Current Principles, Challenges, and New Metrics in pH-Responsive Drug Delivery Systems for Systemic Cancer Therapy

Chemotoxic and phototoxic effects of liposomal co-delivery of green synthesized silver nanoparticles and ZnPcS4 for enhanced photodynamic therapy in MCF-7 breast cancer cells: An in vitro study

Breast cancer remains a significant challenge in oncology, despite notable advances in treatment methods. Traditional therapies such as surgery, chemotherapy, radiation, and hormonal treatments have long been used to manage breast cancer. However, often patients experience treatment failure, resulting in disease recurrence and progression. Therefore, this study explores the therapeutic potential of green-synthesized silver nanoparticles (AgNPs), using the root methanol (MeOH) extract of the African medicinal plant Dicoma anomala (D. anomala) as a reducing agent, to combat breast cancer. AgNPs were synthesized using a bottom-up approach and later modified with liposomes (Lip) loaded with the photosensitizer zinc phthalocyanine tetrasulfonate (Lip@ZnPcS4) through the thin film hydration method. Prior to in vitro cell culture studies, UV-Vis spectroscopy was used to study the in vitro drug release kinetics of nanoparticles (NPs) at pH 5.8 and 7.4 respectively. After a 24 h treatment period, MCF-7 breast cancer cells were evaluated for cell cytotoxicity using lactate dehydrogenase Cyto-Tox96® Non-Radioactive Cytotoxicity Assay Kit LDH and cell viability using the CellTiter-Glo® ATP luminescence assay kit. Cell death studies were analyzed using an inverted light microscope for morphological changes, fluorescence microscopy for reactive oxygen species (ROS) detection and Live/Dead cell viability, human p53 protein analysis using enzyme-linked immunosorbent assay (ELISA), apoptotic and anti-apoptotic protein analysis by immunofluorescence, and gene expression analysis using real-time reverse transcription polymerase chain reaction (RT-PCR) assay. The experiments were conducted in quadruplicate (n = 4), and the results were analyzed using IBM SPSS statistical software version 27, with a 95 % confidence interval. The synthesized NPs and nanocomplexes, including AgNPs, AgNPs-Lip, Lip@ZnPcS4, and AgNPs-Lip@ZnPcS4, demonstrated significant cytotoxicity and therapeutic potential against MCF-7 breast cancer cells. Notably, apoptosis was induced, primarily through the activation of the intrinsic pathway. Given the difficult prognosis associated with breast cancer, these findings highlight the promise of liposomal nanoformulations (NFs) in cancer photodynamic therapy (PDT), supporting further investigation in in vivo settings.

Understanding the interplay between pH and charges for theranostic nanomaterials

Nanotechnology has emerged as a highly promising platform for theranostics, offering dual capabilities in targeted imaging and therapy. Interactions between the nanomaterial and biological components determine the in vivo fate of these materials which makes the control of their surface properties of utmost importance. Nanoparticles with neutral or negative surface charge have a longer circulation time while positively charged nanoparticles have higher affinity to cells and better cellular uptake. This trade-off presents a key challenge in optimizing surface charge for theranostic applications. A sophisticated solution is an on-demand switch of surface charge, enabled by leveraging the distinct pH conditions at the target site. In this review, we explore the intricate relationship between pH and charge modulation, summarizing recent advances in pH-induced charge-switchable nanomaterials for theranostics over the past five years. Additionally, we discuss how these innovations enhance targeted drug delivery and imaging contrast and provide perspectives on future directions for this transformative field.

