e. smoking, lack of exercise and low consumption of fresh fruits) were associated with positive FITkit results. In conclusion, CRC screening can be performed in the community with a single FITkit. Although CRC knowledge and awareness is poor in lowincome communities, the average return rate of the FIT kits and rate of colonoscopy examination were 91.2% and 70.3%, respectively.
Ternary Copper (II) Complex Induced Apoptosis and Cell Cycle Arrest in Colorectal Cancer Cells

Arikrishnan S, Loh JS, Teo XW, Bin Norizan F, Low ML, Lee SH, et al.

Anticancer Agents Med Chem, 2021 Jul 07.
PMID: 34238173 DOI: 10.2174/1871520621666210708100019

BACKGROUND: The lack of specificity, severe side effects, and development of drug resistance have largely limited the use of platinum-based compounds in cancer treatment. Therefore, copper complexes have emerged as potential alternatives to platinum-based compounds.
OBJECTIVE: Ternary copper (II) complex incorporated with 1-10-phenanthroline and L-tyrosine was investigated for its anti-cancer effects in HT-29 colorectal cancer cells.
METHODS: Cytotoxic effects of ternary copper (II) complex in HT-29 cells were evaluated using MTT assay, Real-Time Cell Analysis (RTCA), and lactate dehydrogenase (LDH) assay. Cell cycle analysis was performed using flow cytometry. Apoptosis induction was studied by Annexin V-FITC/propidium iodide (PI) staining and mitochondrial membrane potential analysis (JC-10 staining) using flow cytometry. Intracellular reactive oxygen species (ROS) were detected by DCFH-DA assay. The expression of proteins involved in the apoptotic signalling pathway (p53, caspases, and PARP-1) was evaluated by western blot analysis.
RESULTS: Ternary copper (II) complex reduced the cell viability of HT-29 cells in a time- and dose-dependent manner, with IC50 of 2.4 ± 0.4 and 0.8 ± 0.04 µM at 24 and 48 hours, respectively. Cell cycle analysis demonstrated induction of S-phase cell cycle arrest. Morphological evaluation and Annexin V-FITC/PI flow cytometry analysis confirmed induction of apoptosis that was further supported by cleavage and activation of caspase-8, caspase-9, caspase-3, and PARP-1. Mutant p53 was also downregulated in a dose-dependent manner. No LDH release, mitochondrial membrane potential disruption, and ROS production were observed.
CONCLUSION: Ternary copper (II) complex holds great potential to be developed for colorectal cancer treatment.
Ruthenium(II) polypyridyl complexes as emerging photosensitisers for antibacterial photodynamic therapy

Ng XY, Fong KW, Kiew LV, Chung PY, Liew YK, Delsuc N, et al.

J Inorg Biochem, 2024 Jan;250:112425.
PMID: 37977020 DOI: 10.1016/j.jinorgbio.2023.112425

Photodynamic therapy (PDT) has recently emerged as a potential valuable alternative to treat microbial infections. In PDT, singlet oxygen is generated in the presence of photosensitisers and oxygen under light irradiation of a specific wavelength, causing cytotoxic damage to bacteria. This review highlights different generations of photosensitisers and the common characteristics of ideal photosensitisers. It also focuses on the emergence of ruthenium and more specifically on Ru(II) polypyridyl complexes as metal-based photosensitisers used in antimicrobial photodynamic therapy (aPDT). Their photochemical and photophysical properties as well as structures are discussed while relating them to their phototoxicity. The use of Ru(II) complexes with recent advancements such as nanoformulations, combinatory therapy and photothermal therapy to improve on previous shortcomings of the complexes are outlined. Future perspectives of these complexes used in two-photon PDT, photoacoustic imaging and sonotherapy are also discussed. This review covers the literature published from 2017 to 2023.
Fulltext Lighting up cancer: latest discoveries in ruthenium(ii) polypyridyl complexes for anticancer photodynamic therapy

Tan PY, Lee KH, Tan KT, Chia XQ, Kong EWJ, Lim WM, et al.

RSC Adv, 2026 Oct 21;16(46):59072-59104.
PMID: 42840481 DOI: 10.1039/d6ra01698g

Photodynamic therapy (PDT), which utilises light-sensitive compounds to specifically target cancer cells while preventing harm to neighbouring healthy tissues, presents a potentially viable alternative treatment option. Ruthenium (Ru) polypyridyl complexes have garnered considerable attention as prospective PDT agents owing to their capability to generate stable and selective molecules by structural modification through ligands replacement. Additionally, their intricate geometries and oxidation states contribute to their therapeutic potential. This review provides the evolution and application of Ru(ii) polypyridyl complexes in PDT as a cancer treatment modality. It analyses the efficacy, mechanisms of action, and advancements of these complexes in comparison to conventional methods. We present the design and optimisation of these complexes, emphasising their critical importance in combination therapies to circumvent the shortcomings of existing PDT methods and achieve enhanced therapeutic outcomes. Our review subsequently examines the practical implications of the results, highlighting the need for further in vivo experiments to validate Ru(ii) polypyridyl complexes as viable therapeutic agents for cancer. Future studies aiming to enhance the effectiveness of PDT could significantly benefit from the incorporation of nanotechnology and advanced delivery systems.
New insight into the structural, electrochemical and biological aspects of macroacyclic Cu(II) complexes derived from S-substituted dithiocarbazate schiff bases

Low ML, Maigre L, Tahir MI, Tiekink ER, Dorlet P, Guillot R, et al.

