Exploring the current advancements of quercetin nanoformulations alleviating respiratory diseases

Keywords: :

• nanoformulations
• nanoparticles
• quercetin
• respiratory diseases

1. Introduction

Respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD) and lung cancer place an immense global burden, not only on the quality of life of patients but also on each country's economy [1,2]. It was found in 2019 that chronic respiratory diseases had a worldwide prevalence of 454.6 million cases and were responsible for 4 million deaths, representing the third leading cause of death [2]. Research on phytoceuticals for multiple medical conditions, especially respiratory diseases, has gained much interest, and with the advancement of nanotechnology where the applications of nanoformulations have been increasingly used [3,4]. This includes the use of nanotechnology in research into the benefits of phytoceuticals, and there are numerous types of nanoformulations; these can consist of polymer, lipid or surfactant-based nanosystems, cyclodextrin-based or inorganic nanoparticles [4]. Using nanoparticles and nanocarriers to deliver phytoceuticals may overcome current issues limiting the clinical application of phytoceuticals such as low solubility and low permeation, leading to increased bioavailability and effectiveness [5,6].

Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is a naturally occurring flavonoid that is found in a wide variety of foods and plants such as apples, potatoes, eggplants, Ginkgo biloba, Hypericum perforatum (Saint John's wort) and Sambucus canadensis (common elderberry) [7]. It is a known antioxidant and has been acknowledged to have anti-cancer activity, preventing the progression of certain cancers such as liver, lung, colon, prostate, cervical and breast [8]. Not only anti-cancer activities, but it also has established anti-inflammatory properties in conditions such as heart disease, allergies, asthma, hay fever and arthritis [9]. Besides this, quercetin has been reported to have antiviral and antimicrobial activities, as well as the potential to reduce the risk of cardiovascular and neurodegenerative diseases, Type II diabetes and obesity [8,9]. Although quercetin (QUE) has many potential beneficial properties that can be used for many conditions, its clinical translation is negated by its poor solubility, susceptibility to the metabolic transformation of its chemical structure and poor absorption, all factors limiting its bioavailability and the resulting therapeutic application [10]. With the advancement of nanotechnology, formulating bioactive phytoceuticals as nanoparticles or with nanocarriers as the delivery system improves their pharmacokinetics properties and solubility profile, enhancing absorption, reducing toxicity by decreasing particle size and modifying the surface properties [5,6].

2. Nanoformulations containing quercetin on respiratory diseases

Several QUE-based nanoformulations have been researched in in vitro and in vivo studies for therapeutic activity against respiratory diseases. A study by Loo et al. investigated the anticancer potential of formulated polyvinyl alcohol-coated QUE nanoparticles, manufactured using the solvent-antisolvent method, to be delivered via the pulmonary route. In this study, the nanoparticles were tested on an air–liquid interface cell culture of human lung adenocarcinoma cells (A549). The study found that QUE nanoparticles significantly decreased the A549 cell viability with IC₃₀ 13.3 μM, IC₅₀ 31.1 μM and IC₇₀ 72.7 μM, while not significantly affecting the viability of normal human bronchial epithelial (BEAS-2B) cells. Pro-inflammatory cytokine expression was also investigated by inducing the A549 air–liquid interface cell culture with lipopolysaccharide (LPS) as an inductor of pro-inflammatory markers. The QUE nanoparticles were found to significantly decrease IL-8 from 550 ± 29 pg/ml to 380 ± 27 pg/ml, and TNF-α expression decreased from ∼180 pg/ml (expression was estimated from a figure as the exact expression of control was not provided) to 158 ± 30 pg/ml [11]. It is known that inflammation is a significant component of various respiratory diseases, and numerous studies have shown that pro-inflammatory cytokines IL-8 and TNF-α are involved in multiple inflammatory pathways in conditions such as lung cancer, asthma, cigarette-induced inflammation and chronic obstructive pulmonary disease [3,12]. In part two of the study by Loo et al., it was also found that the QUE nanoparticles, which were delivered to the air–liquid interface culture of A549 cells via nebulization, were shown to be successfully internalized into the cells and caused approximately 30% death and induction of apoptotic in 19.8 ± 1.3% of A549 cells [13]. A study by Arbain et al. investigated the effect of QUE on A549 lung cancer cells using an oil-in-water nanoemulsion as the nanocarrier. It was found that the QUE-loaded nanoemulsion had a cytotoxic effect on A549 cells, with an IC₅₀ of 0.99 mM (calculated from original authors of 300 μg/ml, using quercetin molecular weight of 302.23 g from PubChem compound summary [14]) with incubation of 48 h, concomitantly with no cytotoxic effects on healthy human lung fibroblast (MRC5) cells up to a concentration of 1.65 mM (calculated from original authors of 500 μg/ml using quercetin molecular weight of 302.23 g from PubChem compound summary [14]). The study also found that the cytotoxic effects were time-dependent, as when the A549 cells were treated with the QUE-loaded nanoemulsion for 72 h, the IC₅₀ reduced to 0.33 mM (calculated from original authors of 100 μg/ml using quercetin molecular weight of 302.23 g from PubChem compound summary [14]), which was thought to be due to the efficient internalization of the nanoemulsion and the cells being treated for a more extended period of time [15].

Yong et al. investigated QUE-loaded nanoparticles in asthma, using QUE-loaded liquid crystalline nanoparticles (LCN) formulated by utilizing the ultrasonication method and surface-modified liquid crystalline nanoparticles (sm-LCN) with hydrophilic polymers. The QUE-loaded LCN were tested for their capacity to downregulate LPS-induced pro-inflammatory markers on the human minimally immortalized bronchial epithelial cell line (BCi-NS1.1). It was found that both QUE-loaded LCNs and sm-LCNs significantly decreased the pro-inflammatory cytokines IL-1β, IL-6 and IL8 in LPS-induced at 25 μM equivalent QUE concentration [16]. This potentially suppresses and prevents the development of exacerbations associated with asthma by decreasing crucial pro-inflammatory mediators implicated in these processes.

