Superparamagnetic Reduction/pH/Temperature Multistimuli-Responsive Nanoparticles for Targeted and Controlled Antitumor Drug Delivery

One-Step Preparation of Thermo-Responsive Poly(N-isopropylacrylamide)-Based Block Copolymer Nanoparticles by Aqueous Photoinitiated Polymerization-Induced Self-Assembly

Poly(N-isopropylacrylamide) (PNIPAM) is an important thermo-responsive polymer that finds applications in many areas. However, the preparation of PNIPAM-based block copolymer nanoparticles with higher-order morphologies at high solids is challenging. Herein, aqueous photoinitiated polymerization-induced self-assembly (photo-PISA) of N-isopropylacrylamide (NIPAM) using an asymmetrical cross-linker is developed for one-step preparation of PNIPAM-based block copolymer nanoparticles with various morphologies (spheres, worms, and vesicles). It is demonstrated that reaction temperature has a great effect on both polymerization kinetics and morphologies of block copolymer nanoparticles. Reversible addition-fragmentation chain transfer (RAFT) reactive groups embedded inside the PNIPAM core provide a landscape for further functionalization. PNIPAM-based block copolymer nanoparticles with different surface properties are prepared by seeded photo-PISA at room temperature. Finally, these block copolymer nanoparticles are also used as additives to tune mechanical properties of hydrogels via covalent cross-linking.

Core-shell nanostructures: perspectives towards drug delivery applications

Nanosystems have shown encouraging outcomes and substantial progress in the areas of drug delivery and biomedical applications. However, the controlled and targeted delivery of drugs or genes can be limited due to their physicochemical and functional properties. In this regard, core-shell type nanoparticles are promising nanocarrier systems for controlled and targeted drug delivery applications. These functional nanoparticles are emerging as a particular class of nanosystems because of their unique advantages, including high surface area, and easy surface modification and functionalization. Such unique advantages can facilitate the use of core-shell nanoparticles for the selective mingling of two or more different functional properties in a single nanosystem to achieve the desired physicochemical properties that are essential for effective targeted drug delivery. Several types of core-shell nanoparticles, such as metallic, magnetic, silica-based, upconversion, and carbon-based core-shell nanoparticles, have been designed and developed for drug delivery applications. Keeping the scope, demand, and challenges in view, the present review explores state-of-the-art developments and advances in core-shell nanoparticle systems, the desired structure-property relationships, newly generated properties, the effects of parameter control, surface modification, and functionalization, and, last but not least, their promising applications in the fields of drug delivery, biomedical applications, and tissue engineering. This review also supports significant future research for developing multi-core and shell-based functional nanosystems to investigate nano-therapies that are needed for advanced, precise, and personalized healthcare systems.

Hybrid micelles based on Pt (IV) polymeric prodrug and TPGS for the enhanced cytotoxicity in drug-resistant lung cancer cells

Multidrug resistance (MDR) is a primary cause of failure in oncotherapy and interest is growing in the design of multi-stimuli responsive nano-carriers to synergistically deliver chemotherapeutic agents and P-gp inhibitors to reverse MDR. The hybrid micelles based on a Platinum (IV)-coordinate polymeric prodrugs and TPGS were developed to improve chemotherapy and reduce side effects. The pH/redox dual-sensitive polymers were synthesized by condensation polymerization using ortho ester monomer and diamminedichlorodisuccinatoplatinum (DSP). The hybrid micelles possessed uniform size (38 nm) and displayed good stability in various physiological conditions. In contrast, in vitro drug release profiles indicated that these micelles could be completely depolymerized under acidic and reducing environment, thereby more than 80 % cisplatin were released within 12 h at pH 5.0 plus 10 mM DTT. More importantly, a large amount of TPGS released simultaneously could effectively inhibit the function of drug efflux pumps, which significantly enhanced the cytotoxicity of cisplatin against A549/DDP cells. The growth inhibition rate of micelles on A549/DDP multicellular spheroids was 79.5 %, while that of free cisplatin was only 6.8 %. Therefore, these hybrid micelles are promising in overcoming tumor MDR and worth doing further research in vivo and extend to other therapeutic agents.

