Galactosylated PVDF membrane promotes hepatocyte attachment and functional maintenance

Hypotonic, gel-forming delivery system for vaginal drug administration

Vaginal drug delivery is often preferred over systemic delivery to reduce side effects and increase efficacy in treating diseases and conditions of the female reproductive tract (FRT). Current vaginal products have drawbacks, including spontaneous ejection of drug-eluting rings and unpleasant discharge from vaginal creams. Here, we describe the development and characterization of a hypotonic, gel-forming, Pluronic-based delivery system for vaginal drug administration. The rheological properties were characterized with and without common hydrogel polymers to demonstrate the versatility. Both qualitative and quantitative approaches were used to determine the Pluronic F127 concentration below the critical gel concentration (CGC) that was sufficient to achieve gelation when formulated to be hypotonic to the mouse vagina. The hypotonic, gel-forming formulation was found to form a thin, uniform gel layer along the vaginal epithelium in mice, in contrast to the rapidly forming conventional gelling formulation containing polymer above the CGC. When the hypotonic, gel-forming vehicle was formulated in combination with a progesterone nanosuspension (ProGel), equivalent efficacy was observed in the prevention of chemically-induced preterm birth (PTB) compared to commercial Crinone® vaginal cream. Further, ProGel showed marked benefits in reducing unpleasant discharge, reducing product-related toxicity, and improving compatibility with vaginal bacteria in vitro. A hypotonic, gel-forming delivery system may be a viable option for therapeutic delivery to the FRT.

Fabrication of carboxymethyl cellulose-based thermo-sensitive hydrogels and inhibition of corneal neovascularization

Corneal neovascularization (CNV) is a common multifactorial sequela of anterior corneal segment inflammation, which could lead to visual impairment and even blindness. The main treatments available are surgical sutures and invasive drug injections, which could cause serious ocular complications. To solve this problem, a thermo-sensitive drug-loaded hydrogel with high transparency was prepared in this study, which could achieve the sustained-release of drugs without affecting normal vision. In briefly, the thermo-sensitive hydrogel (PFNOCMC) was prepared from oxidized carboxymethyl cellulose (OCMC) and aminated poloxamer 407 (PF127-NH2). The results proved the PFNOCMC hydrogels possess high transparency, suitable gel temperature and time. In the CNV model, the PFNOCMC hydrogel loading bone morphogenetic protein 4 (BMP4) showed significant inhibition of CNV, this is due to the hydrogel allowed the drug to stay longer in the target area. The animal experiments on the ocular surface were carried out, which proved the hydrogel had excellent biocompatibility, and could realize the sustained-release of loaded drugs, and had a significant inhibitory effect on the neovascularization after ocular surface surgery. In conclusion, PFNOCMC hydrogels have great potential as sustained-release drug carriers in the biomedical field and provide a new minimally invasive option for the treatment of neovascular ocular diseases.

Fe (III)@TA@IGF-2 microspheres loaded hydrogel for liver injury treatment

As one of the most commonly used materials in liver tissue engineering, hydrogel has received much attention in recent years. In this work, we prepared a gelatin methacrylate (GelMA)/oxidized hyaluronic acid (OHA)/galactosylated chitosan (Gal-CS)/Fe (III)@TA@IGF-2 200 (TA200) hydrogel loaded with insulin-like growth factor 2 (IGF-2) for regeneration of damaged hepatocytes. Fe (III)@TA microspheres served as carrier to achieve sustained release of IGF-2 to promote hepatocytes regeneration. Galactose ligands could bind to the asialoglycoprotein receptor (ASGPR) on the surface of hepatocytes. Galactosylated chitosan could significantly increase the specific function of hepatocytes. The hydrogel we prepared had a storage modulus of 1100 Pa and was suitable for migration of hepatocytes. The release ratio of IGF-2 could reach up to 90% within 14 days. For carbon tetrachloride (CCl₄) induced human hepatic stellate cell line LX2 damage, GelMA/OHA/Gal-CS/TA200 hydrogel could significantly improve the survival of LX2 cells. The expression of HNF-4α and transferrin was detected in LX2 cells treated with hydrogel, indicating that the specific function of the liver was also restored. In summary, the GelMA/OHA/Gal-CS/TA200 hydrogels could be used as new tissue engineering scaffolds for the construction of artificial livers.

