Inducing endoplasmic reticulum stress in cancer cells using graphene oxide-based nanoparticles

Biomaterials for Targeting Endoplasmic Reticulum in Cancer

Endoplasmic reticulum (ER) is one of the most important sub-cellular organelles which controls myriads of biological functions including protein biosynthesis with proper functional folded form, protein misfolding, protein transport into Golgi body for secretion, Ca2+ homeostasis and so on. Subsequently, dysregulation in ER function leads to ER stress followed by disease pathology like cancer. Hence, targeting ER in the cancer cells emerged as one of the futuristic strategies for cancer treatment. However, the major challenge is to selectively and specifically target ER in the sub-cellular milieu in the cancer tissues, due to the lack of ER targeting chemical moieties to recognize the ER markers. To address this, in the last decade, numerous biomaterials were explored to selectively impair and image ER in cancer cells to induce ER stress. This review outlines those biomaterials which consists of carbon and silicon materials, lipid nanoparticles (liposomes and micelles), supramolecular self-assembled nanostructures, cell membrane-coated nanoparticles and metallic nanoparticles. Moreover, we also discuss the challenges and possible solutions of this promising field to usher the readers towards next-generation ER targeted cancer therapy.

Carbohydrate polymers-based surface modified nano delivery systems for enhanced target delivery to colon cancer - A review

Carbohydrate polymers-based surface-modified nano-delivery systems have gained significant attention in recent years for enhancing targeted delivery to colon cancer. These systems leverage carbohydrate polymers' unique properties, such as biocompatibility, biodegradability, and controlled release. These properties make them suitable candidates for drug delivery applications. Nano-delivery systems loaded with bioactive compounds are well-studied for targeted colorectal cancer delivery. However, those drugs' target reach is still limited in various nano-delivery systems. To overcome this limitation, surface modification of nanoparticles with carbohydrate polymers like chitosan, pectin, alginate, and guar gum showed enhanced target-reaching capacity along with enhanced anticancer efficacy. Recently, a chitosan-decorated PLGA nanoparticle was constructed with tannic acid and vitamin E and showed long-term release of specific targets along with higher anticancer efficacy. Similarly, Chitosan-conjugated glucuronic acid-coated silica nanoparticles loaded with capecitabine were studied against colon cancer and found to be the pH-responsive controlled release of capecitabine with higher anticancer efficacy. Surface-modified carbohydrate polymers have promising potential for improving colon cancer target delivery. By leveraging the unique properties of these polymers, such as surface modification, pH responsiveness, mucoadhesion, controlled drug release, and combination therapy, researchers are working toward developing more effective and targeted treatment strategies for colon cancer.

Intricate subcellular journey of nanoparticles to the enigmatic domains of endoplasmic reticulum

It is evident that site-specific systemic drug delivery can reduce side effects, systemic toxicity, and minimal dosage requirements predominantly by delivering drugs to particular pathological sites, cells, and even subcellular structures. The endoplasmic reticulum (ER) and associated cell organelles play a vital role in several essential cellular functions and activities, such as the synthesis of lipids, steroids, membrane-associated proteins along with intracellular transport, signaling of Ca2+, and specific response to stress. Therefore, the dysfunction of ER is correlated with numerous diseases where cancer, neurodegenerative disorders, diabetes mellitus, hepatic disorder, etc., are very common. To achieve satisfactory therapeutic results in certain diseases, it is essential to engineer delivery systems that can effectively enter the cells and target ER. Nanoparticles are highly biocompatible, contain a variety of cargos or payloads, and can be modified in a pliable manner to achieve therapeutic effectiveness at the subcellular level when delivered to specific organelles. Passive targeting drug delivery vehicles, or active targeting drug delivery systems, reduce the nonselective accumulation of drugs while reducing side effects by modifying them with small molecular compounds, antibodies, polypeptides, or isolated bio-membranes. The targeting of ER and closely associated organelles in cells using nanoparticles, however, is still unsymmetrically understood. Therefore, here we summarized the pathophysiological prospect of ER stress, involvement of ER and mitochondrial response, disease related to ER dysfunctions, essential therapeutics, and nanoenabled modulation of their delivery to optimize therapy.

