pH-responsive chitosan copolymer synthesized via click chemistry for design of polymeric nanoparticles for targeted drug delivery

The polymeric nanoparticles (PNPs) loaded with prednisolone were developed to exhibit pH-responsive properties owing to the attachment of a hydrazone linkage between the copolymer chitosan and mPEG. In the diseased cellular environment, the hydrazone bond tends to break due to reduced pH, leading to the release of the drug from the PNPs at the required site of action. The fabricated PNPs exhibit spherical morphology, optimum size (∼200 nm), negative surface charge, and monodispersed particle size distribution. The encapsulation efficiency of the PNPs was determined to be 71.1 ± 0.79 % and two experiments (polymer weight loss and drug release) confirmed the pH-responsive properties of the PNPs. The cellular study cytotoxicity assay showed biocompatibility of PNPs and drug molecule-mediated toxicity to A549 cells. The ligand atrial natriuretic peptide-attached PNPs internalized into A549 cells via natriuretic peptide receptor-A to achieve target specificity. The PNPs cytotoxicity and pH-response medicated inflammation reduction functionality was studied in inflammation-induced RAW264.7 cell lines. The study observed the PNPs effectively reduced the inflammatory mediators NO and ROS levels in RAW264.7. The results showed that pH-responsive properties of PNPs and this novel fabricated delivery system effectively treat inflammatory and cancer diseases.

Promotion of the genipin crosslinked chitosan-fiber hydrogel loaded with sustained release of clemastine fumarate in diabetic wound repair

Diabetic skin disorders are lingering and refractory clinical diseases. In this study, a genipin-crosslinked porous chitosan fiber (CSF) hydrogel was fabricated to achieve rapid wound healing. By embedding clemastine fumarate (CF) in the CSF hydrogel pores, we synthesised a CSF/CF hydrogel for the treatment of diabetic wounds. The microstructure, chemical elements, spectral variation, mechanical properties, swelling ratios, degradability, and toxicity of the CSF/CF hydrogels were studied. Compared with the typical CS power hydrogel, the porous CSF hydrogel crosslinked with genipin possesses a stable structure and improved physicochemical properties. Moreover, CF was slowly released from the CSF hydrogel. Molecular simulation also showed that CF was evenly embedded inside the cavity formed by the novel CSF hydrogel. The results suggested that CF can resist damage from high glucose levels and promote proliferation, tube formation, and migration of endothelial cells (ECs) and fibroblasts. The CSF/CF hydrogel promoted wound healing in a rat model. Mechanistically, the beneficial effect of CF on wound healing may be related to activation of the MEK/ERK and PI3K/Akt signalling pathways. In conclusion, genipin-crosslinked CSF/CF hydrogel can accelerate wound healing and may be an effective therapeutic method for treating diabetic skin lesions.

A bionic multichannel nanofiber conduit carrying Tubastatin A for repairing injured spinal cord

Spinal cord injury is a kind of nerve injury disease with high disability rate. The bioscaffold, which presents a biomimetic structure, can be used as “bridge” to fill the cavity formed by the liquefaction and necrosis of spinal nerve cells, and connects the two ends of the fracture to promote the effective recovery of nerve function. Tubasatin A (TUBA) is a potent selective histone deacetylase 6 (HDAC6) inhibitor, which can inhibit the overexpression of HDAC6 after spinal cord injury. However, TUBA is limited by high efflux ratios, low brain penetration and uptake in the treatment of spinal cord injury. Therefore, an effective carrier with efficient load rate, sustained drug release profile, and prominent repair effect is urgent to be developed. In this study, we have prepared a bionic multichannel Tubasatin A loaded nanofiber conduit (SC-TUBA(+)) through random electrospinning and post-triple network bond crosslinking for inhibiting HDAC6 as well as promoting axonal regeneration during spinal cord injury treatment. The Tubasatin A-loaded nanofibers were shown to be successfully contained in poly(glycolide-co-ε-caprolactone) (PGCL)/silk fibroin (SF) matrix, and the formed PGCL/SF-TUBA nanofibers exhibited an uniform and smooth morphology and appropriate surface wettability. Importantly, the TUBA loaded nanofibers showed a sustained-release profile, and still maintains activity and promoted the extension of axonal. In addition, the total transection large span model of rat back and immunofluorescent labeling, histological, and neurobehavioral analysis were performed for inducing spinal cord injury at T9-10, evaluating therapeutic efficiency of SC-TUBA(+), and elucidating the mechanism of TUBA release system in vivo. All the results demonstrated the significantly reduced glial scar formation, increased nerve fiber number, inhibited inflammation, reduced demyelination and protected bladder tissue of TUBA-loaded nanofibers for spinal cord injury compared to SC-TUBA, SC and Control groups, indicating their great potential for injured spinal cord healing clinically.

