Fine and Clean Photothermally Controlled NIR Drug Delivery from Biocompatible Nickel-bis(dithiolene)-Containing Liposomes

Synthesis and coordination behaviour of 1H-1,2,3-triazole-4,5-dithiolates

The preparative access to and first group 10 metal complexes of novel 1H-1,2,3-triazole-4,5-dithiolate ligands (tazdt^2-) are reported. A set of S-protected 1H-1,2,3-triazole-4,5-dithiol derivatives with R¹ = 2,6-dimethylphenyl (Xy) or benzyl (Bn) at N1 and with R² = Bn or trimethylsilylethyl (TMS-ethyl) at both S atoms were synthesized by a 1,3-dipolar cycloaddition catalysed by either Ru(II) or Cu(I). Extensive investigations on the removal of the protective groups resulted the reductive removal of benzyl groups to be superior in isolating the free 4,5-dithiols of R¹N₃C₂(SH)₂ with R¹ = Xy (H₂-8) or Bn (H₂-9). Coordination of these ligands led to the formation of the metal complexes [(η⁵-C₅H₅)₂Ti(8)], [Ni(dppe)(8)], [Ni(dppe)(9)], [Pd(dppe)(9)] {dppe = bis(diphenylphosphanyl)ethane} and homoleptic (NBu₄)_n[Ni(8)₂] (n = 1, 2). All complexes were fully characterized including structure determination by single crystal XRD. The electronic properties of the Ni and Pd complexes were determined by cyclic voltammetry, UV/vis and EPR spectroscopy supported by DFT calculations. According to the spectral and electrochemical data, the tazdt^2- complexes resemble the corresponding benzene-1,2-dithiolate (bdt^2-) type compounds reflecting the restricted influence of the electron-withdrawing N₃ moiety in the backbone. DSC-TGA measurements with [(η⁵-C₅H₅)₂Ti(8)] and [Ni(dppe)(8)] indicate a well-defined thermal process involving simultaneous elimination of both N₂ and CS.

Metal complex-based liposomes: Applications and prospects in cancer diagnostics and therapeutics

Metal complexes are of increasing interest as pharmaceutical agents in cancer diagnostics and therapeutics, while some of them suffer from issues such as limited water solubility and severe systemic toxicity. These drawbacks severely hampered their efficacy and clinical applications. Liposomes hold promise as delivery vehicles for constructing metal complex-based liposomes to maximize the therapeutic efficacy and minimize the side effects of metal complexes. This review provides an overview on the latest advances of metal complex-based liposomal delivery systems. First, the development of metal complex-mediated liposomal encapsulation is briefly introduced. Next, applications of metal complex-based liposomes in a variety of fields are overviewed, where drug delivery, cancer imaging (single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic resonance imaging (MRI)), and cancer therapy (chemotherapy, phototherapy, and radiotherapy) were involved. Moreover, the potential toxicity, action of toxic mechanisms, immunological effects of metal complexes as well as the advantages of metal complex-liposomes in this content are also discussed. In the end, the future expectations and challenges of metal complex-based liposomes in clinical cancer therapy are tentatively proposed.

Near-Infrared Absorption Properties of Neutral Bis(1,2-dithiolene) Platinum(II) Complexes Using Density Functional Theory

Small metal complexes are highly interesting for bioimaging because of their excellent near-infrared (NIR) absorption properties. In this study, neutral complexes of platinum(II) connected to two monoreduced 1,3-diisopropylimidazoline-2,4,5-trithione ligands—namely, [Pt(iPr₂timdt)₂]—were investigated. Theoretical studies using the density functional theory (DFT) and GW-BSE approximation verified the effects of the geometry of the isopropyl moieties on the NIR absorption spectra. The calculated absorption spectra showed excellent correspondence with the experimental results. The geometry of the isopropyl groups considerably influenced the electronic structures of the metal complexes, which altered the absorption profiles of the respective geometries, as demonstrated in this research.

Tunable NIR Absorption Property of a Dithiolene Nickel Complex: A Promising NIR-II Absorption Material for Photothermal Therapy

Exogenous photothermal agents absorbing in the second near-infrared optical window (NIR-II, 1000-1700 nm) have received much attention due to their use in noninvasive photothermal therapy. A small quantity of organic NIR-II photothermal agents have been exploited, and the development of organic NIR-II photothermal materials is an urgent need for biological applications. In this study, we designed and synthesized three dithiolene nickel(II) complexes with different ligands-bis(phenyl) dithiolene for NiBD-Ph, bis(fluorenyl) dithiolene for NiBD-Fl, and bis(carbazolyl) dithiolene for NiBD-Cz-and investigated their photophysical properties. These complexes exhibited ligand-dependent NIR absorption performance, centered at 854 nm for NiBD-Ph, 942 nm for NiBD-Fl, and 1010 nm for NiBD-Cz, respectively. NiBD-Cz is wrapped in ethylene oxide/propylene oxide block copolymer (F-127) through a hydrophilic-hydrophobic interaction to form water-soluble NiBD-Cz/F-127 nanoparticles (NiBD-Cz NPs), and the absorption peak of NiBD-Cz NPs are red-shifted to 1036 nm. NiBD-Cz NPs exhibit good dispersibility in water, robust photostability, and a high photothermal conversion efficiency (PCE) of 63.6% under 1064 nm laser irradiation, which is the highest PCE among metal bis(dithiolene) complexes up to now. The high PCE makes it possible to achieve better photothermal treatment effects even at low concentrations and under low-power laser irradiation.

