Biocompatible Drug Carriers Research Articles

Near infrared dye-labelled polymeric micro- and nanomaterials: in vivo imaging and evaluation of their local persistence.

The use of micro- and nanomaterials as carriers of therapeutic molecules can enhance the efficiency of treatments while avoiding side effects thanks to the development of controlled drug delivery systems. The binding of a dye to a drug or to a drug carrier has opened up a wide range of possibilities for an effective in vivo optical tracing of drug biodistribution by using non-invasive real-time technologies prior to their potential use as therapeutic vectors. Here, we describe the fluorescent tagging of polymeric micro- and nanomaterials based on poly(lactic-co-glycolic) acid and on the thermoresponsive poly(N-isopropylacrylamide) with the fluorescent probe IR-820 which was chemically modified for its covalent coupling to the materials. The chemical modification of the dye and the polymers yielded micro- and nanoparticulated labelled materials to be potentially used as drug depots of different therapeutic molecules. In vitro biological studies revealed their reduced cytotoxicity. A spatiotemporal in vivo micro- and nanoparticle tracking allowed the evaluation of the biodistribution of materials showing their local persistence and high biocompatibility after pathological studies. These results underline the suitability of these materials for the local, sustained, not harmful and/or on-demand drug delivery and the remarkable importance of evaluating the biodistribution of materials and tissue persistence for their use as local drug depots.

Synthesis and Characterization of Tissue Plasminogen Activator-Functionalized Superparamagnetic Iron Oxide Nanoparticles for Targeted Fibrin Clot Dissolution.

Superparamagnetic iron oxide nanoparticles (SPIONs) have attracted great attention in many biomedical fields and are used in preclinical/experimental drug delivery, hyperthermia and medical imaging. In this study, biocompatible magnetite drug carriers, stabilized by a dextran shell, were developed to carry tissue plasminogen activator (tPA) for targeted thrombolysis under an external magnetic field. Different concentrations of active tPA were immobilized on carboxylated nanoparticles through carbodiimide-mediated amide bond formation. Evidence for successful functionalization of SPIONs with carboxyl groups was shown by Fourier transform infrared spectroscopy. Surface properties after tPA immobilization were altered as demonstrated by dynamic light scattering and ζ potential measurements. The enzyme activity of SPION-bound tPA was determined by digestion of fibrin-containing agarose gels and corresponded to about 74% of free tPA activity. Particles were stored for three weeks before a slight decrease in activity was observed. tPA-loaded SPIONs were navigated into thrombus-mimicking gels by external magnets, proving effective drug targeting without losing the protein. Furthermore, all synthesized types of nanoparticles were well tolerated in cell culture experiments with human umbilical vein endothelial cells, indicating their potential utility for future therapeutic applications in thromboembolic diseases.

Amphiphilic Peptide Nanorods Based on Oligo-Phenylalanine as a Biocompatible Drug Carrier.

Peptide nanostructure has been widely explored for drug-delivery systems in recent studies. Peptides possess comparatively lower cytotoxicity and are more efficient than polymeric carriers. Here, we propose a peptide nanorod system, composed of an amphiphilic oligo-peptide RH3F8 (Arg-His3-Phe8), as a drug-delivery carrier. Arginine is an essential amino acid in typical cell-penetration peptides, and histidine induces endo- and lysosomal escape because of its proton sponge effect. Phenylalanine is introduced to provide rich hydrophobicity for stable self-assembly and drug encapsulation. The self-assembled structure of RH3F8 showed nanorod-shaped morphology, positive surface charge, and retained formation in water for 35 days. RH3F8, labeled with Nile Red, showed high cellar uptake and accumulation in both cytoplasm and nucleus. The RH3F8 nanorods demonstrated negligible cytotoxicity, as shown by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), and hemolysis assays. To confirm the efficiency of drug delivery, curcumin was encapsulated in the RH3F8 nanorod system (RH3F8-Cur). RH3F8-Cur showed high encapsulation efficiency (24.63%) under the conditions of 200 μM curcumin. The RH3F8-Cur retained nanoscale size and positive surface charge, similar to those of the empty RH3F8 nanorods. RH3F8-Cur displayed a robust anticancer effect in HeLa and A549 cells, and inhibited the proliferation of cancer cells in a zebrafish model. These results indicate that the RH3F8 nanorods may be a promising candidate for a safe and effective drug-delivery system.

