A review of emerging bone tissue engineering via PEG conjugated biodegradable amphiphilic copolymers

Defects in bones can be caused by a plethora of reasons, such as trauma or illness, and in many cases, it poses challenges to the current treatment approaches for bone repair. With increasing demand of bone bioengineering in tissue transplant, there is a need to source for sustainable solutions to induce bone regeneration. Polymeric biomaterials have been identified as a promising approach due to its excellent biocompatibility and controllable biodegradability. Specifically, poly(ethylene glycol) (PEG) is one of the most commonly investigated polymer for use in bio-related application due to its bioinertness and versatility. Furthermore, the hydrophilic nature enables it to be incorporated with hydrophobic but biodegradable polymers like, polylactide (PLA) and polycaprolactone (PCL), to create an amphiphilic polymer. This article reviews the recent synthetic strategies available for the construction of PEG conjugated polymeric system, analysis of PEG influence on the material properties, and provides an overview of its application in bone engineering.

Stimuli-Responsive Supramolecular Hydrogels and Their Applications in Regenerative Medicine

Supramolecular hydrogels are a class of self-assembled network structures formed via non-covalent interactions of the hydrogelators. These hydrogels capable of responding to external stimuli are considered to be smart materials due to their ability to undergo sol-gel and/or gel-sol transition upon subtle changes in their surroundings. Such stimuli-responsive hydrogels are intriguing biomaterials with applications in tissue engineering, delivery of cells and drugs, modulating tissue environment to promote innate tissue repair, and imaging for medical diagnostics among others. This review summarizes the recent developments in stimuli-responsive supramolecular hydrogels and their potential applications in regenerative medicine. Specifically, various structural aspects of supramolecular hydrogelators involved in self-assembly, the role of external stimuli in tuning/controlling their phase transitions, and how these functions could be harnessed to advance applications in regenerative medicine are focused on. Finally, the key challenges and future prospects for these versatile materials are briefly described.

The effective treatment of multi-drug resistant tumors with self-assembling alginate copolymers

Alginates of two different chain lengths were alkyne functionalized on the hydroxyl group, leaving all carboxylic groups intact.

A multifunctional polymeric gene delivery system for circumventing biological barriers

Crucial light-controlled-ROS and pH-stimulus-responsive functionalities are tailored into a triblock copolymer for manufacture of gene delivery vehicles.

Sustained delivery of anti-VEGFs from thermogel depots inhibits angiogenesis without the need for multiple injections

Polyurethane thermogels show sustained delivery of bioactive anti-VEGFs therapeutics to the eye.

Surfactant Free Delivery of Docetaxel by Poly[(R)-3-hydroxybutyrate-(R)-3-hydroxyhexanoate]-Based Polymeric Micelles for Effective Melanoma Treatments

Docetaxel (DTX) is a new semisynthetic chemical in the taxoid family and serves a wide spectrum of chemotherapeutics. Current commercial formulation of DTX is based on the addition of the nonionic surfactants (i.e., ethanol and Tween 80), which are reported to cause severe hemolysis, hypersensitivity reactions, or neurotoxic toxicity and greatly hinders patient tolerance or compliance. In this report, a novel low-toxic, biodegradable, and amphiphilic poly[(R)-3-hydroxybutyrate-(R)-3-hydroxyhexanoate] (PHBHx)-based polyurethane (a copolymer made of hydrophobic PHBHx with biocompatible D-3-hydroxybutyric acid as degradation product, thermosensitive polypropylene glycol (PPG), and hydrophilic polyethylene glycol (PEG) segments) with nanosized micelle formation ability to encapsulate DTX, as a surfactant free formulation, is reported. Interestingly, this DTX-loaded poly(PHBHx/PEG/PPG urethane) micelle formulation with >90% drug loading efficiency shows significantly improved DTX solubility in aqueous medium, reduced hemolysis for better blood compatibility, and increased drug uptake in A375 melanoma cells, which provides the possibility of systematic delivery of DTX. As a proof-of-concept, an A375 melanoma xenograft mouse model is established to verify the therapeutic effect of this DTX-loaded poly(PHBHx/PEG/PPG urethane) micelle formulation, indicating the promising application of PHBHx-based polymeric nanosized micelle as a surfactant free formulation of chemotherapeutics which might greatly be beneficial for controllable delivery of pharmaceutics and cancer therapy.

