Ferrocene-Modified Phospholipid: An Innovative Precursor for Redox-Triggered Drug Delivery Vesicles Selective to Cancer Cells

Enhanced wound healing via ROS-triggered release of ascorbyl tetraisopalmitate loaded in ferrocene-based polymer nanoparticles

Ascorbyl tetraisopalmitate (AT), a vitamin C derivative, exhibits better stability and transdermal absorption than vitamin C and shows potential for skin whitening and wound healing. However, their low water solubility and specific storage requirements limit their application. To overcome these limitations, in this study, we aimed to develop AT-loaded ferrocene polymer nanoparticles (AT@FNPs) using biocompatible amphiphilic polymers. The nanoprecipitated nanoparticles exhibited enhanced AT stability, loading efficiency, and controlled release in reactive oxygen species (ROS)-rich wound environments. Moreover, the ROS ROS-trigger of AT@FNPs facilitated targeted drug release and ROS scavenging, thereby enhancing the antioxidant activity. The release of AT from the AT@FNPs in wounds promoted cell proliferation and accelerated wound closure in a mouse model. Overall, our findings highlight the potential of the developed ROS-triggered AT@FNPs as smart drug delivery systems for wound healing and skin treatment.

Photoresponsive prodrug-based liposomes for controllable release of the anticancer drug chlorambucil

The on-demand delivery and release of chemotherapeutic drugs have attracted great attention, among which photoresponsive prodrug systems have shown specific advantages for effective cancer treatment due to their spatiotemporal control, non-invasive nature and easy operation. Unlike the traditional strategy of physical encapsulation of drugs in liposomes, we herein report a biomimetic and photoresponsive drug delivery system (DDS) based on a lipid prodrug liposomal formulation (LNC), which combines the features of the prodrug and nanomedicines, and can realize photocontrollable release of anticancer drugs. The lipid prodrug comprises three functional moieties: a single-arm phospholipid (Lyso PC), an o-nitrobenzyl alcohol (NB) and chlorambucil (CBL). Before irradiation, LNC formed liposomal assemblies in water with an average size of about 200 nm, and upon light irradiation, the efficient photocleavage reaction of NB facilitated the disintegration of liposomal assemblies and the release of drug CBL. Photolysis analysis showed that LNC exhibited accurate and controllable drug release in response to UV 365 nm irradiation. Cell viability assays showed that LNC liposomes demonstrated very low cytotoxicity in the dark and high cellular toxicity upon light irradiation, with toxicity even higher than free CBL. Our results suggest that our photoresponsive lipid prodrug represents a promising strategy to construct controlled DDS for cancer therapy.

Advances of medical nanorobots for future cancer treatments

Early detection and diagnosis of many cancers is very challenging. Late stage detection of a cancer always leads to high mortality rates. It is imperative to develop novel and more sensitive and effective diagnosis and therapeutic methods for cancer treatments. The development of new cancer treatments has become a crucial aspect of medical advancements. Nanobots, as one of the most promising applications of nanomedicines, are at the forefront of multidisciplinary research. With the progress of nanotechnology, nanobots enable the assembly and deployment of functional molecular/nanosized machines and are increasingly being utilized in cancer diagnosis and therapeutic treatment. In recent years, various practical applications of nanobots for cancer treatments have transitioned from theory to practice, from in vitro experiments to in vivo applications. In this paper, we review and analyze the recent advancements of nanobots in cancer treatments, with a particular emphasis on their key fundamental features and their applications in drug delivery, tumor sensing and diagnosis, targeted therapy, minimally invasive surgery, and other comprehensive treatments. At the same time, we discuss the challenges and the potential research opportunities for nanobots in revolutionizing cancer treatments. In the future, medical nanobots are expected to become more sophisticated and capable of performing multiple medical functions and tasks, ultimately becoming true nanosubmarines in the bloodstream.

Updates on Responsive Drug Delivery Based on Liposome Vehicles for Cancer Treatment

Liposomes are well-known nanoparticles with a non-toxic nature and the ability to incorporate both hydrophilic and hydrophobic drugs simultaneously. As modern drug delivery formulations are produced by emerging technologies, numerous advantages of liposomal drug delivery systems over conventional liposomes or free drug treatment of cancer have been reported. Recently, liposome nanocarriers have exhibited high drug loading capacity, drug protection, improved bioavailability, enhanced intercellular delivery, and better therapeutic effect because of resounding success in targeting delivery. The site targeting of smart responsive liposomes, achieved through changes in their physicochemical and morphological properties, allows for the controlled release of active compounds under certain endogenous or exogenous stimuli. In that way, the multifunctional and stimuli-responsive nanocarriers for the drug delivery of cancer therapeutics enhance the efficacy of treatment prevention and fighting over metastases, while limiting the systemic side effects on healthy tissues and organs. Since liposomes constitute promising nanocarriers for site-targeted and controlled anticancer drug release, this review focuses on the recent progress of smart liposome achievements for anticancer drug delivery applications.

