Chiral polymer modified nanoparticles selectively induce autophagy of cancer cells for tumor ablation

Antibacterial Mechanism of d-Cysteine/Polyethylene Glycol-Functionalized Gold Nanoparticles and Their Potential for the Treatment of Bacterial Infections

Bacterial infection has always posed a severe threat to public health. Gold nanoparticles (Au NPs) exhibit exceptional biocompatibility and hold immense potential in biomedical applications. However, their antibacterial effectiveness is currently unsatisfactory. Herein, a chiral antibacterial agent with high stability was prepared by the modification of Au NPs with d-cysteine with the assistance of polyethylene glycol (PEG). The as-synthesized d-cysteine/PEG-Au NPs (D/P-Au NPs) exhibited a stronger (99.5-99.9%) and more stable (at least 14 days) antibacterial performance against Gram-negative (Escherichia coli and Listeria monocytogenes) and Gram-positive (Salmonella enteritidis and Staphylococcus aureus) bacteria, compared with other groups. The analysis of the antibacterial mechanism revealed that the D/P-Au NPs mainly affected the assembly of ribosomes, the biosynthesis of amino acids and proteins, as well as the DNA replication and mismatch repair, ultimately leading to bacterial death, which is significantly different from the mechanism of reactive oxygen species-activated metallic antibacterial NPs. In particular, the D/P-Au NPs were shown to effectively accelerate the healing of S. aureus-infected wounds in mice to a rate comparable to or slightly higher than that of vancomycin. This work provides a novel approach to effectively design chiral antibacterial agents for bacterial infection treatment.

Expanding the Role of Chiral Drugs and Chiral Nanomaterials as a Potential Therapeutic Tool

Chirality, the property of molecules having mirror-image forms, plays a crucial role in pharmaceutical and biomedical research. This review highlights its growing importance, emphasizing how chiral drugs and nanomaterials impact drug effectiveness, safety, and diagnostics. Chiral molecules serve as precise diagnostic tools, aiding in accurate disease detection through unique biomolecule interactions. The article extensively covers chiral drug applications in treating cardiovascular diseases, CNS disorders, local anesthesia, anti-inflammatories, antimicrobials, and anticancer drugs. Additionally, it explores the emerging field of chiral nanomaterials, highlighting their suitability for biomedical applications in diagnostics and therapeutics, enhancing medical treatments.

Nanomaterials in crossroad of autophagy control in human cancers: Amplification of cell death mechanisms

Cancer is the result of genetic abnormalities that cause normal cells to grow into neoplastic cells. Cancer is characterized by several distinct features, such as uncontrolled cell growth, extensive spreading to other parts of the body, and the ability to resist treatment. The scientists have stressed the development of nanostructures as novel therapeutic options in suppressing cancer, in response to the emergence of resistance to standard medicines. One of the specific mechanisms with dysregulation during cancer is autophagy. Nanomaterials have the ability to specifically carry medications and genes, and they can also enhance the responsiveness of tumor cells to standard therapy while promoting drug sensitivity. The primary mechanism in this process relies on autophagosomes and their fusion with lysosomes to break down the components of the cytoplasm. While autophagy was initially described as a form of cellular demise, it has been demonstrated to play a crucial role in controlling metastasis, proliferation, and treatment resistance in human malignancies. The pharmacokinetic profile of autophagy modulators is poor, despite their development for use in cancer therapy. Consequently, nanoparticles have been developed for the purpose of delivering medications and autophagy modulators selectively and specifically to the cancer process. Furthermore, several categories of nanoparticles have demonstrated the ability to regulate autophagy, which plays a crucial role in defining the biological characteristics and response to therapy of tumor cells.

All Roads Lead to Rome: Comparing Nanoparticle- and Small Molecule-Driven Cell Autophagy

Autophagy, vital for removing cellular waste, is triggered differently by small molecules and nanoparticles. Small molecules, like rapamycin, non-selectively activate autophagy by inhibiting the mTOR pathway, which is essential for cell regulation. This can clear damaged components but may cause cytotoxicity with prolonged use. Nanoparticles, however, induce autophagy, often causing oxidative stress, through broader cellular interactions and can lead to a targeted form known as "xenophagy." Their impact varies with their properties but can be harnessed therapeutically. In this review, the autophagy induced by nanoparticles is explored and small molecules across four dimensions: the mechanisms behind autophagy induction, the outcomes of such induction, the toxicological effects on cellular autophagy, and the therapeutic potential of employing autophagy triggered by nanoparticles or small molecules. Although small molecules and nanoparticles each induce autophagy through different pathways and lead to diverse effects, both represent invaluable tools in cell biology, nanomedicine, and drug discovery, offering unique insights and therapeutic opportunities.

Autophagy flux in bladder cancer: Cell death crosstalk, drug and nanotherapeutics

Autophagy, a self-digestion mechanism, has emerged as a promising target in the realm of cancer therapy, particularly in bladder cancer (BCa), a urological malignancy characterized by dysregulated biological processes contributing to its progression. This highly conserved catabolic mechanism exhibits aberrant activation in pathological events, prominently featured in human cancers. The nuanced role of autophagy in cancer has been unveiled as a double-edged sword, capable of functioning as both a pro-survival and pro-death mechanism in a context-dependent manner. In BCa, dysregulation of autophagy intertwines with cell death mechanisms, wherein pro-survival autophagy impedes apoptosis and ferroptosis, while pro-death autophagy diminishes tumor cell survival. The impact of autophagy on BCa progression is multifaceted, influencing metastasis rates and engaging with the epithelial-mesenchymal transition (EMT) mechanism. Pharmacological modulation of autophagy emerges as a viable strategy to impede BCa progression and augment cell death. Notably, the introduction of nanoparticles for targeted autophagy regulation holds promise as an innovative approach in BCa suppression. This review underscores the intricate interplay of autophagy with cell death pathways and its therapeutic implications in the nuanced landscape of bladder cancer.

Enantioselective Antiviral Activities of Chiral Zinc Oxide Nanoparticles

Chiral nanoparticles (C-NPs) play a crucial role in biomedical applications, especially in their biological effects on cytotoxicity and metabolism. However, there are rare reports about the antivirus property of C-NPs and their working mechanism. Here, three different types of chiral ZnO NPs (l-ZnO, d-ZnO, and dl-ZnO) were prepared as enantioselective antivirals. Biocompatibility test results showed that the three different chiral ZnO NPs varied significantly in cytotoxicity. Evaluation of their effects against porcine reproductive and respiratory syndrome virus (PRRSV) indicated that compared with d-ZnO and dl-ZnO NPs, l-ZnO NPs exhibited stronger anti-PRRSV activity due to their higher cognate cell adhesion and uptake. Furthermore, the high concentration of l-ZnO NPs can obviously reduce cellular reactive oxygen species (ROS) in MARC-145 cells, thus effectively preventing PRRSV-induced oxidative damage. This study demonstrated the outstanding antiviral properties of l-ZnO NPs, which may facilitate the development and application of C-NPs in antiviral drugs and tissue engineering.