Another class of QUE-loaded nanoparticles, investigated for their anti-cancer potential by Baksi et al. on A549 cells in vitro and in vivo, is QUE-loaded chitosan nanoparticles obtained by ionic gelation method [17]. Chitosan is biodegradable, biocompatible, has low toxicity, low allergenicity, is easy to prepare and is claimed to have anti-oxidant, anti-microbial and anti-tumor properties [18]. In this study, the in vitro testing of the cytotoxicity of QUE-loaded chitosan nanoparticles on the A549 cells showed that a significantly lower IC₅₀ concentration was obtained for QUE-loaded chitosan nanoparticles ∼84.4 μM compared with free QUE ∼132.6 μM (concentrations were estimated from a figure as the exact concentrations were not provided). The study also investigated the in vivo anti-tumor properties of the free QUE and QUE-loaded chitosan nanoparticles at a dose of 25 mg/kg body weight in tumor xenograft models obtained by injecting the same A549 cells in a heterotopic model at the shoulder blade region in C57BL6 mice. The free QUE treatment resulted in a significant reduction in tumor volume in just four weeks, and by the fifth week, the tumor volume had reduced significantly by 31.13% compared with the disease control group. QUE-loaded chitosan nanoparticles, the tumor volume also decreased significantly by 62.86% compared with the disease control group, which was greater than the free QUE. In the study, the antioxidant activity was also investigated by measuring the superoxide dismutase (SOD) enzyme concentration. Briefly, SODs catalyse the conversion of superoxide into oxygen and hydrogen peroxide, and its activity limits the levels of reactive oxygen and nitrogen species, thereby limiting the potential oxidative damage to cells [19]. Therefore, high levels of SOD inhibit autophagy and leads to cancer cell death [17,19]. It was found that, within the A549 xenograft treated with both free QUE and QUE-loaded, there were a significant increase of SOD activity (∼2.91 U/ml and ∼3.45 U/ml, respectively) compared with the disease control groups (∼1.95 U/ml) (serum SOD levels were estimated from a figure as the exact levels were not provided). The increased levels of SOD led to cancer cell death (A549 lung carcinoma epithelial cells) and resultant decreased tumor volume [17].

A study by Lin et al. investigated a novel nanoparticle delivery system, which uses quercetin-derived carbonized nanogels (prepared by the mild pyrolysis of quercetin at different pre-heated temperatures) for its antiviral activity against the H1N1 influenza A virus. Infected mice with H1N1 virus were sprayed by aerosolization with either quercetin or quercetin-derived carbonized nanogel₂₇₀ (pyrolysis at 270°C) at concentrations of 1.65 mM (calculated from original authors of 500 μg/ml using quercetin molecular weight of 302.23 g from PubChem compound summary [14]) into the chambers. It was found that the mice treated by daily aerosol inhalation with quercetin-derived carbonized nanogel₂₇₀ had fewer abnormal changes in the lung parenchyma and interstitium than that of H1N1-infected with no treatment and H1N1-infected with free quercetin treatment. The rodent model showed that the quercetin-derived carbonized nanogel₂₇₀ could prevent the H1N1 virus from entering the cells and the subsequent inflammatory response triggered by the virus, while free quercetin did not block the H1N1 virus [20].

3. Conclusion & future perspective

The research studies discussed in the present manuscript have demonstrated that QUE has potent anti-inflammatory, antioxidant, anti-cancer and antiviral activities. Furthermore, its formulation in nanoparticular form or loading into nanoparticles, has been shown to decrease pro-inflammatory cytokine expression and increase antioxidant activity by increasing SOD activity leading to potential cancer cell death and the overall reduction of cancer cell viability. Also, using a novel formulation, quercetin-derived carbonized nanogel has been shown to prevent H1N1 viral infection. These studies clearly highlight the advantage of encapsulating phytoceuticals such as QUE within advanced drug delivery systems to improve their delivery and therapeutic efficacy. Therefore, both nanoparticular QUE, QUE-loaded nanoparticles, and novel formulations of QUE hold promise for treating various diseases, especially respiratory diseases such as asthma, COPD, lung cancer and respiratory viral infections. As there is an increased need for targeted therapies and personalised medicines, the use of QUE in nanoformulations may further advance the prevention, management and treatment of various other respiratory diseases. Future investigations should focus on in vivo studies that can potentially pave a new path to respiratory treatment in clinics.

Financial disclosure

Authors would like to acknowledge the funding support from Maridulu Budyari Gumal- The Sydney Partnership for Health, Education, Research and Enterprise (SPHERE) funding 2022 and 2023, Triple I CAG secondment/exchange grant-2023 and Triple I skills advancement grant-2023, University of Technology Key Technology Partnership (UTS-KTP) grant-2023. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Writing disclosure

No writing assistance was utilized in the production of this manuscript.

Acknowledgments

Authors would like to acknowledge the funding support from Maridulu Budyari Gumal- The Sydney Partnership for Health, Education, Research and Enterprise (SPHERE) funding 2022 and 2023, Triple I CAG secondment/exchange grant-2023 and Triple I skills advancement grant-2023, University of Technology Key Technology Partnership (UTS-KTP) grant-2023.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

Authors would like to acknowledge the funding support from Maridulu Budyari Gumal- The Sydney Partnership for Health, Education, Research and Enterprise (SPHERE) funding 2022 and 2023, Triple I CAG secondment/exchange grant-2023 and Triple I skills advancement grant-2023, University of Technology Key Technology Partnership (UTS-KTP) grant-2023.