Ultrasonically assisted preparation of poly(acrylic acid)/calcium phosphate hybrid nanogels as pH-responsive drug carriers

Biocompatible, biodegradable and stimuli-responsive nanomaterials can be used as drug carriers and to achieve controlled drug delivery, which is crucial for treating tumors and lowering drug side effects. Calcium phosphate (CaP) nanoparticles and poly(acrylic acid) (PAA) hydrogels can be used as biocompatible and pH-responsive drug carriers. In this study, based on the ultrasound effect, PAA/CaP hybrid nanogels (approximately 100nm, PDI<0.2) are obtained via the cross-linking of CaP nanoparticles and PAA molecules between the Ca2+ ions and –COOH groups. The PAA/CaP hybrid nanogels show good stability in biological media as well as no hemolysis and no cytotoxicity to L02 cells. Moreover, the PAA/CaP hybrid nanogels display an enhanced loading capacity (approximately 32%) for doxorubicin hydrochloride (DOX) compared to pure CaP nanoparticles (approximately 7.5%) and a pH-controlled drug release due to their dissolution in acidic environment. DOX can be delivered into cancer cells by the PAA/CaP hybrid nanogels, which show an inhibitory effect comparable to that of free DOX, although the inhibitory effect is delayed due to the slow release of DOX from the carriers. In vivo, the PAA/CaP hybrid nanogels cannot avoid the capture by the reticuloendothelial system; however, they show passive tumor targeting ability. In brief, the biocompatible, biodegradable and pH-responsive PAA/CaP hybrid nanogels have the potential to act as drug carriers for controlled drug release.

Preparation of nanogels by radiation-induced cross-linking of interpolymer complexes of poly (acrylic acid) with poly (vinyl pyrrolidone) in aqueous medium

Functional nanogels were prepared from interpolymer complexes (IPC) of poly (vinyl pyrrolidone) and poly (acrylic acid) by gamma irradiation of their aqueous solutions. The coil size of IPCs prepared under different experimental conditions (polymer molecular weight, concentration, mixing ratios, pH and temperature) were measured by Dynamic Light Scattering (DLS) technique prior to irradiation. At relatively low absorbed doses of 5 and 10kGy, IPC nanogels with a range of 30–250nm diameters, −12 to −28mV zeta potentials and polydispersities lower than 0.17 were obtained. The sizes of the nanogels were found to be smaller than the size of the precursor IPC coil sizes (40–300nm) due to the formation of intra-chain crosslinks. Thus a recipe of preparing multifunctional nanogels with double amphiphilic properties carrying polyacidic and nonionic polymer structures with the range of above listed properties has been developed. These nanogels show narrow size distribution and high colloidal stability increasing their potential to be used as biocompatible drug carriers with controlled-release properties. PVP-PAA IPC nanogels were characterized by dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques.

Design of polyaspartic acid peptide-poly (ethylene glycol)-poly (ε-caprolactone) nanoparticles as a carrier of hydrophobic drugs targeting cancer metastasized to bone.