Autophagy-targeted nanoparticles in breast carcinoma: A systematic review

Breast cancer is a commonly known cancer type and the leading cause of cancer death among females. One of the unresolved problems in cancer treatment is the increased resistance of the tumor to existing treatments, which is a direct result of apoptotic defects. Calculating an alternative to cell death (autophagy) may be the ultimate solution to maximizing cancer cell death. Our aim in this study was to investigate the potential of free nanoparticles (un-drug-loaded) in the induction or inhibition of autophagy and consider this effect on the therapy process. When the studies met the inclusion criteria, the full texts of all relevant articles were carefully examined and classified. Of the 25 articles included in the analysis, carried out on MCF-7, MDA-MB-231, MDA-MB-231-TXSA, MDA-MB-468, SUM1315, and 4T1 cell lines. Twenty in vitro studies and five in vivo/in vitro studies applied five different autophagy tests: Acridine orange, western blot, Cyto-ID Autophagy Detection Kit, confocal microscope, and quantitative polymerase chain reaction. Nanoparticles (NPs) in the basic format, including Ag, Au, Y2 O3 , Se, ZnO, CuO, Al, Fe, vanadium pentoxide, and liposomes, were prepared in the included articles. Three behaviors of NPs related to autophagy were seen: induction, inhibition, and no action. Screened and presented data suggest that most of the involved free NPs (metallic NPs) in this systematic review had reactive oxygen species-mediated pathways with autophagy induction (36%). Also, PI3K/Akt/mTOR and MAPK/ERK signaling pathways were mentioned in just four studies (16%). An impressive percentage of studies (31%) did not examine the NP-related autophagy pathway.

Self-Assembling Polymers with p-Aminosalicylate Anions Supported by Encapsulation of p-Aminosalicylate for the Improvement of Drug Content and Release Efficiency

Bioactive linear choline-based copolymers were developed as micellar carriers for drug delivery systems (DDSs). The polymethacrylates containing trimethylammonium groups with p-aminosalicylate anions (PAS-based copolymers: series 1) or chloride anions (Cl-based copolymers: series 2) differing in ionic content and chain length were selected for drug loading. The diverse structures of amphiphilic copolymers made it possible to adjust the encapsulation efficiency of a well-known antibiotic, i.e., p-aminosalicylate in the form of sodium salt (PASNa) or acid (PASA), providing single drug systems. Goniometry was applied to verify the self-assembly capacity of the copolymers using the critical micelle concentration (CMC = 0.03-0.18 mg/mL) and the hydrophilicity level quantifying the surface wettability of polymer film using the water contact angle (WCA = 30-53°). Both parameters were regulated by the copolymer composition, indicating that the increase in ionic content caused higher CMC and lower WCA, but the latter was also modified to a less hydrophilic surface by drug encapsulation. The drug content (DC) in the PAS-based polymers was increased twice by encapsulation of PASNa and PASA (47-96% and 86-104%), whereas in the chloride-based polymer systems, the drug was loaded in 43-96% and 73-100%, respectively. Efficient drug release was detected for PASNa (80-100% series 1; 50-100% series 2) and PASA as complete in both series. The strategy of loading extra drug by encapsulation, which enhances the drug content in the copolymers containing anions of the same pharmaceutics, provided promising characteristics, which highlight the potential of PAS-loaded micellar copolymers for drug delivery.

Rational targeting of autophagy in colorectal cancer therapy: From molecular interactions to pharmacological compounds

The abnormal progression of tumors has been a problem for treatment of cancer and therapeutic should be directed towards targeting main mechanisms involved in tumorigenesis in tumors. The genomic mutations can result in changes in biological mechanisms in human cancers. Colorectal cancer is one of the most malignant tumors of gastrointestinal tract and its treatment has been faced some difficulties due to development of resistance in tumor cells and also, their malignant behavior. Hence, new therapeutic modalities for colorectal cancer are being investigated. Autophagy is a "self-digestion" mechanism that is responsible for homeostasis preserving in cells and its aberrant activation/inhibition can lead to tumorigenesis. The current review focuses on the role of autophagy mechanism in colorectal cancer. Autophagy may be associated with increase/decrease in progression of colorectal cancer due to mutual function of this molecular mechanism. Pro-survival autophagy inhibits apoptosis to increase proliferation and survival rate of colorectal tumor cells and it is also involved in cancer metastasis maybe due to EMT induction. In contrast, pro-death autophagy decreases growth and invasion of colorectal tumor cells. The status of autophagy (upregulation and down-regulation) is a determining factor for therapy response in colorectal tumor cells. Therefore, targeting autophagy can increase sensitivity of colorectal tumor cells to chemotherapy and radiotherapy. Interestingly, nanoparticles can be employed for targeting autophagy in cancer therapy and they can both induce/suppress autophagy in tumor cells. Furthermore, autophagy modulators can be embedded in nanostructures in improving tumor suppression and providing cancer immunotherapy.

Advances in Enantiomer-Dependent Nanotherapeutics

The nanoscale properties of nanomaterials, especially nanoparticles, including size, shape, and surface charge, have been extensively studied for their impact on nanomedicine. Given the inherent chiral nature of biological systems and their high enantiomeric selectivity, there is rising interest to manipulate the chirality of nanomaterials to enhance their biomolecular interactions and improve nanotherapeutics. Chiral nanostructures are currently more prevalently used in biosensing and diagnostic applications owing to their distinctive physical and optical properties, but they hold great promise for use in nanomedicine. In this Review, we first discuss stereospecific interactions between chiral nanomaterials and biomolecules before comparing the synthesis and characterization methods of chiral nanoparticles and nanoassemblies. Finally, we examine the applications of chiral nanotherapeutics in cancer, immunomodulation, and neurodegenerative diseases and propose plausible mechanisms in which chiral nanomaterials interact with cells for biological manipulation. This Review on chirality is a timely reminder of the arsenal of nanoscale modifications to boost research in nanotherapeutics.

