Porous hybrid microspheres were fabricated by the synthesized calcium gluconate-g-poly(D,L-lactide) (CG-g-PDLLA) composites. These hybrid microspheres were treated with an alkaline solution for different period of time to control the amount of generated carboxylate groups and remained CG on the surface. The microspheres were then incubated in a supersaturated simulated body fluid (1.5 SBF) solution for different time to investigate their biomimetic mineralization behavior. The depositions were found to have a fine cluster morphology, a similar crystal structure and chemical structure to natural hydroxyapatite, and a medium Ca/P of approximately 1.30. The effect of surface treating time on the structure and mineralization behavior of these microspheres has been discussed in detail. The results indicate that the nucleation and growth of apatite on the surface are influenced by the induced carboxylate groups and the remained CG. The hybrid CG-g-PDLLA microspheres have the potential as a novel alternative in bone tissue engineering.

The formation and development of cancer is usually accompanied by angiogenesis and is related to multiple pathways. The inhibition of one pathway by monotherapy might result in the occurrence of drug resistance, tumor relapse, or metastasis. Thus, a combinatory therapeutic system that targets several independent pathways simultaneously is preferred for the treatment. To this end, we prepared combinatory drug delivery systems consisting of cytotoxic drug SN38, pro-apoptotic KLAK peptide, and survivin siRNA with high drug loading capacity and reductive responsiveness for the treatment of multi-drug-resistant (MDR) cancer. With the help of positive charge and the synergistic effect of different drug, the combinatory systems inhibited the growth of doxorubicin-resistant breast cancer cells (MCF-7/ADR) efficiently. Interestingly, the systems without siRNA showed more superior in vivo anticancer efficacy than those with siRNA which exhibited enhanced in vitro cytotoxicity and pro-apoptotic ability. This phenomenon could be attributed to the preferential tumor accumulation, strong tumor penetration, and excellent tumor vasculature targeting ability of the combinatory micelles of SN38 and KLAK. As a result, a combinatory multitarget therapeutic system with positive charge induced tumor accumulation and vasculature targeting which can simultaneously inhibit the growth of both tumor cell and tumor vasculature was established. This work also enlightened us to the fact that the design of combinatory drug delivery systems is not just a matter of simple drug combination. Besides the cytotoxicity and pro-apoptotic ability, tumor accumulation, tumor penetration, or vascular targeting may also influence the eventual antitumor effect of the combinatory system.Keywords: combination therapy; drug delivery; multidrug resistance; positive charge; tumor vasculature targeting;

Nanocomposite microspheres with tunable porous structures were studied in this work as hemostatic agents. Hydroxyapatite nanoparticles-graft-poly(D,L-lactide) (nHA-g-PDLLA) nanocomposites were synthesized first and then fabricated into porous microspheres by a modified double emulsion solvent evaporation technique. Alkaline treatment were carried out on nanocomposite microspheres for the exposure of HA nanoparticles on the surface of porous microspheres. The porous structure and nanocomposition endue the nHA-g-PDLLA microspheres with huge specific surface area and excellent interfaces for blood clotting. This work reveals the great potentials of nHA-g-PDLLA nanocomposite microspheres as hemostatic agents.

Porous microspheres of cellulose-graft-poly(L-lactide) (cellulose-g-PLLA) copolymers were fabricated by a water/oil/water (W/O/W) emulsion evaporation method. Their morphology, hydrophilicity and amount of hydroxyl group content (–OH content) on the surface were adjustable with the change of molar substitution of PLLA (MSPLLA). After a hydrolysis post-processing, surface physical properties of microspheres were regulated further. The influence of physical properties of microspheres on cell cultivation was investigated by setting hepatocellular liver carcinoma cell line (HepG-2) as the example. Compared with the cells on PLLA microspheres, HepG-2 cells with more pseudopods spread well on the surface of cellulose-g-PLLA microspheres. Particularly, the cellulose-g-PLLA microspheres with MSPLLA of 11.5 were the most appropriate candidate for cell adhesion and proliferation. Therefore, a moderate PLLA content of cellulose-g-PLLA copolymers was beneficial to the cell cultivation. This work indicated that combining cellulose with PLLA was an available route to developing cellulose-based materials for cell cultivation.