Tumor Microenvironment pH-Sensitive Peptidomimetics for Targeted Anticancer Drug Delivery

Cell-penetrating peptides (CPPs) are known for their effective intracellular transport of bioactives such as therapeutic proteins, peptides, nucleic acid, and small molecule drugs. However, the excessive cationic charges that promote their membrane permeability result in nonselective delivery and cellular toxicity. In this study, we report a decamer cell-penetrating peptidomimetic, Hkd, designed to selectively deliver anticancer drugs into tumor cells in response to the acidic microenvironment. The pH-sensitive histidine (H) imidazole side chain undergoes protonation in acidic environments, facilitating membrane permeability. The rigid cyclic dipeptide (CDP) core (kd) of Hkd has multiple hydrogen bond donor and acceptor sites, enabling selective interaction-driven cellular uptake. Pharmacokinetic studies revealed the excellent serum stability of Hkd. Cellular uptake studies of Hkd showed improved uptake at a lower pH than physiological pH. Conjugation of Hkd to the anticancer drug camptothecin (Cpt) reduced nonselective drug transport to normal cells while effectively delivering the drug into cancerous cells at the tumor microenvironment pH and retaining the therapeutic potential of the drug. The systematic design of pH-sensitive peptidomimetics offers a viable method to overcome the challenges of stability and selectivity faced by traditional highly cationic CPPs, potentially expanding the application range of this delivery system.

Rational Design of Nanozymes for Engineered Cascade Catalytic Cancer Therapy

Nanozymes have shown significant potential in cancer catalytic therapy by strategically catalyzing tumor-associated substances and metabolites into toxic reactive oxygen species (ROS) in situ, thereby inducing oxidative stress and promoting cancer cell death. However, within the complex tumor microenvironment (TME), the rational design of nanozymes and factors like activity, reaction substrates, and the TME itself significantly influence the efficiency of ROS generation. To address these limitations, recent research has focused on exploring the factors that affect activity and developing nanozyme-based cascade catalytic systems, which can trigger two or more cascade catalytic processes within tumors, thereby producing more therapeutic substances and achieving efficient and stable cancer therapy with minimal side effects. This area has shown remarkable progress. This Perspective provides a comprehensive overview of nanozymes, covering their classification and fundamentals. The regulation of nanozyme activity and efficient strategies of rational design are discussed in detail. Furthermore, representative paradigms for the successful construction of cascade catalytic systems for cancer treatment are summarized with a focus on revealing the underlying catalytic mechanisms. Finally, we address the current challenges and future prospects for the development of nanozyme-based cascade catalytic systems in biomedical applications.

Gold nanoparticle encapsulated hybrid MOF: synthesis, characterization, and co-drug delivery of 5-fluorouracil and curcumin

The unique features of Metal-Organic Frameworks (MOFs), including structural flexibility, high surface area, and variable pore size, have drawn attention in cancer therapy. However, despite advances in surface functionalization, engineering structural features, and porosity, achieving controlled release, stability, scalability, and toxicity remains a challenge. The current study reports gold nanoparticle (AuNP) encapsulated dual metal-organic frameworks (MOFs) comprising zeolitic imidazolate (ZIF8) and cobalt-imidazole (ZIF67) by a simple precipitation method for dual drug delivery applications. This combination associates the advantages of AuNPs and MOFs, creating a potent platform for cancer theranostics that combines diagnosis and treatment into one unit. The synthesized composite (AuNPs@ZIF-8/ZIF-67) is functionalized with Folic acid (FA) and loaded with the anticancer agents Curcumin (C) and 5-fluorouracil (5-FU) for co-drug delivery The synthesized composites, namely Au/ZIF8, Au/ZIF8/ZIF67/FA, Au/ZIF8/ZIF67/FA/5-FU, and Au/ZIF8/ZIF67/FA/5-FU/C were characterized using diverse analytical techniques such as FESEM, XRD, FTIR, TEM, and BET. The characterization methods showed that the hybrid MOF structure was stable and intact after AuNP encapsulation and drug loading. The dual MOF composite exhibits a better affinity for loading C and 5-FU with 60% and 40% drug loading capacity, respectively. The simultaneous drug release studies suggest that AuNPs@ZIF-8/ZIF-67 are more responsive to the acidic pH and show a higher cumulative drug release of 5FU and C at the lower value of pH 5. For further validation, the release kinetics data were fitted into the Korsmeyer-Peppas model in the current study. The observed value of n which is less than 0.5 suggests the pseudo-Fickian diffusion mechanism for drug release, demonstrating long-term release of 5FU and C from Au/ZIF8/ZIF67/FA/5-FU/C. The targeted drug delivery system is anticipated to display synergistic therapeutic efficacy from the combined effect of the two anticancer agents and the pH-responsive nature of ZIF systems.