Treatment of cancer metastasized to bone is still a challenge due to hydrophobicity, instability, and lack of target specificity of anticancer drugs. Poly (ethylene glycol)-poly (ε-caprolactone) polymer (PEG-PCL) is an effective, biodegradable, and biocompatible hydrophobic drug carrier, but lacks bone specificity. Polyaspartic acid with eight peptide sequences, that is, (Asp)8, has a strong affinity to bone surface. The aim of this study was to synthesize (Asp)8-PEG-PCL nanoparticles as a bone-specific carrier of hydrophobic drugs to treat cancer metastasized to bone. 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, and transmission electron microscopy data showed that (Asp)8-PEG-PCL nanoparticles (size 100 nm) were synthesized successfully. (Asp)8-PEG-PCL nanoparticles did not promote erythrocyte aggregation. Fluorescence microscopy showed clear uptake of Nile red-loaded (Asp)8-PEG-PCL nanoparticles by cancer cells. (Asp)8-PEG-PCL nanoparticles did not show cytotoxic effect on MG63 and human umbilical vein endothelial cells at the concentration of 10–800 μg/mL. (Asp)8-PEG-PCL nanoparticles bound with hydroxyapatite 2-fold more than PEG-PCL. Intravenously injected (Asp)8-PEG-PCL nanoparticles accumulated 2.7-fold more on mice tibial bone, in comparison to PEG-PCL. Curcumin is a hydrophobic anticancer drug with bone anabolic properties. Curcumin was loaded in the (Asp)8-PEG-PCL. (Asp)8-PEG-PCL showed 11.07% loading capacity and 95.91% encapsulation efficiency of curcumin. The curcumin-loaded (Asp)8-PEG-PCL nanoparticles gave sustained release of curcumin in high dose for >8 days. The curcumin-loaded (Asp)8-PEG-PCL nanoparticles showed strong antitumorigenic effect on MG63, MCF7, and HeLa cancer cells. In conclusion, (Asp)8-PEG-PCL nanoparticles were biocompatible, permeable in cells, a potent carrier, and an efficient releaser of hydrophobic anticancer drug and were bone specific. The curcumin-loaded (Asp)8-PEG-PCL nanoparticles showed strong antitumorigenic ability in vitro. Therefore, (Asp)8-PEG-PCL nanoparticles could be a potent carrier of hydrophobic anticancer drugs to treat the cancer metastasized to bone.

Self-Assembled Upconversion Nanoparticle Clusters for NIR-controlled Drug Release and Synergistic Therapy after Conjugation with Gold Nanoparticles.

Fabricated three-dimensional (3D) upconversion nanoclusters (abbreviated as EBSUCNPs) are obtained via an emulsion-based bottom-up self-assembly of NaGdF4:Yb/Er@NaGdF4 nanoparticles (abbreviated as UCNPs), which comprise a NaGdF4:Yb/Er core and a NaGdF4 shell. The EBSUCNPs were then coated with a thin mesoporous amino-functionalized SiO2 shell (resulting in EBSUCNPs@SiO2 precursor) and further conjugated with gold nanoparticles to give the novel EBSUCNPs@SiO2@Au material. Finally, EBSUCNPs@SiO2@Au was applied as a biocompatible and efficient drug carrier for doxorubicin (DOX), thus giving rise to a multifunctional EBSUCNPs@SiO2-DOX@Au nanocomposite. This final material, EBSUCNPs@SiO2-DOX@Au, and the precursor nanoparticles, EBSUCNPs@SiO2@Au, were both fully characterized and their luminescence was investigated in detail. In addition, the drug release properties and photothermal effects of EBSUCNPs@SiO2-DOX@Au were also discussed. Interestingly, when under NIR irradiation, an increasing DOX release was achieved owing to the thermal effect of the Au NPs after absorbing the green light from the upconversion nanoclusters based on the fluorescence resonance energy transfer (FRET) effect. Thus, a near-infrared (NIR)-controlled "on-off" pattern of drug release behavior can be achieved. Moreover, compared with a single therapy method, the assembled nanocomposites exhibit a good synergistic therapy against cancer cells that combines chemotherapy with photothermal therapy. In addition, the in vitro fluorescence microscopy images of EBSUCNPs@SiO2-DOX@Au show a higher enhancement in the red region due to the loading of DOX molecules with respect to EBSUCNPs@SiO2@Au. Therefore, this novel multifunctional 3D cluster architecture can be used in the biomedical field after modification and may pave a new way in other application areas of UCNPs clusters.

Biocompatible hyperbranched polyester magnetic nanocarrier for stimuli-responsive drug release

A novel biocompatible magnetic nanocomposite drug carrier was developed by first chemically modifying a hyperbranched polyester (HBPE) with dodecenyl succinic anhydride (DDSA) functional groups to produce HBPE-DDSA. The magnetic nanocomposite Fe3O4/HBPE-DDSA was then synthesized by dispersing superparamagnetic iron oxide (Fe3O4) nanoparticles within HBPE-DDSA. The structure and magnetic properties of the nanocomposite were characterized by 1H NMR, MALDI-MS, XRD, FTIR, TEM, and SQUID analyses. Isoniazid (INH) was selected as a model antituberculosis drug to investigate the in vitro drug release properties of Fe3O4/HBPE-DDSA/INH. The cytotoxicity of the magnetic nanocomposites was assessed by CCK-8 assay. The results indicated that Fe3O4/HBPE-DDSA is a promising potential drug carrier for a magnetic-targeted drug delivery system.