Isoginkgetin-loaded reactive oxygen species scavenging nanoparticles ameliorate intervertebral disc degeneration via enhancing autophagy in nucleus pulposus cells

Excessive reactive oxygen species (ROS) in nucleus pulposus cells (NPCs) promote extracellular matrix (ECM) degradation and cellular inflammatory responses by activating a variety of cellular pathways, ultimately inducing cell apoptosis and leading to the development of low back pain. Here, we designed and fabricated an isoginkgetin-loaded ROS-responsive delivery system (IGK@SeNP) based on diselenide block copolymers. Successfully encapsulated IGK was released intelligently and rapidly in a microenvironment with high ROS levels in degenerative disc. Controlled-release IGK not only efficiently scavenged ROS from the intervertebral disc together with diselenide block copolymers but also effectively enhanced autophagy in NPCs to inhibit ECM degradation and cell apoptosis, and showed significant therapeutic effects in the rat intervertebral disc degeneration (IDD) model. Overall, the synergistic effects of IGK@SeNP in ROS scavenging and autophagy enhancement endowed it with an attractive therapeutic strategy for IDD treatment.

Nanomedicine for autophagy modulation in cancer therapy: a clinical perspective

In recent years, progress in nanotechnology provided new tools to treat cancer more effectively. Advances in biomaterials tailored for drug delivery have the potential to overcome the limited selectivity and side effects frequently associated with traditional therapeutic agents. While autophagy is pivotal in determining cell fate and adaptation to different challenges, and despite the fact that it is frequently dysregulated in cancer, antitumor therapeutic strategies leveraging on or targeting this process are scarce. This is due to many reasons, including the very contextual effects of autophagy in cancer, low bioavailability and non-targeted delivery of existing autophagy modulatory compounds. Conjugating the versatile characteristics of nanoparticles with autophagy modulators may render these drugs safer and more effective for cancer treatment. Here, we review current standing questions on the biology of autophagy in tumor progression, and precursory studies and the state-of-the-art in harnessing nanomaterials science to enhance the specificity and therapeutic potential of autophagy modulators.

Chiral polypeptide nanoparticles as nanoadjuvants of nanovaccines for efficient cancer prevention and therapy

The chirality of bioactive molecules is closely related to their functions. D-amino acids commonly distributed in the bacterial cell walls trigger a robust anti-infective immune response. Inspired by that, two kinds of chiral polypeptides, poly(L-phenylalanine)-block-poly(L-lysine) (P_L-K) and poly(L-phenylalanine)-block-poly(D-lysine) (P_D-K), were synthesized and used as nanoadjuvants of nanovaccines for cancer prevention and therapy. The amphiphilic polypeptides self-assembled into nanoparticles with a diameter of about 30 nm during ultrasonic-assisted dissolution in phosphate-buffered saline. The nanovaccines P_L-K-OVA and P_D-K-OVA were easily prepared by mixing solutions of P_L-K or P_D-K and the model antigen chicken ovalbumin (OVA), respectively, with loading efficiencies of almost 100%. Compared to P_L-K-OVA, P_D-K-OVA more robustly induced dendritic cell maturation, antigen cross-presentation, and adaptive immune response. More importantly, it effectively prevented and treated the OVA-expressed B16-OVA melanoma model. P_D-K-OVA achieved a tumor inhibition rate of 94.9% and even 97.0% by combining with anti-PD-1 antibody. Therefore, the chiral polypeptide nanoparticles represent simple, efficient, and extensively applicable nanoadjuvants for various nanovaccines.

In vitro-in vivo correlation in nanocarriers: From protein corona to therapeutic implications

Understanding and establishing a link between the physicochemical characteristics of nanoparticles (NPs) and their biological interactions poses to be a great challenge in the field of nanotherapeutics. Recent analytical advancements concerning bio-nanointerfaces have accelerated the quest to comprehend the fate of nanocarrier systems in vivo. Scientists have discovered that protein corona, an adsorbed layer of biomolecules on the surface of NPs takes a leading part in interacting with cells and in the cellular uptake process, thereby determining the in vivo behaviour of NPs. Another useful method to assess the in vivo fate of NPs is by performing dissolution testing. This forms the basis for in vitro in vivo correlation (IVIVC), relating in vitro dissolution of NPs and their in vivo properties. Scientists are continuously directing their efforts towards establishing IVIVC for different nanocarrier systems while concurrently gaining insights into protein corona. This review primarily summarizes the importance of protein corona and its interaction with nanoparticles. It also gives an insight into the factors affecting the interaction and various in vitro dissolution media used for varied nanocarrier systems. The article concludes with a discussion of the limitations of IVIVC modelling and its position from a regulatory perspective.

Chirality-Dependent Tumor Phototherapy Using Amino Acid-Engineered Chiral Phosphorene

Phosphorene, also known as black phosphorus nanosheet (BPNS), has been investigated as a nanoagent for tumor therapy. However, promoting its intracellular accumulation while preventing the cytoplasmic decomposition remains challenging. Herein, for the first time, we propose a chiral BPNS designed through surface engineering based on amino acids with high biocompatibility and an abundant source for application in chirality-dependent tumor phototherapy based on its intracellular metabolism. The advantage of using cysteine (Cys) over other amino acids was that its d, l, or dl-form could efficiently work as the chirality inducer to modify the BPNS through electrostatic interaction and prevent alterations in the intrinsic properties of the BPNS. In particular, d-Cys-BPNS displayed an approximately threefold cytotoxic effect on tumor cells compared with l-Cys-BPNS, demonstrating a chirality-dependent therapy behavior. d-Cys-BPNS not only promoted high intracellular content but also showed resistance to cytoplasmic decomposition. Cys-engineered BPNS also demonstrated chirality-dependent phototherapy effects on tumor-bearing mice, in proximity to the results in vitro. Chiral engineering is expected to open new avenues that could promote the use of BPNS in tumor phototherapy and boost chiral nanomedicine.

Chiral-engineered supraparticles: Emerging tools for drug delivery

The handedness of chiral-engineered supraparticles (CE-SPs) influences their interactions with cells and proteins, as evidenced by the increased penetration of breast, cervical, and myeloma cell membranes by d-chirality-coordinated SPs. Quartz crystal dissipation and isothermal titration calorimetry have been used to investigate such chiral-specific interactions. d-SPs are more thermodynamically stable compared with l-SPs in terms of their adhesion. Proteases and other endogenous proteins can be shielded by the opposite chirality of d-SPs, resulting in longer half-lives. Incorporating nanosystems with d-chirality increases uptake by cancer cells and prolongs in vivo stability, demonstrating the importance of chirality in biomaterials. Thus, as we discuss here, chiral nanosystems could enhance drug delivery systems, tumor markers, and biosensors, among other biomaterial-based technologies, by allowing for better control over their features.