One-step dry synthesis of an iron based nano-biocomposite for controlled release of drugs

Bio-based drug carriers have gained significant importance in Control Drug Delivery Systems (CDDS). In the present work, a new iron-based magnetic nano bio-composite (nano-Fe-CNB) is developed in a one-step dry calcination process (solventless) using a seaweed-based biopolymer. The detailed analysis of the developed nano Fe-CNB is carried out using FE-SEM, HR-TEM, P-XRD, XPS, Raman spectroscopy, FTIR etc. and shows that nano-Fe-CNB consists of nanoparticles of 5–10 nm decorated on 7–8 nm thick 2-D graphitic carbon material. The impregnation of nano-Fe-CNB into the calcium alginate (CA) hydrogel beads is found to have good drug loading capacity as well as pH responsive control release behavior which is demonstrated using doxorubicin (DOX) as a model cancer drug. The drug loading experiments exhibit ∼94% loading of DOX and release shows ∼38% and ∼8% release of DOX at pH 5.4 and 7.4 respectively. The developed nano Fe-CNB facilitates strong electrostatic interactions with cationic DOX molecules at pH 7.4 and thereby restricts the release of the drug at physiological pH. However, at cancer cell pH (5.4), the interaction between the drug and nano-Fe-CNB reduces which facilitates more drug release at pH 5.4. Thus, the developed nano-biocomposite has the potential to reduce the undesired side effects associated with faster release of drugs.

Schematics for synthesis and application of magnetic nano-biocomposite for control release of DOX.

Reduction-responsive molecularly imprinted nanogels for drug delivery applications

Degradable molecularly imprinted polymers (MIPs) with affinity for S-propranolol were prepared by the copolymerization of methacrylic acid as functional monomer and a disulfide-containing cross-linker, bis(2-methacryloyloxyethyl)disulfide (DSDMA), using bulk polymerization or high dilution polymerization for nanogels synthesis. The specificity and the selectivity of DSDMA-based molecularly imprinted polymers toward S-propranolol were studied in batch binding experiments, and their binding properties were compared to a traditional ethylene glycol dimethacrylate (EDMA)-based MIP. Nanosized MIPs prepared with DSDMA as crosslinker could be degraded into lower molecular weight linear polymers by cleaving the disulfide bonds and thus reversing cross-linking using different reducing agents (NaBH4, DTT, GSH). Turbidity, viscosity, polymer size and IR-spectra were measured to study the polymer degradation. The loss of specific recognition and binding capacity of S-propranolol was also observed after MIP degradation. This phenomenon was applied to modulate the release properties of the MIP. In presence of GSH at its intracellular concentration, the S-propranolol release was higher, showing that these materials could potentially be applied as intracellular controlled drug delivery system.

Tumor-specific fluorescent Cdots-based nanotheranostics by acid-labile conjugation of doxorubicin onto reduction-cleavable Cdots-based nanoclusters

Carbon quantum dots (Cdots) have attracted more and more interests in bioimaging and tumor theranostics. However, their practical application has been limited due to the small particle size and non-tumor-specific fluorescence. Here, reduction-cleavable disulfide-linked Cdots-based nanoclusters were fabricated to conjugate doxorubicin (DOX) via an acid-labile hydrazone bond. Owing to the pH and reduction dual-stimuli responsiveness, the proposed Cdots-based nanotheranostics possessed unique tumor-specific fluorescent property and tumor-specific controlled drug release performance, indicating their promising potential for the in-situ real-time fluorescent monitoring of therapeutic response in future tumor therapy.

pH/Reduction Dual-Stimuli-Responsive Cross-Linked Micelles Based on Multi-Functional Amphiphilic Star Copolymer: Synthesis and Controlled Anti-Cancer Drug Release

Novel approach has been constructed for preparing the amphiphilic star copolymer pH/reduction stimuli-responsive cross-linked micelles (SCMs) as a smart drug delivery system for the well-controlled anti-tumor drug doxorubicin (DOX) release. The SCMs had a low CMC value of 5.3 mg/L. The blank and DOX-loaded SCMs both had a spherical shape with sizes around 100-180 nm. In addition, the good stability and well pH/reduction-sensitivity of the SCMs were determined by dynamic light scattering (DLS) as well. The SCMs owned a low release of DOX in bloodstream and normal tissues while it had a fast release in tumor higher glutathione (GSH) concentration and/or lower pH value conditions, which demonstrates their pH/reduction dual-responsiveness. Furthermore, we conducted the thermodynamic analysis to study the interactions between the DOX and polymer micelles in the DOX release process. The values of the thermodynamic parameters at pH 7.4 and at pH 5.0 conditions indicated that the DOX release was endothermic and controlled mainly by the forces of an electrostatic interaction. At pH 5.0 with 10 mM GSH condition, electrostatic interaction, chemical bond, and hydrophobic interactions contributed together on DOX release. With the low cytotoxicity of blank SCMs and well cytotoxicity of DOX-loaded SCMs, the results indicated that the SCMs could form a smart cancer microenvironment-responsive drug delivery system. The release kinetic and thermodynamic analysis offer a theoretical foundation for the interaction between drug molecules and polymer matrices, which helps provide a roadmap for the oriented design and control of anti-cancer drug release for cancer therapy.