Micropatterning of reagent-free, high energy crosslinked gelatin hydrogels for bioapplications.

Hydrogels are crosslinked polymeric gels of great interest in the field of tissue engineering, particularly as biocompatible cell or drug carriers. Reagent-free electron irradiated gelatin is simple to manufacture, inexpensive and biocompatible. Here, the potential to micropattern gelatin hydrogel surfaces during electron irradiation crosslinking was demonstrated as a promising microfabrication technique to produce thermally stable structures on highly relevant length scales for bioapplications. In the present work, grooves of 3.75 to 170 µm width and several hundred nanometers depth were transferred onto gelatin hydrogels during electron irradiation and characterized by 3D confocal microscopy after exposure to ambient and physiological conditions. The survival and influence of these microstructures on cellular growth was further characterized using NIH 3T3 fibroblasts. Topographical modifications produced surface structures on which the cultured fibroblasts attached and responded by adapting their morphologies. This developed technique allows for simple and effective structuring of gelatin and opens up new possibilities for irradiation crosslinked hydrogels in biomedical applications in which cell attachment and contact guidance are favored. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 320-330, 2018.

On-Demand Drug Delivery System Using Micro-organogels with Gold Nanorods.

In this study, we designed a biocompatible drug carrier: micro-organogels prepared by emulsification using vegetable oils and self-assembled gelator fibers. Flurbiprofen was chosen as a hydrophobic model drug and is classified as a nonsteroidal anti-inflammatory drug. In the absence of NIR light, flurbiprofen encapsulated in micro-organogels with gold nanorods (GNRs) was released slowly, while release was accelerated in the presence of NIR light due to the increase in the temperature surrounding the GNRs that transforms the gels into liquid. These results suggest that our system can be efficiently used as a versatile scaffold for on-demand drug delivery systems.

Controlled release of anti-inflammatory peptides from reducible thermosensitive nanoparticles suppresses cartilage inflammation

Characterized by pain, cartilage degradation, and inflammation, osteoarthritis is often treated with anti-inflammatory therapies that provide short-term relief but can have adverse side effects; intra-articular drug delivery systems with controlled release of anti-inflammatory peptides using degradable poly(N-isopropylacrylamide) (pNIPAM) nanoparticles could prolong relief and minimize these side effects. Nanoparticles provide a biocompatible drug carrier that can protect encapsulated therapeutics from enzymatic degradation and increase payload delivery upon encountering a degradation stimulus. Here we demonstrate passive targeting of inflamed cartilage ex vivo by uptake of PEGylated pNIPAM nanoparticles with degradable disulfide crosslinks (abbreviated as NGPEGSS) into chondrocytes and subsequent intracellular release of an anti-inflammatory peptide KAFAKLAARLYRKALARQLGVAA (KAFAK). The KAFAK-loaded NGPEGSS treatment reduced ex vivo inflammation to a greater extent compared to its non-degradable counterparts. This study highlights a nanoparticle system that delivers therapeutics intracellularly with improved efficacy by triggered degradation and suppresses inflammation in multiple cell types within an inflamed joint.

Doxorubicin loaded large-pore mesoporous hydroxyapatite coated superparamagnetic Fe3O4 nanoparticles for cancer treatment

In the present study, a series of multifunctional drug delivery systems based on mesostructured hydroxyapatite coating and superparamagnetic nanoparticles with pH-responsive characters was prepared. The structure of each new synthesized nanoscale composite was fully characterized by XRD, FTIR, TEM, VSM and BET. The results showed a good ordered mesostructure having large pores, high pore volume, high surface area, and varied super paramagnetic properties. The mesoporous hydroxyapatite coated super paramagnetic Fe3O4 nanoparticles were applied as a drug delivery carrier loaded with doxorubicin (DOX) as a model drug. The storage/release properties of the developed nonocarriers in phosphate buffer saline (PBS) were studied in two certain pHs: pH=7.4 (the human blood pH) and pH=5.5 (pH of cancer cells). The large pores in the synthesized mesoporous acted as an excellent carrier for DOX molecules with a loading efficiency of ≈93% which is much higher than that of the conventional hydroxyapatite particles. When the pH of the release medium (PBS) was changed from 7.4 to 5.5, the drug release increased significantly from 10% of the adsorbed drug to about 70%. DOX-loaded mesostructure hydroxyapatite reduced the viability of SKBR3 and T47D cells by 54.7 and 57.3%, respectively, which were very similar to 56.8 and 60.4% reduction resulted from free DOX incubation. This new drug delivery system which benefits from both super paramagnetic properties and pH-responsive performances may serve as a suitable platform for developing new biocompatible drug carriers and could have a good potential use in targeted cancer therapy.

