Premature Drug Leakage Research Articles

PEGylated Oxidized Alginate-DOX Prodrug Conjugate Nanoparticles Cross-Linked with Fluorescent Carbon Dots for Tumor Theranostics.

Theranostic nanomedicine has recently emerged as an appealing approach for tumor chemotherapy. Here, for the first time, fluorescent carbon dots (Cdots) were used as cross-linker for tumor theranostic nanoparticles. Novel theranostic nanoparticles of approximately 27 nm with a doxorubicin (DOX) content of 0.2532 mg/mg (mPEG-OAL-DOX/Cdots) were designed by conjugating DOX onto mPEG-OAL/Cdots nanoparticles that were prepared by cross-linking the PEGylated oxidized alginate (mPEG-OAL) with Cdots. Due to the acid-labile Schiff base conjugating linkage, the theranostic prodrug nanoparticles showed low levels of DOX release in the simulated physiological media, which indicated premature drug leakage could be reduced during body circulation. Interestingly, the in vitro DOX release was triggered in the simulated tumor microenvironment without burst release. MTT assay and CLSM analysis showed that the mPEG-OAL/Cdots nanoparticles were noncytotoxic, but that the mPEG-OAL-DOX/Cdots theranostic nanoparticles exhibited high degrees of inhibition of cancer cells due to their nucleus-targeting DOX delivery. In addition, their cellular fluorescence characteristic demonstrated a potential application for imaging-guided drug delivery in tumor treatment.

PH/Reductant Dual-Responsive Core-Cross-Linked Micelles via Facile in Situ ATRP for Tumor-Targeted Delivery of Anticancer Drug with Enhanced Anticancer Efficiency.

Anticancer drugs cause severe side effects on normal tissues and organs due to their nonspecific delivery. Thus, tumor-targeting delivery of anticancer drugs remains a serious challenge in chemotherapy. Here a facile strategy was established for the pH/reductant dual-responsive core-cross-linked (CCL) micelles for tumor-targeted delivery of anticancer drug, via in situ atom transfer radical polymerization (ATRP). In the in vitro controlled release experiments with doxorubicin (DOX) as a model drug, the premature drug leakage rate was only 13.4% in the physiological medium within 36 h, while the cumulative release rate in the stimulated tumor microenvironment reached 78.7%, demonstrating the excellent tumor microenvironment responsive controlled release behavior upon acidic medium with high GSH level. As a folate receptor (FR) mediated targeting drug delivery system (DDS), the micelles showed excellent cytocompatibility, and enhanced anticancer efficiency after loading of DOX, compared with free DOX.

Folate-Conjugated Polylactic Acid-Silica Hybrid Nanoparticles as Degradable Carriers for Targeted Drug Delivery, On-Demand Release and Simultaneous Self-Clearance.

Improving the therapeutic efficacy of cancer chemotherapy and reducing the side effects in patients are appealing goals but represent critical challenges. In this work, a novel SiO2 -based nanocarrier coated with polylactic acid and folate has been fabricated to destroy tumors in vivo. Folic acid promotes the targeted intracellular delivery of drug molecules to cancer cells overexpressing the folate receptor for improving the efficacy of the therapy. The polylactic acid layer prevents the premature leakage of drug until the polylactic acid is degraded as a response to low pH and enzymes; this mechanism is designed for sustained and on-demand drug release to prevent undesired side effects. Escape of the drug molecules then triggers decomposition of the SiO2 carrier, improving its elimination from the patient. The strategy of combining the engineering flexibility of inorganic nanocarriers with the stimuli-responsive biodegradability of organic molecules will offer new directions in on-demand and sustained drug release for chemotherapy.

Preparation of HIFU-triggered tumor-targeted hyaluronic acid micelles for controlled drug release and enhanced cellular uptake