Polymeric micelles of amphiphilic block copolymers have been studied for decades for their application as a targeting delivery agent of anti-tumor drugs. However, the targeting micelles may cause an immunological response because of the surface distributed ligands. In this work, mixed micelles were developed to improve the specificity of cancer cell uptake under tumor-acidic conditions. This was achieved by the co-assembly of an active targeting amphiphilic polymer, i.e. cyclic (Arg-Gly-Asp-D-Phe-Lys) c(RGDfK) functionalized poly(ethylene oxide)-b-poly(ε-caprolactone) (cRGD-PEO-b-PCL), and a pH sensitive drug conjugate, i.e. benzoic-imine linked PEGylated doxorubicin (PEG-DOX). Because the PEG-DOX is cleavable at the extracellular pH of a solid tumor, the characteristics of the mixed micelles turn from “stealthy” to cancer cell-affinitive due to the detachment of PEG from the micelle surface and hence allow the action of the c(RGDfK) in the cRGD-PEO-b-PCL with the cancer cell membrane. Besides, the mixed micelles exhibited the capacity for encapsulating hydrophobic drugs such as paclitaxel to form a combination formulation. Our results indicate that co-assembly is a facile but efficient strategy to coordinate the characteristics of each individual component and thus provide combinatorial functions to the delivery system.

The isothermal crystallization behavior and morphology of neat poly(l-lactic acid) (PLLA) and its blends with poly(d-lactic acid) (PDLA) and PDLA-b-poly(ethylene glycol) (PEG)-b-PDLA have been investigated. The glass transition temperature of the PLLA/PDLA blend, and especially the PLLA/PDLA-b-PEG-b-PDLA blend, is much lower than that of neat PLLA, indicating the plasticization effect of both low molecular weight PDLA and flexible PEG block. Both the PLLA/PDLA and PLLA/PDLA-b-PEG-b-PDLA blends can form stereocomplex (SC) crystals. However, the PDLA in the PLLA/PDLA blend postponed the crystallization rate of the blend, whereas the PEG chains in PLLA/PDLA-b-PEG-b-PDLA not only promoted the formation of SC crystals but also facilitated the crystallization of the PLLA matrix. The evolution of the crystal structure and morphologies of PLLA and its blends during the isothermal crystallization process have revealed the significant role of flexible PEG chains in the stereocomplex crystallization.Keywords: Blend; Morphology; PDLA-b-PEG-b-PDLA; Poly(l-lactic acid); Stereocomplex crystallization

A new series of cellulose-graft-poly(N-isopropylacrylamide) (cellulose-g-PNIPAM) copolymers were prepared by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide monomers from a cellulose-based macro-initiator, which was homogeneously synthesized in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The composition of cellulose-g-PNIPAM copolymers could be adjusted by altering the feeding ratio and reaction time. The resultant copolymers with relatively high content of PNIPAM segments (molar substitution of PNIPAM ≥ 18.3) were soluble in water at room temperature. Aqueous solutions of cellulose-g-PNIPAM copolymers exhibited clear temperature-sensitive behavior, and their sol-to-gel phase transition properties were investigated by dynamic light scattering (DLS) and UV measurements. Compared with pure PNIPAM, the cellulose-g-PNIPAM copolymers possessed higher lower critical solution temperatures (LCST) in a range from 36.9 °C to 40.8 °C, which are close to normal human body temperature, and could be tuned by adjusting the content of PNIPAM segments in copolymers. Spherical structure of cellulose-g-PNIPAM copolymers formed at temperatures above LCST and its morphology was observed by TEM and SEM. These novel cellulose-g-PNIPAM copolymers may be attractive substrates for some biomedical applications, such as drug release and tissue engineering.

Poly(D,L-lactide-co-glycolide) (PLGA) microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell (denoted by hollow in brief) and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin (BSA) was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior.