Cyclodextrin-based delivery systems for cancer treatment

Cyclodextrins, one of safe excipients, are able to form host-guest complexes with fitted molecules given the unique nature imparted by their structure in result of a number of pharmaceutical applications. On the other hand, targeted or responsive materials are appealing therapeutic platforms for the development of next-generation precision medications. Meanwhile, cyclodextrin-based polymers or assemblies can condense DNA and RNA in result to be used as genetic therapeutic agents. Armed with a better understanding of various pharmaceutical mechanisms, especially for cancer treatment, researchers have made lots of works about cyclodextrin-based drug delivery systems in materials chemistry and pharmaceutical science. This Review highlights recent advances in cyclodextrin-based delivery systems for cancer treatment capable of targeting or responding to the physiological environment. Key design principles, challenges and future directions, including clinical translation, of cyclodextrin-based delivery systems are also discussed.

Poly-Gamma-Glutamic Acid (γ-PGA)-Based Encapsulation of Adenovirus to Evade Neutralizing Antibodies

In recent years, there has been an increasing interest in oncolytic adenoviral vectors as an alternative anticancer therapy. The induction of an immune response can be considered as a major limitation of this kind of application. Significant research efforts have been focused on the development of biodegradable polymer poly-gamma-glutamic acid (γ-PGA)-based nanoparticles used as a vector for effective and safe anticancer therapy, owing to their controlled and sustained-release properties, low toxicity, as well as biocompatibility with tissue and cells. This study aimed to introduce a specific destructive and antibody blind polymer-coated viral vector into cancer cells using γ-PGA and chitosan (CH). Adenovirus was successfully encapsulated into the biopolymer particles with an encapsulation efficiency of 92% and particle size of 485 nm using the ionic gelation method. Therapeutic agents or nanoparticles (NPs) that carry therapeutics can be directed specifically to cancerous cells by decorating their surfaces using targeting ligands. Moreover, in vitro neutralizing antibody response against viral capsid proteins can be somewhat reduced by encapsulating adenovirus into γ-PGA-CH NPs, as only 3.1% of the encapsulated adenovirus was detected by anti-adenovirus antibodies in the presented work compared to naked adenoviruses. The results obtained and the unique characteristics of the polymer established in this research could provide a reference for the coating and controlled release of viral vectors used in anticancer therapy.

Biodegradable polyester unimolecular systems as emerging materials for therapeutic applications

Unimolecular micelles, as a class of single-molecular micelles, are structurally stable regardless of their concentrations or alterations of the outer environment such as pH, temperature, ion strength etc. in comparison with conventional polymeric micelles. Polyester unimolecular micelles are extensively applied in bio-medical fields because of their stability, biocompatibility, biodegradability, structural-controllabilty etc. In this review, the most recent developments in polyester unimolecular micelle designs in terms of Boltorn polymer H40 core, cyclodextrin, dendrimer or dendrimer-like polymer, or polyhedral oligomeric silsesquioxane (POSS) based polyester unimolecular micelles are presented. The significance and application in biomedical fields including drug delivery, bio-imaging and theranostics are also classified in this review. Finally, the remaining challenges and future perspectives for further development of unimolecular micelles as therapeutic materials are also discussed.