In this study, a novel type of high intensity focused ultrasound (HIFU)-triggered active tumor-targeting polymeric micelle was prepared and investigated for controlled drug release and enhanced cellular uptake. Amphiphilic hyaluronic acid (HA) conjugates were synthesized to form docetaxel loaded micelles in aqueous conditions with high encapsulation efficiencies of over 80%. The micelle sizes were limited to less than 150nm, and they varied slightly according to the encapsulated drug amount. Modifying the micellar surface modification with polyethylene glycol diamine successfully inhibited premature drug leakage at a certain level, and it can be expected to prolong the circulation time of the particles in blood. In addition, high-intensity focused ultrasound was introduced to control the release of docetaxel from micelles, to which the release behavior of a drug can be tuned. The in-vitro cell cytotoxicity of docetaxel-loaded micelles was verified against CT-26 and MDA-MB-231 cells. The IC50 values of drug-loaded micelles to CT-26 and MDA-MB-231 cells were 1230.2 and 870.9ng/mL, respectively. However, when exposed to HIFU, the values decreased significantly, to 181.9 and 114.3ng/mL, suggesting that HIFU can enhance cell cytotoxicity by triggering the release of a drug from the micelles. Furthermore, cellular uptake tests were conducted via the quantitative analysis of intracellular drug concentration within CT-26 (CD44 negative), MDA-MB-231 (CD44 positive), and MDA-MB-231 (CD44 blocked), and then imaged with coumarin-6 loaded micelles. The results verified that intracellular drug delivery can be enhanced efficiently via the CD44 receptor-mediated endocytosis of HA micelles. Moreover, HIFU enhanced the cellular uptake behavior by altering the permeability of the cell membrane. It was also able to aid with the extravasation of micelles into the interior of tumors, which will be explained in further research. Therefore, the present study demonstrates that the micelles prepared in this study can emerge as promising nanocarriers of chemotherapeutic agents for controlled drug release and tumor targeting in cancer treatment.

Versatile surface engineering of porous nanomaterials with bioinspired polyphenol coatings for targeted and controlled drug delivery.

The development of biocompatible drug delivery systems with targeted recognition and controlled release has experienced a number of design challenges, including, for example, complicated preparation steps and premature drug release. Herein, we address these problems through an in situ self-polymerization method that synthesizes biodegradable polyphenol-coated porous nanomaterials for targeted and controlled drug delivery. As a proof of concept, we synthesized polyphenol-coated mesoporous silica nanoparticles, termed MSN@polyphenol. The polyphenol coatings not only improved colloidal stability and prevented premature drug leakage, but also provided a scaffold for immobilization of targeting moieties, such as aptamers. Both immobilization of targeting aptamers and synthesis of polyphenol coating are easily accomplished without the aid of any other organic reagents. Importantly, the polyphenol coating (EGCg) used in this study could be biodegraded by acidic pH and intracellular glutathione, resulting in the release of trapped anticancer drugs. Based on confocal fluorescence microscopy and cytotoxicity experiments, drug-loaded and polyphenol-coated MSNs were shown to possess highly efficient internalization and an apparent cytotoxic effect on target cancer, but not control, cells. Our results suggest that these highly biocompatible and biodegradable polyphenol-coated MSNs are promising vectors for controlled-release biomedical applications and cancer therapy.

High drug loading and pH-responsive targeted nanocarriers from alginate-modified SPIONs for anti-tumor chemotherapy.

To increase the accumulation of nanocarriers at the tumor site and reduce premature drug leakage, we fabricated alginate modified superparamagnetic iron oxide nanoparticles (SPIONs) with magnetic targeting capability for pH-responsive release of the anticancer drug doxorubicin (DOX) in tumor-cell microenvironments. The drug loading content (DLC) of SPION-4 was as high as 48.98% with a stable size of 135 nm, whereas the DLC of SPION-2 (amine-functionalized SPIONs as the control) was 7.58%. The in vitro release studies revealed that the acidic environment (pH 6.5 and pH 5.0) triggered the effective release of DOX from DOX-loaded SPION-4 twice and thrice as much as the neutral condition (pH 7.4) after 10.7 h, respectively. These nanocarriers exhibited good cytocompatibility towards both normal cells (LO2) and cancer cells (HepG2), but higher cytotoxicity against HepG2 cells for DOX-loaded SPION-4 than that against LO2 cells could be observed due to the effects of an additional magnet and the acidic microenvironment of cancer cells, which greatly improved the cellular uptake of magnetic nanoparticles and released more DOX in the cytoplasm and nucleus. The in vivo biodistribution and anti-tumor efficacy demonstrated that DOX-loaded SPION-4 under an external magnetic field could obviously increase the DOX concentration in tumor tissues to remarkably inhibit tumor growth and significantly reduce side effects of free DOX. Therefore, this work suggested that these SPION-4 nanoparticles may be a potential carrier to deliver chemotherapeutic agents in anti-tumor treatment.