Astatine-211-Labeled Gold Nanoparticles for Targeted Alpha-Particle Therapy via Intravenous Injection

Alpha-particle radiotherapy has gained considerable attention owing to its potent anti-cancer effect. ²¹¹At, with a relatively short half-life of 7.2 h, emits an alpha particle within a few cell diameters with high kinetic energy, which damages cancer cells with high biological effectiveness. In this study, we investigated the intravenous injection of ²¹¹At-labeled gold nanoparticles (AuNPs) for targeted alpha-particle therapy (TAT). Different kinds of surface-modified gold nanoparticles can be labeled with ²¹¹At in high radiochemical yield in 5 min, and no purification is necessary. The in vivo biodistribution results showed the accumulation of 5 nm ²¹¹At-AuNPs@mPEG at 2.25% injection dose per gram (% ID/g) in tumors within 3 h via the enhanced permeability and retention (EPR) effect. Additionally, we observed a long retention time in tumor tissues within 24 h. This is the first study to demonstrate the anti-tumor efficacy of 5 nm ²¹¹At-AuNPs@mPEG that can significantly suppress tumor growth in a pancreatic cancer model via intravenous administration. AuNPs are satisfactory carriers for ²¹¹At delivery, due to simple and efficient synthesis processes and high stability. The intravenous administration of 5 nm ²¹¹At-AuNPs@mPEG has a significant anti-tumor effect. This study provides a new framework for designing nanoparticles suitable for targeted alpha-particle therapy via intravenous injection.

Mitophagy Induced by Metal Nanoparticles for Cancer Treatment

Research on nanoparticles, especially metal nanoparticles, in cancer therapy is gaining momentum. The versatility and biocompatibility of metal nanoparticles make them ideal for various applications in cancer therapy. They can bring about apoptotic cell death in cancer cells. In addition to apoptosis, nanoparticles mediate a special type of autophagy facilitated through mitochondria called mitophagy. Interestingly, nanoparticles with antioxidant properties are capable of inducing mitophagy by altering the levels of reactive oxygen species and by influencing signaling pathways like PINK/Parkin pathway and P13K/Akt/mTOR pathway. The current review presents various roles of metal nanoparticles in inducing mitophagy in cancer cells. We envision this review sheds some light on the blind spots in the research related to mitophagy induced by nanoparticles for cancer treatment.

Chirality-Dependent Dynamic Evolution of the Protein Corona on the Surface of Quantum Dots

Elucidating the biological behavior of engineered nanoparticles, for example, the protein corona, is important for the development of safe and efficient nanomedicine, but our current understanding is still limited due to its highly dynamic nature and lack of adequate analytical tools. In the present work, we demonstrate the establishment of a fluorescence resonance energy transfer (FRET)-based platform for monitoring the dynamic evolution behavior of the protein corona in complex biological media. With human serum albumin and lysozyme as the model serum proteins, the protein exchange process of the preformed corona on the surface of chiral quantum dots (QDs) upon feeding either individual protein or human serum was monitored in situ by FRET. Important parameters characterizing the evolution process of protein corona could be obtained upon quantitative analysis of FRET data. Further combining real-time FRET monitoring with gel electrophoresis experiments revealed that the nature of the protein initially adsorbed on the surface of QDs significantly affects the subsequent dynamic exchange behavior of the protein corona. Furthermore, our results also revealed that only a limited proportion of proteins are involved in the protein exchange, and the exchange process exhibits a significant dependence on the surface chirality of QDs. This work demonstrates the feasibility of FRET as a powerful tool to exploit the dynamic evolution process of the protein corona, which can provide theoretical guidance for further design of advanced nanomaterials for biomedical applications.

Effects of polymer carriers on the occurrence and development of autophagy in drug delivery

Autophagy is an evolutionarily conserved catabolic process that can degrade cytoplasmic materials and recycle energy to maintain metabolite homeostasis in cells. Autophagy is closely related to various physiological or pathological processes. Macromolecular materials are widely used in drug delivery systems and disease treatments due to their intrinsic effects, such as altered pharmacokinetics and biodistribution. Interaction of autophagic flux or the signal pathway with macromolecules may cause autophagy inhibition or autophagy cell death. This review covers autophagy regulation pathways and macromolecular materials (including functional micelles, biodegradable and pH-sensitive polymers, biomacromolecules, dendrimers, coordination polymers, and hybrid nanoparticles) mediated autophagy modulation.

Chiral NIR-II fluorescent Ag2S quantum dots with stereospecific biological interactions and tumor accumulation behaviors

Near-infrared II (NIR-II) fluorescent nanoprobes hold great potential for biomedical applications. Elucidating the relationship between surface properties of NIR-II nanoprobes and their biological behaviors is particularly important for future probe design and their performance optimization. Despite the rapid development of NIR-II nanoprobes, the distinct role of surface chirality on their biological fates has rarely been exploited. Herein, chiral NIR-II fluorescent Ag₂S quantum dots (QDs) are synthesized to investigate the relationship between their chirality and biological functions at both in vitro and in vivo levels. D-/L-Ag₂S QDs exhibit significant differences on their interactions with serum proteins, which further affect the cellular uptake. As a result, D-Ag₂S QDs can be internalized with higher efficiency (over 2-fold) than that of L-Ag₂S QDs. Moreover, in vivo studies reveal that the chirality determines the primary localization of these chiral QDs, where a more efficient renal elimination of D-Ag₂S QDs was observed than that of L-Ag₂S QDs. Importantly, D-Ag₂S QDs show preferential accumulation in tumor region than that of L-Ag₂S QDs in orthotopic kidney tumor model, which points out a new avenue of enhancing targeting capabilities of nanoprobes by engineering their surface chirality.

Long-Chain Poly-d-Lysines Interact with the Plasma Membrane and Induce Protective Autophagy and Intense Cell Necrosis

Polylysines have been frequently used in drug delivery and antimicrobial and cell adhesion studies. Because of steric hindrance, chirality plays a major role in the functional difference between poly-l-lysine (PLL) and poly-d-lysine (PDL), especially when they interact with the plasma membranes of mammalian cells. Therefore, it is speculated that the interaction between chiral polylysines and the plasma membrane may cause different cellular behaviors. Here, we carefully investigated the interaction pattern of PLL and PDL with plasma membranes. We found that PDL could be anchored onto the plasma membrane and interact with the membrane lipids, leading to the rapid morphological change and death of A549 cells (a human lung cancer cell line) and HPAEpiCs (a human pulmonary alveolar epithelial cell line). In contrast, PLL exhibited good cytocompatibility and was not anchored onto the plasma membranes of these cells. Unlike PLL, PDL could trigger protective autophagy to prevent cells in a certain degree, and the PDL-caused cell death occurred via intense necrosis (featured by increased intracellular Ca²⁺ content and plasma membrane disruption). In addition, it was found that the short-chain PDL with a repeat unit number of 9 (termed DL9) could locate in lysosomes and induce autophagy at high concentrations, but it could not elicit drastic cell death, which proved that the repeat unit number of polylysine could affect its cellular action. This research confirms that the interaction between chiral polylysines and the plasma membrane can induce autophagy and intense necrosis, which provides guidance for the future studies of chiral molecules/drugs.