Multi-stimuli-responsive nanomicelles fabricated using synthetic polymer polylysine conjugates for tumor microenvironment dependent drug delivery

A poly(lysine)-synthetic polymer hybrid nanomicelles were fabricated as promising platform for efficient tumor targeting and glutathione/pH/temperature-responsive anticancer drug delivery.

Pharmaceutical Applications of Iron-Oxide Magnetic Nanoparticles

Advances of nanotechnology led to the development of nanoparticulate systems with many advantages due to their unique physicochemical properties. The use of iron-oxide magnetic nanoparticles (IOMNPs) in pharmaceutical areas increased in the last few decades. This article reviews the conceptual information about iron oxides, magnetic nanoparticles, methods of IOMNP synthesis, properties useful for pharmaceutical applications, advantages and disadvantages, strategies for nanoparticle assemblies, and uses in the production of drug delivery, hyperthermia, theranostics, photodynamic therapy, and as an antimicrobial. The encapsulation, coating, or dispersion of IOMNPs with biocompatible material(s) can avoid the aggregation, biodegradation, and alterations from the original state and also enable entrapping the bioactive agent on the particle via adsorption or covalent attachment. IOMNPs show great potential for target drug delivery, improving the therapy as a consequence of a higher drug effect using lower concentrations, thus reducing side effects and toxicity. Different methodologies allow IOMNP synthesis, resulting in different structures, sizes, dispersions, and surface modifications. These advantages support their utilization in pharmaceutical applications, and getting suitable drug release control on the target tissues could be beneficial in several clinical situations, such as infections, inflammations, and cancer. However, more toxicological clinical investigations about IOMNPs are necessary.

Dual-Responsive Alginate Hydrogels for Controlled Release of Therapeutics

In this work, with the drug oxytetracycline (OTC) released, cell cytotoxicity and antimicrobial studies of dual-responsive sodium alginate and N-Isopropylacrylamide hydrogels (SA/pNIPAAm) with enclosed OTC were investigated. The molecular OTC release was explored with different acid-base conditions and temperature conditions. In order to characterize cell cytotoxicity and antimicrobial efficacy, time-dependent OTC release analysis of different acid-base conditions was performed in SA/pNIPAAm hydrogels. OTC@SA/pNIPAAm hydrogels showed excellent time-dependent antimicrobial efficacy, in which the IC50 values were 50.11 μg mL⁻¹, 34.27 μg mL⁻¹, and 22.39 μg mL⁻¹ among three consecutive days, respectively. Meanwhile, the human cells showed excellent viability at the IC50 dosage of OTC@SA/pNIPAAm (50.11 μg mL⁻¹). OTC@SA/pNIPAAm performed in this study indicated that SA/pNIPAAm may serve as drug carriers for sustainable release at a specific concentration and for being employed as substrates for decreasing drug toxicity. Besides, pH-responsive and thermos-responsive SA/pNIPAAm may lead to the better selectivity of drug release in the ideal location or site. Finally, the results demonstrate that the designed, dual-responsive, biocompatible OTC@SA/pNIPAAm hydrogels showed excellent antimicrobial efficacy and may potentially be found to have enormous applicability in the field of pharmaceutics.

Formation of enzymatic/redox-switching nanogates on mesoporous silica nanoparticles for anticancer drug delivery

In this study, we demonstrate a simple approach to developing mesoporous nanohybrids via a process of pre-loading of an anticancer drug (doxorubicin, DOX) into mesoporous silica nanoparticles (MSN), followed by assembly with a kind of naturally-derived polymer (gelatin, cleavable by matrix metalloproteinase 2 overexpressed by tumor). The gelatin shell is then in situ crosslinked by degradable N,N'-bis(acryloyl)cystamine (BAC) to form enzymatic and redox switchable nanogates on the mesoporous nanoparticles. The nanohybrids displayed pH/redox/enzymatic sensitivity in DOX release under conditions mimicking tumor microenvironments. The nanocarriers can be effectively taken up by A549 cells (a carcinomic human alveolar basal epithelial cell line), resulting in a high DOX intracellular accumulation and an improved anticancer cytotoxicity when compared with free DOX, suggesting their potential as a nanoplatform for therapeutic delivery.