Formation of Oxidation- and Acid-Sensitive Assemblies from Sterols and a Quaternary Ammonium Ferrocene Derivative: Quatsome- and Onion-like Vesicles and Extended Nanoribbons

Quatsomes are a class of nonphospholipid vesicles in which bilayers are formed from mixtures of quaternary ammonium (QA) amphiphiles and sterols. We describe the formation of oxidation and acid-sensitive quatsome-like vesicles and other bilayer assemblies from mixtures of a ferrocenylated QA amphiphile (FTDMA) and several cholesterol derivatives. The influence of the sterol and the preparation method (extrusion or probe sonication) on the stability and morphology of the resulting vesicles is explored; a variety of structures can be obtained from small (ca. 30 nm) spherical unilamellar and oligolamellar quatsome-like vesicles to large (ca. 200 nm) multilamellar onion-like vesicles to extended nanoribbons many micrometers long. FTDMA-sterol vesicles undergo drastic shifts in vesicle and membrane structure when treated with a chemical oxidant (Frémy's salt), a feature previously observed in liposomes containing FTDMA and now confirmed in nonphospholipid vesicles. Size distributions of spherical quatsome-like vesicles obtained from cryo-TEM are examined to estimate the membrane bending rigidity, and a hypothesis is presented to explain the underlying mechanism of the profound membrane alterations observed as a consequence of ferrocene oxidation.

Assembling Alkaline-Responsive Chitosan@Giant Liposomes through an Ultrasound-Integrated Microfluidic Approach

This paper presents the fabrication of an alkaline-responsive drug carrier, chitosan@giant liposome (CS-GL), by using an ultrasound-integrated microfluidic approach. On the microfluidic chip, water/oil/water droplets are first prepared and then move through an area of ultrasonic radiation to improve the regional saturation of organic solvent and accelerate its removal. At the same time, phospholipid molecules in the oil phase of the droplets are efficiently self-assembled into giant liposomes (GLs). Subsequently, microfluidic channels combined with an up-down separated structure can help in the fabrication and purification of the GLs. Due to the electrostatic interaction between the amino group of chitosan and the phosphate group of phospholipids, the GLs and chitosan are assembled into CS-GLs. The change of ζ potential after this operation indicates that chitosan is coated on the surface of GLs. The formed CS-GLs are monodispersed with a 54.1 ± 0.7 μm diameter and high drug encapsulation efficiency (∼96%), and the structural integrity can be kept without leakage of contents for more than a week in an acid medium (pH = 1.2). When this structure is placed in an aqueous solution of pH = 7.8, chitosan precipitates gradually and detaches from the GL, causing its rupture. The drug encapsulated in a single CS-GL can be rapidly released within 4 s, and 99.6% of the CS-GL carriers can complete the release within 10 min.

A general computational framework for the dynamics of single- and multi-phase vesicles and membranes

The dynamics of thin, membrane-like structures are ubiquitous in nature. They play especially important roles in cell biology. Cell membranes separate the inside of a cell from the outside, and vesicles compartmentalize proteins into functional microregions, such as the lysosome. Proteins and/or lipid molecules also aggregate and deform membranes to carry out cellular functions. For example, some viral particles can induce the membrane to invaginate and form an endocytic vesicle that pulls the virus into the cell. While the physics of membranes has been extensively studied since the pioneering work of Helfrich in the 1970's, simulating the dynamics of large scale deformations remains challenging, especially for cases where the membrane composition is spatially heterogeneous. Here, we develop a general computational framework to simulate the overdamped dynamics of membranes and vesicles. We start by considering a membrane with an energy that is a generalized functional of the shape invariants and also includes line discontinuities that arise due to phase boundaries. Using this energy, we derive the internal restoring forces and construct a level set-based algorithm that can stably simulate the large-scale dynamics of these generalized membranes, including scenarios that lead to membrane fission. This method is applied to solve for shapes of single-phase vesicles using a range of reduced volumes, reduced area differences, and preferred curvatures. Our results match well the experimentally measured shapes of corresponding vesicles. The method is then applied to explore the dynamics of multiphase vesicles, predicting equilibrium shapes and conditions that lead to fission near phase boundaries.