Eur J Med Chem, 2016 Sep 14;120:1-12.
PMID: 27183379 DOI: 10.1016/j.ejmech.2016.04.027

Copper (II) complexes synthesized from the products of condensation of S-methyl- and S-benzyldithiocarbazate with 2,5-hexanedione (SMHDH2 and SBHDH2 respectively) have been characterized using various physicochemical (elemental analysis, molar conductivity, magnetic susceptibility) and spectroscopic (infrared, electronic) methods. The structures of SMHDH2, its copper (II) complex, CuSMHD, and the related CuSBHD complex as well as a pyrrole byproduct, SBPY, have been determined by single crystal X-ray diffraction. In order to provide more insight into the behaviour of the complexes in solution, electron paramagnetic resonance (EPR) and electrochemical experiments were performed. Antibacterial activity and cytotoxicity were evaluated. The compounds, dissolved in 0.5% and 5% DMSO, showed a wide range of antibacterial activity against 10 strains of Gram-positive and Gram-negative bacteria. Investigations of the effects of efflux pumps and membrane penetration on antibacterial activity are reported herein. Antiproliferation activity was observed to be enhanced by complexation with copper. Preliminary screening showed Cu complexes are strongly active against human breast adenocarcinoma cancer cell lines MDA-MB-231 and MCF-7.
Copper complex derived from S-benzyldithiocarbazate and 3-acetylcoumarin induced apoptosis in breast cancer cell

Foo JB, Low ML, Lim JH, Lor YZ, Zainol Abidin R, Eh Dam V, et al.

Biometals, 2018 08;31(4):505-515.
PMID: 29623473 DOI: 10.1007/s10534-018-0096-4

Copper complexes have been widely studied for the anti-tumour application as cancer cells are reported to take up greater amounts of copper than normal cells. Preliminary study revealed that the newly synthesised copper complex [Cu(SBCM)2] displayed marked anti-proliferative towards triple-negative MDA-MB-231 breast cancer cells. Therefore, Cu(SBCM)2 has great potential to be developed as an agent for the management of breast cancer. The present study was carried out to investigate the mode of cell death induced by Cu(SBCM)2 towards MDA-MB-231 breast cancer cells. The inhibitory and morphological changes of MDA-MB-231 cells treated with Cu(SBCM)2 was determined by using MTT assay and inverted light microscope, respectively. The safety profile of Cu(SBCM)2 was also evaluated towards human dermal fibroblast (HDF) normal cells. Confirmation of apoptosis and cell cycle arrest were determined by flow cytometry analysis. The expression of p53, Bax, Bcl-2 and MMP2 protein were detected with western blot analysis. Cu(SBCM)2 significantly inhibited the growth of MDA-MB-231 cells in a dose-dependent manner with GI50 18.7 ± 3.06 µM. Indeed, Cu(SBCM)2 was less toxic towards HDF normal cells with GI50 31.8 ± 4.0 µM. Morphological study revealed that Cu(SBCM)2-treated MDA-MB-231 cells experienced cellular shrinkage, membrane blebbing, chromatin condensation and formation of apoptotic bodies, suggesting that Cu(SBCM)2 induced apoptosis in the cells, which was confirmed by Annexin-V/PI flow cytometry analysis. It was also found that Cu(SBCM)2 induced G2/M phase cell cycle arrest towards MDA-MB-231 cells. The induction of apoptosis and cell cycle arrest in the present study is possibly due to the down-regulation of the mutant p53 and MMP2 protein. In conclusion, Cu(SBCM)2 can be developed as a targeted therapy for the treatment of triple-negative breast cancer.
Synthesis, characterization and multiple targeting with selectivity: Anticancer property of ternary metal phenanthroline-maltol complexes

Ng CH, Tan TH, Tioh NH, Seng HL, Ahmad M, Ng SW, et al.