Optimizing the therapeutic efficacy of cisplatin PEGylated liposomes via incorporation of different DPPG ratios: In vitro and in vivo studies

The anionic lipid DPPG is known to enhance the cellular uptake of liposomes by forming phase boundaries of high fusogenic potentials in vesicular membranes. The focus of this study is to optimize DPPG concentrations to improve the therapeutic efficacy of cisplatin-loaded liposomes. First, cisplatin liposomes composed of HSPC, mPEG2000-DSPE and cholesterol with increasing amounts of DPPG (10, 20 and 30% mol) were prepared by ethanol injection. Liposomes were then characterized by their size, zeta potential and cytotoxicity against C26 colon carcinoma cells. In an experimental system, based upon C26 tumor bearing BALB/c, mice were treated with administering i.v. doses of different formulations, once weekly for total of three weeks. Although with the highest DPPG ratio (30% mol) liposomes exhibited the highest toxicity in vitro, at 10% DPPG better stability of the encapsulated drug was obtained in the presence of serum. In addition, survival of animals was substantially improved at 10% DPPG compared to the higher DPPG contents. It is thus presumable that the high density of negatively charged residues of DPPG gave rise to repulsive forces between phospholipids in concentric lipid bilayers, which resulted in the instability of lipid structure and the subsequent premature drug leakage. Results indicated that cisplatin liposome fabricated with the inclusion of 10% DPPG, maintains the stability while in circulation, and improves therapeutic efficacy due to fusogenic properties; therefore might serve as an effective and stable formulation of cisplatin. However, further investigations are required to confirm the potential anti-tumor effects of cisplatin anionic nanoliposomes in various tumor types.

Hybrid lipid-capped mesoporous silica for stimuli-responsive drug release and overcoming multidrug resistance.

Multidrug resistance (MDR) is known to be a great obstruction to successful chemotherapy, and considerable efforts have been devoted to reverse MDR including designing various functional drug delivery systems. In this study, hybrid lipid-capped mesoporous silica nanoparticles (LTMSNs), aimed toward achieving stimuli-responsive drug release to circumvent MDR, were specially designated for drug delivery. After modifying MSNs with hydrophobic chains through disulfide bond on the surface, lipid molecules composing polymer d-α-tocopherol polyethylene glycol 1000 succinate (TPGS) with molar ratio of 5:1 were subsequently added to self-assemble into a surrounded lipid layer via hydrophobic interaction acting as smart valves to block the pore channels of carrier. The obtained LTMSNs had a narrow size distribution of ca. 190 nm and can be stably dispersed in body fluids, which may ensure a long circulating time and ideal enhanced permeability and retention effect. Doxorubicin (DOX) was chosen as a model drug to be encapsulated into LTMSNs. Results showed that this hybrid lipid-capped mesoporous silica drug delivery system can achieve redox and pH-responsive release of DOX, thereby avoiding the premature leakage of drug before reaching the specific site and releasing DOX within the cancerous cells. Owing to the presence of TPGS-containing lipid layer, LTMSNs-DOX exhibited higher uptake efficiency, cytotoxicity, and increased intracellular accumulation in resistant MCF-7/Adr cells compared with DOX solution, proving to be a promising vehicle to realize intracellular drug release and inhibit drug efflux.

Enhanced anticancer potency using an acid-responsive ZnO-incorporated liposomal drug-delivery system.

The development of stimuli-responsive nanocarriers is becoming important in chemotherapy. Liposomes, with an appropriate triggering mechanism, can efficiently deliver their encapsulated cargo in a controlled manner. We explored the use of acid-sensitive zinc oxide nanoparticles (ZNPs) as modulators of the responsive properties of liposomes. Nanocomplexes formed by the incorporation of ZNPs in liposomes (ZNP-liposomes) were designed to demonstrate the pH-responsive release of a drug (daunorubicin) without premature drug leakage and with the maintenance of the relevant therapeutic concentrations. The nanocomplexes were spherical in shape with a narrow size distribution and showed a high drug-encapsulating efficiency. Under acidic conditions, the ZNP-liposome nanocomplexes released the loaded drug more rapidly than bare liposomes. Using flow cytometry, confocal microscopy and an MTT assay, we demonstrated that these nanocomplexes were readily taken up by cancer cells, resulting in significantly enhanced cytotoxicity. On exposure to the acidic conditions inside cancer cells, the ZNPs rapidly decomposed, releasing the entrapped drug molecules from the ZNP-liposome nanocomplexes, producing widespread cytotoxic effects. The incorporated ZNPs were multimodal in that they not only resulted in a pH-responsive drug-delivery system, but they also had a synergistic chemo-photodynamic anticancer action. This design provides a significant step towards the development of multimodal liposome structures.