Demolish and Rebuild: Controlling Lipid Self-Assembly toward Triggered Release and Artificial Cells

The ability to modulate the structures of lipid membranes, predicated on our nuanced understanding of the properties that drive and alter lipid self-assembly, has opened up many exciting biological applications. In this Perspective, we focus on two endeavors in which the same principles are invoked to achieve completely opposite results. On one hand, controlled liposome decomposition enables triggered release of encapsulated cargo through the development of synthetic lipid switches that perturb lipid packing in the presence of disease-associated stimuli. In particular, recent approaches have utilized artificial lipid switches designed to undergo major conformational changes in response to a range of target conditions. On the other end of the spectrum, the ability to drive the in situ formation of lipid bilayer membranes from soluble precursors is an important component in the establishment of artificial cells. This work has culminated in chemoenzymatic strategies that enable lipid manufacturing from simple components. Herein, we describe recent advancements in these two unique undertakings that are linked by their reliance on common principles of lipid self-assembly.

Novel α-tocopherol-ferrocene conjugates for the specific delivery of transgenes in liver cancer cells under high serum conditions

The delivery of therapeutic genes to a specific organ has drawn significant research attention. Among the pool of various delivery vectors, cationic liposomes (non-viral) are potential candidates for delivering therapeutic genes due to their low immunogenic response. Here, we have developed novel ferrocene-conjugated cationic tocopheryl aggregates as non-viral vectors. These formulations can transfer a reporter gene (pGL3; encoded for luciferase protein) specifically to liver cancer cells (HepG2 and Huh7) instead of non-hepatic cancer cells, such as Caco-2 (human colon carcinoma) and HeLa (cervical cancer) cells. The transfection efficiency (TE) of the optimum liposomal formulation is more significant than commercially available Lipofectamine 2000 (L2K). Notably, it retains its TE under high serum conditions (up to 50% FBS). A coupled effect from conjugated ferrocene and tocopherol in the cationic liposomal formulation might be responsible for the cell-specific delivery and higher serum compatibility. Therefore, the present proposed delivery system may provide a platform for further progress in terms of developing hepatotropic gene delivery systems.

EDTA-Gradient Loading of Doxorubicin into Ferrocene-Containing Liposomes: Effect of Lipid Composition and Visualization of Triggered Release by Cryo-TEM

Efficient delivery of therapeutic compounds to their sites of action has been a ubiquitous concern throughout the history of human medicine. The tumor microenvironment offers a variety of endogenous stimuli that may be exploited by a responsive nanocarrier, including heterogeneities in redox potential. In the early stages of the design of such responsive delivery systems, it is necessary to develop a comprehensive understanding of the biophysical mechanism by which the stimulus response occurs, as well as how the response may change from the inclusion of cargo compounds. We describe the optimization of lipid compositions for liposomes containing synthetic ferrocene-appended lipids to achieve highly efficient loading of doxorubicin via an ethylenediaminetetraacetic acid (EDTA) gradient. Liposomes containing ferrocenylated phospholipid are shown to be unstable to the loading conditions, while those including a ferrocenylated alkylammonium amphiphile obtain a near-quantitative loading efficiency. Calorimetric studies demonstrate that this instability is the consequence of the relative degree of lipid hydrolysis that occurs under the acidic loading conditions. Drug-loaded liposomes of the optimized composition are studied by cryo-TEM; the presence of doxorubicin aggregates is observed inside vesicles, and doxorubicin release, as well as the changes in membrane structure resulting from oxidant treatment, is also observed by cryogenic transmission electron microscopy (cryo-TEM). These results further demonstrate the potential of ferrocene lipids in the design of redox-responsive nanocarriers and begin to explore their possible role as probes of membrane dynamics.

Stimulus-responsive liposomes for biomedical applications

Liposomes are amphipathic lipidic supramolecular aggregates that are able to encapsulate and carry molecules of both hydrophilic and hydrophobic nature. They have been widely used as in vivo drug delivery systems for some time because they offer features such as synthetic flexibility, biodegradability, biocompatibility, low immunogenicity, and negligible toxicity. In recent years, the chemical modification of liposomes has paved the way to the development of smart liposome-based drug delivery systems, which are characterized by even more tunable and disease-directed features. In this review, we highlight the different types of chemical modification introduced to date, with a particular focus on internal stimuli-responsive liposomes and prodrug activation.