Structure-Based Varieties of Polymeric Nanocarriers and Influences of Their Physicochemical Properties on Drug Delivery Profiles

Carriers are equally important as drugs. They can substantially improve bioavailability of cargos and safeguard healthy cells from toxic effects of certain therapeutics. Recently, polymeric nanocarriers (PNCs) have achieved significant success in delivering drugs not only to cells but also to subcellular organelles. Variety of natural sources, availability of different synthetic routes, versatile molecular architectures, exploitable physicochemical properties, biocompatibility, and biodegradability have presented polymers as one of the most desired materials for nanocarrier design. Recent innovative concepts and advances in PNC-associated nanotechnology are providing unprecedented opportunities to engineer nanocarriers and their functions. The efficiency of therapeutic loading has got considerably increased. Structural design-based varieties of PNCs are widely employed for the delivery of small therapeutic molecules to genes, and proteins. PNCs have gained ever-increasing attention and certainly paves the way to develop advanced nanomedicines. This article presents a comprehensive investigation of structural design-based varieties of PNCs and the influences of their physicochemical properties on drug delivery profiles with perspectives highlighting the inevitability of incorporating both the multi-stimuli-responsive and multi-drug delivery properties in a single carrier to design intelligent PNCs as new and emerging research directions in this rapidly developing area.

Incorporation of Low Concentrations of Gold Nanoparticles: Complex Effects on Radiation Response and Fate of Cancer Cells

(1) Background: In oncology research, a long-standing discussion exists about pros and cons of metal nanoparticle-enhanced radiotherapy and real mechanisms behind the tumor cell response to irradiation (IR) in presence of gold nanoparticles (GNPs). A better understanding of this response is, however, necessary to develop more efficient and safety nanoparticle (NP) types designed to disturb specific processes in tumor cells. (2) Aims and Methods: We combined 3D confocal microscopy and super-resolution single molecule localization microscopy (SMLM) to analyze, at the multiscale, the early and late effects of 10 nm-GNPs on DNA double strand break (DSB) induction and repair in tumor cells exposed to different doses of photonic low-LET (linear energy transfer) radiation. The results were correlated to different aspects of short and long-term cell viability. SkBr3 breast cancer cells (selected for the highest incidence of this cancer type among all cancers in women, and because most breast tumors are treated with IR) were incubated with low concentrations of GNPs and irradiated with ⁶⁰Co γ-rays or 6 MV X-rays. In numerous post-irradiation (PI) times, ranging from 0.5 to 24 h PI, the cells were spatially (3D) fixed and labeled with specific antibodies against γH2AX, 53BP1 and H3K9me3. The extent of DSB induction, multi-parametric micro- and nano-morphology of γH2AX and 53BP1 repair foci, DSB repair kinetics, persistence of unrepaired DSBs, nanoscale clustering of γH2AX and nanoscale (hetero)chromatin re-organization were measured by means of the mentioned microscopy techniques in dependence of radiation dose and GNP concentration. (3) Results: The number of γH2AX/53BP1 signals increased after IR and an additional increase was observed in GNP-treated (GNP(+)) cells compared to untreated controls. However, this phenomenon reflected slight expansion of the G2-phase cell subpopulation in irradiated GNP(+) specimens instead of enhanced DNA damage induction by GNPs. This statement is further supported by some micro- and nano-morphological parameters of γH2AX/53BP1 foci, which slightly differed for cells irradiated in absence or presence of GNPs. At the nanoscale, Ripley’s distance frequency analysis of SMLM signal coordinate matrices also revealed relaxation of heterochromatin (H3K9me3) clusters upon IR. These changes were more prominent in presence of GNPs. The slight expansion of radiosensitive G2 cells correlated with mostly insignificant but systematic decrease in post-irradiation survival of GNP(+) cells. Interestingly, low GNP concentrations accelerated DSB repair kinetics; however, the numbers of persistent γH2AX/53BP1 repair foci were slightly increased in GNP(+) cells. (4) Conclusions: Low concentrations of 10-nm GNPs enhanced the G2/M cell cycle arrest and the proportion of radiosensitive G2 cells, but not the extent of DNA damage induction. GNPs also accelerated DSB repair kinetics and slightly increased presence of unrepaired γH2AX/53BP1 foci at 24 h PI. GNP-mediated cell effects correlated with slight radiosensitization of GNP(+) specimens, significant only for the highest radiation dose tested (4 Gy).

Improved Photodynamic Activity of Phthalocyanine by Adjusting the Chirality of Modified Amino Acids

Herein, four zinc phthalocyanines (ZnPcs) with chiral lysine modification were synthesized. We found that the chirality of lysine and the chiral structure position strongly influence the properties of ZnPcs. Among the four ZnPcs, d-lysine-modified ZnPc through -NH₂ on C_ε [denoted N(ε)-d-lys-ZnPc] showed superior properties, including tumor enrichment, cancer cell uptake, and tumor retention capability, compared to the other three ZnPcs. Thus, chiral molecule modification is a simple and effective strategy to regulate the abovementioned properties to achieve a satisfactory antitumor outcome of drugs.

Influence of the chirality of carbon nanodots on their interaction with proteins and cells

Carbon nanodots with opposite chirality possess the same major physicochemical properties such as optical features, hydrodynamic diameter, and colloidal stability. Here, a detailed analysis about the comparison of the concentration of both carbon nanodots is carried out, putting a threshold to when differences in biological behavior may be related to chirality and may exclude effects based merely on differences in exposure concentrations due to uncertainties in concentration determination. The present study approaches this comparative analysis evaluating two basic biological phenomena, the protein adsorption and cell internalization. We find how a meticulous concentration error estimation enables the evaluation of the differences in biological effects related to chirality.

Autophagy and the Lysosomal System in Cancer

Autophagy and the lysosomal system, together referred to as the autophagolysosomal system, is a cellular quality control network which maintains cellular health and homeostasis by removing cellular waste including protein aggregates, damaged organelles, and invading pathogens. As such, the autophagolysosomal system has roles in a variety of pathophysiological disorders, including cancer, neurological disorders, immune- and inflammation-related diseases, and metabolic alterations, among others. The autophagolysosomal system is controlled by TFEB, a master transcriptional regulator driving the expression of multiple genes, including autophagoly sosomal components. Importantly, Reactive Oxygen Species (ROS) production and control are key aspects of the physiopathological roles of the autophagolysosomal system, and may hold a key for synergistic therapeutic interventions. In this study, we reviewed our current knowledge on the biology and physiopathology of the autophagolysosomal system, and its potential for therapeutic intervention in cancer.