Polymeric Encapsulation of Turmeric Extract for Bioimaging and Antimicrobial Applications

As a herb of the ginger family, the turmeric plant has been used as spice and colorant in the Oriental countries. The rhizome part of the plant is rich in curcumin, which has been proven to be the main ingredient responsible for turmeric's biological effects. Most research endeavors have been upon the investigation of pharmaceutical activities of curcumin, yet the fluorescence of curcumin is a bit far from well-studied. The major drawbacks associated with curcumin are its poor aqueous solubility and low stability. In this communication, the encapsulation of fluorescent turmeric extract into polymeric nanoparticles (NPs) for bioimaging and antibacterial applications is reported. Through poly(d,l-lactic-co-glycolic acid) (PLGA) encapsulation, solubility of curcumin is greatly increased, and the biodegradable nature of PLGA further enhances the biocompatibility of curcumin. These Cur-PLGA NPs are successfully demonstrated to be efficient fluorescence probes for bioimaging, and promising for antibacterial application.

Targeted and Sustained Corelease of Chemotherapeutics and Gene by Injectable Supramolecular Hydrogel for Drug-Resistant Cancer Therapy

Coadministration of chemotherapeutics as well as therapeutic gene could play a synergistic effect on cancer treatment. It is noteworthy that targeted and sustained codelivery of chemotherapeutic and therapeutic gene was rarely achieved in previous reports, while it might serve as an important platform for treating solid tumor with possible surrounding lesions. Herein, an injectable supramolecular hydrogel formed by α-cyclodextrin (α-CD) and cationic amphiphilic copolymer made of methoxy-poly(ethylene glycol)-b-poly(ε-caprolactone)-b-poly(ethylene imine) with folic acid targeted group (MPEG-PCL-PEI-FA), is rationally designed to achieve sustained codelivery of chemotherapeutic paclitaxel (PTX) and B-cell lymphoma-2 (Bcl-2) conversion gene Nur77 in the form of nanocomplex up to 7 days, to effectively inhibit the growth of folate receptor overexpressing H460/Bcl-2 therapeutic-resistant tumors (induced by overexpression of anti-apoptotic Bcl-2 protein), with peritumoral injection rather than direct intratumoral injection of hydrogel. To the best of our knowledge, this is a pioneer report on injectable MPEG-PCL-PEI-FA/α-CD supramolecular hydrogel with the ability to codeliver and sustainedly release PTX and Nur77 gene to combat Bcl-2 overexpressed therapeutic-resistant tumors in a targeted manner, which might be beneficial for further design in personalized medicine.

Polymeric Janus Nanoparticles: Recent Advances in Synthetic Strategies, Materials Properties, and Applications

Polymeric Janus nanoparticles with two sides of incompatible chemistry have received increasing attention due to their tunable asymmetric structure and unique material characteristics. Recently, with the rapid progress in controlled polymerization combined with novel fabrication techniques, a large array of functional polymeric Janus particles are diversified with sophisticated architecture and applications. In this review, the most recently developed strategies for controlled synthesis of polymeric Janus nanoparticles with well-defined size and complex superstructures are summarized. In addition, the pros and cons of each approach in mediating the anisotropic shapes of polymeric Janus particles as well as their asymmetric spatial distribution of chemical compositions and functionalities are discussed and compared. Finally, these newly developed structural nanoparticles with specific shapes and surface functions orientated applications in different domains are also discussed, followed by the perspectives and challenges faced in the further advancement of polymeric Janus nanoparticles as high performance materials.

Controlled self-assembly into diverse stimuli-responsive microstructures: from microspheres to branched cylindrical micelles and vesicles

A series of amphiphilic PDMAEMA–SS–PCL chains with variable ratios of hydrophilic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) to hydrophobic poly(ε-caprolactone) (PCL) were prepared via ring-opening polymerization, in which the two different moieties were linked via a disulfide bond with reduction responsiveness. After cross-linking by the photodegradable o-nitrobenzyl linkage, the amphiphilic chains could self-assemble into microspheres, branched cylindrical micelles and vesicles, which were responsive to the reduction agent dl-dithiothreitol and UV light irradiation through different mechanisms.

A series of cross-linked amphiphilic PDMAEMA–SS–PCL were prepared, which could self-assemble into diverse microstructures with reduction and light responsiveness.