Good's buffer derived highly emissive carbon quantum dots: excellent biocompatible anticancer drug carrier.

Here, a facile one-step approach has been developed for the synthesis of carbon quantum dots (CQDs) from Good's buffer. The as-synthesized CQDs emit a bright greenish blue coloured fluorescence after exposure to a 365 nm UV-lamp illumination. The bright fluorescence nature of the CQDs has proven them to be excellent probes for cellular imaging. The CQDs are highly biocompatible in nature, which has been validated by an MTT assay test. The in vitro MTT assay demonstrates a more than 95% survival rate when HEK293 (human embryonic kidney) and H357 (human oral squamous carcinoma) cells were treated with CQDs. The low cytotoxicity of Good's buffer derived CQDs opens the door to biomedical applications. The anticancer drug doxorubicin (DOX) was successfully loaded on the CQDs and their delivery efficiency to the target cells via in vitro treatment of cancerous cells was explored. The CQDs supported DOX showed a higher killing rate of the cancer cells compared to bare DOX due to its ease of internalization and efficient pH-triggered release inside the cells.

Applicability of avidin protein coated mesoporous silica nanoparticles as drug carriers in the lung.

Mesoporous silica nanoparticles (MSNs) exhibit unique drug delivery properties and are thus considered as promising candidates for next generation nano-medicines. In particular, inhalation into the lungs represents a direct, non-invasive delivery route for treating lung disease. To assess MSN biocompatibility in the lung, we investigated the bioresponse of avidin-coated MSNs (MSN-AVI), as well as aminated (uncoated) MSNs, after direct application into the lungs of mice. We quantified MSN distribution, clearance rate, cell-specific uptake, and inflammatory responses to MSNs within one week after instillation. We show that amine-functionalized (MSN-NH2) particles are not taken up by lung epithelial cells, but induced a prolonged inflammatory response in the lung and macrophage cell death. In contrast, MSN-AVI co-localized with alveolar epithelial type 1 and type 2 cells in the lung in the absence of sustained inflammatory responses or cell death, and showed preferential epithelial cell uptake in in vitro co-cultures. Further, MSN-AVI particles demonstrated uniform particle distribution in mouse lungs and slow clearance rates. Thus, we provide evidence that avidin functionalized MSNs (MSN-AVI) have the potential to serve as versatile biocompatible drug carriers for lung-specific drug delivery.

Transiently Responsive Block Copolymer Micelles Based on N-(2-Hydroxypropyl)methacrylamide Engineered with Hydrolyzable Ethylcarbonate Side Chains

The lack of selectivity and low solubility of many chemotherapeutics impels the development of different biocompatible nanosized drug carriers. Amphiphilic block copolymers, composed of a hydrophilic and hydrophobic domain, show great potential because of their small size, large solubilizing power and loading capacity. In this paper, we introduce a new class of degradable temperature-responsive block copolymers based on the modification of N-(2-hydroxypropyl)methacrylamide (HPMA) with an ethyl group via a hydrolytically sensitive carbonate ester, polymerized by radical polymerization using a PEG-based macroinitiatior. The micellization and temperature-responsive behavior of the PEG-poly(HPMA-EC) block copolymer were investigated by dynamic light scattering (DLS). We observed that the polymer exhibits lower critical solution temperature (LCST) behavior and that above the cloud point (cp) of 17 °C the block copolymer self-assembles in micelles with a diameter of 40 nm. Flow cytometry analysis and confocal microscopy show a dose-dependent cellular uptake of the micelles loaded with a hydrophobic dye. The block copolymer nanoparticles were capable of delivering the hydrophobic payload into cancer cells in both 2D and 3D in vitro cultures. The block copolymer has excellent cytocompatibility, whereas loading the particles with the hydrophobic anticancer drug paclitaxel results in a dose-dependent decrease in cell viability.