Collagen modulates functional activity of hepatic cells inside alginate-galactosylated chitosan hydrogel microcapsules

To provide comparable hepatic tissue microenvironment and induce functional behavior for hepatocytes, galctosylated-chitosan (GC) as well as collagen (Col) was added to alginate microcapsule coated with extra layer of chitosan. Four different hydrogel groups of alginate/chitosan (AC); alginate-galactosylated chitosan/chitosan (AGC/C); alginate-collagen/chitosan (ACol/C); and alginate-galactosylated chitosan-collagen/chitosan (AGCCol/C) were prepared and characterized for physical properties such as porosity, swelling, degradation rate, and stiffness. Introduction of GC as well as Col to alginate regulated significantly the physical properties of the resultant hydrogels. GC addition decreased dramatically swelling, degradation, pore size and mechanical properties of the resultant hydrogel. However, the influence of GC on the physical properties in the presence of Col (AGCCol/A) was in a reverse manner, as compared to the AGC/C hydrogel. The AGCCol/C microenvironment also promoted proliferation of microencapsulated HepG2 cells, as a model of hepatocyte, compared to the control-matched groups. Biochemical analysis after 10 days revealed a superior effect of AGCCol/C on the secretion of albumin and urea compared to other groups (P < 0.05). These features were coincided with the mRNA up-regulation of P450 and albumin in the AGCCol/C groups compared to the AGC/C and ACol/C groups (P < 0.05). The study demonstrated that enrichment of alginate-based hydrogels with Col and GC could be touted as an appropriate 3D platform for modular hepatic tissue engineering.

Harmine-loaded galactosylated pluronic F68-gelucire 44/14 mixed micelles for liver targeting

Harmine (HM), a phytoconstituent has wide range of pharmacological activities including antimicrobial, antifungal, antioxidative, and anticancer. HM has shown promising anticancer activity against liver cancer cells. However, poor aqueous solubility, multidrug pump P-gp efflux, extensive in vivo metabolism, and rapid elimination due to glucuronidation/sulfation limit clinical utility of HM. In order to overcome the drawbacks of HM, the current work reports preparation of HM-loaded galactosylated pluronic F-68 (PF68)-Gelucire^® 44/14 (GL44) mixed micelles (HM-MM). 3² factorial design was used to investigate the effect of formulation variables on formation HM-loaded mixed micelles. Solvent evaporation method was used for preparation of HM-MM. The optimized HM-MM was evaluated for size, percent drug entrapped (EE), in vitro HM release, oral bioavailability, and biodistribution in rats. HM-MM with an average size 277.5 ± 3.24 nm had an EE of 86.5 ± 1.51% w/w. HM-MM released HM in a controlled manner. Additionally, HM-MM showed significant enhancement in oral bioavailability (around six-folds) of HM when compared to HM alone. Further, HM-MM showed around sevenfold higher amount of HM in the liver when compared to HM alone revealing efficient drug targeting capability. Such significant improvement in oral bioavailability of HM when formulated into mixed micelles could be attributed to solubilization of hydrophobic HM into micellar core along with P-gp inhibition effect of both galactosylated PF68 and GL44. Thus, the present work highlights galactosylated PF68 and GL44 mixed micelles as an efficient carrier system having drug targeting capability and potential to enhance bioavailability of BCS class II drugs.

Galangin loaded galactosylated pluronic F68 polymeric micelles for liver targeting

Galangin possess wide range of pharmacological activities including antiarthritic, hepatoprotective, anti-inflammatory, antibacterial, and anticancer especially in hepatocellular carcinoma. However, its biological use has been limited owing to its poor aqueous solubility, P-gp efflux and rapid in vivo metabolism by cytochrome enzymes. In order to address the drawbacks of galangin, the current work was designed with an objective to prepare liver targeted galangin loaded galactosylated pluronic F68 polymeric (GF68-Gal) micelles. Galactosylated pluronic F68 copolymer was successfully synthesized usi reduction amination method and used for micelle preparation. The prepared micelles were evaluated for micelle size, entrapment efficiency, zeta potential, in vitro galangin release and in vivo biodistribution. The average size of GF68-Gal micelles was found to be around 242±4.6 nm with an entrapment efficiency of about 77.5± 0.34% w/w. In vitro dissolution profile of GF68-Gal micelles revealed controlled release of galangin. Further, biodistribution studies of GF68-Gal micelles showed significant improvement in the amount of galangin in liver at 15 min (around 2.6 folds) and after 30 min (around 7.18 folds) as compared to galangin solution. Such significant increase in galangin amount in the liver for GF68-Gal micelles could be attributed to their efficient targeting to the liver by galactose moieties having affinity towards ASGPR receptor, P-gp and cytochrome enzyme inhibition activity of pluronic F68 reducing the rate of metabolism and in turn elimination. Thus, galactosylated pluronic F68 copolymer can act as a promising carrier system for improving liver targeting of hydrophobic drugs susceptible to P-gp efflux and cytochrome enzyme associated metabolism.

