Elsevier

Analytica Chimica Acta

Volume 1059, 20 June 2019, Pages 113-123
Analytica Chimica Acta

Chemiluminescent liposomes as a theranostic carrier for detection of tumor cells under oxidative stress

https://doi.org/10.1016/j.aca.2019.01.045Get rights and content

Highlights

  • Chemiluminescent liposomes as a carrier for PO-CL reaction in water environment.

  • Curcumin-loaded in liposome possessed increased bio-accessibility and sensitized in PO-CL system.

  • PO-CL reaction has sensitivity and selectivity for detection of tumour cells under oxidative stress.

  • The chemiluminescent liposomes detect hydrogen peroxide at nanomolar concentrations.

Abstract

Hydrogen peroxide (H2O2) is one of the main source of oxidative stress and a typical marker of reactive oxygen species (ROS)-associated diseases. Therefore, selective detection and scavenging of overproduced H2O2 provide enormous benefits to the successful treatment of ROS-related diseases. The authors took advantage of this property to detect cancer cells using chemiluminescent peroxyoxalate reaction. Here, a new contrast agent presented for hydrogen peroxide, termed peroxyoxalate liposomes, which detect hydrogen peroxide through chemiluminescence reaction, and have the physical/chemical properties needed for imaging applications. The peroxyoxalate liposomes are composed of Bis (2, 4, 6-trichlorphenyl) oxalate (TCPO) and curcumin as fluorophore. Experimental factors such as TCPO, imidazole, hydrogen peroxide and curcumin concentration were optimized. Moreover, application of curcumin makes it possible to design a system for selective tumor destruction. In the reaction of peroxyoxalate, it acts as an oxalate activator with intracellular hydrogen peroxide and experiences excitation as a result of the reaction. In addition, curcumin also acts as a photosensitizer (PS) causing cell damage. In the optimum conditions, the measurable concentration range of 0.86–220 μM of hydrogen peroxide were evaluated from the linear calibration curve with satisfactory RSD% and corresponding detection limits of 650 nM. Therefore, it has the sensitivity needed to detect physiological concentrations of hydrogen peroxide. Moreover, cellular uptake experiments showed that the liposomes enhance extravasation into permeable membranes and significantly increased the bioavailability of curcumin.

Graphical abstract

Peroxyoxalate chemiluminescence (PO-CL) reaction with endogenous H2O2 results in light emission of curcumin.

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Introduction

Hydrogen peroxide is one of the biological reactive oxygen species (ROS) in living systems. This would be a great messenger molecule in the transmission of various redox-dependent cellular signals, and its homeostasis can have physiological and pathological consequences [1,2]. Typically, superoxide anion, hydroxyl radical, and hydrogen peroxide cause irreversible damage of lipids, proteins and DNA, leading to disturbances in the cellular organs [3]. Excessive and unregulated production of hydrogen peroxide is known to cause oxidative stress and the accumulation of oxidative stress damages over time is associated with many life-threatening diseases. It can refer to cardiovascular diseases, cancer, Alzheimer and development of many inflammatory diseases [4,5]. Therefore, hydrogen peroxide has a great potential as a diagnostic biomarker for detecting inflammatory responses and selective detection of that provide enormous benefits to the successful treatment of ROS-related diseases [6]. Although photodynamic therapy (PDT) has significantly progressed in technical development, it is not free from limitations. One of them is the opacity of tissues which interferes with application of PDT for detection of tumors [7]. To overcome this limitation, chemiluminescent reactions have been proposed as a source of light. Chemiluminescence (CL) is a highly sensitive and specific analytical technique that can be used in the determination of various compounds in different matrices, depending on their role in the CL reaction as precursors, catalysts, inhibitors, and oxidants [[8], [9], [10]].

Among several CL detection modalities, peroxyoxalate chemiluminescence (PO-CL) is one of the most effective one (Quantum yield up to 50%). In the indirect CL, there is a three-component reaction between hydrogen peroxide, activated oxalic acid derivatives, and fluorescent dyes for highly sensitive imaging of H2O2. The rate of this reaction was accelerated by presence of suitable basic catalysts such as sodium salicylate or imidazole [11,12]. In principle, peroxy oxalate esters are oxidized by peroxide anion with a nucleophilic attack to form high energy dioxetanedione intermediates. They produce an excited species nearby fluorophore to generate chemically ignited fluorescence according to a chemically initiated electron exchange luminescence (CIEEL) process [13,14].