Mesoporous Silica Nanoparticles Coated by Layer-by-Layer Self-assembly Using Cucurbit[7]uril for in Vitro and in Vivo Anticancer Drug Release.

Mesoporous silica nanoparticles (MSNs) are promising solid supports for controlled anticancer drug delivery. Herein, we report biocompatible layer-by-layer (LbL) coated MSNs (LbL-MSNs) that are designed and crafted to release encapsulated anticancer drugs, e.g., doxorubicin hydrochloride (DOX), by changing the pH or by adding competitive agents. The LbL coating process comprises bis-aminated poly(glycerol methacrylate)s (BA-PGOHMAs) and cucurbit[7]uril (CB[7]), where CB[7] serves as a molecular bridge holding two different bis-aminated polymeric layers together by means of host–guest interactions. This integrated nanosystem is tuned to respond under specific acidic conditions or by adding adamantaneamine hydrochloride (AH), attributed to the competitive binding of hydronium ions or AH to CB[7] with BA-PGOHMAs. These LbL-MSN hybrids possess excellent biostability, negligible premature drug leakage at pH 7.4, and exceptional stimuli-responsive drug release performance. The pore sizes of the MSNs and bis-aminated compounds (different carbon numbers) of BA-PGOHMAs have been optimized to provide effective integrated nanosystems for the loading and release of DOX. Significantly, the operating pH for the controlled release of DOX matches the acidifying endosomal compartments of HeLa cancer cells, suggesting that these hybrid nanosystems are good candidates for autonomous anticancer drug nanocarriers actuated by intracellular pH changes without any invasive external stimuli. The successful cellular uptake and release of cargo, e.g., propidium iodide (PI), in human breast cancer cell line MDA-231 from PI-loaded LbL-MSNs have been confirmed by confocal laser scanning microscopy (CLSM), while the cytotoxicities of DOX-loaded LbL-MSNs have been quantified by the Cell Counting Kit-8 (CCK-8) viability assay against HeLa cell lines and fibroblast L929 cell lines. The uptake of DOX-loaded LbL-MSNs by macrophages can be efficiently reduced by adding biocompatible hydrophilic poly(ethylene glycol) or CB[7] without destroying the capping. In vivo tumor-growth inhibition experiments with BALB/c nude mice demonstrated a highly efficient tumor-growth inhibition rate of DOX-loaded LbL-MSNs, suggesting that the novel type of LbL-MSN materials hold great potentials in anticancer drug delivery.

Optimized thermosensitive liposomes for selective doxorubicin delivery: Formulation development, quality analysis and bioactivity proof

In our study we examined thermosensitive liposomal formulations (TL) from the perspective to minimize the general toxicity drawbacks of chemotherapy. The TL become active in response to local hyperthermia (LH), and remain inactive at physiological conditions. Here, we formulated novel doxorubicin loaded thermoliposomes (Dox-TL) with optimized characteristics and tested their biological activity in vitro. The liposomal membrane composition of Dox-TL and their preparation technology were adjusted for high drug loading and extended formulation stability. The 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC):1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC):cholesterol(Chol):1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimide(polyethylene glycol)-2000] (ammonium salt) (DSPE-PEG-2000) in molar ratio 9:1:0.2:0.02:0.2 and drug/lipid weight ratio 0.13–0.20/1 composition has demonstrated best results. The freshly-prepared vesicles contained 94% doxorubicin. The Dox-TL, freeze-dried with 4% sucrose, maintained high level of encapsulated drug, remained stable in serum and prevented premature drug leakage. The Dox-TL proved to be significantly less toxic at 37°C than free Dox. In combination with local hyperthermia of 42.5°C Dox-TL were as effective as free Dox in cell survival, and even outperformed free Dox in proliferation activity suppression, colony proliferation rate, and cellular uptake. These findings represent a solid basis for a safer and more effective antitumor therapy.

