In Vitro Cytotoxicity of Polyphosphoester as a Novel Injectable Alveolar Replacement Material

The aim of this study was to investigate the in vitro cytotoxicity of polyphosphoester polymer used as a novel injectable alveolar bone substitutes for controlled delivery of tetracycline. Cell culture medium was exposed to the polymer （0.01-10 mg/mL） for 24 h. The L-929 mouse fibro- blasts were then exposed to the treated cell culture medium for 24 h. Finally, cell viability and growth were assessed by using MTT assay and Alamar Blue assay. No significant cytotoxicity of the polyphosphoester against L-929 mouse fibroblasts was observed at a concentration up to 10 mg/mL （P〉0.05）. The two evaluation methods showed no significant differences （P〉0.05）. This study suggests that polyphosphoester does not demonstrate any significant toxic effects to cells in vitro and has the potential to be used both as a medical device and as scaffolds in tissue engineering applications.

Monoclonal Antibody-conjugated Polyphosphoester-hyd-DOX Prodrug Nanoparticles for Targeted Chemotherapy of Liver Cancer Cells

In order to overcome the limitation of traditional active nano-therapeutic drugs on tumor targeting efficiency which cannot reach the receptor/target in sufficient amount in the body,in this work,we developed a monoclonal antibody(mAb)and a polymer-hyd-doxorubicin prodrug conjugate,which enables the self-assembled nanoparticles to have precise targeting,tumor tissue aggregation and pH-sensitive drug release.We first prepared an amphiphilic polymer prodrug,abbreviated as H2N-PEEP-b-PBYP-hyd-DOX,via a combination of ring-opening polymerization(ROP)and"click"chemistry,in which PEEP and PBYP represent two kinds of phosphoester segmemts,-hyd-is hydrazone bond.After self-assembly into prodrug nanoparticles(PDNPs)with a diameter of about 93 nm,CD147 mAb was conjugated onto the PDNPs by EDC/NHS chemistry to form mAb-PDNPs.For the PDNPs and mAb-PDNPs,we also investigated their stability,in vitro drug release behavior and cellular uptake.The results showed that the pH-responsive PDNPs can remain relatively stable under the condition of PB 7.4 buffer solution.However,under acidic conditions or in the presence of phosphodiesterase I(PDE I),both the amount and rate of DOX release increased at the same incubation period.Cytotoxicity assay showed that mAb-PDNPs exhibited higher cytotoxicity(IC50:1.12 mg·L^(-1))against HepG2 cells than PDNPs(IC50:2.62 mg·L^(-1))without monoclonal antibody.The nanoparticles with antibodies mAb-PDNPs have relatively better stability and can directly achieve the targeting drug delivery through CD147 mAb.

Polyphosphoester-modified Cellulose Nanocrystals for Stabilizing Pickering Emulsion Polymerization of Styrene

The structure and properties of functional nanoparticles are important for stabilizing Pickering emulsion polymerization.Recently,cellulose nanocrystals(CNCs)are increasingly favored as a bio-based stabilizer for Pickering emulsions.In this study,we reported a novel functionalized polyphosphoester-grafted CNCs for the stabilization of oil-in-water Pickering emulsions and the emulsion polymerization of styrene.First,polyphosphoester containing an amino group at one end of the chain,abbreviated as PBYP-NH2,was prepared by ring-opening polymerization(ROP)and hydrolysis reaction,wherein PBYP represents poly[2-(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane].Subsequently,CNC-COOH was obtained via 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)oxidation of CNCs.The functionalized nanocrystals CNC-PBYP-COOH with carboxyl groups and polyphosphoester on the surface were obtained by the amidation reaction of PBYP-NH2 with CNC-COOH.Finally,we used CNC-PBYP-COOH as sole particle emulsifiers to stabilize styrene-in-water Pickering emulsions and studied its effects on the emulsions in details by using dynamic light scattering(DLS).The results indicated that the properties of these emulsions depended on the concentration of hydrophobically modified CNCs,volume ratios of oil to water,and pH values.The modified CNCs had higher ability to stabilize the styrene-in-water emulsions relative to the unmodified CNCs,and a stable oil-in-water(o/w)Pickering emulsion with diameter of hundreds of nanometers could be obtained.The resulting emulsions could be polymerized to yield nanosized latexes.The polyphosphoester-modified CNCs as green particle emulsifiers can efficiently stabilize nanoemulsions and latexes,which would promote the development of novel environmentally friendly materials.