Lactobionic acid-functionalized polyethersulfone hollow fiber membranes promote HepG2 attachment and function

Surface modification of polyethersulfone hollow fibers, which are important in bio-artificial liver, is increasingly used to improve biocompatibility and promote the adhesion and proliferation of hepatocytes resulting in improved cell functionality. Hepatocytes are anchorage-dependent cells, and membrane surface modification enhances the hepatic cell adhesion and proliferation. Specific interaction of the asialoglycoprotein receptor on hepatocyte cell surfaces with a galactose moiety enhances the attachment of the cells on a biocompatible substrate. In this study, the outer surface of the polyethersulfone (P) hollow fiber membranes (HFMs) was chemically modified by covalent coupling with lactobionic acid (LBA). The energy dispersive X-ray spectrometry elemental mapping, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy confirmed the LBA-coupling on the outer surface of P-LBA HFMs. Hemocompatibility study indicated the suitability of the modified membranes with human blood. These membranes showed remarkably improved biocompatibility with human primary mesenchymal stem cells and HepG2 cells. Characteristic multi-cellular spheroids of HepG2 cells were observed under scanning electron and confocal microscopy. HepG2 cell functional activity was measured by quantifying the urea synthesis, albumin secretion and glucose consumption in the culture media, which indicated the improved HepG2 functions. These experimental results clearly suggest the potentiality of these LBA-modified P HFMs as a suitable biocompatible substrate for promoting HepG2 attachment and function leading to their application in bioreactors and bio-artificial liver devices.

Surface modification of polyethersulfone hollow fibers, which are important in bio-artificial liver, is increasingly used to improve biocompatibility and promote the adhesion and proliferation of hepatocytes resulting in improved cell functionality.

Ion-Selective Nanosensor for Photoacoustic and Fluorescence Imaging of Potassium

Ion-selective optodes (ISOs), the optical analog of ion-selective electrodes, have played an increasingly important role in chemical and biochemical analysis. Here we extend this technique to ion-selective photoacoustic optodes (ISPAOs) that serve at the same time as fluorescence-based ISOs, and apply it specifically to potassium (K⁺). Notably, the potassium ion is one of the most abundant cations in biological systems, involved in numerous physiological and pathological processes. Furthermore, it has been recently reported that the presence of abnormal extracellular potassium concentrations in tumors suppresses the immune responses and thus suppresses immunotherapy. However, unfortunately, sensors capable of providing potassium images in vivo are still a future proposition. Here, we prepared an ion-selective potassium nanosensor (NS) aimed at in vivo photoacoustic (PA) chemical imaging of the extracellular environment, while being also capable of fluorescence based intracellular ion-selective imaging. This potassium nanosensor (K⁺ NS) modulates its optical properties (absorbance and fluorescence) according to the potassium concentration. The K⁺ NS is capable of measuring potassium, in the range of 1 mM to 100 mM, with high sensitivity and selectivity, by ISPAO based measurements. Also, a near infrared dye surface modified K⁺ NS allows fluorescence-based potassium sensing in the range of 20 mM to 1 M. The K⁺ NS serves thus as both PA and fluorescence based nanosensor, with response across the biologically relevant K⁺ concentrations, from the extracellular 5 mM typical values (through PA imaging) to the intracellular 150 mM typical values (through fluorescence imaging).

Convection enhanced delivery of panobinostat (LBH589)-loaded pluronic nano-micelles prolongs survival in the F98 rat glioma model

Background

The pan-histone deacetylase inhibitor panobinostat is a potential therapy for malignant glioma, but it is water insoluble and does not cross the blood–brain barrier when administered systemically. In this article, we describe the in vitro and in vivo efficacy of a novel water-soluble nano-micellar formulation of panobinostat designed for administration by convection enhanced delivery (CED).

Materials and methods

The in vitro efficacy of panobinostat-loaded nano-micelles against rat F98, human U87-MG and M059K glioma cells and against patient-derived glioma stem cells was measured using a cell viability assay. Nano-micelle distribution in rat brain was analyzed following acute CED using rhodamine-labeled nano-micelles, and toxicity was assayed using immunofluorescent microscopy and synaptophysin enzyme-linked immunosorbent assay. We compared the survival of the bioluminescent syngenic F98/Fischer344 rat glioblastoma model treated by acute CED of panobinostat-loaded nano-micelles with that of untreated and vehicle-only-treated controls.