Graphene quantum dot formulation for cancer imaging and redox-based drug delivery

This work develops a new multifunctional biocompatible anticancer nanoformulation to provide targeted image-guided cancer-selective therapeutics. It consists of three active covalently bound components: (1) biocompatible nitrogen-doped graphene quantum dots (GQDs) as a multifunctional delivery and imaging platform, (2) hyaluronic acid (HA) unit targeted to the CD44 receptors on a variety of cancer cells, and (3) oxidative stress-based cancer-selective ferrocene (Fc) therapeutic. The biocompatible GQD platform synthesized from glucosamine exhibits high-yield intrinsic fluorescence. It is utilized for tracking Fc-GQD-HA formulation in vitro indicating internalization enhancement in HeLa cells targeted by the HA over non-cancer HEK-293 cells not overexpressing CD44 receptor. Fc-GQD-HA, non-toxic at 1 mg/mL to HEK-293 cells, induces cytotoxic response in HeLa enhanced over time, while therapeutic ROS generation by Fc-GQD-HA is ~3 times greater than that of Fc alone. This outlines the targeted delivery, imaging, and cancer-specific treatment capabilities of the new Fc-GQD-HA formulation enabling desired cancer-focused nanotherapeutic approach.

Nanoplatforms for Targeted Stimuli-Responsive Drug Delivery: A Review of Platform Materials and Stimuli-Responsive Release and Targeting Mechanisms

To achieve the promise of stimuli-responsive drug delivery systems for the treatment of cancer, they should (1) avoid premature clearance; (2) accumulate in tumors and undergo endocytosis by cancer cells; and (3) exhibit appropriate stimuli-responsive release of the payload. It is challenging to address all of these requirements simultaneously. However, the numerous proof-of-concept studies addressing one or more of these requirements reported every year have dramatically expanded the toolbox available for the design of drug delivery systems. This review highlights recent advances in the targeting and stimuli-responsiveness of drug delivery systems. It begins with a discussion of nanocarrier types and an overview of the factors influencing nanocarrier biodistribution. On-demand release strategies and their application to each type of nanocarrier are reviewed, including both endogenous and exogenous stimuli. Recent developments in stimuli-responsive targeting strategies are also discussed. The remaining challenges and prospective solutions in the field are discussed throughout the review, which is intended to assist researchers in overcoming interdisciplinary knowledge barriers and increase the speed of development. This review presents a nanocarrier-based drug delivery systems toolbox that enables the application of techniques across platforms and inspires researchers with interdisciplinary information to boost the development of multifunctional therapeutic nanoplatforms for cancer therapy.

Stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles for drug delivery and theranostics

Liposomes represent one of the most successful nano-drug delivery systems among enormous nano-carriers. Although great progress has been made in conventional liposomes, the emerging shortcomings still impair the therapeutic index. The proposal of stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles solves the challenges that conventional liposomes are faced with, showing great potential for cancer diagnosis and therapy. Herein, we intend to overview the current progress and unique advantages of stimuli-responsive PDCs-based nanovesicles. First, the challenges of conventional liposomes and the development of PDCs-based nanovesicles are summarized. Next, the stimuli-responsive elements used in current stimuli-responsive PDCs-based nanovesicles are outlined. Then, the unique superiorities of stimuli-responsive PDCs-based nanovesicles for drug delivery and theranostics are highlighted in detail. Finally, the future opportunities and challenges of stimuli-responsive PDCs-based nanovesicles for clinical translation are put forward.

Protein Transport Studied by a Model Asymmetric Membrane Army Arranged in a Dimple Chip

Reconstituted model membrane systems are powerful platforms to tackle interesting problems existing in membrane biology. One of the barriers to efficient drug delivery, as therapeutics to disease, is the physical membrane barrier of the cell. Small molecule can typically diffuse through the membrane; however, biomolecules such as proteins or nucleic acids cannot passively diffuse the bilayer and thus much research has been geared to engineering protein and/or nucleic acids delivery methods. One delivery method uses cell penetrating peptides (CPPs). In this chapter, we introduce the model "membrane army" arranged in dimple chip to study the delivery of β-galactosidase by a CPP known as Pep-1. This method uses droplet interface bilayer technology (DIB). It accelerates the speed to screen through the working conditions in CPP-assisted protein translocations because each chip provides dimples that can accommodate 36 pairs of droplets or 18 model bilayers. We will use one of the successful translocation conditions of β-galactosidase delivery as the example to illustrate how the model "membrane army" is built and utilized.