Modulation of Autophagy Direction to Enhance Antitumor Effect of Endoplasmic-Reticulum-Targeted Therapy: Left or Right?

Strategies that induce dysfunction in the endoplasmic reticulum (ER) hold great promise for anticancer therapy, but remain unsatisfactory due to the compensatory autophagy induction after ER disruption. Moreover, as autophagy can either promote or suppress cell survival, which direction of autophagy better suits ER-targeting therapy remains controversial. Here, a targeted nanosystem is constructed, which efficiently escorts anticancer therapeutics into the ER, triggering substantial ER stress and autophagy. Concurrently, an autophagy enhancer or inhibitor is combined into the same nanoparticle, and their impacts on ER-related activities are compared. In the orthotopic breast cancer mouse model, the autophagy enhancer increases the antimetastasis effect of ER-targeting therapy and suppresses over 90% of cancer metastasis, while the autophagy inhibitor has a bare effect. Mechanism studies reveal that further enhancing autophagy accelerates central protein snail family transcriptional repressor 1 (SNAI1) degradation, suppressing downstream epithelial-mesenchymal transition, while inhibiting autophagy does the opposite. With the same trend, ER-targeting therapy combined with an autophagy enhancer provokes stronger immune response and tumor inhibition than the autophagy inhibitor. Mechanism studies reveal that the autophagy enhancer elevates Ca2+ release from the ER and functions as a cascade amplifier of ER dysfunction, which accelerates Ca2+ release, resulting in immunogenic cell death (ICD) induction and eventually triggering immune responses. Together, ER-targeting therapy benefits from the autophagy-enhancing strategy more than the autophagy-inhibiting strategy for antitumor and antimetastasis treatment.

Graphene oxide nanoarchitectures in cancer biology: Nano-modulators of autophagy and apoptosis

Nanotechnology is a growing field, with many potential biomedical applications of nanomedicine for the treatment of different diseases, particularly cancer, on the horizon. Graphene oxide (GO) nanoparticles can act as carbon-based nanocarriers with advantages such as a large surface area, good mechanical strength, and the capacity for surface modification. These nanostructures have been extensively used in cancer therapy for drug and gene delivery, photothermal therapy, overcoming chemotherapy resistance, and for imaging procedures. In the current review, we focus on the biological functions of GO nanoparticles as regulators of apoptosis and autophagy, the two major forms of programmed cell death. GO nanoparticles can either induce or inhibit autophagy in cancer cells, depending on the conditions. By stimulating autophagy, GO nanocarriers can promote the sensitivity of cancer cells to chemotherapy. However, by impairing autophagy flux, GO nanoparticles can reduce cell survival and enhance inflammation. Similarly, GO nanomaterials can increase ROS production and induce DNA damage, thereby sensitizing cancer cells to apoptosis. In vitro and in vivo experiments have investigated whether GO nanomaterials show any toxicity in major body organs, such as the brain, liver, spleen, and heart. Molecular pathways, such as ATG, MAPK, JNK, and Akt, can be regulated by GO nanomaterials, leading to effects on autophagy and apoptosis. These topics are discussed in this review to shed some lights towards the biomedical potential of GO nanoparticles and their biocompatibility, paving the way for their future application in clinical trials.