Results

Nano-micellar panobinostat is cytotoxic to rat and human glioma cells in vitro in a dose-dependent manner following short-time exposure to drug. Fluorescent rhodamine-labelled nano-micelles distribute with a volume of infusion/volume of distribution (Vi/Vd) ratio of four and five respectively after administration by CED. Administration was not associated with any toxicity when compared to controls. CED of panobinostat-loaded nano-micelles was associated with significantly improved survival when compared to controls (n=8 per group; log-rank test, P<0.001). One hundred percent of treated animals survived the 60-day experimental period and had tumour response on post-mortem histological examination.

Conclusion

CED of nano-micellar panobinostat represents a potential novel therapeutic option for malignant glioma and warrants translation into the clinic.

SPECT/CT Imaging of Pluronic Nanocarriers with Varying Poly(ethylene oxide) Block Length and Aggregation State

Optimal biodistribution and prolonged circulation of nanocarriers improve diagnostic and therapeutic effects of enhanced permeability and retention-based nanomedicines. Despite extensive use of Pluronics in polymer-based pharmaceuticals, the influence of different poly(ethylene oxide) (PEO) block length and aggregation state on the biodistribution of the carriers is rather unexplored. In this work, we studied these effects by evaluating the biodistribution of Pluronic unimers and cross-linked micelles with different PEO block size. In vivo biodistribution of (111)In-radiolabeled Pluronic nanocarriers was investigated in healthy mice using single photon emission computed tomography. All carriers show fast uptake in the organs from the reticuloendothelial system followed by a steady elimination through the hepatobiliary tract and renal filtration. The PEO block length affects the initial renal clearance of the compounds and the overall liver uptake. The aggregation state influences the long-term accumulation of the nanocarriers in the liver. We showed that the circulation time and elimination pathways can be tuned by varying the physicochemical properties of Pluronic copolymers. Our results can be beneficial for the design of future Pluronic-based nanomedicines.

Interactions of Pluronic nanocarriers with 2D and 3D cell cultures: Effects of PEO block length and aggregation state

This work reveals how the physicochemical properties of Pluronic block copolymers influence significantly their interactions with cancer cells, whether in monolayer or spheroid cultures, and how different clinical applications can be foreseen. Two-dimensional (2D) and three-dimensional (3D) cell culture models were used to investigate the interactions of Pluronic carriers with different PEO block length and aggregation state (unimers versus cross-linked micelles) in HeLa and U87 cancer cells. Stabilized micelles of Pluronic P94 or F127 were obtained by polymerization of a crosslinking agent in the micelles hydrophobic core. Nanocarriers were functionalized with a fluorescent probe for visualization, and with a chelator for radiolabeling with Indium-111 and gamma-quantification. The 2D cell models revealed that the internalization pathways and ultimate cellular localization of the Pluronic nanocarriers depended largely on both the PEO block size and aggregation state of the copolymers. The smaller P94 unimers with an average radius of 2.1nm and the shortest PEO block mass (1100gmol(-1)) displayed the highest cellular uptake and retention. 3D tumor spheroids were used to assess the penetration capacity and toxicity potential of the nanocarriers. Results showed that cross-linked F127 micelles were more efficiently delivered across the tumor spheroids, and the penetration depth depends mostly on the transcellular transport of the carriers. The Pluronic P94-based carriers with the shortest PEO block length induced spheroid toxicity, which was significantly influenced by the spheroid cellular type.

Thermo-triggered drug release from actively targeting polymer micelles

How to deliver the drug to the target area at the right time and at the right concentration is still a challenge in cancer therapy. In this study, we present a facile strategy to control drug release by precisely controlling the thermo-sensitivity of the nanocarriers to the variation of environmental temperature. One type of thermoresponsive Pluronic F127-poly(d,l-lactic acid) (F127-PLA, abbreviated as FP) copolymer micelles was developed and decorated with folate (FA) for active targeting. FP100 micelles assembled from FP with PLA segment having polymerization degree of 100 had a low critical solution temperature of 39.2 °C close to body temperature. At 37 °C, little amount of encapsulated anticancer drug DOX is released from the FP100 micelles, while at a slightly elevated temperature (40 °C), the shrinkage of thermoresponsive segments causes a rapid release of DOX and instantly increases the drug concentration locally. The cytocompatibility analysis and cellular uptake efficiency were characterized with the fibroblast cell line NIH 3T3 and human cervix adenocarcinoma cell line HeLa. The results demonstrate that this copolymer has excellent cytocompatibility, and FA-decorated FP100 micelles present much better efficiency of cellular uptake and higher cytotoxicity to folate receptor (FR)-overexpressed HeLa cells. In particular, under hyperthermia (40 °C) the cytotoxicity of DOX-loaded FA-FP100 micelles against HeLa cells was significantly more obvious than that upon normothermia (37 °C). Therefore, these temperature-responsive micelles have great potential as a drug vehicle for cancer therapy.

