Characterization of Chitosan Hydrogels Obtained through Phenol and Tripolyphosphate Anionic Crosslinking

Chitosan is a deacetylated polymer of chitin that is extracted mainly from the exoskeleton of crustaceans and is the second-most abundant polymer in nature. Chitosan hydrogels are preferred for a variety of applications in bio-related fields due to their functional properties, such as antimicrobial activity and wound healing effects; however, the existing hydrogelation methods require toxic reagents and exhibit slow gelation times, which limit their application in biological fields. Therefore, a mild and rapid gelation method is necessary. We previously demonstrated that the visible light-induced gelation of chitosan obtained through phenol crosslinking (ChPh) is a rapid gelation method. To further advance this method (<10 s), we propose a dual-crosslinked chitosan hydrogel obtained by crosslinking phenol groups and crosslinking sodium tripolyphosphate (TPP) and the amino groups of chitosan. The chitosan hydrogel was prepared by immersing the ChPh hydrogel in a TPP solution after phenol crosslinking via exposure to visible light. The physicochemical properties of the dual-crosslinked hydrogels, including Young's moduli and water retentions, were subsequently investigated. Young's moduli of the dual-crosslinked hydrogels were 20 times higher than those of the hydrogels without TPP ion crosslinking. The stiffness could be manipulated by varying the immersion time, and the water retention properties of the ChPh hydrogel were improved by TPP crosslinking. Ion crosslinking could be reversed using an iron chloride solution. This method facilitates chitosan hydrogel use for various applications, particularly tissue engineering and drug delivery.

Toxicity of Water-Soluble D-g-PNIPAM Polymers in a Complex with Chemotherapy Drugs and Mechanism of Their Action In Vitro

The application of a biocompatible polymer nanocarrier can provide target delivery to tumor tissues, improved pharmacokinetics, controlled drug release, etc. Therefore, the proposed strategy was to use the water-soluble star-like copolymers with a Dextran core and Poly(N-isopropylacrylamide) grafts (D-g-PNIPAM) for conjugation with the widely used chemotherapy drugs in oncology-Cisplatin (Cis-Pt) and Doxorubicin (Dox). The molecular characteristics of the copolymer were received using size-exclusion chromatography. The physicochemical characterization of the D-g-PNIPAM-Cis-Pt (or Dox) nanosystem was conducted using dynamic light scattering and FTIR spectroscopy. Using traditional biochemical methods, a comparative analysis of the enhancement of the cytotoxic effect of free Cis-Pt and Dox in combination with D-g-PNIPAM copolymers was performed in cancer cells of the Lewis lung carcinoma line, which are both sensitive and resistant to Dox; in addition, the mechanism of their action in vitro was evaluated.

Intelligent responsive copper-diethyldithiocarbamate-based multifunctional nanomedicine for photothermal-augmented synergistic cancer therapy

The design of multifunctional nanomedicine through the combination of multimodal treatments to achieve the optimal antitumor effect is essential for cancer therapy. Herein, we design and develop a multifunctional theranostic nanoplatform using an iron ion-doxorubicin (DOX) nanoscale coordination polymer (Fe/DOX NCP) as a shell coating on the surface of polyvinyl pyrrolidone (PVP) stabilized copper-diethyldithiocarbamate nanoparticles (Cu(DDC)2 NPs) for combined tumor chemo-/photothermal/chemodynamic therapy. The obtained Cu(DDC)2@Fe/DOX NPs display pH/laser dual-responsive degradation behavior and also exhibit favorable photothermal performance. Under 808 nm laser irradiation, Cu(DDC)2@Fe/DOX NPs can convert light into heat, which not only kills tumor cells via hyperthermia in photothermal therapy (PTT), but also accelerates the degradation of Fe/DOX NCPs to release Fe3+ and DOX. The liberated Fe3+ can be used to catalyze hydrogen peroxide via the Fenton reaction to produce highly toxic hydroxyl radicals (˙OH) in chemodynamic therapy (CDT). The released DOX and the exposed Cu(DDC)2 can cause significant cell death in combined chemotherapy via a superimposed effect. In vitro and in vivo results prove that Cu(DDC)2@Fe/DOX NPs with laser irradiation present remarkable anticancer performances in hyperthermia-enhanced chemo-/CDT. Therefore, this study provides a new strategy for highly efficient synergistic cancer therapy.