Changes in Functional Activity of Platelets under the Influence of Submicron Particles Based on Mesoporous Silica and pH-Sensitive Polymers

In vitro and in vivo effects of mesoporous silica nanoparticles (MSN) on the functional activity of platelets were studied in experiments on white rats. MSN particles, neither uncoated nor coated with calcium alginate, induced spontaneous platelet aggregation when added to platelet-rich plasma, but significantly enhanced ADP-induced platelet aggregation. Subcutaneous administration of uncoated and calcium alginate-coated MSN resulted in increased maximum size and rate of platelet aggregate formation 1 day post-injection. In contrast, cellulose-coated MSN had no significant effect on platelet function in vitro or in vivo, suggesting their potential as carriers for targeted drug delivery.

GdVO4:Eu3+ and LaVO4:Eu3+ Nanoparticles Exacerbate Oxidative Stress in L929 Cells: Potential Implications for Cancer Therapy

The therapeutic potential of redox-active nanoscale materials as antioxidant- or reactive oxygen species (ROS)-inducing agents was intensely studied. Herein, we demonstrate that the synthesized and characterized GdVO4:Eu3+ and LaVO4:Eu3+ nanoparticles, which have been already shown to have redox-active, anti-inflammatory, antibacterial, and wound healing properties, both in vitro and in vivo, worsen oxidative stress of L929 cells triggered by hydrogen peroxide or tert-butyl hydroperoxide (tBuOOH) at the concentrations that are safe for intact L929 cells. This effect was observed upon internalization of the investigated nanosized materials and is associated with the cleavage of caspase-3 and caspase-9 without recruitment of caspase-8. Such changes in the caspase cascade indicate activation of the intrinsic caspase-9-dependent mitochondrial but not the extrinsic death, receptor-mediated, and caspase-8-dependent apoptotic pathway. The GdVO4:Eu3+ and LaVO4:Eu3+ nanoparticle-induced apoptosis of oxidatively compromised L929 cells is mediated by ROS overgeneration, Ca2+ overload, endoplasmic reticulum stress-associated JNK (c-Jun N-terminal kinase), and DNA damage-inducible transcript 3 (DDIT3). Our findings demonstrate that GdVO4:Eu3+ and LaVO4:Eu3+ nanoparticles aggravate the oxidative stress-induced damage to L929 cells, indicating that they might potentially be applied as anti-cancer agents.

Recent Progress of pH-Responsive Peptides, Polypeptides, and Their Supramolecular Assemblies for Biomedical Applications

Peptides and polypeptides feature a variety of active functional groups on their side chains (including carboxylic acid, hydroxyl, amino, and thiol groups), enabling diverse chemical modifications. This versatility makes them highly valuable in stimuli-responsive systems. Notably, pH-responsive peptides and polypeptides, due to their ability to respond to pH changes, hold significant promise for applications in cellular pathology and tumor targeting. Extensive researches have highlighted the potentials of low pH insertion peptides (pHLIPs), peptide-drug conjugates (PDCs), and antibody-drug conjugates (ADCs) in biomedicine. Peptide self-assemblies, with their structural stability, ease of regulation, excellent biocompatibility, and biodegradability, offer immense potentials in the development of novel materials and biomedical applications. We also explore specific examples of their applications in drug delivery, tumor targeting, and tissue engineering, while discussing future challenges and potential advancements in the field of pH-responsive self-assembling peptide-based biomaterials.