Glucose transporter and folic acid receptor-mediated Pluronic P105 polymeric micelles loaded with doxorubicin for brain tumor treating

In this study, glucose transporter and folic acid (FA) receptor-mediated Pluronic P105 polymeric micelles loaded with DOX (GF-DOX) were prepared for enhancing the blood-brain barrier (BBB) transportation and improving the drug accumulation in the glioma cells. The pH-triggered DOX release of GF-DOX indicating a comparatively fast drug release at weak acidic condition and stable state of the carrier at physiological environment. The transport of GF-DOX across the in vitro BBB model showed that GF-DOX exhibited higher BBB transportation ability with the transporting ratio of 21.47% in 4 h. The carrier was internalized into C6 glioma cells upon crossing the BBB model for the combined effect of the brain targeting by transportation of glucose transporter and active tumor cell targeting by FA receptor-mediated endocytosis. Moreover, minimized weight changes and high suppression ratio of tumor growth were observed after intravenous injection of GF-DOX. In conclusion, the glucose transporter and FA dual-targeting micelles would provide a safe and effective strategy for new modalities to treat brain tumor.

Galactosylated reversible hydrogels as scaffold for HepG2 spheroid generation

Various galactosylated scaffolds have been developed for hepatocyte culture because galactose ligands help maintain cell viability, facilitate the formation of multicellular spheroids and help maintain a high level of liver-specific functions. However, it is difficult to harvest the cell spheroids generated inside the three-dimensional scaffolds for their further biological analysis and applications. Here we developed a new galactosylated hydrogel scaffold which solidifies in situ upon heating to physiological temperature, but liquefies again upon cooling back to room temperature. The new scaffold is composed of poly(N-isopropylacrylamide) (PNIPAM) microgel and poly(ethylene glycol) (PEG). Because of the thermosensitivity of PNIPAM microgel, the mixed dispersions gel upon heating and liquefy upon cooling. PEG was added to reduce the shrinkage of the gels. Part of the PNIPAM microgel was replaced with a galactosylated one to provide a series of blend gels with various galactose ligand contents. HepG2 cells, a human hepatocarcinoma cell line, were encapsulated in the in situ-formed gels. As expected, the cell viability increases with increasing content of galactose ligands. In addition, compact multicellular spheroids were obtained in gels containing galactose ligands, while loose spheroids formed in gel without galactose ligands. The cells cultured in galactose-containing gels also exhibit a higher level of liver-specific functions, in terms of both albumin secretion and urea synthesis, than those cultured in gel without these ligands. The new galactosylated scaffold not only promotes the formation of hepatocyte spheroids, but also allows for their harvest. By cooling back to room temperature to liquefy the gel, the hepatocyte spheroids can be facilely harvested from the scaffold. The reversible galactosylated scaffold developed here may be used for large scale fabrication of hepatocyte spheroids.

Galactosylated collagen matrix enhanced in vitro maturation of human embryonic stem cell-derived hepatocyte-like cells

Due to their important biomedical applications, functional human embryonic stem cell-derived hepatocyte-like cells (hESC-HLCs) are an attractive topic in the field of stem cell differentiation. Here, we have initially differentiated hESCs into functional hepatic endoderm (HE) and continued the differentiation by replating them onto galactosylated collagen (GC) and collagen matrices. The differentiation of hESC-HE cells into HLCs on GC substrate showed significant up-regulation of hepatic-specific genes such as ALB, HNF4α, CYP3A4, G6P, and ASGR1. There was more albumin secretion and urea synthesis, as well as more cytochrome p450 activity, in differentiated HLCs on GC compared to the collagen-coated substrate. These results suggested that GC substrate has the potential to be used for in vitro maturation of hESC-HLCs.