Chiral nanomaterials for tumor therapy: autophagy, apoptosis, and photothermal ablation

Chirality is a fundamental characteristic of natural molecules and a crucial factor in the biochemical reactions of living cells and organisms. Recently, researchers have successfully introduced chiral molecules to the surfaces of nanomaterials, creating chiral nanomaterials that exhibit an upscaling of chiral behavior from the molecular scale to the nanoscale. These chiral nanomaterials can selectively induce autophagy, apoptosis, and photothermal ablation in tumor cells based on their chirality, making them promising for application in anti-tumor therapy. However, these interesting and important phenomena have hitherto received little attention. Accordingly, we herein present a review of recent research progress in the field of chiral nanomaterials for tumor therapy along with brief looks at the mechanistic details of their actions. Finally, the current challenges and future perspectives of chiral nanomaterials in terms of maximizing their potential in tumor therapy are discussed. Thus, this review provides a helpful introduction to the design of chiral nanomaterials and will hopefully highlight the importance of chirality in tumor therapy.

Influence of enantiomeric polylysine grafted on gold nanorods on the uptake and inflammatory response of bone marrow-derived macrophages in vitro

The macrophages take significant roles in homeostasis, phagocytosis of pathogenic organisms, and modulation of host defense and inflammatory processes. In this study, the enantiomeric poly-D-lysine (PDL) and poly-L-lysine (PLL) were conjugated to gold nanorods (AuNRs) to study their influence on the polarization of macrophages. The AuNRs capped with cetyl trimethyl ammonium bromide (CTAB) (AuNRs@CTAB) exhibited larger toxicity to macrophages when their concentration was higher than 50 μg/ml, whereas the AuNRs@PDL and AuNRs@PLL showed neglectable toxicity at the same concentration compared with the control. The AuNRs@PDL and AuNRs@PLL were internalized into the macrophages with a higher value than the AuNRs@CTAB as revealed by transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) characterization. Unlike the grafted PDL/PLL on flat substrates, the AuNRs@PDL and AuNRs@PLL were not able to polarize M0 macrophages to any other phenotype after internalization as confirmed by ELISA, flow cytometry, and fluorescence microscopy analysis. Nonetheless, the expression of M1 phenotype markers was reduced after the internalization of AuNRs@PDL and AuNRs@PLL by M1 macrophages. The assays of ELISA, flow cytometry, and reactive oxygen species levels exhibited decrease in inflammation of the M1 macrophages.

Molecular Perspective of Nanoparticle Mediated Therapeutic Targeting in Breast Cancer: An Odyssey of Endoplasmic Reticulum Unfolded Protein Response (UPRER) and Beyond

Breast cancer (BC) is the second most frequent cause of death among women. Representing a complex and heterogeneous type of cancer, its occurrence is attributed by both genetic (gene mutations, e.g., BRCA1, BRCA2) and non-genetic (race, ethnicity, etc.) risk factors. The effectiveness of available treatment regimens (small molecules, cytotoxic agents, and inhibitors) decreased due to their poor penetration across biological barriers, limited targeting, and rapid body clearance along with their effect on normal resident cells of bone marrow, gastrointestinal tract, and hair follicles. This significantly reduced their clinical outcomes, which led to an unprecedented increase in the number of cases worldwide. Nanomedicine, a nano-formulation of therapeutics, emerged as a versatile delivering module for employment in achieving the effective and target specific delivery of pharmaceutical payloads. Adoption of nanotechnological approaches in delivering therapeutic molecules to target cells ensures not only reduced immune response and toxicity, but increases the stability of therapeutic entities in the systemic circulation that averts their degradation and as such increased extravasations and accumulation via enhanced permeation and the retention (EPR) effect in target tissues. Additionally, nanoparticle (NP)-induced ER stress, which enhances apoptosis and autophagy, has been utilized as a combative strategy in the treatment of cancerous cells. As nanoparticles-based avenues have been capitalized to achieve better efficacy of the new genera of therapeutics with enhanced specificity and safety, the present study is aimed at providing the fundamentals of BC, nanotechnological modules (organic, inorganic, and hybrid) employed in delivering different therapeutic molecules, and mechanistic insights of nano-ER stress induced apoptosis and autophagy with a perspective of exploring this avenue for use in the nano-toxicological studies. Furthermore, the current scenario of USA FDA approved nano-formulations and the future perspective of nanotechnological based interventions to overcome the existing challenges are also discussed.

l-cysteine-modified chiral gold nanoparticles promote periodontal tissue regeneration

Gold nanoparticles (AuNPs) with surface-anchored molecules present tremendous potential in tissue regeneration. However, little is known about chiral-modified AuNPs. In this study, we successfully prepared L/D-cysteine-anchored AuNPs (L/D-Cys-AuNPs) and studied the effects of chiral-modified AuNPs on osteogenic differentiation and autophagy of human periodontal ligament cells (hPDLCs) and periodontal tissue regeneration. In vitro, more L-Cys-AuNPs than D-Cys-AuNPs tend to internalize in hPDLCs. L-Cys-AuNPs also significantly increased the expression of alkaline phosphatase, collagen type 1, osteocalcin, runt-related transcription factor 2, and microtubule-associated protein light chain 3 II and decreased the expression of sequestosome 1 in hPDLCs compared to the expression levels in the hPDLCs treated by D-Cys-AuNPs. In vivo tests in a rat periodontal-defect model showed that L-Cys-AuNPs had the greatest effect on periodontal-tissue regeneration. The activation of autophagy in L-Cys-AuNP-treated hPDLCs may be responsible for the cell differentiation and tissue regeneration. Therefore, compared to D-Cys-AuNPs, L-Cys-AuNPs show a better performance in cellular internalization, regulation of autophagy, cell osteogenic differentiation, and periodontal tissue regeneration. This demonstrates the immense potential of L-Cys-AuNPs for periodontal regeneration and provides a new insight into chirally modified bioactive nanomaterials.

•

L/D-Cys-AuNPs exert a chirality-dependent effect on hPDLCs.

•

L-Cys-AuNPs efficiently induced osteogenic differentiation in hPDLCs.

•

L-Cys-AuNPs significantly improved periodontal tissue regeneration.