Hybrid Nanosystems for Biomedical Applications

Inorganic/organic hybrid nanosystems have been increasingly developed for their versatility and efficacy at overcoming obstacles not readily surmounted by nonhybridized counterparts. Currently, hybrid nanosystems are implemented for gene therapy, drug delivery, and phototherapy in addition to tissue regeneration, vaccines, antibacterials, biomolecule detection, imaging probes, and theranostics. Though diverse, these nanosystems can be classified according to foundational inorganic/organic components, accessory moieties, and architecture of hybridization. Within this Review, we begin by providing a historical context for the development of biomedical hybrid nanosystems before describing the properties, synthesis, and characterization of their component building blocks. Afterward, we introduce the architectures of hybridization and highlight recent biomedical nanosystem developments by area of application, emphasizing hybrids of distinctive utility and innovation. Finally, we draw attention to ongoing clinical trials before recapping our discussion of hybrid nanosystems and providing a perspective on the future of the field.

Light: A Magical Tool for Controlled Drug Delivery

Light is a particularly appealing tool for on-demand drug delivery due to its noninvasive nature, ease of application and exquisite temporal and spatial control. Great progress has been achieved in the development of novel light-driven drug delivery strategies with both breadth and depth. Light-controlled drug delivery platforms can be generally categorized into three groups: photochemical, photothermal, and photoisomerization-mediated therapies. Various advanced materials, such as metal nanoparticles, metal sulfides and oxides, metal-organic frameworks, carbon nanomaterials, upconversion nanoparticles, semiconductor nanoparticles, stimuli-responsive micelles, polymer- and liposome-based nanoparticles have been applied for light-stimulated drug delivery. In view of the increasing interest in on-demand targeted drug delivery, we review the development of light-responsive systems with a focus on recent advances, key limitations, and future directions.

Near-infrared light-responsive UCST-nanogels using an efficient nickel-bis(dithiolene) photothermal crosslinker

A new kind of near-infrared (NIR) light-responsive polymer nanogel is demonstrated.

Liposomes Containing Nickel-Bis(dithiolene) Complexes for Photothermal Theranostics

New thermosensitive liposomes with a phase transition at 42 °C, containing nickel-bis(dithiolene) complexes as efficient and stable photothermal agents, have been formulated and characterized. These liposomes are highly stable and keep their contents at 37 °C for more than 30 days. On the contrary, the mild hyperthermia generated by the nickel-bis(dithiolene) complex under 940 nm NIR irradiation allows for the fine controlled release of the liposome contents, making such liposomes highly suitable for on-demand drug delivery in the human body under NIR laser irradiation. These liposomes can also be directly used, as shown here, as nanoagents for photothermal therapy. In fact, strong cell death can be generated under laser irradiation in the presence of these photothermally active nanocargos containing less than 10% w/w of metal complex. We also demonstrate, for the first time, that nickel-bis(dithiolene) complexes are good photoacoustic agents, generating easily detectable ultrasonic signals directly proportional to the concentration of complexes and the used laser power.

Mesoporous NiS2 nanospheres as a hydrophobic anticancer drug delivery vehicle for synergistic photothermal–chemotherapy

Monodispersed mesoporous NiS₂ nanospheres (mNiS₂ NSs) have been successfully developed here through a facile solvothermal method to act as a hydrophobic drug delivery vehicle for synergistic photothermal–chemo treatment of cancer.

Biophysical, molecular dynamics and cellular studies on the interaction of nickel oxide nanoparticles with tau proteins and neuron-like cells

Nickel oxide nanoparticles (NiO NPs) have been used in the biological and medical sciences. However, their toxic effects against biological systems such as nervous system have not been well studied. Therefore, the adverse effect of NiO NPs on tau structure was investigated by fluorescence and CD spectroscopic methods as well as TEM study. Also, molecular dynamic study was run to extend the experimental data. Cytotoxic activity of NiO NPs against SH-SY5Y cell was determined by trypan blue exclusion, cell morphology, ROS, and apoptosis assays. ANS, Nile red, ThT assays and electron micrograph investigation revealed that NiO NPs can increase the hydrophobic portions of tau and induce the formation of amorphous tau aggregates. Far and near CD spectroscopic methods revealed that NiO NPs can change the secondary and tertiary structure of tau, respectively. Theoretical studies depicted that NiO NPs lead to folding of tau structure. In the cellular view, NiO NPs induced significant mortality and morphological effects against SH-SY5Y cells. NiO NPs also provided a significant impact on generating intracellular ROS and apoptosis induction. This study determined that NiO NPs could mediate the induction of some undesired effects on the nervous system.

Biocompatible nanoparticles containing hydrophobic nickel-bis(dithiolene) complexes for NIR-mediated doxorubicin release and photothermal therapy

Nickel-bis(dithiolene) containing NPs: controlled release of Dox and photothermal therapy under NIR Irradiation.