Colloidal stability and thermo-responsive properties of iron oxide nanoparticles coated with polymers: advantages of Pluronic® F68-PEG mixture

Superparamagnetic iron oxide nanoparticles (SPIONs) are recognized to be an attractive platform for developing novel drug delivery approaches and thus several types of functionalized magnetic nanocarriers based on SPIONs have been synthesized and studied. The coating of the metal oxide surface was achieved in a one-pot synthesis with biocompatible polyethylene glycol (PEG) and thermo-responsive modified Pluronic® F68. The resulting thermo-responsive magnetic nanocarriers can incorporate water insoluble drugs into their hydrophobic compartment and later release them in a temperature dependent manner. Here we report novel magnetic nanocarriers with significant improvements regarding the colloidal stability and critical temperature obtained by mixing various molar ratios of hydrophilic PEG with thermo-responsive Pluronic® F68 bearing different end group functionalities. Various methods have been employed to characterize the magnetic nanocarriers, such as photon correlation spectroscopy (DLS), atomic absorption, FT-IR spectroscopy, and surface-enhanced Raman scattering. The transition temperature that determines changes in the conformation of the block copolymer chain was studied by DLS as a function of temperature. Moreover, the drug loading properties of SPION-(F68-OMe)-(F68-FA) and SPION-PEG-F68-FA were analyzed with a hydrophobic fluorescent dye, DID oil. The behavior of the encapsulated DID into the nanocarrier shell was studied as a function of temperature via fluorescence spectroscopy. These results offer original insights into the enhanced colloidal stability and thermo-sensitive properties of the novel synthesized magnetic nanocarriers.

A novel therapeutic system for malignant glioma: nanoformulation, pharmacokinetic, and anticancer properties of cell-nano-drug delivery

Macrophage carriage, release, and antitumor activities of polymeric nanoformulated paclitaxel (PTX) were developed as a novel delivery system for malignant glioma. To achieve this goal, the authors synthesized PTX-loaded nanoformulations (nano-PTX), then investigated their uptake, release, and toxicological properties. Chemosensitivity was significant in U87 cells (P < 0.05) at concentrations from 10(-4) to 10(-8) M following 72 hours' exposure to bone-marrow-derived macrophages (BMM)-nano-PTX in comparison with treatment with nano-PTX alone. The most significant reductions in U87 cell viability (P < 0.05) were observed in the transwell cocultures containing BMM-nano-PTX. Limited toxicity to BMM was observed at the same concentrations. BMM functions were tested by analysis of microtubules and actin filaments, as the cytoarchitecture, demonstrating a similar cytoskeleton pattern before and after nano-PTX was loaded into cells. This data indicate that nanoformulations of PTX facilitate cell uptake, delay toxicity, and show improved therapeutic efficacy by BMM-nano-PTX delivery.

FROM THE CLINICAL EDITOR

In this study the delivery, release, and antitumor activity of polymeric nanoformulated paclitaxel carried by macrophages are described as a novel and efficient system for treatment of resistant malignant glioma.

Regulation of epithelial cell morphology and functions approaching to more in vivo-like by modifying polyethylene glycol on polysulfone membranes

Cytocompatibility is critically important in design of biomaterials for application in tissue engineering. However, the currently well-accepted “cytocompatible" biomaterials are those which promote cells to sustain good attachment/spreading. The cells on such materials usually lack the self-assembled cell morphology and high cell functions as in vivo. In our view, biomaterials that can promote the ability of cells to self-assemble and demonstrate cell-specific functions would be cytocompatible. This paper examined the interaction of polyethylene glycol (PEG) modified polysulfone (PSf) membranes with four epithelial cell types (primary liver cells, a liver tumor cell line, and two renal tubular cell lines). Our results show that PSf membranes modified with proper PEG promoted the aggregation of both liver and renal cells, but the liver cells more easily formed aggregates than the renal tubular cells. The culture on PEG-modified PSf membranes also enhanced cell-specific functions. In particular, the cells cultured on F127 membranes with the proper PEG content mimicked the in vivo ultrastructure of liver cells or renal tubules cells and displayed the highest cell functions. Gene expression data for adhesion proteins suggest that the PEG modification impaired cell-membrane interactions and increased cell-cell interactions, thus facilitating cell self-assembly. In conclusion, PEG-modified membrane could be a cytocompatible material which regulates the morphology and functions of epithelial cells in mimicking cell performance in vivo.