Internally bridged nanosilica for loadings and release of sparsely soluble compounds

The engineering of a new monodisperse colloid with a sea urchin-like structure with a large complex internal structure is reported, in which silica surfaces are bridged by an aromatic organic cross-linker to serve as a nanocarrier host for drugs such as doxorubicin (DOX) against breast cancer cells. While dendritic fibrous nanosilica (DFNS) was employed and we do not observe a dendritic structure, these particles are referred to as sea urchin-like nanostructured silica (SNS). Since the structure of SNS consists of many silica fibrils protruding from the core, similar to the hairs of a sea urchin. For the aromatic structured cross-linker, bis(propyliminomethyl)benzene (b(PIM)B-S or silanated terephtaldehyde) were employed, which are prepared with terephtaldehyde and 3-aminopropyltriethoxy-silane (APTES) through a simple Schiff base reaction. b(PIM)B-S bridges were introduced into SNS under open vessel reflux conditions. SPS refers to the product obtained by incorporating the cross-linker b(PIM)B-S in ultra-small colloidal SNS particles. In-situ incorporation of DOX molecules resulted in SPS-DOX. The pH-responsive SPS nanocomposites were tested as biocompatible nanocarriers for controllable doxorubicin (DOX) delivery. We conclude that SPS is a unique colloid which has promising potential for technological applications such as advanced drug delivery systems, wastewater remediation and as a catalyst for green organic reactions in water.

Material characterization of GPX®: A versatile in situ solidifying embolic platform technology

Endovascular embolization is a minimally invasive procedure during which blood flow to targeted tissues is selectively occluded. The list of clinical indications for embolization continues to expand. Liquid embolic agents are injectable compositions that transition into a solid or semi-solid form when introduced into blood vessels. The mechanism that triggers the liquid-to-solid transition is a key distinguishing feature of liquid embolic agents. GPX is a waterborne liquid embolic agent comprising oppositely charged polyelectrolytes: polyguanidinum and inorganic polyphoshate. In situ solidification is driven by electrostatic condensation of the polyelectrolytes, triggered by ionic strength differentials. We report in vitro characterization of the material properties of GPX, it is in vivo effectiveness in acute animal studies, and its potential for chemoembolization. The viscosity of GPX can be varied over a wide range by adjusting the polyguanidinium MW and/or concentration. Formulation of GPX with either tantalum microparticles (30 wt%) or iodinated radiocontrast agents (300 mgI ml^-1) did not significantly change the flow behavior of GPX; the viscosity was independent of shear rate and remained within a clinically practical range (80-160 cP). Formulation of GPX with doxorubicin substantially increased viscosity at low shear rates and resulted in a power law dependence on shear rate. High contrast and effective vascular occlusion were demonstrated in both swine kidneys and rete mirabile. Contrast from iodinated compounds was temporary, dissipating within hours. The doxorubicin in vitro release profile was linear over 90 days. The results demonstrate that GPX is a versatile liquid embolic platform that can be formulated with a wide range of viscosities injectable at clinically practical flow rates, with either transient or permanent contrast, and that can provide prolonged zero-order delivery of doxorubicin to embolized tissues.

pH-triggered cancer-targeting polymers: From extracellular accumulation to intracellular release

Stimuli-responsive polymers are promising to achieve targeted delivery, improved stability during circulation, and controlled release of therapeutic and diagnostic agents. Among them, pH-responsive polymeric nanocarriers have attracted significant attention as pH varies in different body fluids (e.g., stomach, intestine, and colon) and intracellular organelles (e.g., endosome, lysosome, and mitochondria) to maintain homeostasis, while distinctive pH changes are also found in certain pathological states. For example, the extracellular environment of the tumor is acidic, which can be employed to drive selective delivery. During the internalization process, since most nanocarriers enter cells upon endocytosis where a drop of pH from 6.5 to 5.0 can occur from endosome to lysosome, pH-sensitive groups have been developed for enhanced cargo release. In this review, both non-covalent and covalent interactions responsive to pH changes are introduced, with a focus on the structure-property relationship and their applications in cancer targeting and endosomal escape.