Cyclodextrin-Based Star-Like Amphiphilic Cationic Polymer as a Potential Pharmaceutical Carrier in Macrophages

Effective delivery of therapeutic genes or small molecular drugs into macrophages is important for cell based immune therapy, but it remains a challenge due to the intracellular reactive oxygen species and endosomal degradation of therapeutics inside immune cells. In this report, the star-like amphiphilic biocompatible β-cyclodextrin-graft-(poly(ε-caprolactone)-block-poly(2-(dimethylamino) ethyl methacrylate)_x (β-CD-g-(PCL-b-PDMAEMA)_x ) copolymer, consisting of a biocompatible cyclodextrin core, hydrophobic poly(ε-caprolactone) PCL segments and hydrophilic PDMAEMA blocks with positive charge, is optimized to achieve high efficiency gene transfection with enhanced stability, due to the micelle formation by hydrophobic PCL segments. In comparison with lipofetamine, a currently popular nonviral gene carrier, β-CD-g-(PCL-b-PDMAEMA)_x copolymer, shows better transfection efficiency of plasmid desoxyribose nucleic acid in RAW264.7 macrophages. More interestingly, this delivery platform by β-CD-g-(PCL-b-PDMAEMA)_x not only shows low toxicity but also better dexamethasone delivery efficiency, which might indicate its great potential in immunotherapy.

A Recent Perspective on Noncovalently Formed Polymeric Hydrogels

Chemically crosslinked covalent hydrogels form a permanent and often strong network, and have been extensively used so far in drug delivery and tissue engineering. However, it is more difficult to induce dynamic and highly tunable changes in these hydrogels. Noncovalently formed hydrogels show promise as inherently reversible systems with an ability to change in response to dynamic environments, and have garnered strong interest recently. In this Personal Account, we elucidate a few key attractive properties of noncovalent hydrogels and describe recent developments in hydrogels crosslinked using various different noncovalent interactions. These hydrogels offer huge control for modulating material properties and could be more relevant mimics for biological systems.

Synergistic Lysosomal Activatable Polymeric Nanoprobe Encapsulating pH Sensitive Imidazole Derivative for Tumor Diagnosis

Developing optical tumor imaging probes with minimal background noise is very important for its early detection of small lesions and accurate diagnosis of cancer. To overcome the bottleneck of low signal to noise ratio and sensitivity, it needs further improvement in fluorescent probe design and understanding of tumor development process. Recent reports reveal that lysosome's acidity in cancer cells can be below 4.5 with high Na⁺ /H⁺ exchange activity, which makes it an ideal target intracellular organelle for cancer diagnosis based on the variation of pH. Herein, a boron 2-(2'-pyridyl) imidazole complex derivative (BOPIM-N) is developed, with the ability to show a pH-activatable "OFF-ON" fluorescent switch by inhibiting twisted intramolecular charge transfer upon protonation at pH 3.8-4.5, which is studied for its selective viable cancer cell imaging ability in both in vitro and in vivo experiments. Interestingly, BOPIM-N can specifically emit green fluorescence in lysosomes of cancer cells, indicating its promising cancer cell specific imaging ability. More importantly, nanoformulated BOPIM-N probes can be specifically light-ON in tumor bearing site of nude mice with resolution up to cellular level, indicating its potential application in tumor diagnosis and precision medicine.

Dual Drug Delivery System Based on Biodegradable Organosilica Core-Shell Architectures

To overcome drug resistance, efficient cancer therapeutic strategies using a combination of small-molecule drugs and macromolecule drugs is highly desired. However, because of their significant differences in molecular weight and size, it is difficult to load them simultaneously in one vector and to release them individually. Here, a biodegradable organosilica-based core-shell-structured nanocapsule was designed and used as a dual stimuli-responsive drug vector to solve this problem. Biodegradable organosilica shell coated outside the macromolecule model drug "core" would be disrupted by high glutathione (GSH) levels inside tumor cells, resulting in the escape of the entrapped drugs. Small-molecule drugs capping on the surface of the organosilica shell via pH-responsive imine bonds can be cut and released in the acidic lysosomal environment. Transmission electron microscopy has shown that the framework of the organosilica shell was dissolved and degraded after 8 h incubation with 5 mM GSH. Confocal imaging confirmed that small-molecule and macromolecular drugs were individually released from the nanoparticles because of the pH or redox-triggered degradation under the tumor microenvironment and thus led to the strong fluorescence recovery in the cytoplasm. As expected, these biodegradable organosilica nanoparticles could not release drugs into normal cells but could specifically release them into tumor cells owing to their tumor-triggered targeting capability. This system will serve as an efficient shuttle for multidrug delivery and also provide a potential strategy to overcome drug resistance.