Synthesis of multiple stimuli-responsive degradable block copolymers via facile carbonyl imidazole-induced postpolymerization modification

A robust approach that centers on carbonyl imidazole chemistry was used to synthesize a triple-stimuli-responsive degradable block copolymer labeled with acetal, disulfide, and o-nitrobenzyl groups exhibiting acid, reduction, and light responses.

Drug release evaluation of Paclitaxel/Poly-L-Lactic acid nanoparticles based on a microfluidic chip

Paclitaxel is a commonly used drug in the medical field because of its strong anticancer effect. However, it may produce relatively severe side effects (i.e., allergic reactions). A major characteristic of paclitaxel is low solubility in water. Special solvents are used for dissolving paclitaxel and preparing the paclitaxel drugs, while the solvents themselves will cause certain effects. Polyoxyethylene castor oil, for example, can cause severe allergic reactions in some people, and the clinical use is limited. In this study, we developed a new Paclitaxel/Poly-L-Lactic Acid (PLLA) nanoparticle drug, which is greatly soluble in water, and carried out in vitro drug sustained release research on it and the original paclitaxel drug. However, because the traditional polymer drug carrier usually uses dialysis bag and thermostatic oscillation system to measure the drug release degree in vitro, the results obtained are greatly different from the actual drug release results in human body. Therefore, this paper adopts the microfluidic chip we previously developed to mimic the human blood vessels microenvironment to study the sustained-release of Paclitaxel/PLLA nanoparticles to make the results closer to the release value in human body. The experimental results showed that compared with the original paclitaxel drug, Paclitaxel/PLLA nanoparticles have a long-sustained release time and a slow drug release, realizing the sustained low-dose release of paclitaxel, a cell cycle-specific anticancer drug, and provided certain reference significance and theoretical basis for the research and development of anticancer drugs.

Synthesis, micellar structures and emission mechanisms of an AIE and DDED-featured fluorescent pH- and thermo-meter

A new nanoprobe, the luminescent diblock copolymer PNIPAM(MAh-4)-b-P4VP (PN4P), with pH- and thermo-responsive deprotonation-driven emission decay (DDED) and aggregation-induced emission (AIE) features was designed and synthesized. The nanoprobe PN4P can form micellar structures in water with reversible dual-responsive fluorescence (FL) behavior within a wide pH range of 2–11. The critical solution temperature was found at about 32, 30 and 27 °C as the pH switched from 2, 7 to 11. The critical pH value of the probe was about 4.0, and the micelles showed a core–shell inversion in response to pH and thermal stimuli, accompanied by a desirable emission tunability. P4VP as the micellar shell at pH = 2 was more easily dehydrated with the increase in temperature as compared to PNIPAM as the micellar shell at pH > 4. The strongest dehydration of the P4VP shell would make PN4P the most strongly aggregated and the most AIE-active, which supports the 2.10-fold most distinguished thermal-responsive emission enhancement at pH = 2. Moreover, a dramatic acidochromic redshift of the emission band from 450 (pH > 4) to 490 nm (pH = 2) was observed, and the maximum emission at pH = 2 was enhanced by about 2.07-fold as compared with that at pH = 7. Therefore, the probe displays the desired dual responses and good reversibility. AIE and DDED are the two major mechanisms responsible for the dual-responsive emission change, with AIE playing a more important role than DDED. This work offers a promising approach to interpreting temperature (range from 28 to 40 °C) and pH changes (range from 2 to 7) in water.

A nanoprobe in water features pH- and thermal-responsive micellar/clustering structures, deprotonation-driven emission decay (DDED) and aggregation-induced emission (AIE).

Light, temperature, and pH control of aqueous azopyridine-terminated poly(N-isopropylacrylamide) solutions

Azopyridines (AzPy) act as light-sensitive groups that undergo reversible cis–trans isomerization upon UV irradiation, as hydrogen-bond acceptors, and as ionizable moieties.

Facile fabrication of positively-charged helical poly(phenyl isocyanide) modified multi-stimuli-responsive nanoassembly capable of high efficiency cell-penetrating, ratiometric fluorescence imaging, and rapid intracellular drug release

High efficiency cell-penetrating helical chain functionalized polymeric micelles capable of co-delivery of cargoes and rapid release were reported.