Organelle-targeted therapies: a comprehensive review on system design for enabling precision oncology

Cancer is a major threat to human health. Among various treatment methods, precision therapy has received significant attention since the inception, due to its ability to efficiently inhibit tumor growth, while curtailing common shortcomings from conventional cancer treatment, leading towards enhanced survival rates. Particularly, organelle-targeted strategies enable precise accumulation of therapeutic agents in organelles, locally triggering organelle-mediated cell death signals which can greatly reduce the therapeutic threshold dosage and minimize side-effects. In this review, we comprehensively discuss history and recent advances in targeted therapies on organelles, specifically including nucleus, mitochondria, lysosomes and endoplasmic reticulum, while focusing on organelle structures, organelle-mediated cell death signal pathways, and design guidelines of organelle-targeted nanomedicines based on intervention mechanisms. Furthermore, a perspective on future research and clinical opportunities and potential challenges in precision oncology is presented. Through demonstrating recent developments in organelle-targeted therapies, we believe this article can further stimulate broader interests in multidisciplinary research and technology development for enabling advanced organelle-targeted nanomedicines and their corresponding clinic translations.

Cellular and subcellular interactions of graphene-based materials with cancerous and non-cancerous cells

Despite significant advances in early detection and personalized treatment, cancer is still among the leading causes of death globally. One of the possible anticancer approaches that is presently receiving a lot of attention is the development of nanocarriers capable of specific and efficient delivery of anticancer drugs. Graphene-based materials are promising nanocarriers in this respect, due to their high drug loading capacity and biocompatibility. In this review, we present an overview on the interactions of graphene-based materials with normal mammalian cells at the molecular level as well as cellular and subcellular levels, including plasma membrane, cytoskeleton, and membrane-bound organelles such as lysosomes, mitochondria, nucleus, endoplasmic reticulum, and peroxisome. In parallel, we assemble the knowledge about the interactions of graphene-based materials with cancerous cells, that are considered as the potential applications of these materials for cancer therapy including metastasis treatment, targeted drug delivery, and differentiation to non-cancer stem cells. We highlight the influence of key parameters, such as the size and surface chemistry of graphene-based materials that govern the efficiency of internalization and biocompatibility of these particles in vitro and in vivo. Finally, this review aims to correlate the key parameters of graphene-based nanomaterials specially graphene oxide, such as size and surface modifications, to their interactions with the cancerous and non-cancerous cells for designing and engineering them for bio-applications and especially for therapeutic purposes.

Toxicity mechanism of nanomaterials: Focus on endoplasmic reticulum stress

Over the years, although the broad application of nanomaterials has not brought convenience to people's life, growing concern surrounds their safety. Recently, much emphasis has been placed on exploring the toxicity mechanism of nanoparticles. Currently established toxic mechanisms include oxidative stress, inflammatory response, autophagy, and DNA damage. In recent years, endoplasmic reticulum stress (ERS) has gained widespread attention as another toxic mechanism of nanomaterials. It is widely acknowledged that the endoplasmic reticulum (ER) is an important site for protein synthesis, and lipids and Ca⁺ storage, playing an esseential role in the normal operation of the body functions. When the body's internal environment is damaged, the structure and function of the endoplasmic reticulum are destroyed, leading to a series of biological reactions called endoplasmic reticulum stress (ERS.) This paper reviews the mechanism of ERS in nanomaterial-associated toxicity. The process of ERS and its related unfolded protein response were briefly introduced, summarizing the factors affecting the nanoparticle ability to induce ERS and expounding on the changes of ER morphology after exposure to nanoparticles. Finally, the specific role and molecular mechanism of ERS under the action of different nanoparticles were comprehensively analyzed, including the relationship between ERS and inflammation, oxidative stress, lipid metabolism and apoptosis. This review provides a foothold for future studies on the toxic mechanism of nanoparticles, and provides novel insights into the safe application of nanoparticles and the treatment of diseases.