Microfluidic production and characterization of biofunctionalized giant unilamellar vesicles for targeted intracellular cargo delivery

Lipid-based vesicles have found widespread applications in the life sciences, allowing for fundamental insights into membrane-based processes in cell biology and as carrier systems for drug delivery purposes. So far, mostly small unilamellar vesicles (SUVs) with diameters of ~100 nm have been applied as carrier systems for biomedical applications. Despite this progress, several systematic limitations have arisen due to SUV dimensions, e.g., the size and total amount of applicable cargo is limited. Giant unilamellar vesicles (GUVs) might offer a pragmatic alternative for efficient cargo delivery. However, due to the lack of reliable high-throughput production technologies for GUV-carrier systems, only little is known about their interaction with cells. Here we present a microfluidic-based mechanical droplet-splitting pipeline for the production of carrier-GUVs with diameters of ~2 μm. The technology developed allows for highly efficient cargo loading and unprecedented control over the biological and physicochemical properties of GUV membranes. By generating differently charged (between -31 and + 28 mV), bioligand-conjugated (e.g. with E-cadherin, NrCam and antibodies) and PEG-conjugated GUVs, we performed a detailed investigation of attractive and repulsive GUV-cell interactions. Fine-tuning of these interactions allowed for targeted cellular GUV delivery. Moreover, we evaluated strategies for intracellular GUV cargo release by lysosomal escape mediated by the pH sensitive lipid DOBAQ, enabling cytoplasmic transmission. The presented GUV delivery technology and the systematic characterization of associated GUV-cell interactions could provide a means for more efficient drug administration and will pave the way for hitherto impossible approaches towards a targeted delivery of advanced cargo such as microparticles, viruses or macromolecular DNA-robots.

Synthesis, characterization, and anticancer activity of folate γ-ferrocenyl conjugates

Novel folate γ-ferrocene conjugates were synthesized through a regiospecific route, and showed selectivity and enhanced cytotoxicity against Frα-positive malignant cells.

Recent advances in metallopolymer-based drug delivery systems

Metallopolymers (MPs) or metal-containing polymers have shown great potential as new drug delivery systems (DDSs) due to their unique properties, including universal architectures, composition, properties and surface chemistry. Over the past few decades, the exponential growth of many new classes of MPs that deal with these issues has been demonstrated. This review presents and assesses the recent advances and challenges associated with using MPs as DDSs. Among the most widely used MPs for these purposes, metal complexes based on synthetic and natural polymers, coordination polymers, metal-organic frameworks, and metallodendrimers are distinguished. Particular attention is paid to the stimulus- and multistimuli-responsive metallopolymer-based DDSs. Of considerable interest is the use of MPs for combination therapy and multimodal systems. Finally, the problems and future prospects of using metallopolymer-based DDSs are outlined. The bibliography includes articles published over the past five years.

Breast Cancer Targeted Treatment Strategies: Promising Nanocarrier Approaches

Breast cancer is the second most common cancer that causes death among women worldwide. Incidence of breast cancer is increasing worldwide, and the age at which breast cancer develops has shifted from 50- 70 years to 30-40 years. Chemotherapy is the most commonly used effective treatment strategy to combat breast cancer. However, one of the major drawbacks is low selective site-specificity and the consequent toxic insult to normal healthy cells. The nanocarrier system is consistently utilised to minimise the various limitations involved in the conventional treatment of breast cancer. The nanocarrier based targeted drug delivery system provides better bioavailability, prolonged circulation with an effective accumulation of drugs at the tumour site either by active or passive drug targeting. Active targeting has been achieved by receptor/protein anchoring and externally guided magnetic nanocarriers, whereas passive targeting accomplished by employing the access to the tunnel via leaky tumour vasculature, utilising the tumour microenvironment, because the nanocarrier systems can reduce the toxicity to normal cells. As of now a few nanocarrier systems have been approved by FDA, and various nanoformulations are in the pipeline at the preclinical and clinical development for targeting breast cancer; among them, polymeric micelles, microemulsions, magnetic microemulsions, liposomes, dendrimers, carbon nanotubes, and magnetic Nanoparticles (NPs) are the most common. The current review highlights the active and passive targeting potential of nanocarriers in breast cancer and discusses their role in targeting breast cancer without affecting normal healthy cells.