Differentiation therapy revisited

The concept of differentiation therapy emerged from the fact that hormones or cytokines may promote differentiation ex vivo, thereby irreversibly changing the phenotype of cancer cells. Its hallmark success has been the treatment of acute promyelocytic leukaemia (APL), a condition that is now highly curable by the combination of retinoic acid (RA) and arsenic. Recently, drugs that trigger differentiation in a variety of primary tumour cells have been identified, suggesting that they are clinically useful. This Opinion article analyses the basis for the clinical successes of RA or arsenic in APL by assessing the respective roles of terminal maturation and loss of self-renewal. By reviewing other successful examples of drug-induced tumour cell differentiation, novel approaches to transform differentiating drugs into more efficient therapies are proposed.

Synthesis of well-defined star, star-block, and miktoarm star biodegradable polymers based on PLLA and PCL by one-pot azide–alkyne click reaction

Based on the “arm-first” strategy, ring-opening polymerization (ROP) and one-pot azide–alkyne click reaction, well-defined star-shaped polymers with different architectures have been successfully synthesized, including the star homopolymers four-arm star-shaped polycaprolactone (4sPCL) and four-arm star-shaped poly(l-lactic acid) (4sPLLA), star-block copolymer 4sPCL-b-PLLA and miktoarm star-shaped copolymer PCL₂PLLA₂. The star homopolymers 4sPCL and 4sPLLA were synthesized by a click reaction of an azide small molecule initiator and HC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C-PCL or HCC-PLLA. The star-block copolymer 4sPCL-b-PLLA was synthesized by a click reaction of an azide small molecule initiator and the block copolymer HCC-PCL-b-PLLA. The miktoarm star polymer PCL₂PLLA₂ was synthesized by a one-pot azide–alkyne click reaction of simultaneous addition of equal proportions of HCC-PCL and HCC-PLLA. The structures of these star-shaped polymers have been confirmed by NMR, FT-IR and GPC. Furthermore, the melting and crystallization behaviors investigated using DSC and WXRD also confirm the formation of star-shaped polymers with different architectures.

Star, star-block, and miktoarm star biodegradable polymers were synthesized by an “arm-first” strategy, ring-opening polymerization and one-pot azide-alkyne click reaction.

Exploring the reversible host–guest chemistry of a crystalline octanuclear Ag(i) metallosupramolecular macrocycle formed from a simple pyrazinylpyridine ligand

High nuclearity Ag(i) assemblies are prepared from simple polytopic ligands, including an octanuclear metallomacrocycle which exhibits reversible and selective guest exchange.

Protective effect of acacetin on sepsis-induced acute lung injury via its anti-inflammatory and antioxidative activity

Sepsis is a clinical syndrome with no effective protective or therapeutic treatments. Acacetin, a natural flavonoid compound, has anti-oxidative and anti-inflammatory effects which can potentially work to reduce sepsis. We investigated the potential protective effect of acacetin on sepsis-induced acute lung injury (ALI) ALI and dissect out the underlying mechanisms. Mice were divided into five groups: a sham group, a sepsis-induced ALI group, and three sepsis groups pre-treated with 20, 40, and 80 mg/kg body weight of acacetin. We found that acacetin significantly attenuated sepsis-induced ALI, in histological examinations and lung edema. Additionally, acacetin treatment decreased protein and inflammatory cytokine concentration and the number of infiltrated inflammatory cells in BALF compared with that in the non-treated sepsis mice. Pulmonary myeloperoxidase (MPO) activity was lower in the acacetin-pre-treated sepsis groups than in the sepsis group. The mechanism underlying the protective effect of acacetin on sepsis is related to the regulation of certain antioxidation genes, including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), superoxide dismutases (SODs), and heme oxygenase 1 (HO-1).Taken together, our results indicate that acacetin pre-treatment inhibits sepsis-induced ALI through its anti-inflammatory and antioxidative activity, suggesting that acacetin may be a potential protective agent for sepsis-induced ALI.