Multifunctional graphene oxide nanoparticles for drug delivery in cancer

Recent advancements in nanotechnology have enabled us to develop sophisticated multifunctional nanoparticles or nanosystems for targeted diagnosis and treatment of several illnesses, including cancers. To effectively treat any solid tumor, the therapy should preferably target just the malignant cells/tissue with minor damage to normal cells/tissues. Graphene oxide (GO) nanoparticles have gained considerable interest owing to their two-dimensional planar structure, chemical/mechanical stability, excellent photosensitivity, superb conductivity, high surface area, and good biocompatibility in cancer therapy. Many compounds have been functionalized on the surface of GO to increase their biological applications and minimize cytotoxicity. The review presents an overview of the physicochemical characteristics, strategies for various modifications, toxicity and biocompatibility of graphene and graphene oxide, current trends in developing GO-based nano constructs as a drug delivery cargo and other biological applications, including chemo-photothermal therapy, chemo-photodynamic therapy, bioimaging, and theragnosis in cancer. Further, the review discusses the challenges and opportunities of GO, GO-based nanomaterials for the said applications. Overall, the review focuses on the therapeutic potential of strategically developed GO nanomedicines and comprehensively discusses their opportunities and challenges in cancer therapy.

The Multifarious Applications of Copper Nanoclusters in Biosensing and Bioimaging and Their Translational Role in Early Disease Detection

Nanoclusters possess an ultrasmall size, amongst other favorable attributes, such as a high fluorescence and long-term colloidal stability, and consequently, they carry several advantages when applied in biological systems for use in diagnosis and therapy. Particularly, the early diagnosis of diseases may be facilitated by the right combination of bioimaging modalities and suitable probes. Amongst several metallic nanoclusters, copper nanoclusters (Cu NCs) present advantages over gold or silver NCs, owing to their several advantages, such as high yield, raw abundance, low cost, and presence as an important trace element in biological systems. Additionally, their usage in diagnostics and therapeutic modalities is emerging. As a result, the fluorescent properties of Cu NCs are exploited for use in optical imaging technology, which is the most commonly used research tool in the field of biomedicine. Optical imaging technology presents a myriad of advantages over other bioimaging technologies, which are discussed in this review, and has a promising future, particularly in early cancer diagnosis and imaging-guided treatment. Furthermore, we have consolidated, to the best of our knowledge, the recent trends and applications of copper nanoclusters (Cu NCs), a class of metal nanoclusters that have been gaining much traction as ideal bioimaging probes, in this review. The potential modes in which the Cu NCs are used for bioimaging purposes (e.g., as a fluorescence, magnetic resonance imaging (MRI), two-photon imaging probe) are firstly delineated, followed by their applications as biosensors and bioimaging probes, with a focus on disease detection.

Research on endoplasmic reticulum-targeting fluorescent probes and endoplasmic reticulum stress-mediated nanoanticancer strategies: A review

Subcellular localization of organelles can achieve accurate drug delivery and maximize drug efficacy. As the largest organelle in eukaryotic cells, the endoplasmic reticulum (ER) plays an important role in protein synthesis, folding, and posttranslational modification; lipid biosynthesis; and calcium homeostasis. Observing the changes in various metal ions, active substances, and the microenvironment in the ER is crucial for diagnosing and treating many diseases, including cancer. Excessive endoplasmic reticulum stress (ERS) can have a killing effect on malignant cells and can mediate cell apoptosis, proper modulation of ERS can provide new perspectives for the treatment of many diseases, including cancer. Therefore, the ER is used as a new anticancer target in cancer treatment. This review discusses ER-targeting fluorescent probes and ERS-mediated nanoanticancer strategies.

Mitochondria-targeted nanoparticles (mitoNANO): An emerging therapeutic shortcut for cancer