Thioether Phosphatidylcholine Liposomes: A Novel ROS-Responsive Platform for Drug Delivery

Liposomes are the most valuable nanocarriers in clinical use because of their biocompatibility, biodegradation, and effective encapsulation of hydrophilic or hydrophobic drugs. However, their applications are limited by the structure and functions of the most common phospholipids used as the main component of the liposomes. In this work, novel series of thioether phosphatidylcholines (S-PCs) and S-PC-based liposomes (S-LPs) were developed for reactive oxygen species (ROS)-responsive drug release. First of all, S-PCs with different chain lengths were synthesized by a combination of click reaction and heterogeneous esterification. Differential scanning calorimetry studies indicated that S-PCs had different phase transition temperatures depending on their chain lengths. Their critical aggregation concentrations were measured by the fluorescence probe technique indicating the self-assembly ability. After that, S-PC-based stealth liposomes (S-LPs) containing DSPE-PEG₂₀₀₀ and cholesterol were prepared via a classic thin-film method. Doxorubicin (DOX) as a model drug was loaded in the stealth liposomes (DOX/S-LPs) by using the ammonium sulfate gradient method with high encapsulation efficiency. DOX/S-LPs were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and cryogenic TEM, confirming their spherical structure with the bilayer thickness of about 4 nm. The ROS sensitivity of S-PCs and S-LPs was carefully evaluated in the presence of H₂O₂ by means of mass spectrometry, DLS, TEM, and ultraviolet spectroscopy and release study. The results indicated the significant structural change of S-LPs after H₂O₂ treatment, which demonstrated that S-LPs possessed an efficient ROS-triggered disintegration because of thioether oxidation of S-PCs. Finally, in vitro and in vivo anticancer efficiency assays revealed the improved drug potency of DOX/S-LPs, which can be attributed to ROS-triggered destruction of S-LPs after the uptake by tumor cells followed by rapid release of DOX. All together, as alternatives of traditional phosphatidylcholines, S-PC-based stealth liposomes are promising ROS-responsive carriers for the controlled delivery of drugs.

Preparation and Properties of Semi-Self-Assembled Lipopeptide Vesicles

Novel lipopeptide vesicles are prepared from self-assembled nanomembranes through an extrusion method. The size of vesicles can be controlled by the pore diameter of the extrusion filter. The vesicles are rather stable because hydrogen bonds exist among the peptide headgroups. When doxorubicin hydrochloride (DOX·HCl) is encapsulated in the vesicles, it could be released sustainably, and its side effect would also be reduced due to encapsulation. The leakage rate of DOX·HCl depends on the pH via charge regulation. As drug carriers, lipopeptide vesicles have been proved to have nontoxicity to normal cells. A magnetic surfactant CH₃(CH₂)₁₄CH₂N(CH₃)₃⁺ [FeCl₃Br]^- (CTAFe) was mixed with lipopeptide to modify the vesicles. Also, the results demonstrated that the vesicles is endowed with magnetic property after the addition of CTAFe. We believe that the strategy of lipopeptide vesicle preparation would enrich the drug carrier family and expand the application of lipopeptide materials.

Toll-Like Receptors and Relevant Emerging Therapeutics with Reference to Delivery Methods

The built-in innate immunity in the human body combats various diseases and their causative agents. One of the components of this system is Toll-like receptors (TLRs), which recognize structurally conserved molecules derived from microbes and/or endogenous molecules. Nonetheless, under certain conditions, these TLRs become hypofunctional or hyperfunctional, thus leading to a disease-like condition because their normal activity is compromised. In this regard, various small-molecule drugs and recombinant therapeutic proteins have been developed to treat the relevant diseases, such as rheumatoid arthritis, psoriatic arthritis, Crohn’s disease, systemic lupus erythematosus, and allergy. Some drugs for these diseases have been clinically approved; however, their efficacy can be enhanced by conventional or targeted drug delivery systems. Certain delivery vehicles such as liposomes, hydrogels, nanoparticles, dendrimers, or cyclodextrins can be employed to enhance the targeted drug delivery. This review summarizes the TLR signaling pathway, associated diseases and their treatments, and the ways to efficiently deliver the drugs to a target site.

Redox-Triggered Disassembly of Nanosized Liposomes Containing Ferrocene-Appended Amphiphiles

We report a redox-responsive liposomal system capable of oxidatively triggered disassembly. We describe the synthesis, electrochemical characterization, and incorporation into vesicles of an alternative redox lipid with significantly improved synthetic efficiency and scalability compared to a ferrocene-appended phospholipid previously employed by our group in giant vesicles. The redox-triggered disassembly of both redox lipids is examined in nanosized liposomes as well as the influence of cholesterol mole fraction on liposome disassembly and suitability of various chemical oxidants for  in vitro disassembly experiments. Electronic structure density functional theory calculations of membrane-embedded ferrocenes are provided to characterize the role of charge redistribution in the initial stages of the disassembly process.