In vitro and in vivo protein release and anti-ischemia/reperfusion injury properties of bone morphogenetic protein-2-loaded glycyrrhetinic acid-poly(ethylene glycol)-b-poly(l-lysine) nanoparticles

Here, we describe a bone morphogenetic protein-2 (BMP-2) nanocarrier based on glycyrrhetinic acid (GA)-poly(ethylene glycol) (PEG)-b-poly(l-lysine) (PLL). A protein nanocarrier was synthesized, characterized and evaluated as a BMP-2 delivery system. The designed nanocarrier was synthesized based on the ring-opening polymerization of amino acid N-carboxyanhydride. The final product was measured with ¹H nuclear magnetic resonance. GA-PEG-b-PLL nanocarrier could combine with BMP-2 through electrostatic interaction to form polyion complex (PIC) micelles. BMP-2 could be rapidly and efficiently encapsulated through the GA-PEG-b-PLL nanocarrier under physiological conditions, exhibiting efficient encapsulation and sustained release. In addition, the GA-PEG-b-PLL-mediated BMP-2 delivery system could target the liver against hepatic diseases as it has GA-binding receptors. The anti-hepatic ischemia/reperfusion injury (anti-HI/RI) effect of BMP-2/GA-PEG-b-PLL PIC micelles was investigated in rats using free BMP-2 and BMP-2/PEG-b-PLL PIC micelles as controls, and the results showed that BMP-2/GA-PEG-b-PLL PIC micelles indicated significantly enhanced anti-HI/RI property compared to BMP-2 and BMP-2/PEG-b-PLL. All results suggested that GA-PEG-b-PLL could be used as a potential BMP-2 nanocarrier.

The Natural Flavone Acacetin Blocks Small Conductance Ca2+-Activated K+ Channels Stably Expressed in HEK 293 Cells

The natural flavone acacetin inhibits several voltage-gated potassium currents in atrial myocytes, and has anti-atrial fibrillation (AF) effect in experimental AF models. The present study investigates whether acacetin inhibits the Ca²⁺-activated potassium (K_Ca) currents, including small conductance (SK_Ca1, SK_Ca2, and SK_Ca3), intermediate conductance (IK_Ca), and large-conductance (BK_Ca) channels stably expressed in HEK 293 cells. The effects of acacetin on these K_Ca channels were determined with a whole-cell patch voltage-clamp technique. The results showed that acacetin inhibited the three subtype SK_Ca channel currents in concentration-dependent manner with IC₅₀ of 12.4 μM for SK_Ca1, 10.8 μM for SK_Ca2, and 11.6 μM for SK_Ca3. Site-directed mutagenesis of SK_Ca3 channels generated the mutants H490N, S512T, H521N, and A537V. Acacetin inhibited the mutants with IC₅₀ of 118.5 μM for H490N, 275.2 μM for S512T, 15.3 μM for H521N, and 10.6 μM for A537V, suggesting that acacetin interacts with the P-loop helix of SK_Ca3 channel. However, acacetin at 3–10 μM did not decrease, but induced a slight increase of BK_Ca (+70 mV) by 8% at 30 μM. These results demonstrate the novel information that acacetin remarkably inhibits SK_Ca channels, but not IK_Ca or BK_Ca channels, which suggests that blockade of SK_Ca by acacetin likely contributes to its anti-AF property previously observed in experimental AF.