Well-defined water-soluble block copolymers poly(ethylene glycol)-b-poly(N-(2-hydroxypropyl) methacrylamide-co-N-methacryloylglycylglycine) (PEG-b-P(HPMA-co-MAGG)) and their doxorubicin (Dox) conjugates with different composition and molecular weight were synthesized. These Dox conjugates can form micelles in buffer solution. The physicochemical properties, in vivo biodistribution, blood clearance, and especially the tumor accumulation of copolymers and micelles were studied. Severe liver accumulation can be observed for PEG-b-PMAGG copolymers. This was quite different from their Dox conjugate for which decreased RES uptake and elevated kidney accumulation could be observed. When decrease the negative charge to an appropriate amount such as 8–10 mol %, both RES uptake and kidney accumulation could be suppressed. Obvious tumor accumulation could be achieved especially when the molecular weight were increased from ∼40 to ∼80 KDa. These results provided us with a guideline for the design of nanoscaled drug delivery system as well as a potential option for treating kidney-related cancers.

Well-defined water-soluble block copolymers poly(ethylene glycol)-b-poly(N-(2-hydroxypropyl) methacrylamide-co-N-methacryloylglycylglycine) (PEG-b-P(HPMA-co-MAGG)) with different compositions and narrow polydispersity were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The in vivo blood clearance and biodistribution of copolymers with different compositions were studied in normal BALB/c mice. The results showed that the electronegative copolymers were rapidly eliminated from blood and tended to accumulate in the liver and spleen. However, the copolymers with neutral or a small amount of negative charges showed a prolonged circulation time and low non-specific organ uptake. Combined with the quantitative analysis of in vitro hepatocyte uptake, we conclude that this was due to the balance between (i) the electrostatic repulsion between the copolymer and the cell membrane and (ii) the tendency of macrophage-like cells to capture the negative charged copolymers. This work also revealed the significant roles of the PEG chain length, negative charge and molecular weight for the copolymers as anticancer drug carriers with prolonged circulation time and optimal biodistribution.

A series of four-armed poly(ε-caprolactone)-b-poly(d-lactic acid) diblock copolymers (4a-PCL-b-PDLA) with well controlled composition were synthesized. The effect of length of PCL and PDLA blocks on the crystallization and enzymatic/alkaline degradation was studied. It was found that the PDLA blocks have great influence on the crystallization of PCL blocks under two different crystallization conditions. The copolymers with shorter PDLA blocks showed faster degradation rate but different spherulite structures after enzymatic degradation or alkaline degradation. The morphological changes of spherulites depended on the PCL chains which were trapped inside or excluded from the spherulites of PDLA when the copolymer crystallized at 80 °C or 30 °C (i.e. above or lower the glass transition temperature of PDLA chains). The spherulite morphology and porous morphology of copolymer films after degradation were well discussed. This work revealed that the crystalline morphology and degradation rate of PCL-b-PDLA films could be well controlled by copolymer composition and confined crystallization of PCL chains within the previously formed lamellar stacks of PDLA.

Oriented and non-oriented Teflon films, which were found to have the same crystalline structure, but different surface morphologies, were used to sandwich poly(butylene adipate) (PBA) films during isothermal crystallization. It was found that both the Teflon surface structure and the PBA polymorphic structure are the determining factors to induce epitaxial crystallization. The oriented Teflon film was able to induce epitaxial crystallization of PBA α crystal, while the non-oriented Teflon did not induce any epitaxial crystallization of PBA. Epitaxial crystallization did not occurred for PBA β crystals between neither the oriented nor the non-oriented Teflon films. The enzymatic degradation rate of PBA films was not determined by the epitaxial crystallization, in fact it was still dependent on the polymorphic crystal structure of PBA. The morphological changes of PBA films after enzymatic degradation confirmed again that the epitaxial crystallization only occurred for the PBA film with α crystal structure which was produced by being sandwiched between oriented Teflon films, and it happened only on the surface of PBA films.