Modification of fliposomes with a polycation can enhance the control of pH-induced release

PURPOSE

Nowadays, the development of stimuli-sensitive nanocontainers for targeted drug delivery is of great value. Encapsulation of a drug in a pH-sensitive liposomal container not only provides protective and transport functions, but also helps to create a system with a controlled release mechanism.

METHODS

In this study, we investigated the influence of a cationic polypeptide on the pH-induced release of anticancer drug doxorubicin (DXR) from the anionic fliposomes - liposomes consisting of a neutral lipid, an anionic lipid (prone to interact with a polycation), and a lipid trigger (imparting the pH-sensitivity).

RESULTS

First, we showed the possibility to control the pH-induced release by the simple modification of the anionic fliposomes with linear polylysine. Second, we optimized the fliposomal composition such that the obtained fliposomes responded to the pH changes only when complexed with the polycation ("turning on" the release). Finally, pH-induced release from the polylysine-modified anionic fliposomes was tested on an anticancer drug DXR.

CONCLUSION

We have succeeded in developing "smart" stimuli-sensitive nanocontainers capable of tunable controlled release of a drug. Moreover, based on the data on release of a low molecular salt, one can predict the release profile of DXR.

Stimuli-responsive nanoscale drug delivery systems for cancer therapy

Currently, with the rapid development of nanotechnology, novel drug delivery systems (DDSs) have made rapid progress, in which nanocarriers play an important role in the tumour treatment. In view of the conventional chemotherapeutic drugs with many restrictions such as nonspecific systemic toxicity, short half-life and low concentration in the tumour sites, stimuli-responsive DDSs can deliver anti-tumour drugs targeting to the specific sites of tumours. Owing to precise stimuli response, stimuli-responsive DDSs can control drug release, so as to improve the curative effects, reduce the damage of normal tissues and organs, and decrease the side effects of traditional anticancer drugs. At present, according to the physicochemical properties and structures of nanomaterials, they can be divided into three categories: (1) endogenous stimuli-responsive materials, including pH, enzyme and redox responsive materials; (2) exogenous stimuli-responsive materials, such as temperature, light, ultrasound and magnetic field responsive materials; (3) multi-stimuli responsive materials. This review mainly focuses on the researches and developments of these novel stimuli-responsive DDSs based on above-mentioned nanomaterials and their clinical applications.

Ferrocene-containing amphiphilic polynorbornenes as biocompatible drug carriers

Ferrocene-containing diblock and random polynorbornene-based copolymers were synthesized by ROMP and used as biocompatible drug carrier micelles.

A strategic approach to the synthesis of ferrocene appended chalcone linked triazole allied organosilatranes: Antibacterial, antifungal, antiparasitic and antioxidant studies

A series of ferrocene appended chalcone allied triazole coupled organosilatranes (FCTSa 7-FCTSa 12) were synthesised with the aim of amalgamating the pharmacological action of the constituting moieties into a single molecular scaffold. All the synthesised silatranes were well characterized by various spectroscopic techniques like IR, ¹H NMR, ¹³C NMR and elemental analysis. Organosilatranes were then evaluated for their biological alacrity against bacterial and fungal strains compared with the standard drugs Rifampicin and Amphotericin B respectively. The ferrocene conjugates were found to be only moderately effective against the tested microbes. However, the organosilatranes conceded excellent efficacy against parasite G. lamblia with FCTSa 11 arraying the leading results. On the other hand against another parasite T. vaginalis, FCTSa 8 has emerged as an outstanding composite. Further, Total Antioxidant Assay (TAA) with 2,2'-azino-bis-3-(ethylbenzothiazoline-6-sulphonic acid) revealed FCTSa 10 to be the best claimant for radical scavenging activity. Along these lines, introducing some different substituents in the synthesised hybrids may act as a useful strategy for increasing the biological profile of the drugs.

Overcoming the Blood-Brain Barrier: The Role of Nanomaterials in Treating Neurological Diseases

Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood-brain barrier (BBB), arguably the most tightly regulated interface in the human body, which routinely excludes most therapeutics. Advances in the engineering of nanomaterials and their application in biomedicine (i.e., nanomedicine) are enabling new strategies that have the potential to help improve our understanding and treatment of neurological diseases. Herein, the various mechanisms by which therapeutics can be delivered to the brain are examined and key challenges facing translation of this research from benchtop to bedside are highlighted. Following a contextual overview of the BBB anatomy and physiology in both healthy and diseased states, relevant therapeutic strategies for bypassing and crossing the BBB are discussed. The focus here is especially on nanomaterial-based drug delivery systems and the potential of these to overcome the biological challenges imposed by the BBB. Finally, disease-targeting strategies and clearance mechanisms are explored. The objective is to provide the diverse range of researchers active in the field (e.g., material scientists, chemists, engineers, neuroscientists, and clinicians) with an easily accessible guide to the key opportunities and challenges currently facing the nanomaterial-mediated treatment of neurological diseases.