TCT-594 Initial Report Of The ASCENT Registry: Observational Experience With The New Alpha Coronary Stent

The ALPHA coronary stent delivery system includes a cobalt-chromium, flexible, thin-strut platform, a bio-stable and biocompatible fluoro-polymer based drug carrier, sirolimus and a hydrophilic, rapid-exchange delivery catheter. It is designed to create a competitive alternative to other drug-

Evaluation of surface acetylated and internally quaternized poly(propylene imine) dendrimer as a biocompatible drug carrier for piroxicam as a model drug

Two types of new surface acetylated and internally quaternized poly(propylene imine) dendrimers QPPI-NHAc (G2)/(G3) were prepared, characterized and then demonstrated as potential and biocompatible drug carriers using piroxicam as a model drug.

Synthesis and characterization of pH-responsive nanohydrogels as biocompatible drug carriers based on chemically modified tragacanth gum polysaccharide

In this work, the preparation and application of pH-responsive nanohydrogels based on tragacanth gum polysaccharide and glycidyl methacrylate were investigated.

Solubilization power of an amino acid-based gemini surfactant towards the hydrophobic drug amphotericin B

Amphotericin B (AmB) is a hydrophobic polyene antibiotic used in the therapy of systemic fungal infections. Due to its poor water solubility, it is formulated as a colloidal suspension for intravenous administration using deoxycholate as the solubilizing agent (Fungizone). However, severe toxicity of the formulation has prompted the development of more efficient and safer delivery agents. Gemini amino acid-based surfactants constitute a promising alternative to the biological bile salt surfactant(s), as both biocompatible and biodegradable drug carriers. The supramolecular behaviour of an anionic gemini surfactant derived from cysteine, (C8Cys)2, was characterized by tensiometry and its solubilization capability towards the hydrophobic drug AmB was evaluated under biomimetic conditions (phosphate buffered-saline, pH 7.4). Important aggregation parameters, such as critical micelle concentration (CMC), surface tension at the CMC (γcmc), maximum surface excess concentration (Γmax) and minimum area occupied per molecule at the water/air interface (Amin) were determined. Solubilization power was quantified in terms of molar solubilization ratio (χ), micelle-water partition coefficient (Kp) and Gibbs energy of solubilization (ΔGs0). The aggregation state of AmB in the micellar media was assayed by UV–Vis spectroscopy and in vitro antifungal activity was evaluated. Results were compared with the ones obtained for sodium deoxycholate (NaDC) and discussed in terms of drug loading, efficacy and efficiency. Complementary rheological measurements were performed as NaDC solutions formed a shear-thinning gel at concentrations of 0.01 mol L−1 and higher, in the experimental conditions employed.

One-step sonochemical preparation of redox-responsive nanocapsules for glutathione mediated RNA release.

Efficient RNA delivery to targeted cells requires the use of stable interactive carriers that provide RNA protection during the extracellular transit and trigger release once internalised. One strategy to avoid the premature extracellular RNA drain coupled to sufficient intracellular release is the use of stimuli-responsive delivery materials exploiting as a triggering mechanism the redox gradient between the extra- and intracellular compartments. This work describes a facile route for the preparation of redox-active nanocarriers containing disulphides that combine RNA protection and delivery on demand based on intracellular glutathione (GSH) levels. A one-step sonochemical technology was employed to generate thiolated chitosan (TC) nanocapsules with a diameter between 250 and 570 nm and simultaneously load them with RNA. Their size and physiological stability were directly proportional to the extent of disulphide cross-linking, which in turn could be ruled by adjusting the processing pH and degree of chitosan thiolation. TC processing into nanocapsules showed to be advantageous in terms of RNA condensation and protection compared to the typically employed nanocomplexation. Fluorescence microscopy imaging revealed that: (i) the nanocapsules enter the human fibroblasts and migrate to the perinuclear regions within 1 h, and (ii) the cargo release may occur after the internalisation. These redox-responsive and biocompatible drug carriers demonstrated an effective (∼60%) and sustained (up to 72 h) RNA release at intracellular GSH concentrations (10 mM) in vitro, based on disulphide reduction and consequent capsule disassembly.