Codelivery of Hydrophobic and Hydrophilic Drugs by Graphene-Decorated Magnetic Dendrimers

In this study, a nanocarrier was prepared for the codelivery of a hydrophilic drug (doxorubicin) and a hydrophobic drug (curcumin) to cancer cells. In this nanocarrier, the edges of graphene oxide sheets were decorated with a magnetic-functionalized polyamidoamine dendrimer with hydrazone groups at the end of the polymer. The edge functionalization of graphene sheets not only improved the solubility and dispersibility of graphene sheets but also imparted the magnetic properties to the nanocarrier. The resulting nanocarrier was loaded with doxorubicin through the covalent linkage and curcumin through π-π stacking. The nanocarrier showed a pH-sensitive release for both drugs, and the drug release behavior was also improved by the coimmobilization of both drugs. The cytotoxicity assay of nanocarrier showed low toxicity toward MCF-7 cell compared to unmodified graphene oxide, which was attributed to the presence of a magnetic dendrimer. Besides, the drug-loaded nanocarrier was highly toxic for cells even more than for free drugs. The cellular uptake images revealed higher drug internalization for coloaded nanocarrier than for the nanocarrier loaded with one drug alone. All of the results showed that the codelivery of curcumin and doxorubicin in the presence of the nanocarrier was more effective in chemotherapy than the nanocarrier loaded with one drug.

Photoresponsive Block Copolymer Prodrug Nanoparticles as Delivery Vehicle for Single and Dual Anticancer Drugs

In recent decades, drug delivery systems (DDSs) based on polymer nanoparticles have been explored due to their potential to deliver drugs with poor water solubility. Some of the limitations of nanoparticle-based DDSs can be overcome by developing an appropriate polymer prodrug. In this work, poly(NIPA)-b-poly(HMNPPA)-b-poly(PEGMA-stat-BA) was synthesized using reversible addition fragmentation chain transfer polymerization and Chlorambucil (Cbl), an anticancer drug, was conjugated to the copolymer via 3-(3-(hydroxymethyl)-4-nitrophenoxy)propyl acrylate (HMNPPA) units to prepare the prodrug. A few biotin acrylate (BA) units were also incorporated to bring potential targeting capability to the prodrug in the copolymer. This polymer prodrug formed spherical micellar nanoparticles in physiological conditions, which were characterized by dynamic light scattering and transmission electron microscopy measurements. The very low critical aggregation concentration (cac) (0.011 mg/mL) of the prodrug, as measured from Nile Red fluorescence, makes it stable against dilution. The polymer prodrug was shown to release Cbl on photoirradiation by soft UV (λ ≥ 365 nm) and laser (λ = 405 nm) light. The prodrug micellar nanoparticles were capable of encapsulating a second drug (doxorubicin, DOX) in their hydrophobic core. On photoirradiation with UV and laser light of the DOX-loaded nanoparticles, both Cbl and DOX were released. Light-induced breaking of photolabile ester bond resulted in the release of Cbl and caused disruption of the nanoparticles facilitating release of DOX. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay confirmed the nontoxicity of the polymers and effectiveness of the dual drug-loaded micellar nanoparticles toward cancer cells. Confocal microscopy results showed a better cellular internalization capability of the DOX-loaded nanoparticles in cancer cells, possibly due to the presence of cancer cell targeting biotin molecules in the polymer. This new photoresponsive potentially biocompatible and cancer cell-targeted polymer prodrug may be useful for delivery of single and/or multiple hydrophobic drugs.

Environmental temperature affects physiology and survival of nanosecond pulsed electric field-treated cells

Nanosecond pulsed electric field (nsPEF) is a novel non-thermal tumor ablation technique. However, how nsPEF affect cell physiology at different environmental temperature is still kept unknown. But this issue is of critical clinical practice relevance. This work aim to investigate how nsPEF treated cancer cells react to different environmental temperatures (0, 4, 25, and 37°C). Their cell viability, apoptosis, mitochondrial membrane potential, and reactive oxygen species (ROS) were examined. Lower temperature resulted in higher apoptosis rate, decreased mitochondria membrane potential, and increased ROS levels. Sucrose and N-acetylcysteine (NAC) pre-incubation inhibit ROS generation and increase cell survival, protecting nsPEF-treated cells from low temperature-caused cell death. This work provides an experimental basis for hypothermia and fluid transfusion during nsPEF ablation with anesthesia.