WITHDRAWN: A novel therapeutic system for malignant glioma: nanoformulation, pharmacokinetic, and anticancer properties of cell-nano-drug delivery

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Role of biomaterials, therapeutic molecules and cells for hepatic tissue engineering

Current liver transplantation strategies face severe shortcomings owing to scarcity of donors, immunogenicity, prohibitive costs and poor survival rates. Due to the lengthy list of patients requiring transplant, high mortality rates are observed during the endless waiting period. Tissue engineering could be an alternative strategy to regenerate the damaged liver and improve the survival and quality of life of the patient. The development of an ideal scaffold for liver tissue engineering depends on the nature of the scaffold, its architecture and the presence of growth factors and recognition motifs. Biomimetic scaffolds can simulate the native extracellular matrix for the culture of hepatocytes to enable them to exhibit their functionality both in vitro and in vivo. This review highlights the physiology and pathophysiology of liver, the current treatment strategies, use of various scaffolds, incorporation of adhesion motifs, growth factors and stem cells that can stabilize and maintain hepatocyte cultures for a long period.

Fabrication of Piezoelectric Polyvinylidene Fluoride (PVDF) Microstructures by Soft Lithography for Tissue Engineering and Cell Biology Applications

A method for the fabrication of piezoelectric polyvinylidene fluoride (PVDF) microstructures is described. Embossed and individual features with highly defined geometries at the microscale were obtained using soft lithography-based techniques. Various structure geometries were obtained, including pillars (three different aspect ratios), parallel lines, and criss-crossed lines. SEM characterization revealed uniform patterns with dimensions ranging from 2 μm ñ 15 μm. Human osteosarcoma (HOS) cell cultures were used to evaluate the cytocompatibility of the microstructures. SEM and fluorescence microscopy showed adequate cell adhesion, proliferation, and strong interaction with tips and corners of the microdiscontinuities. Microfabricated piezoelectric PVDF structures could find applications in the fabrication of mechanically active tissue engineering scaffolds, and the development of dynamic sensors at the cellular and subcellular levels.

Multifunctional Pluronic P123/F127 mixed polymeric micelles loaded with paclitaxel for the treatment of multidrug resistant tumors

The aim of this study was to exploit the possibility of combination of active targeting function of folic acid by folate receptor-mediated endocytosis and overcoming multidrug resistance (MDR) by Pluronic block copolymers to promote drug delivery to MDR tumor following intravenous administration with paclitaxel (PTX) as model drug. Folic acid functionalized Pluronic P123/F127 mixed micelles encapsulating PTX (FPF-PTX) was firstly developed and tested in vitro and in vivo, while PTX-loaded Pluronic P123/F127 mixed micelles (PF-PTX) and Taxol were used as control. FPF-PTX was about 20 nm in diameter with spherical shape and high encapsulation efficiency. Cellular uptake of FPF-PTX was found to be higher than that of PF-PTX due to the folate receptor-mediated endocytosis effect. In vitro cytotoxicity, cell apoptosis and cell cycle arrest studies also revealed that FPF-PTX was more potent than those of PF-PTX and Taxol. In vivo pharmacokinetic study in rats showed that the polymeric micelles significantly enhanced the bioavailability of PTX (∼3 fold) than Taxol. Moreover, in BALB/c mice bearing KBv MDR tumor xenografts, stronger antitumor efficacy was shown in FPF-PTX group, with good correlation between in vitro and in vivo. In conclusion, folate-conjugated Pluronic micelles could be a potential vehicle for delivering hydrophobic chemotherapeutic drugs to MDR tumors.

Application of conductive polymers, scaffolds and electrical stimulation for nerve tissue engineering

Among the numerous attempts to integrate tissue engineering concepts into strategies to repair nearly all parts of the body, neuronal repair stands out. This is partially due to the complexity of the nervous anatomical system, its functioning and the inefficiency of conventional repair approaches, which are based on single components of either biomaterials or cells alone. Electrical stimulation has been shown to enhance the nerve regeneration process and this consequently makes the use of electrically conductive polymers very attractive for the construction of scaffolds for nerve tissue engineering. In this review, by taking into consideration the electrical properties of nerve cells and the effect of electrical stimulation on nerve cells, we discuss the most commonly utilized conductive polymers, polypyrrole (PPy) and polyaniline (PANI), along with their design and modifications, thus making them suitable scaffolds for nerve tissue engineering. Other electrospun, composite, conductive scaffolds, such as PANI/gelatin and PPy/poly(ε-caprolactone), with or without electrical stimulation, are also discussed. Different procedures of electrical stimulation which have been used in tissue engineering, with examples on their specific applications in tissue engineering, are also discussed.