Synthesis and Characterization of UPPE-PLGA-rhBMP2 Scaffolds for Bone Regeneration

A novel unsaturated polyphosphoester(UPPE) was devised in our previous research,which is a kind of promising scaffold for improving bone regeneration.However,the polymerization process of UPPE scaffolds was unfavorable,which may adversely affect the bioactivity of osteoinductive molecules added if necessary,such as recombinant human bone morphogenetic protein-2(rhBMP2).The purpose of this study was to build a kind of optimal scaffold named UPPE-PLGA-rhBMP2(UPB) and to investigate the bioactivity of rhBMP2 in this scaffold.Furthermore,the cytotoxicity and biocompatibility of UPB scaffold was assessed in vitro.A W1/O/W2 method was used to fabricate PLGA-rhBMP2 microspheres,and then the microspheres were added to UPPE for synthesizing UPB scaffold.The morphological characters of PLGA-rhBMP2 microspheres and UPB scaffolds were observed under the scanning electron microscopy and laser scanning confocal microscopy.The cumulative release of UPB scaffolds was detected by using ELISA.The cytotoxicity and biocompatibility of UPB scaffolds were evaluated through examining the adsorption and apoptosis of bone marrow stromal cells(bMSCs) seeded on the surface of UPB scaffolds.The bioactivity of rhBMP2 in UPB scaffolds was assessed through measuring the alkaline phosphates(ALP) activity in bMSCs seeded.The results showed that UPB scaffolds sequentially exhibited burst and sustained release of rhBMP2.The cytotoxicity was greatly reduced when the scaffolds were immersed in buffer solution for 2 h.bMSCs attached and grew on the surface of soaked UPB scaffolds,exerting well biocompatibility.The ALP activity of bMSCs seeded was significantly enhanced,indicating that the bioactivity of rhBMP2 remained and still took effect after the unfavorable polymerization process of scaffolds.It was concluded that UPB scaffolds have low cytotoxicity,good biocompatibility and preserve bioactivity of rhBMP2.UPB scaffolds are promising in improving bone regeneration.

Composition and Structure of Fibrous Hydroxyapatite Growth on an Injectale Bone Tissue Engineering Scaffolds Material

Fibrous hydroxyapatite （ HA ） wns grown upwards from the crosslinked unsaturated polyphosphoester（ UPPE ） which was used us an injectable bone tissue engineering scaffolds. Composition of fibrous HA was determined by FT- IR, XRD and EDX, which suggested that the fibrous HA was calcium deficient carbonated apatitie with low crystallinity. SEM micrographs indicated that the fibrous HA had a hollow tubing structure and tube wall wus a flakelike assembly. The fibre with poor mechanical property arm with a growth rate about 0. 5 mm/min reached several centimeters in length after 2 hours. The growth was at the tip of the fibre suggested that the procedure of forming fibrous HA was as follows ： Co^2＋ ions were firstly incorporated into the crosslinked UPPE by dipping in Ca^2＋ solution, then supplied through micropores of the material reacted with PO4^3- ions to form α small tuhe , the osmotic pressure or capillary force lead the Ca^2＋ continuously gushed oat into the PO4^3- solution, thus fibrous HA was obtained.

Syntheses of amphiphilic biodegradable copolymers of poly(ethyl ethylene phosphate) and poly(3-hydroxybutyrate) for drug delivery

Biodegradable and amphiphilic triblock copolymers poly(ethyl ethylene phosphate)-poly(3-hydroxybutyrate)-poly(ethyl ethylene phosphate) (PEEP-b-PHB-b-PEEP) have been successfully synthesized through ring-opening polymerization. The structures are confirmed by gel permeation chromatography and NMR analyses. Crystallization investigated by X-ray diffraction reveals that the block copolymer with higher content of poly(ethyl ethylene phosphate) (PEEP) is more amorphous, showing decreased crystallizability. The obtained copolymers self-assemble into biodegradable nanoparticles with a coreshell micellar structure in aqueous solution, verified by the probe-based fluorescence measurements and transmission electronic microscopy (TEM) observation. The hydrophobic poly(3-hydroxybutyrate) (PHB) block serves as the core of the micelles and the micelles are stabilized by the hydrophilic PEEP block. The size and size distribution are related to the compositions of the copolymers. Paclitaxel (PTX) has been encapsulated into the micelles as a model drug and a sustained drug release from the micelles is observed. MTT assay also demonstrates that the block copolymers are biocompatible, rendering these copolymers attractive for drug delivery.

Multiresponsive Polymer Assemblies Achieved by a Subtle Chain Terminal Modification

Inspired by the influence of chemical structure of end groups on the phase transition temperature of thermoresponsive polymers,we demonstrated a strategy to control the multi-responsiveness of polymer assemblies via subtle modification of end groups of thermoresponsive polymer segments and revealed its potential application for drug delivery.By developing polymer assemblies composed of poly(aliphatic ester) as the inner core and thermoresponsive polyphosphoester as the outer shell,we showed that end groups of thermoresponsive polyphosphoester segments controlled the surface property of assemblies and further determined the stimuli-responsive behavior.The phase-transition temperatures of the unmodified polymer assemblies are tightly controlled by their surface properties due to the hydrophilic to hydrophobic transitions of end groups in response to an environmental stimulus (e.g.pH or light irradiation).External control over these surface properties can by asserted by adjusting the chemical structure and composition of the terminal groups of the thermoresponsive polyphosphoesters.