Overcoming STC2 mediated drug resistance through drug and gene co-delivery by PHB-PDMAEMA cationic polyester in liver cancer cells

Stanniocalcin 2 (STC2) overexpression in hepatocellular carcinoma (HCC) could lead to poor prognosis, which might be due to its induced P-glycoprotein and Bcl-2 protein expression level increase. P-glycoprotein or membrane pump induced drug efflux and altered prosurvival Bcl-2 expression are key mechanisms for drug resistance leading to failure of chemotherapy in HCC. However, current strategy to overcome both P-glycoprotein and Bcl-2 protein induced drug resistance was rarely reported. In this work, we utilized an amphiphilic poly[(R)-3-hydroxybutyrate] (PHB)-b-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) cationic polyester to encapsulate chemotherapeutic paclitaxel (PTX) in hydrophobic PHB domain and Bcl-2 convertor Nur77/ΔDBD gene (Nur77 without DNA binding domain for mitochondria localization) by formation of polyplex due to cationic PDMAEMA segment, to effectively inhibit the drug resistant HepG2/STC2 and SMCC7721/STC2 liver cancer cell growth. Thanks to the cationic nanoparticle complex formation ability and high transfection efficiency to express Bcl-2 conversion proteins, PHB-PDMAEMA/PTX@polyplex could partially impair P-glycoprotein induced PTX efflux and activate the apoptotic function of previous prosurvival Bcl-2 protein. This is the pioneer report of cationic amphiphilic polyester PHB-PDMAEMA to codeliver anticancer drug and therapeutic plasmid to overcome both pump and non-pump mediated chemotherapeutic resistance in liver cancer cells, which might be inspiring for the application of polyester in personalized cancer therapy.

Acetal-linked PEGylated paclitaxel prodrugs forming free-paclitaxel-loaded pH-responsive micelles with high drug loading capacity and improved drug delivery

Endosomal pH-responsive micellar nanoparticles were prepared by self-assembly of an amphiphilic poly(ethylene glycol)-acetal-paclitaxel (PEG-acetal-PTX) prodrug, and free PTX could be encapsulated in the hydrophobic core of the nanoparticles. These nanoparticles exhibited excellent storage stability for over 6months under normal conditions, but disassembled quickly in response to faintly acidic environment. Incorporating physical encapsulation and chemical conjugation, the PTX concentration in the nanoparticles solution could reach as high as 3665μg/mL, accompanying with a high drug loading capacity of 60.3%. Additionally, benefitting from the difference in drug release mechanism and rate between encapsulated PTX and conjugated PTX, a programmed drug release behavior was observed, which may result in higher intracellular drug concentration and longer action time. CCK-8 assays showed that the nanoparticles demonstrated superior antitumor activity than free PTX against both HeLa and MDA-MB-231 cells. These prodrug-based nanomedicines have a great potential in developing translational PTX formulations for cancer therapy.

α-Cyclodextrin concentration-controlled thermo-sensitive supramolecular hydrogels

Supramolecular hydrogels (SHGs) built from inclusion complex of macrocyclic compound α-cyclodextrin (α-CD) and poly(ethylene glycol) (PEG) have attracted much interest due to their excellent biocompatibility and great potential for biomedical applications. In this work, the hydrogen bond of nucleic acid was introduced into the above-mentioned SHG by syntheses of nucleobase guanine/cytosine (G/C)-terminated PEG (G-PEG-G/C-PEG-C). The base-pairing interaction between G and C as an additional network junction effectively enhanced storage moduli (G's) of the hydrogels. Moreover, the prepared hydrogels exhibited excellent cytocompatibility and property for controlled drug release, outlining the potential of thermo-sensitive construct for biomedical applications, such as local chemotherapy of cancers.