Recent advances in three-dimensional multicellular spheroid culture for biomedical research

Many types of mammalian cells can aggregate and differentiate into 3-D multicellular spheroids when cultured in suspension or a nonadhesive environment. Compared to conventional monolayer cultures, multicellular spheroids resemble real tissues better in terms of structural and functional properties. Multicellular spheroids formed by transformed cells are widely used as avascular tumor models for metastasis and invasion research and for therapeutic screening. Many primary or progenitor cells on the other hand, show significantly enhanced viability and functional performance when grown as spheroids. Multicellular spheroids in this aspect are ideal building units for tissue reconstruction. Here we review the current understanding of multicellular spheroid formation mechanisms, their biomedical applications, and recent advances in spheroid culture, manipulation, and analysis techniques.

Separation of hematopoietic stem cells from human peripheral blood through modified polyurethane foaming membranes

Cell separation from peripheral blood was investigated using polyurethane (PU) foam membranes having 5.2 mum pore size and coated with Pluronic F127 or hyaluronic acid. The permeation ratio of hematopoietic stem cells (CD34(+) cells) and lymphocytes through the membranes was lower than for red blood cells and platelets. Adhered cells were detached from membrane surfaces using human serum albumin (HSA) solution after permeation of blood through the membranes, allowing isolation of CD34(+) cells in the permeate (recovery) solution. High-yield isolation of CD34(+) cells was achieved using Pluronic-coated membranes. This was because the Pluronic coating dissolved into the recovery solution at 4 degrees C, releasing adhered cells from the surfaces of the membranes during permeation of HSA solution through these membranes. Dextran and/or bovine serum albumin solutions were also evaluated for use as recovery solutions after blood permeation. A high recovery ratio of CD34(+) cells was achieved at 4 degrees C in a process using 20% dextran solution through PU membranes having carboxylic acid groups.

Technique for the control of spheroid diameter using microfabricated chips

This paper describes a new technique for the control of spheroid diameter in liver-derived cell lines using microfabricated chips that were prepared by combining microfabrication with chemical surface modification. The chip possesses multicavities in a triangular arrangement in the central region (10 mm x 10 mm) of a polymethylmethacrylate (PMMA) plate (24 mm x 24 mm), and the surface of the chip was modified with polyethylene glycol, thereby producing a surface that is non-adhesive to cells. HepG2 cells, a model liver-derived cell line, inoculated onto the chip were trapped within each cavity and proliferated to gradually form spheroids with smooth surfaces and high circularity. Although the spheroid diameters increased with cell proliferation during the initial 10 days of culture, they remained constant thereafter. The spheroid diameters were dependent on the scales of the multicavities on the chip, and the spheroid configuration with uniform diameter was maintained for at least 1 month. In particular, it was demonstrated using chips of various designs that the cavity diameter and the pitch between cavities were effective factors in controlling the spheroid diameter. Furthermore, the protein secretion activities of the spheroid formed on the chip were higher than those of the monolayers for at least 1 month of culture. These results indicate that this chip is a useful technique for the control of spheroid diameter and for the mass preparation of uniform spheroids.

Affinity chromatography using biocompatible and reusable biotinylated membranes

A novel, reusable biotinylated affinity chromatography strategy for the bio-specific binding of bioactive avidin tagged enzymes or polypeptides is reported. Using an avidin coupled peroxidase fusion protein as a test system; non-specific protein shielding and matrix regeneration were also shown. The amphiphilic surfactant Pluronic F108 was used as an affinity linker, by non-covalent binding to membrane chromatographic matrices while the terminal hydroxyl groups of Pluronic were covalently coupled to the biological ligand biotin. Planar nonporous membranes of varying surface chemistry were synthesised to test the matrix dependent affinity binding of biotinylated Pluronic and their respective ability to resist non-specific protein adsorption. Membrane regeneration using sodium dodecyl sulphate (SDS) was capable of displacing both adsorbed proteins and Pluronic. SDS micelles (34 mM) were effective in desorbing membrane bound protein while 5mM SDS removed up to 85% of the bound ligand after 20 h incubation at 20 degrees C. In this study, polyvinylidene membranes had the highest ligand binding capacity of 0.22 mg cm(-2) and specific, competitive affinity binding of avidin-peroxidase was shown in the presence of up to 0.2 mg ml(-1) 'contaminant' proteins. The resultant biocompatible affinity chromatographic system was regenerated and reused with no significant change in performance for up to five cycles.