Functional biomimetic nanoparticles for drug delivery and theranostic applications in cancer treatment

Nanotechnology has been extensively utilized in the design and development of powerful strategies for drug delivery and cancer theranostic. Nanoplatforms as a drug delivery system have many advantages such as in vivo imaging, combined drug delivery, extended circulation time, and systemic controlled release. The functional biomimetic drug delivery could be realized by incorporating stimuli-responsive (pH, temperature, redox potential, etc.) properties into the nanocarrier system, allowing them to bypass biological barriers and arrive at the targeted area. In this review, we discuss the role of internal stimuli-responsive nanocarrier system for imaging and drug delivery in cancer therapy. The development of internal stimuli-responsive nanoparticles is highlighted for precision drug delivery applications, with a particular focus on in vivo imaging, drug release performance, and therapeutic benefits.

New ferrocene modified retinoic acid with enhanced efficacy against melanoma cells via GSH depletion

Malignant melanoma is a highly lethal disease, and advanced stages of melanoma have proven to be resistant to many chemotherapeutic drugs. Cancer stem cells (CSCs) and high levels of intracellular glutathione (GSH) have been proven to play important roles in drug resistance. Retinoic acid (RA) is a promising anticancer agent, which can inhibit proliferation and induce differentiation of CSCs, but its clinical use has been limited by its water insolubility and weak cancer cell killing effect when used alone. Herein, by combining RA and ferrocene, a new type of derivative of retinoic acid (FCRA) was synthesized and then oxidized by FeCl3. The oxidized FCRA (FCRA+) was exploited as a novel anticancer agent. Compared with RA, FCRA+ not only has improved water solubility and stronger anti-cancer effect to melanoma cells through depleting intracellular GSH of the cancer cells, but also can inhibit proliferation and induce differentiation of melanoma CSCs, such as free RA. Therefore, FCRA+ has better application prospects than RA and may replace RA for clinical applications.

Stimulus-responsive liposomes as smart nanoplatforms for drug delivery applications

Liposomes are known to be promising nanoparticles (NPs) for drug delivery applications. Among different types of self-assembled NPs, liposomes stand out for their non-toxic nature, and their possession of dual hydrophilic-hydrophobic domains. Advantages of liposomes include the ability to solubilize hydrophobic drugs, the ability to incorporate different hydrophilic and lipophilic drugs at the same time, lessening the exposure of host organs to potentially toxic drugs and allowing modification of the surface by a variety of different chemical groups. This modification of the surface, or of the individual constituents, may be used to achieve two important goals. Firstly, ligands for active targeting can be attached that are recognized by cognate receptors over-expressed on the target cells of tissues. Secondly, modification can be used to impart a stimulus-responsive or "smart" character to the liposomes, whereby the cargo is released on demand only when certain internal stimuli (pH, reducing agents, specific enzymes) or external stimuli (light, magnetic field or ultrasound) are present. Here, we review the field of smart liposomes for drug delivery applications.

Recent Advances in Stimuli-Responsive Release Function Drug Delivery Systems for Tumor Treatment

Benefiting from the development of nanotechnology, drug delivery systems (DDSs) with stimuli-responsive controlled release function show great potential in clinical anti-tumor applications. By using a DDS, the harsh side effects of traditional anti-cancer drug treatments and damage to normal tissues and organs can be avoided to the greatest extent. An ideal DDS must firstly meet bio-safety standards and secondarily the efficiency-related demands of a large drug payload and controlled release function. This review highlights recent research progress on DDSs with stimuli-responsive characteristics. The first section briefly reviews the nanoscale scaffolds of DDSs, including mesoporous nanoparticles, polymers, metal-organic frameworks (MOFs), quantum dots (QDs) and carbon nanotubes (CNTs). The second section presents the main types of stimuli-responsive mechanisms and classifies these into two categories: intrinsic (pH, redox state, biomolecules) and extrinsic (temperature, light irradiation, magnetic field and ultrasound) ones. Clinical applications of DDS, future challenges and perspectives are also mentioned.