Differential Interactions of Chiral Nanocapsules with DNA

(1) Background: Chiral nanoparticular systems have recently emerged as a compelling platform for investigating stereospecific behavior at the nanoscopic level. We describe chiroselective supramolecular interactions that occur between DNA oligonucleotides and chiral polyurea nanocapsules. (2) Methods: We employ interfacial polyaddition reactions between toluene 2,4-diisocyanate and lysine enantiomers that occur in volatile oil-in-water nanoemulsions to synthesize hollow, solvent-free capsules with average sizes of approximately 300 nm and neutral surface potential. (3) Results: The resultant nanocapsules exhibit chiroptical activity and interact differentially with single stranded DNA oligonucleotides despite the lack of surface charge and, thus, the absence of significant electrostatic interactions. Preferential binding of DNA on D-polyurea nanocapsules compared to their L-counterparts is demonstrated by a fourfold increase in capsule size, a 50% higher rise in the absolute value of negative zeta potential (ζ-potential), and a three times lower free DNA concentration after equilibration with the excess of DNA. (4) Conclusions: We infer that the chirality of the novel polymeric nanocapsules affects their supramolecular interactions with DNA, possibly through modification of the surface morphology. These interactions can be exploited when developing carriers for gene therapy and theranostics. The resultant constructs are expected to be highly biocompatible due to their neutral potential and biodegradability of polyurea shells.

Near-infrared optically active Cu2-xS nanocrystals: sacrificial template-ligand exchange integration fabrication and chirality dependent autophagy effects

We herein report a (sacrificial template-ligand exchange) integration strategy to fabricate near-infrared optically active Cu_2-xS nanocrystals (NCs) and further investigate their interactions with cells, autophagy-induced tumor cell death, and photothermal ablation application potential. Starting from oleic acid capped Cu@Cu_2-xO NCs, water-soluble and chiral d- and l-cysteine modified Cu_2-xS (denoted as d-Cu_2-xS and l-Cu_2-xS, respectively) NCs have been reliably obtained by ligand exchange (from oleic acid to cysteine) accompanied by the core chemical transformation (from Cu@Cu_2-xO to Cu_2-xS). The resulting two enantiomeric Cu_2-xS NCs have almost identical physicochemical properties including size, morphology, chemical composition, extinction band, peroxidase mimicking activity, and photothermal stability. The only exception is that the d- and l-Cu_2-xS NCs exhibit mirror symmetric circular dichroism signals ranging from the ultraviolet to near-infrared region. The cellular uptake of the d-Cu_2-xS NCs is about three times higher than that of their enantiomeric counterparts, which is likely attributed to their higher affinity with the cytomembranes of tumor cells (HepG2 and HeLa cells). As a result, a more prominent cellular autophagy proceeds due to the more significant production of highly reactive oxygen species. Then, the ablation of cells can be further enhanced by photothermal effects of the Cu_2-xS NCs. Meanwhile, for normal cells, due to very limited cellular uptake effects, little cytotoxicity has been observed for both d- and l-Cu_2-xS NCs.

Targeting non-apoptotic cell death in cancer treatment by nanomaterials: Recent advances and future outlook

Many tumors develop resistance to most of the apoptosis-based cancer therapies. In this sense targeting non-apoptotic forms of cell death including necroptosis, autophagy and ferroptosis may have therapeutic benefits in apoptosis-defective cancer cells. Nanomaterials have shown great advantages in cancer treatment owing to their unique characteristics. Besides, the capability of nanomaterials to induce different forms of cell death has gained widespread attention in cancer treatment. Reports in this field reflect the therapeutic potential of necroptotic cell death induced by nanomaterials in cancer. Also, autophagic cell death induced by nanomaterials alone and as a part of chemo-, radio- and photothermal therapy holds great promise as anticancer therapeutic option. Besides, ferroptosis induction by iron-based nanomaterials in drug delivery, immunotherapy, hyperthermia and imaging systems shows promising results in malignancies. Hence, this review is devoted to the latest efforts and the challenges in this field of research and its clinical merits.

Development of pharmaceutically scalable inhaled anti-cancer nanotherapy - Repurposing amodiaquine for non-small cell lung cancer (NSCLC)

New drug and dosage form development faces significant challenges, especially in oncology, due to longer development cycle and associated scale-up complexities. Repurposing of existing drugs with potential anti-cancer activity into new therapeutic regimens provides a feasible alternative. In this project, amodiaquine (AQ), an anti-malarial drug, has been explored for its anti-cancer efficacy through formulating inhalable nanoparticulate systems using high-pressure homogenization (HPH) with scale-up feasibility and high reproducibility. A 3² multifactorial design was employed to better understand critical processes (probe homogenization speed while formulating coarse emulsion) and formulation parameters (concentration of cationic polymer in external aqueous phase) so as to ensure product quality with improved anticancer efficacy in non-small cell lung cancer (NSCLC). Optimized AQ loaded nanoparticles (AQ NP) were evaluated for physicochemical properties, stability profile, in-vitro aerosol deposition behavior, cytotoxic potential against NSCLC cells in-vitro and in 3D simulated tumor spheroid model. The highest probe homogenization speed (25,000 rpm) resulted in lower particle size. Incorporation of cationic polymer, polyethylenimine (0.5% w/v) resulted in high drug loading efficiencies at optimal drug quantity of 5 mg. Formulated nanoparticles (liquid state) exhibited an aerodynamic diameter of 4.7 ± 0.1 μm and fine particle fraction of 81.0 ± 9.1%, indicating drug deposition in the respirable airways. Cytotoxicity studies in different NSCLC cell lines revealed significant reduction in IC₅₀ values with AQ-loaded nanoparticles compared to plain drug, along with significant cell migration inhibition (scratch assay) and reduced % colony growth (clonogenic assay) in A549 cells with AQ NP. Moreover, 3D simulated spheroid studies revealed efficacy of nanoparticles in penetration to tumor core, and growth inhibition. AQ's autophagy inhibition ability significantly increased (increased LC3B-II levels) with nanoparticle encapsulation, along with moderate improvement in apoptosis induction (Caspase-3 levels). No impact was observed on HUVEC angiogenesis suggesting alternative anticancer mechanisms. To conclude, amodiaquine can be a promising candidate for repurposing to treat NSCLC while delivering inhalable nanoparticles developed using a scalable HPH process. Despite the involvement of complex parameters, application of DoE has simplified the process of product and process optimization.

Chirality-Driven Transportation and Oxidation Prevention by Chiral Selenium Nanoparticles

The chirality of nanoparticles directly influences their transport and biological effects under physiological conditions, but the details of this phenomenon have rarely been explored. Herein, chiral GSH-anchored selenium nanoparticles (G@SeNPs) are fabricated to investigate the effect of their chirality on their transport and antioxidant activity. G@SeNPs modified with different enantiomers show opposite handedness with a tunable circular dichroism signal. Noninvasive positron emission tomography imaging clearly reveals that 64 Cu-labeled l-G@SeNPs experience distinctly different transport among the major organs from that of their d-and dl-counterparts, demonstrating that the chirality of the G@SeNPs influences the biodistribution and kinetics. Taking advantage of the strong homologous cell adhesion and uptake, l-G@SeNPs have been shown here to effectively prevent oxidation damage caused by palmitic acid in insulinoma cells.