J Inorg Biochem, 2021 07;220:111453.
PMID: 33895694 DOI: 10.1016/j.jinorgbio.2021.111453

The cobalt(II), copper(II) and zinc(II) complexes of 1,10-phenanthroline (phen) and maltol (mal) (complexes 1, 2, 3 respectively) were prepared from their respective metal(II) chlorides and were characterized by FT-IR, elemental analysis, UV spectroscopy, molar conductivity, p-nitrosodimethylaniline assay and mass spectrometry. The X-ray structure of a single crystal of the zinc(II) analogue reveals a square pyramidal structure with distinctly shorter apical chloride bond. All complexes were evaluated for their anticancer property on breast cancer cell lines MCF-7 and MDA-MB-231, and normal cell line MCF-10A, using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and morphological studies. Complex 2 was most potent for 24, 48 and 72 h treatment of cancer cells but it was not selective towards cancer over normal cells. The mechanistic studies of the cobalt(II) complex 1 involved apoptosis assay, cell cycle analysis, dichloro-dihydro-fluorescein diacetate assay, intracellular reactive oxygen species assay and proteasome inhibition assay. Complex 1 induced low apoptosis, generated low level of ROS and did not inhibit proteasome in normal cells. The study of the DNA binding and nucleolytic properties of complexes 1-3 in the absence or presence of H2O2 or sodium ascorbate revealed that only complex 1 was not nucleolytic.
1,2,3-Triazol-5-ylidene- vs. 1,2,3-triazole-based tricarbonylrhenium(I) complexes: influence of a mesoionic carbene ligand on the electronic and biological properties

Vanucci-Bacqué C, Wolff M, Delavaux-Nicot B, Abdallah AM, Mallet-Ladeira S, Serpentini CL, et al.

Dalton Trans, 2024 Jul 09;53(27):11276-11294.
PMID: 38776120 DOI: 10.1039/d4dt00922c

The tricarbonylrhenium complexes that incorporate a mesoionic carbene ligand represent an emerging and promising class of molecules, the solid-state optical properties of which have rarely been investigated. The aim of this comprehensive study is to compare three of these complexes with their 1,2,3-triazole-based analogues. The Hirshfeld surface analysis of the crystallographic data revealed that the triazolylidene derivatives are more prone to π-π interactions than their 1,2,3-triazole-based counterparts. The FT-IR and electrochemical data indicated a stronger electron donor effect from the organic ligand to the rhenium atom for triazolylidene derivatives, which was confirmed by DFT calculations. All compounds were phosphorescent in solution, where the 1,2,3-triazole-based complexes showed unusually strong dependence on dissolved oxygen. All compounds also emitted in the solid state, some of them exhibited marked solid-state luminescence enhancement (SLE) effect. The 1,2,3-triazole based complex Re-Phe even displayed astounding photoluminescence efficiency with quantum yield up to 0.69, and proved to be an excellent candidate for applications linked to aggregation-induced emission (AIE). Interestingly, one triazolylidene-based complex (Re-T-BOP) showed attractive antibacterial activity. This study highlights the potential of these new molecules for applications in the fields of photoluminescent and therapeutic materials, and provides the first bases for the design of efficient molecules in these research areas.
Induction of Apoptosis and Autophagy by Ternary Copper Complex Towards Breast Cancer Cells

Lee ZY, Leong CH, Lim KUL, Wong CCS, Pongtheerawan P, Arikrishnan SA, et al.

Anticancer Agents Med Chem, 2021 Jul 26.
PMID: 34315396 DOI: 10.2174/1871520621666210726132543

BACKGROUND: Copper complex has been gaining much attention in anticancer research as targeted agent since cancer cells uptake more copper than non-cancerous cells. Our group has synthesised a ternary copper complex which is composed of 1,10-phenanthroline and tyrosine [Cu(phen)(L-tyr)Cl].3H20. These two payloads are designed to cleave DNA and inhibit protein degradation system (proteasome) concurrently in cancer cells, making this copper complex a dual-target compound.
OBJECTIVE: Current study was carried out to investigate the mode of cell death and role of autophagy induced by [Cu(phen)(L-tyr)Cl].3H20 in MCF-7 and MDA-MB-231 breast cancer cells.
METHODS: Growth inhibition of [Cu(phen)(L-tyr)Cl].3H20 towards MDA-MB-231 and human non-cancerous MCF10A breast cells was determined by MTT assay. Annexin-V-FITC/PI and cell cycle analysis were evaluated by flow cytometry. The expression of p53, Bax, caspase-9, caspase-7, caspase-3 and LC3 were determined using western blot analysis. The cells were then co-treated with hydroxychloroquine to ascertain the role of autophagy induced by [Cu(phen)(L-tyr)Cl].3H20.
RESULTS: [Cu(phen)(L-tyr)Cl].3H20 inhibited the growth of cancer cells dose-dependently with less toxicity towards MCF10A cells. Additionally, [Cu(phen)(L-tyr)Cl].3H20 induced apoptosis and cell cycle arrest towards MCF-7 and MDA-MB-231 breast cancer cells possibly via regulation of p53, Bax, caspase-9, caspase-3 and capase-7. The expression of LC3II was upregulated in both cancer cell lines upon treatment with [Cu(phen)(L-tyr) Cl].3H20, indicating the induction of autophagy. Co-treatment with autophagy inhibitor hydroxychloroquine significantly enhanced growth inhibition of both cell lines, suggesting that the autophagy induced by [Cu(phen)(L-tyr) Cl].3H20 in both breast cancer cells was promoting cell survival.
CONCLUSION: [Cu(phen)(L-tyr)Cl].3H20 holds great potential to be developed for breast cancer treatment.

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