Synthesis and characterization of cystamine conjugated chitosan-SS-mPEG based 5-Fluorouracil loaded polymeric nanoparticles for redox responsive drug release

The principle objective of this study was to develop and characterize redox responsive polymeric nanoparticles (PNPs) as a stimuli responsive drug delivery system. The chitosan-cystamine-methoxy poly(ethylene glycol) (CH-SS-mPEG) copolymer was synthesized by conjugation of cystamine appended chitosan with carboxylic acid-terminated mPEG and characterized by FTIR, ¹H NMR, XRD analysis and colorimetric assay. This copolymer could be formulated as 5-Fluorouracil (5-FU) loaded PNPs and the characteristics of PNPs were evaluated. Moreover, folic acid functionalized PNPs were prepared for folate receptor targeted drug delivery. Drug release studies indicated that the redox sensitive PNPs were stable in physiological condition while quickly releasing 5-FU in the trigger of redox potential due to the cleavage of the disulfide linkages. In contrast, less quantity of drug was released from the reduction insensitive chitosan-g-methoxy poly(ethylene glycol) (CH-g-mPEG) based PNPs under both reduction sensitive and non-reductive conditions. From the cytotoxicity studies, it was evident that 5-FU loaded PNPs had higher toxicity against MCF7 cells when compared to 5-FU free PNPs. Subsequently, cellular uptake studies showed significantly increased internalization of folic acid attached PNPs. In conclusion, the developed PNPs appeared to be of great promise in redox responsive drug release for targeted drug delivery.

Construction of A Triple-Stimuli-Responsive System Based on Cerium Oxide Coated Mesoporous Silica Nanoparticles

In this work, a triple-stimuli (GSH, pH and light irradiation) responsive system were designed based on CeO2 nanoparticles (CeO2 NPs) coated doxorubicin (DOX) and photosensitizer hematoporphyrin (HP) dual-loaded mesoporous silica nanoparticles (MSN). Upon entering into cancer cells, both high concentration of intracellular GSH and low pH environment would reduce CeO2 NPs to cerium ions, accompanied with the degradation of CeO2 NPs and the conformational change of HP under light irradiation, the preloaded DOX are thus released from the nanocarrier, resulting in a contrast fluorescence enhancement. Meanwhile, 1O2 generated from HP for potential photodynamic therapy (PDT) upon light irradiation. In comparison, not much influence can be observed for normal cells. This nanosystem not only has a significantly enhanced efficacy for cancer cells but also broad the scope for the future design and applications of multifunctional platforms for synergetic chemotherapy and PDT.

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.

Curcumin-Loading-Dependent Stability of PEGMEMA-Based Micelles Affects Endocytosis and Exocytosis in Colon Carcinoma Cells

Polymeric micelles were formed from poly(poly(ethylene glycol) methyl ether methacrylate)-block-poly(styrene) (P(PEGMEMA)-b-PS) block copolymer of two different chain lengths. The micelles formed were approximately 16 and 46 nm in diameter and used to encapsulate curcumin. Upon loading of the curcumin into the micelles, their size increased to approximately 34 and 80 nm in diameter, respectively, with a loading efficiency of 58%. The unloaded micelles were not cytotoxic to human colon carcinoma cells, whereas only the smaller loaded micelles were cytotoxic after 72 h of exposure. The micelles were rapidly internalized by the cells within minutes of exposure, with the loaded micelles internalized to a greater extent owing to their enhanced stability compared to that of the unloaded micelles. The larger micelles were more rapidly internalized and exocytosed than the smaller micelles, demonstrating the effect of micelle size and drug loading on drug delivery and cytotoxicity.

Polyaspartamide-based multi-responsive micelle with sheddable shell for antitumor drug delivery

A multi-stimuli (pH/thermo/reduction) responsive graft copolymer based on a polyaspartamide derivative is reported for Dox delivery.

Reduction-sensitive polymeric nanocarriers in cancer therapy: a comprehensive review

Redox potential is regarded as a significant signal to distinguish between the extra-cellular and intra-cellular environments, as well as between tumor and normal tissues. Taking advantage of this physiological differentiation, various reduction-sensitive polymeric nanocarriers (RSPNs) have been designed and explored to demonstrate excellent stability during blood circulation but rapidly degrade and effectively trigger drug release in tumor cells. Therefore, this smart RSPN delivery system has attracted much attention in recent years, as it represents one of the most promising drug delivery strategies in cancer therapy. In this review, we will provide a comprehensive overview of RSPNs with various reducible linkages and functional groups up to date, including their design and synthetic strategies, preparation methods, drug release behavior, and their in vitro and in vivo efficacy in cancer therapy. In addition, dual- and triple-sensitive nanocarriers based on reducible disulfide bond-containing linkages will also be discussed.