Spatiotemporally and Sequentially-Controlled Drug Release from Polymer Gatekeeper-Hollow Silica Nanoparticles

Combination chemotherapy has become the primary strategy against cancer multidrug resistance; however, accomplishing optimal pharmacokinetic delivery of multiple drugs is still challenging. Herein, we report a sequential combination drug delivery strategy exploiting a pH-triggerable and redox switch to release cargos from hollow silica nanoparticles in a spatiotemporal manner. This versatile system further enables a large loading efficiency for both hydrophobic and hydrophilic drugs inside the nanoparticles, followed by self-crosslinking with disulfide and diisopropylamine-functionalized polymers. In acidic tumour environments, the positive charge generated by the protonation of the diisopropylamine moiety facilitated the cellular uptake of the particles. Upon internalization, the acidic endosomal pH condition and intracellular glutathione regulated the sequential release of the drugs in a time-dependent manner, providing a promising therapeutic approach to overcoming drug resistance during cancer treatment.

Dynamic Nanoparticle Assemblies for Biomedical Applications

Designed synthesis and assembly of nanoparticles assisted by their surface ligands can create "smart" materials with programmed responses to external stimuli for biomedical applications. These assemblies can be designed to respond either exogenously (for example, to magnetic field, temperature, ultrasound, light, or electric pulses) or endogenously (to pH, enzymatic activity, or redox gradients) and play an increasingly important role in a diverse range of biomedical applications, such as biosensors, drug delivery, molecular imaging, and novel theranostic systems. In this review, the recent advances and challenges in the development of stimuli-responsive nanoparticle assemblies are summarized; in particular, the application-driven design of surface ligands for stimuli-responsive nanoparticle assemblies that are capable of sensing small changes in the disease microenvironment, which induce the related changes in their physico-chemical properties, is described. Finally, possible future research directions and problems that have to be addressed are briefly discussed.

Biocompatible Reduction and pH Dual-Responsive Core Cross-Linked Micelles Based on Multifunctional Amphiphilic Linear-Hyperbranched Copolymer for Controlled Anticancer Drug Delivery

Novel strategy has been developed for fabricating the biocompatible reduction and pH dual-responsive core cross-linked (CCL) micelles as drug delivery system (DDS) for the controlled anticancer drug delivery, via the atom transfer radical polymerization (ATRP) of tert-butyl acrylate (tBA) with N,N'-bis(acryloyl)cystamine (BACy) as cross-linker and a multifunctional amphiphilic linear-hyperbranched copolymer as macroinitiator, which was synthesized via the self-condensing vinyl copolymerization (SCVCP) of tBA and p-chloromethylstyrene (CMS) with a poly(ethylene glycol) (PEG) based initiator (mPEG-Br). The hydrolyzed core cross-linked (HCCL) micelles were obtained as DDS for doxorubicin (DOX) by hydrolysis the tBA units into acrylic acid (AA) ones. The in vitro release performance showed that higher GSH concentration and/or lower pH value would lead to a faster and more efficient DOX release, meaning their reduction and pH dual-responsiveness. Therefore, the proposed HCCL micelles are expected to be potential anticancer drug-carriers for tumor microenvironment responsive controlled delivery.

Investigation on a smart nanocarrier with a mesoporous magnetic core and thermo-responsive shell for co-delivery of doxorubicin and curcumin: a new approach towards combination therapy of cancer

A novel and smart MIO-P(NIPAM-MAm) nanocomposite has been prepared for combinational delivery of Dox and Cur for cancer treatment.

Construction of polymer coated core–shell magnetic mesoporous silica nanoparticles with triple responsive drug delivery

Multi-responsive drug delivery systems are playing a very important role in nanomedicine, as they can feature as smart carriers releasing their payload on demand.

Glutathione responsive polymers and their application in drug delivery systems

Materials which respond to biological cues are the subject of intense research interest due to their possible application in smart drug delivery vehicles.

Facile preparation of pH/reduction dual-responsive prodrug nanohydrogels for tumor-specific intracellular triggered release with enhanced anticancer efficiency

Facile approach was developed for biocompatible and biodegradable pH/reduction dual-responsive nano-prodrug for tumor specific intracellular triggered release.

Temperature-Responsive Smart Nanocarriers for Delivery Of Therapeutic Agents: Applications and Recent Advances

Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external stimulus when heat is applied from the outside, or can be internal when pathological lesions have a naturally elevated termperature. A low critical solution temperature (LCST) is a special feature of some polymeric materials, and most of the temperature-responsive nanocarriers have been designed based on this feature. In this review, we attempt to summarize recent efforts to prepare innovative temperature-responsive nanocarriers and discuss their novel applications.

Metal-free thermally-responsive pseudohybrid nanoparticles based on 2-hydroxypropyl-β-cyclodextrin

Partial decomposition of pseudohybrid nanoparticles based on 2-hydroxypropyl-β-cyclodextrin by heat treatment at 37 °C.