•PM2.5 exposure increases ROS production, which up-regulates a lncRNA named loc146880.•Loc146880 increases the autophagy of A549 cells.•PM2.5-induced ROS and loc146880 promote cell migration, invasion and EMT.BackgroundEvidence shows that individuals who are under long-term exposure to environmental PM2.5 are at increased risk of lung cancer. Various laboratory experiments also suggest several mechanistic links between PM2.5 exposure and lung carcinogenesis. However, a long non-coding RNA (lncRNA) mediated pathogenic change after PM2.5 exposure and its potential roles in tumorigenesis and disease progression have not been reported.MethodsCytotoxicity induced by PM2.5 was assessed by using scanning electron microscopy and transmission electron microscopy. ROS generation, autophagy, and metastasis induced by PM2.5 were detected by using comprehensive approaches. Expression of lncRNA-loc146880 and lc3b (autophagy marker) in A549 cells, lung tissue and serum were determined by RT-PCR and Western blotting.ResultsPM2.5 could be internalized into lung cancer cells, resulting in marked increases in ROS levels and autophagy. ROS may be responsible for increased expression of loc146880 which further up-regulates autophagy. Both loc146880 and autophagy could promote lung tumor cell migration, invasion and EMT. In addition, a positive correlation was observed between loc146880 expression and lc3b levels in tumor tissues and serum of lung cancer patients.ConclusionTaken together, our data suggest that PM2.5 exposure induces ROS, which activates loc146880 expression. The lncRNA, in turn, up-regulates autophagy and promotes the malignant behaviors of lung cancer cells.General significanceThe results show the toxicological effects of PM2.5 in lung tumor progression and metastasis.Download high-res image (48KB)Download full-size image

Polymeric micelles of amphiphilic block copolymers have been studied for decades for their application as a targeting delivery agent of anti-tumor drugs. However, the targeting micelles may cause an immunological response because of the surface distributed ligands. In this work, mixed micelles were developed to improve the specificity of cancer cell uptake under tumor-acidic conditions. This was achieved by the co-assembly of an active targeting amphiphilic polymer, i.e. cyclic (Arg-Gly-Asp-D-Phe-Lys) c(RGDfK) functionalized poly(ethylene oxide)-b-poly(ε-caprolactone) (cRGD-PEO-b-PCL), and a pH sensitive drug conjugate, i.e. benzoic-imine linked PEGylated doxorubicin (PEG-DOX). Because the PEG-DOX is cleavable at the extracellular pH of a solid tumor, the characteristics of the mixed micelles turn from “stealthy” to cancer cell-affinitive due to the detachment of PEG from the micelle surface and hence allow the action of the c(RGDfK) in the cRGD-PEO-b-PCL with the cancer cell membrane. Besides, the mixed micelles exhibited the capacity for encapsulating hydrophobic drugs such as paclitaxel to form a combination formulation. Our results indicate that co-assembly is a facile but efficient strategy to coordinate the characteristics of each individual component and thus provide combinatorial functions to the delivery system.

In addition to intravenous injections (i.v.), topical dosing of doxorubicin hydrochloride (DOX) has also been the focus of cancer treatment recently, although it normally requires well-designed drug carriers. In this work, we found that DOX could form fibril-shaped DOX aggregates via self-assembly in phosphate buffer (PB) and then co-assemble with poly(L-glutamic acid) (PGA) at a proper polymer–drug ratio, giving a unique nano-rod-shaped microstructure. The release rate of DOX from the PGA/DOX nano-rods was thus easily controlled at a slower release rate without being encapsulated by any classic carrier. In vitro cell culture demonstrated that the PGA/DOX nano-rods were not favorably taken up by cancer cells, which can be attributed to the negatively charged nature and the non-spherical shape of the aggregates. These features suggest great potential for the PGA/DOX assemblies for a sustained delivery through the intratumoral pathway (i.t.) as a carrier-free formulation. In the mouse model it diminished organ damage at a dose level of 30 mg kg−1via i.t. injections compared to the serious cardiotoxicity and renal toxicity via typical multiple i.v. dosage of free drug solution at 5 mg kg−1. As a result, the PGA/DOX formulation showed efficient anti-tumor activity. The survival rate of tumor bearing mice was significantly increased by over 35% compared to the i.v. injections of DOX solutions. Therefore, PGA/DOX nano-rods may provide a new and safe delivery route of the common anti-tumor drug.