A Facile Way To Improve the Bioavailability of Nanomedicine Based on the Threshold Theory

One of the most significant barriers to the clinical transformation of nanomedicines is low drug distribution in solid tumors due to quick clearance of nanomedicine after injection. Studies have revealed that the distribution of nanomedicine in tumor sites can be considerably improved when the number of nanoparticles supplied in a short period surpasses the threshold. Most routinely employed nanomaterials have dose-related safety concerns. To resolve this problem, we use highly biocompatible albumin to construct blank nanoparticles and doxorubicin loading nanoparticles. Under the guidance of the threshold theory, when the quantity of drug loading nanoparticles is constant, the drug delivery effectiveness improves with the addition of blank nanoparticles. This enhanced impact was verified both in vitro and in vivo. The area under the curve of the high dose group (19.5 × 10¹¹) is 2.5 times higher than that of the low dose group (6.5 × 10¹¹). In addition, the drug distribution of the high dose group at the tumor site was also improved by 1.5 times compared with the low dose group. The results of histopathological sections also showed that the administration of excess blank nanoparticles within 24 h has no damage to the animals. This study contributes to the clinical transition of nanomedicine by providing fresh ideas for anticancer nanomedicine research.

Tailoring Materials with Specific Wettability in Biomedical Engineering

As a fundamental feature of solid surfaces, wettability is playing an increasingly important role in our daily life. Benefitting from the inspiration of biological paradigms and the development in manufacturing technology, numerous wettability materials with elaborately designed surface topology and chemical compositions have been fabricated. Based on these advances, wettability materials have found broad technological implications in various fields ranging from academy, industry, agriculture to biomedical engineering. Among them, the practical applications of wettability materials in biomedical-related fields are receiving remarkable researches during the past decades because of the increasing attention to healthcare. In this review, the research progress of materials with specific wettability is discussed. After briefly introducing the underlying mechanisms, the fabrication strategies of artificial materials with specific wettability are described. The emphasis is put on the application progress of wettability biomaterials in biomedical engineering. The prospects for the future trend of wettability materials are also presented.

Dynamic nanoassembly-based drug delivery system (DNDDS): Learning from nature

Dynamic nanoassembly-based drug delivery system (DNDDS) has evolved from being a mere curiosity to emerging as a promising strategy for high-performance diagnosis and/or therapy of various diseases. However, dynamic nano-bio interaction between DNDDS and biological systems remains poorly understood, which can be critical for precise spatiotemporal and functional control of DNDDS in vivo. To deepen the understanding for fine control over DNDDS, we aim to explore natural systems as the root of inspiration for researchers from various fields. This review highlights ingenious designs, nano-bio interactions, and controllable functionalities of state-of-the-art DNDDS under endogenous or exogenous stimuli, by learning from nature at the molecular, subcellular, and cellular levels. Furthermore, the assembly strategies and response mechanisms of tailor-made DNDDS based on the characteristics of various diseased microenvironments are intensively discussed. Finally, the current challenges and future perspectives of DNDDS are briefly commented.

A carrier-free anti-inflammatory platinum (II) self-delivered nanoprodrug for enhanced breast cancer therapy

Cisplatin is one of the most used first-line anticancer drugs for various solid tumor therapies. However, cisplatin-based chemotherapy can induce tumor cells to secrete excessive prostaglandin E2 (PGE2) catalyzed by cyclooxygenase-2 (COX-2), which, in turn, counteracts its chemotherapeutic effect and further accelerates tumor metastasis. Here, we report a carrier-free self-delivered nanoprodrug based on platinum (II) coordination bonding coupled with tolfenamic acid (Tolf) (named Tolfplatin). Tolfplatin can spontaneously assemble into uniformly sized nanoparticles (NPs) with a high drug-loading capacity. Compared with cisplatin, Tolfplatin NPs can facilitate cellular uptake, significantly decrease PGE2 secretion by COX-2 inhibition, which further downregulate tumorous anti-apoptotic and metastasis-associated proteins, thereby efficiently inducing apoptotic cell death and significantly inhibit tumor metastasis in vitro and in vivo. Therefore, as the carrier-free nanoprodrug, Tolfplatin NPs are promising anti-tumoral agents to inhibit tumor proliferation and metastasis by enriching the function and promoting the anti-tumor activity of cisplatin.

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.

Functionalization of Polyethyleneimine with Hollow Cyclotriveratrylene and Its Subsequent Supramolecular Interaction with Doxorubicin

In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host-guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform.

Synthetic dimeric-drug phospholipid: a versatile liposomal platform for cancer therapy

An amphiphilic dimeric-podophyllotoxin (PODO) phospholipid was synthesized to assemble into liposomes as a combination of prodrug and nanocarrier. The results have demonstrated that the cell membrane-like delivery system possessed an improved cellular uptake and favorable antitumor efficacy with reduced side-effects. This strategy provides a new effective platform in drug delivery for cancer chemotherapy.