The choice of activated oxalates for PO-CL reactions has been the subject of numerous efforts [11,12]. It has clearly shown that Bis (2,4,6-trichlorphenyl) oxalate (TCPO) is one of the most widely used peroxalates for the PO-CL, firstly, because of its high reactivity in oxidation by hydrogen peroxide. Secondly, the electron withdrawing nature of chlorine facilitated to generation of reactive intermediates, which responsible for the excitation energy transfer to the fluorophore [15]. However, its applications were limited in the aqueous medium because of peroxalate linkages react with water to decompose, but the encapsulation in the hydrophobic core of liposome increased its stability.

In the last decade, curcumin, a hydrophobic polyphenol, has been considered for its attractive biological and pharmacological properties such as antibacterial, antioxidant, anti-inflammatory, and anti-proliferative [[16], [17], [18]]. Despite these potentials, the extremely low bioavailability and the poor water solubility of that greatly limits its applications. Many attempts were made to overcome these curcumin constraints by using various encapsulation methods, such as liposomal incorporation which improved its solubility and stability [[19], [20], [21], [22]].

Although the PO-CL reaction can be applied in different fields of pharmacology and diagnostics, it is challenging to exploit of that for detection of H2O2. Because of it requires a close vicinity of peroxy oxalate and fluorophore, allowing them to perform PO-CL reaction in response to H2O2. Phillip et al. were the first who used PO-CL reaction for elimination of tumor cells [23]. Later, polymeric oxalates such as polyoxalate-containing nanoparticles [6] or peroxalate micelles [24] designed as PO-CL systems to apply for detection of hydrogen peroxide [25]. To date, a few experimental studies have reported that these systems are comparatively resistant to hydrolysis and can be used in an aqueous medium [26]. However, the goal of this study was to produce chemiluminescent liposomes containing peroxyoxalate and curcumin that can detect hydrogen peroxide with a linear correlation between the hydrogen peroxide at nanomolar concentration and CL intensity. Curcumin plays the dual role as an activator in PO-CL reaction as well as an effective photosensitizer for singlet oxygen generation. We also evaluated the potential of chemiluminescent liposomes for the detection of hydrogen peroxide using activated melanoma B16-F10 cells under oxidative stress. Cytotoxicity and membrane permeability of these formulations toward cells were studied.

Section snippets

Materials

Bis (2, 4, 6-trichlorophenyl) oxalate (TCPO), Curcumin, imidazole hydrochloride, and Hoechst 33258 solution were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA) and used as received. 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was provided by Avanti Polar Lipids (Alabaster, Alabama, USA). Dulbecco's Modified Eagle's Medium (DMEM) and fetal bovine serum (FBS) were obtained from Gibco, and 7-Hydroxy-3H-phenoxazin-3-one-10-oxide (Alamar blue assay) from Sigma-Aldrich.

Results and discussion

As the accumulation of hydrogen peroxide in the cells causes oxidative stress, we demonstrated chemiluminescent liposomes which applied to assess the level of that in biological sample. It also has the potential for imaging of hydrogen peroxide-associated diseases. The proposed mechanism for PO-CL reaction shown in Scheme 1, in which an oxalic acid derivative (like TCPO) reacts with H2O2 and a key intermediate 1,2-dioxetanedione is produced after some intramolecular displacements [11,14,29].

Conclusion

The application of the PO-CL reaction for formulations operating in aqueous media is limited by spontaneous hydrolysis of the most active oxalates, which marginally soluble in water. We developed novel multifunctional chemiluminescent liposomes that are able to detect H2O2 and serve as therapeutic agents with potent antioxidant and anti-apoptotic activity. The poor stability limits of their applications under aqueous conditions as well as to increase local concentration of components were

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors gratefully acknowledge the support of this work by research council of Tarbiat Modares University (grant IG-39708) and Iran National Science Foundation (INSF), (grant 96011371).

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    1

    Sanam Sadeghi Mohammadi and Zahra Vaezi contributed equally.

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