Silver nanoparticles regulate autophagy through lysosome injury and cell hypoxia in prostate cancer cells

With the rapid development of nanotechnology, nanomaterials are now being used for cancer treatment. Although studies on the application of silver nanoparticles in cancer treatment are burgeoning, few studies have investigated the toxicology mechanisms of autophagy in cancer cells under exposure to sublethal silver nanoparticles. Here, we clarified the distinct mechanisms of silver nanoparticles for the regulation of autophagy in prostate cancer PC-3 cells under sublethal exposure. Silver nanoparticle treatment caused lysosome injury, including the decline of lysosomal membrane integrity, decrease of lysosomal quantity, and attenuation of lysosomal protease activity, which resulted in blockage of autophagic flux. In addition, sublethal silver nanoparticle exposure activated AMP-activated protein kinase/mammalian target of rapamycin-dependent signaling pathway to modulate autophagy, which resulted from silver nanoparticles-induced cell hypoxia and energy deficiency. Taken together, the results show that silver nanoparticles could regulate autophagy via lysosome injury and cell hypoxia in PC-3 cells under sublethal dose exposure. This study will provide an experimental basis for the cancer therapy of nanomaterials.

Chiral Supraparticles for Controllable Nanomedicine

Chirality is ubiquitous in nature and hard-wired into every biological system. Despite the prevalence of chirality in biological systems, controlling biomaterial chirality to influence interactions with cells has only recently been explored. Chiral-engineered supraparticles (SPs) that interact differentially with cells and proteins depending on their handedness are presented. SPs coordinated with d-chirality demonstrate greater than threefold enhanced cell membrane penetration in breast, cervical, and multiple myeloma cancer cells. Quartz crystal microbalance with dissipation and isothermal titration calorimetry measurements reveal the mechanism of these chiral-specific interactions. Thermodynamically, d-SPs show more stable adhesion to lipid layers composed of phospholipids and cholesterol compared to l-SPs. In vivo, d-SPs exhibit superior stability and longer biological half-lives likely due to opposite chirality and thus protection from endogenous proteins including proteases. This work shows that incorporating d-chirality into nanosystems enhances uptake by cancer cells and prolonged in vivo stability in circulation, providing support for the importance of chirality in biomaterials. Thus, chiral nanosystems may have the potential to provide a new level of control for drug delivery systems, tumor detection markers, biosensors, and other biomaterial-based devices.

Stereospecific interactions between chiral inorganic nanomaterials and biological systems

Chirality is ubiquitous in nature and plays mysterious and essential roles in maintaining key biological and physiological processes.

Effect of Chirality on Cell Spreading and Differentiation: From Chiral Molecules to Chiral Self-Assembly

The influence of chirality on cell behavior is closely related with relevant biological events; however, many recent studies only focus on the apparent chiral influence of supramolecular nanofibers and ignore the respective effects of molecular chirality and supramolecular chirality in biological processes. Herein, the inherent molecular and supramolecular chiral effects on cell spreading and differentiation are studied. Left-handed nanofibers (referring to supramolecular chirality) assembled from l-amino acid derivatives can enhance cell spreading and proliferation compared to flat l-surfaces (referring to molecular chirality). However, compared to the d-surfaces (referring to molecular chirality), right-handed nanofibers (referring to supramolecular chirality) derived from d-amino acid suppress cell spreading and proliferation, overturning the conventional view that a fibrous morphology generally enhances cell adhesion. The results directly suggest that the amplification of chirality from chiral molecules to chiral assemblies significantly enhances the effect on regulated cell behavior by supramolecular helical handedness. Moreover, cell differentiation is found to be chirality dependent. It suggests that both the l-amino acid derivatives and the left-handed fibers facilitate osteogenic differentiation. This study provides useful insight into understanding the origin of chiral expression from the molecular to the macroscopic level in nature.

Targeting autophagy using metallic nanoparticles: a promising strategy for cancer treatment

Despite the extensive genetic and phenotypic variations present in the different tumors, they frequently share common metabolic alterations, such as autophagy. Autophagy is a self-degradative process in response to stresses by which damaged macromolecules and organelles are targeted by autophagic vesicles to lysosomes and then eliminated. It is known that autophagy dysfunctions can promote tumorigenesis and cancer development, but, interestingly, its overstimulation by cytotoxic drugs may also induce cell death and chemosensitivity. For this reason, the possibility to modulate autophagy may represent a valid therapeutic approach to treat different types of cancers and a variety of clinical trials, using autophagy modulators, are currently employed. On the other hand, recent progress in nanotechnology offers plenty of tools to fight cancer with innovative and efficient therapeutic agents by overcoming obstacles usually encountered with traditional drugs. Interestingly, nanomaterials can modulate autophagy and have been exploited as therapeutic agents against cancer. In this article, we summarize the most recent advances in the application of metallic nanostructures as potent modulators of autophagy process through multiple mechanisms, stressing their therapeutic implications in cancer diseases. For this reason, we believe that autophagy modulation with nanoparticle-based strategies would acquire clinical relevance in the near future, as a complementary therapy for the treatment of cancers and other diseases.

Exploiting Nanomaterial-mediated Autophagy for Cancer Therapy

Autophagy is a conserved process that is critical for sequestering and degrading proteins, damaged or aged organelles, and for maintaining cellular homeostasis under stress conditions. Despite its dichotomous role in health and diseases, autophagy usually promotes growth and progression of advanced cancers. In this context, clinical trials using chloroquine and hydroxychloroquine as autophagy inhibitors have suggested that autophagy inhibition is a promising approach for treating advanced malignancies and/or overcoming drug resistance of small molecule therapeutics (i.e., chemotherapy and molecularly targeted therapy). Efficient delivery of autophagy inhibitors may further enhance the therapeutic effect, reduce systemic toxicity, and prevent drug resistance. As such, nanocarriers-based drug delivery systems have several distinct advantages over free autophagy inhibitors that include increased circulation of the drugs, reduced off-target systemic toxicity, increased drug delivery efficiency, and increased solubility and stability of the encapsulated drugs. With their versatile drug encapsulation and surface-functionalization capabilities, nanocarriers can be engineered to deliver autophagy inhibitors to tumor sites in a context-specific and/or tissue-specific manner. This review focuses on the role of nanomaterials utilizing autophagy inhibitors for cancer therapy, with a focus on their applications in different cancer types.