The early understanding of mitochondria posited that they were 'innocent organelles' solely devoted to energy production and utilisation. Intriguingly, recent findings have outlined in detail the 'modern-day' view that mitochondria are an important but underappreciated drug target. Mitochondria have been implicated in the pathophysiology of many human diseases, ranging from neurodegenerative disorders and cardiovascular diseases to infections and cancer. It is now clear that normal mitochondrial function involves the building blocks of a cell to generate lipids, proteins and nucleic acids thereby facilitating cell growth. On the other hand, mitochondrial dysfunction reprograms crucial cellular functions into pathological pathways, and is considered as an integral hallmark of cancer. Therefore, strategies to target mitochondria can provide a wealth of new therapeutic approaches in the fight against cancer, by overcoming a number of problems associated with conventional pharmaceutical drugs, including low solubility, poor bioavailability and non-selective biodistribution. The combination of nanoparticles with 'classical' chemotherapeutic drugs to create biocompatible, multifunctional mitochondria-targeted nanoplatforms has been recently studied. This approach is now rapidly expanding for targeted drug delivery systems, and for hybrid nanostructures that can be activated with light (photodynamic and/or photothermal therapy). The selective delivery of nanoparticles to mitochondria is an elegant shortcut to more selective, targeted, and safer cancer treatment. We propose that the use of nanoparticles to target mitochondria be termed "mitoNANO". The present minireview sheds light on the design and application of mitoNANO as advanced cancer therapeutics, that may overcome drug resistance and show fewer side effects.

Inhibition of microtubule assembly and cytotoxic effect of graphene oxide on human colorectal carcinoma cell HCT116

Nanomaterials, such as graphene oxide (GO), are increasingly being investigated for their suitability in biomedical applications. Tubulin is the key molecule for the formation of microtubules crucial for cellular function and proliferation, and as such an appealing target for developing anticancer drug. Here we employ biophysical techniques to study the effect of GO on tubulin structure and how the changes affect the tubulin/microtubule assembly. GO disrupts the structural integrity of the protein, with consequent retardation of tubulin polymerization. Investigating the anticancer potential of GO, we found that it is more toxic to human colon cancer cells (HCT116), as compared to human embryonic kidney epithelial cells (HEK293). Immunocytochemistry indicated the disruption of microtubule assembly in HCT116 cells. GO arrested cells in the S phase with increased accumulation in Sub-G1 population of cell cycle, inducing apoptosis by generating reactive oxygen species (ROS) in a dose- and time-dependent manner. GO inhibited microtubule formation by intervening into the polymerization of tubulin heterodimers both in vitro and ex vivo, resulting in growth arrest at the S phase and ROS induced apoptosis of HCT116 colorectal carcinoma cells. There was no significant harm to the HEK293 kidney epithelial cells used as control. Our report of pristine GO causing ROS-induced apoptosis of cancer cells and inhibition of tubulin-microtubule assembly can be of interest in cancer therapeutics and nanomedicine.

Endoplasmic Reticulum Stress Provocation by Different Nanoparticles: An Innovative Approach to Manage the Cancer and Other Common Diseases

A proper execution of basic cellular functions requires well-controlled homeostasis including correct protein folding. Endoplasmic reticulum (ER) implements such functions by protein reshaping and post-translational modifications. Different insults imposed on cells could lead to ER stress-mediated signaling pathways, collectively called the unfolded protein response (UPR). ER stress is also closely linked with oxidative stress, which is a common feature of diseases such as stroke, neurodegeneration, inflammation, metabolic diseases, and cancer. The level of ER stress is higher in cancer cells, indicating that such cells are already struggling to survive. Prolonged ER stress in cancer cells is like an Achilles' heel, if aggravated by different agents including nanoparticles (NPs) may be exhausted off the pro-survival features and can be easily subjected to proapoptotic mode. Different types of NPs including silver, gold, silica, graphene, etc. have been used to augment the cytotoxicity by promoting ER stress-mediated cell death. The diverse physico-chemical properties of NPs play a great role in their biomedical applications. Some special NPs have been effectively used to address different types of cancers as these particles can be used as both toxicological or therapeutic agents. Several types of NPs, and anticancer drug nano-formulations have been engineered to target tumor cells to enhance their ER stress to promote their death. Therefore, mitigating ER stress in cancer cells in favor of cell death by ER-specific NPs is extremely important in future therapeutics and understanding the underlying mechanism of how cancer cells can respond to NP induced ER stress is a good choice for the development of novel therapeutics. Thus, in depth focus on NP-mediated ER stress will be helpful to boost up developing novel pro-drug candidates for triggering pro-death pathways in different cancers.