Drug carrier wonders: Synthetic strategies of zeolitic imidazolates frameworks (ZIFs) and their applications in drug delivery and anti-cancer activity

With the rapid advancement of nanotechnology, stimuli-responsive nanomaterials have emerged as a feasible choice for the designing of controlled drug delivery systems. Zeolitic imidazolates frameworks are a subclass of Metal-organic frameworks (MOFs) that are recognized by their excellent porosity, structural tunability and chemical modifications make them promising materials for loading targeted molecules and therapeutics agents. The biomedical industry uses these porous materials extensively as nano-carriers in drug delivery systems. These MOFs not only possess excellent targeted imaging ability but also cause the death of tumor cells drawing considerable attention in the current framework of anticancer drug delivery systems. In this review, the outline of stability, porosity, mechanism of encapsulation and release of anticancer drug have been reported extensively. In the end, we also discuss a brief outline of current challenges and future perspectives of ZIFs in the biomedical world.

Effect of functionalization on the adsorption performance of carbon nanotube as a drug delivery system for imatinib: molecular simulation study

In this study, efficiency of functionalized carbon nanotube as a potential delivery system for imatinib anti-cancer drug was investigated. Accordingly, carboxyl and hydroxyl functionalized carbon nanotube were inspected as a notable candidate for the carriage of this drug in aqueous media. For this purpose, possible interactions of imatinib with pure and functionalized carbon nanotube were considered in aqueous media. The compounds were optimized in gas phase using density functional calculations. Solvation free energies and association free energies of the optimized structures were then studied by Monte Carlo simulation and perturbation method in water environment. Outcomes of quantum mechanical calculations presented that pure and functionalized carbon nanotubes can act as imatinib drug adsorbents in gas phase. However, results of association free energy calculations in aqueous solution indicated that only carboxyl and hydroxyl functionalized carbon nanotubes could interact with imatinib. Monte Carlo simulation results revealed that electrostatic interactions play a vital role in the intermolecular interaction energies after binding of drug and nanotube in aqueous solution. Computed solvation free energies in water showed that the interactions with functionalized carbon nanotubes significantly enhance the solubility of imatinib, which could improve its in vivo bioavailability.

Bioresponsive drug delivery systems

In this review, we highlight the potential of stimuli-responsive drug delivery systems (DDSs) to revolutionize healthcare. Through examining pH, temperature, enzyme, and redox responsiveness, the presented case studies highlight the precision and enhanced therapeutic outcomes achievable with these innovative systems. Challenges, such as complex design and bio-based material optimization, underscore the complete journey from bench to bedside. Clinical strides in magnetically and temperature-responsive systems hint at a promising future for healthcare. However, overcoming issues of stability, durability, penetration depth, sensitivity, and active targeting is crucial. The future envisions theranostic systems, amalgamating targeted therapy and diagnosis, for personalized healthcare. Bio-based materials emerge as pivotal, offering a nuanced approach to complex diseases, such as cancer and diabetes, reshaping the healthcare landscape.

Hyperthermic triggers for drug delivery platforms

Electromagnetic fields can penetrate aqueous media in a homogeneous and instantaneous way, without physical contact, independently of its temperature, pressure, agitation degree and without modifying their chemical compositions nor heat and mass transfer conditions. In addition, superparamagnetic biomaterials can interact with electromagnetic fields by absorbing electromagnetic energy and transforming it in localized heat with further diffusion to surrounding media. This paper is devoted to the exploration of the potential use of hyperthermic effects resulting from the interaction between externally applied electromagnetic fields and superparamagnetic nanoparticles as a trigger for controlled drug release in soft tissue simulating materials. Gelatin based soft tissue simulating materials were prepared and doped with superparamagnetic nanoparticles. The materials were irradiated with externally applied electromagnetic fields. The effects on temperature and diffusion of a drug model in water and phosphate buffer were investigated. Significant hyperthermic effects were observed. The temperature of the soft tissue simulating material resulted increased from 35 °C to 45 °C at 2.5 °C min-1. Moreover, the release of an entrapped model drug reached 89%. The intensity of the hyperthermic effects was found to have a strong dependency on the concentration of superparamagnetic nanoparticles and the power and the pulse frequency of the electromagnetic field.