Multi-Stimuli-Responsive Polymeric Materials

Stimuli-responsive materials are of immense importance because of their ability to undergo alteration of their properties in response to their environment. The properties of such materials can be tuned by subtle adjustments in temperature, pH, light, and so forth. Among such smart materials, multi-stimuli-responsive polymeric materials are of pronounced significance as they offer a wide range of applications and their properties can be tuned through several mechanisms. Here, we aim to highlight some recent studies showcasing the multi-stimuli-responsive character of these polymers, which are still relatively little known compared to their single-stimuli-responsive counterpart.

Self-assembly of cytotoxic peptide conjugated poly(β-amino ester)s for synergistic cancer chemotherapy

DOX-encapsulated self-assembled micelle formation by cytotoxic peptide conjugated poly(β-amino ester)s for synergistic cancer chemotherapy.

Functionalized Pluronic-b-poly(ε-caprolactone) based nanocarriers of paclitaxel: solubilization, antiproliferative efficacy and in vivo pharmaceutic kinetics

Novel paclitaxel (PTX) nanocarriers were developed based on the Pluronic-based pentablock copolymer and their pharmaceutical behaviours were thoroughly evaluated.

Multi-responsive graft copolymer micelles comprising acetal and disulfide linkages for stimuli-triggered drug delivery

Dual-cleavable polymeric aggregates were efficiently used for thermo-, pH and reduction triggered controlled release of doxorubicin due to the stimuli-dependent topological transformation and reaggregation of copolymer aggregates.

Integrin α(V)β(3)-targeted magnetic nanohybrids with enhanced antitumor efficacy, cell cycle arrest ability, and encouraging anti-cell-migration activity

Organic/inorganic nanohybrids, which integrate advantages of the biocompatibility of organic polymers and diversified functionalities of inorganic nanoparticles, have been extensively investigated in recent years. Herein, we report the construction of arginine-glycine-aspartic acid-cysteine (RGDC) tetrapeptide functionalized and 10-hydroxycamptothecin (HCPT)-encapsulated magnetic nanohybrids (RFHEMNs) for integrin αVβ3-targeted drug delivery. The obtained RFHEMNs were near-spherical in shape with a homogeneous size about 50 nm, and exhibited a superparamagnetic behavior. In vitro drug release study showed a sustained and pH-dependent release profile. Cell viability tests revealed that RFHEMNs displayed a significant enhancement of cytotoxicity against αVβ3-overexpressing A549 cells, as compared to free HCPT and nontargeting micelles. Flow cytometry analysis indicated that this cytotoxic effect was associated with dose-dependent S phase arrest. Finally, RFHEMNs exerted encouraging anti-cell-migration activity as determined by an in vitro wound-healing assay and a transwell assay. Overall, we envision that this tumor-targeting nanoscale drug delivery system may be of great application potential in chemotherapy of primary tumor and their metastases.

Reduction-responsive polymeric micelles and vesicles for triggered intracellular drug release

SIGNIFICANCE

The therapeutic effects of current micellar and vesicular drug formulations are restricted by slow and inefficient drug release at the pathological site. The development of smart polymeric nanocarriers that release drugs upon arriving at the target site has received a tremendous amount of attention for cancer therapy.

RECENT ADVANCES

Taking advantage of a high reducing potential in the tumor tissues and in particular inside the tumor cells, various reduction-sensitive polymeric micelles and vesicles have been designed and explored for triggered anticancer drug release. These reduction-responsive nanosystems have demonstrated several unique features, such as good stability under physiological conditions, fast response to intracellular reducing environment, triggering drug release right in the cytosol and cell nucleus, and significantly improved antitumor activity, compared to traditional reduction-insensitive counterparts.

CRITICAL ISSUES

Although reduction-sensitive micelles and polymersomes have accomplished rapid intracellular drug release and enhanced in vitro antitumor effect, their fate inside the cells including the mechanism, site, and rate of reduction reaction remains unclear. Moreover, the systemic fate and performance of reduction-sensitive polymeric drug formulations have to be investigated.

FUTURE DIRECTIONS

Biophysical studies should be carried out to gain insight into the degradation and drug release behaviors of reduction-responsive nanocarriers inside the tumor cells. Furthermore, novel ligand-decorated reduction-sensitive nanoparticulate drug formulations should be designed and explored for targeted cancer therapy in vivo.

Size effects of self-assembled block copolymer spherical micelles and vesicles on cellular uptake in human colon carcinoma cells

Block copolymers, poly(oligo ethylene glycol methyl ether methacrylate)-block-poly(styrene), POEGMEMA-b-PS, with various block lengths were prepared via RAFT polymerization and subsequently self-assembled into various aggregates to investigate their uptake ability into cancer cells.