Bioresponsive Controlled Drug Release Based on Mesoporous Silica Nanoparticles Coated with Reductively Sheddable Polymer Shell

The design of bioresponsive controlled drug delivery systems is a promising approach in cancer therapy, but it still is a major challenge capable of optimum therapeutic efficacy, i.e. no premature drug leakage in blood circulation while having a rapid and complete release in tumor tissues. In this work, a kind of PEGylated core/shell structured composite nanoparticle was developed via precipitation polymerization, where a disulfide-cross-linked poly(N-vinylcaprolactam-co-methacrylic acid) (P(VCL-s-s-MAA)) polymer shell was created to act as sheddable thermo/pH-sensitive gatekeepers, and a carboxylic acid modified mesoporous silica nanoparticles (MSN-COOH) core was applicable as an accessible reservoir to encapsulate high drug doses. At physiological conditions, the P(VCL-s-s-MAA)-PEG shell underwent a distinct transition from a swollen state in pH 7.4 to a collapsed state in pH 5.0. Though sufficiently stable in water, composite nanoparticles were prone to fast dissociation and rupture when subjecting to 10 mM glutathione (GSH), due to the shedding of polymer walls through reductive cleavage of intermediate disulfide bonds, so that the polymer shell was active in moderating the diffusion of embedded drugs in-and-out of MSN channels. The cumulative in vitro release of DOX-loaded composite nanoparticles allowed a low trace of DOX diffusion below volume phase transition temperature (VPTT) and a significant release rate above its VPTT, while the most rapid and perfect release was achieved under a reductive environment (pH 6.5 and 10 mM GSH), mimicking that of intracellular cytosol compartments. The in vitro cell assay of blank carriers to normal cells indicated that the composite nanoparticles were suitable as drug carriers, but DOX-loaded carriers had a similar intensive toxicity to cancer cells compared with free DOX. Therefore, these stimuli-responsive composite nanoparticles with a reductively sheddable and thermo/pH-responsive polymer shell gate could, in principle, be applied for in vivo cancer therapy, and synergistic drug delivery can be accomplished “just in time” in a precise event over the location.

Surface Enhanced Raman Scattering Traceable and Glutathione Responsive Nanocarrier for the Intracellular Drug Delivery

A surface enhanced Raman scattering (SERS) traceable nanocarrier is presented through a simple strategy for the intracellular redox environment triggered drug delivery. Basically, the nanocarrier has a core-shell structure, with the Raman molecule tagged Au@Ag nanorods as the SERS active core and mesoporous silica (MS) as the drug containing shell. In the presented system, the locations of nanocarriers can be tracked by SERS signals while those of drugs can be monitored through their fluorescence, allowing the simultaneous investigation of the intracellular distribution of both the nanocarriers and the drugs. To endow the nanocarrier with the glutathione (GSH) responsive behavior, disulfide, which can be cleaved by GSH, is used to directly attach drug molecules to the MS. Compared with other disulfide based drug delivery strategies, this is a quite simple and efficient method. The experimental results confirmed that the drug release can be triggered by the stimuli. Moreover, after the cellular uptake of the nanocarriers, a gradual drug release from the nanocarriers was observed by monitoring both the fluorescence of the drug molecules and the SERS signals of the nanocarriers. Considering its stimuli-responsive properties, this kind of nanocarrier would have great potential in improving the efficacy of cancer chemotherapy by avoiding premature drug leakage. More importantly, this SERS based tracking method of the nanocarrier would be more powerful than that based only on the fluorescence of the drug in the studies of drug release dynamic processes.

An efficient cell-targeting and intracellular controlled-release drug delivery system based on MSN-PEM-aptamer conjugates

The current work demonstrates an efficient cell-targeting and intracellular controlled-release drug delivery system based on a MSN-PEM-aptamer conjugate. In this system, mesoporous silica nanoparticles (MSN) were employed as drug containers for their high surface area and high loading efficacy. Polyelectrolyte multilayers (PEM) were used to prevent the premature leakage of drugs during the delivery process and controllably released drugs under reducing conditions. Finally, a cancer cell-specific DNA aptamer was selected as the targeting recognition molecule for its high cell recognition. By taking the advantages of high payload, stimuli-response to intracellular environment and high cell recognition ability, this type of delivery vehicle could be used as a promising drug delivery system for specific intracellular delivery and may offer much needed efficacy in cancer therapy.