Efficient synthesis of highly fluorescent carbon dots by microreactor method and their application in Fe3+ ion detection

Rapidly obtaining strong photoluminescence (PL) of carbon dots with high stability is crucial in all practical applications of carbon dots, such as cell imaging and biological detection. In this study, we proposed a rapid, continuous carbon dots synthesis technique by using a microreactor method. By taking advantage of the microreactor, we were able to rapidly synthesized CDs at a large scale in less than 5min, and a high quantum yield of 60.1% was achieved. This method is faster and more efficient than most of the previously reported methods. To explore the relationship between the microreactor structure and CDs PL properties, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were carried out. The results show the surface functional groups and element contents influence the PL emission. Subsequent ion detection experiments indicated that CDs are very suitable for use as nanoprobes for Fe³⁺ ion detection, and the lowest detection limit for Fe³⁺ is 0.239μM, which is superior to many other research studies. This rapid and simple synthesis method will not only aid the development of the quantum dots industrialization but also provide a powerful and portable tool for the rapid and continuous online synthesis of quantum dots supporting their application in cell imaging and safety detection.

α,ω-Diphenylalanine-End-Capping of PEG-PPG-PEG Polymers Changes the Micelle Morphology and Enhances Stability of the Thermogel

Pluronics F127 (P, PEG-PPG-PEG triblock copolymer) was coupled with diphenylalanine (FF) to prepare FF-end-capped Pluronics (FFPFF). With increasing temperature from 10 to 60 °C, the FFPFF self-assembled to vesicles in water. The unimer-to-vesicle transition accompanies endothermic enthalpy of 53.9 kcal/mol. Aqueous P and FFPFF solutions exhibited thermogelation in 15.0-24.0 wt %. The gel phase of FFPFF was stable up to 90 °C, whereas that of P turned into a sol again at 55-86 °C, indicating that end-capping with FF improved the gel stability against heat. In addition, the carboxylic acids of the FF end-groups can form coordination bonds with metal ions, and the gel modulus at 37 °C increased from 15-21 KPa (P) to 20-25 KPa (FFPFF) to 24-28 KPa (FFPFF-Zn), and the duration of gel against water-erosion increased from 24 h (P) to 60 h (FFPFF-Zn), leading to a useful biomaterial for sustained drug delivery. The FFPFF-Zn gels implanted in the rats' subcutaneous layer induced a mild inflammatory responses. Contrary to the previous end-capping of Pluronics by poly(lactic acid), polycarprolactone, carboxylic acid, and so on that weakened the gel stability, the diphenylalanine end-capping strengthened the stability of Pluronics gel against heat and water-erosion. This paper suggests that the control of polymer nanoassemblies directed by FF end-groups improves the mechanical properties and stability of the resulting thermogel and, thus, provides a useful drug delivery carrier with prolonged durability.

Injectable Polypeptide Thermogel as a Tissue Engineering System for Hepatogenic Differentiation of Tonsil-Derived Mesenchymal Stem Cells

A poly(ethylene glycol)-b-poly(l-alanine) (PEG-l-PA) hydrogel incorporating tonsil-derived mesenchymal stem cells (TMSCs), tauroursodeoxycholic acid (TUDCA), hepatocyte growth factor (HGF), and fibroblast growth factor 4 (FGF4) was prepared through thermal gelation of an aqueous polymer solution for an injectable tissue engineering application. The thermal gelation accompanied conformational changes of both PA and PEG blocks. The gel modulus at 37 °C was controlled to be 1000 Pa by using a 14.0 wt % aqueous polymer solution. The gel preserved its physical integrity during the 3D culture of the cells. TUDCA, HGF, and FGF4 were released from the PEG-l-PA hydrogel over 21 days of the 3D cell culture period. TMSCs initially exhibited a spherical shape, whereas some fibers protruded from the cells on days 14-21 of 3D culture. The injectable system exhibited pronounced expressions of the hepatic biomarkers at both mRNA and protein levels, which are significantly better than the commercially available hyaluronic acid gel. In particular, the hepatogenically differentiated cells from the TMSCs in the injectable system demonstrated hepatic biofunctions comparable to HepG2 cells for the uptakes of low density lipoproteins (52%) and indocyanine green (76%), and the production of albumin (40%) and urea (52%), which are also significantly better than the 3D-cultured cells in the commercially available hyaluronic acid gel. Our studies suggest that the PEG-l-PA thermogel incorporating TMSCs, TUDCA, and growth factors is highly promising as an in situ forming tissue engineering system.