Iron Oxide Nanoparticles as Carriers for DOX and Magnetic Hyperthermia after Intratumoral Application into Breast Cancer in Mice: Impact and Future Perspectives

There is still a need for improving the treatment of breast cancer with doxorubicin (DOX). In this paper, we functionalized magnetic nanoparticles (MNPs) with DOX and studied the DOX-induced antitumor effects in breast cancer cells (BT474) in the presence of magnetic hyperthermia (43 °C, 1 h). We show that i) intratumoral application of DOX-functionalized MNPs (at least at a concentration of 9.6 nmol DOX/100 mm³ tumor volume) combined with magnetic hyperthermia favors tumor regression in vivo, and there is evidence for an increased effect compared to magnetic hyperthermia alone or to the intratumoral application of free DOX and ii) the presence of the pseudopeptide NucAnt (N6L) on the MNP surface might well be beneficial in its function as carrier for MNP internalization into breast cancer cells in vitro, which could further augment the possibility of the induction of intracellular heating spots and cell death in the future.

A stimuli-responsive anticancer drug delivery system with inherent antibacterial activities

We describe a novel class of stimuli-sensitive sulfonium-based synthetic lipids, which exhibit several favorable biophysical properties of phospholipids. The potent sulfonium-based lipid was successfully disassembled by glutathione to release the encapsulated drug molecules in a controlled manner. The cationic lipid also showed lower cytotoxicity against mammalian cells and displayed moderate antibacterial activities.

Reduction-Triggered Paclitaxel Release Nano-Hybrid System Based on Core-Crosslinked Polymer Dots with a pH-Responsive Shell-Cleavable Colorimetric Biosensor

Herein, we describe the fabrication and characterization of carbonized disulfide core-crosslinked polymer dots with pH-cleavable colorimetric nanosensors, based on diol dye-conjugated fluorescent polymer dots (L-PD), for reduction-triggered paclitaxel (PTX) release during fluorescence imaging-guided chemotherapy of tumors. L-PD were loaded with PTX (PTX loaded L-PD), via π-π stackings or hydrophobic interactions, for selective theragnosis by enhanced release of PTX after the cleavage of disulfide bonds by high concentration of glutathione (GSH) in a tumor. The nano-hybrid system showed fluorescence quenching behavior with less than 2% of PTX released under physiological conditions. However, in a tumor microenvironment, the fluorescence recovered at an acidic-pH, and PTX (approximately 100% of the drug release) was released efficiently out of the matrix by reduction caused by the GSH level in the tumor cells, which improved the effectiveness of the cancer treatment. Therefore, the colorimetric nanosensor showed promising potential in distinguishing between normal and cancerous tissues depending on the surrounding pH and GSH concentrations so that PTX can be selectively delivered into cancer cells for improved cancer diagnosis and chemotherapy.

DOX Loaded Aggregation-induced Emission Active Polymeric Nanoparticles as a Fluorescence Resonance Energy Transfer Traceable Drug Delivery System for Self-indicating Cancer Therapy

In this study, an AIE-active polymer (FTP) was successfully prepared and employed to load anti-cancer drug doxorubicin (DOX) for self-indicating cancer therapy via dual FRET process. Our results demonstrated that the FTP polymer could self-assemble into nanoparticles (NPs) in aqueous solutions to give strong fluorescence emission via intramolecular FRET process. The DOX loaded FTP NPs (drug loading content: 21.77%) were homogeneous particles with size around 50 nm and neutral surface charge, which showed preferable colloidal stability, hemolysis and selective drug release with comparable in vivo antitumor effects to DOX·HCl. In particular, the FRET process between FTP (donor) and DOX (acceptor) could serve as indicator for monitoring the in vitro and in vivo drug release profile, which might be a promising platform to realize real-time monitoring of drug localization and release during the delivery process. STATEMENT OF SIGNIFICANCE: 1. An amphiphilic polymer containing aggregation-induced emission segments and polyethylene glycol (PEG) chains (FTP) was firstly synthesized, which is capable of exerting strong fluorescence via intramolecular Förster resonance energy transfer (FRET) in the aggregate state. 2. The FTP polymer could self-assembled into homogeneous nanoparticles in aqueous environment with decent DOX loading capacity. 3. The DOX loaded FTP nanoparticles can afford FRET-traceable monitoring of the drug release both in vitro and in vivo.