Gene delivery system based on highly specific recognition of surface-vimentin with N-acetylglucosamine immobilized polyethylenimine

Extracellular vimentin as a versatile immune suppressive protein in cancer

The interest in finding new targets in the tumor microenvironment for anti-cancer therapy has increased rapidly over the years. More specifically, the tumor-associated blood vessels are a promising target. We recently found that the intermediate filament protein vimentin is externalized by endothelial cells of the tumor vasculature. Extracellular vimentin was shown to sustain angiogenesis by mimicking VEGF and supporting cell migration, as well as endothelial cell anergy, the unresponsiveness of the endothelium to proinflammatory cytokines. The latter hampers immune cell infiltration and subsequently provides escape from tumor immunity. Other studies showed that extracellular vimentin plays a role in sustained systemic and local inflammation. Here we will review the reported roles of extracellular vimentin with a particular emphasis on its involvement in the interactions between immune cells and the endothelium in the tumor microenvironment. To this end, we discuss the different ways by which extracellular vimentin modulates the immune system. Moreover, we review how this protein can alter immune cell-vessel wall adhesion by altering the expression of adhesion proteins, attenuating immune cell infiltration into the tumor parenchyma. Finally, we discuss how vimentin-targeting therapy can reverse endothelial cell anergy and promote immune infiltration, supporting anti-tumor immunity.

Polyethylenimine (PEI) in gene therapy: Current status and clinical applications

Polyethlyenimine (PEI) was introduced 1995 as a cationic polymer for nucleic acid delivery. PEI and its derivatives are extensively used in basic research and as reference formulations in the field of polymer-based gene delivery. Despite its widespread use, the number of clinical applications to date is limited. Thus, this review aims to consolidate the past applications of PEI in DNA delivery, elucidate the obstacles that hinder its transition to clinical use, and highlight potential prospects for novel iterations of PEI derivatives. The present review article is divided into three sections. The first section examines the mechanism of action employed by PEI, examining fundamental aspects of cellular delivery including uptake mechanisms, release from endosomes, and transport into the cell nucleus, along with potential strategies for enhancing these delivery phases. Moreover, an in-depth analysis is conducted concerning the mechanism underlying cellular toxicity, accompanied with approaches to overcome this major challenge. The second part is devoted to the in vivo performance of PEI and its application in various therapeutic indications. While systemic administration has proven to be challenging, alternative localized delivery routes hold promise, such as treatment of solid tumors, application as a vaccine, or serving as a therapeutic agent for pulmonary delivery. In the last section, the outcome of completed and ongoing clinical trials is summarized. Finally, an expert opinion is provided on the potential of PEI and its future applications. PEI-based formulations for nucleic acid delivery have a promising potential, it will be an important task for the years to come to introduce innovations that address PEI-associated shortcomings by introducing well-designed PEI formulations in combination with an appropriate route of administration.

The Biocompatibility Analysis of Artificial Mucin-Like Glycopolymers

The ocular surface is covered by a tear film consisting of an aqueous/mucin phase and a superficial lipid layer. Mucins, highly O-glycosylated proteins, are responsible for lubrication and ocular surface protection. Due to contact lens wear or eye disorders, lubrication of the ocular surface can be affected. Artificial glycopolymers which mimic natural mucins could be efficient in ophthalmic therapy. Various neutral, positively, and negatively charged mucin-mimicking glycopolymers were synthesized (n = 11), cultured in different concentrations (1%, 0.1%, and 0.01% w/v) with human corneal epithelial cells (HCE), and analyzed by various cytotoxicity/viability, morphology, and immunohistochemistry (IHC) assays. Six of the eleven glycopolymers were selected for further analysis after cytotoxicity/viability assays. We showed that the six selected glycopolymers had no cytotoxic effect on HCE cells in the 0.01% w/v concentration. They did not negatively affect cell viability and displayed both morphology and characteristic markers as untreated control cells. These polymers could be used in the future as mucin-mimicking semi-synthetic materials for lubrication and protection of the ocular surface.

Cross-Linked Gamma Polyglutamic Acid/Human Hair Keratin Electrospun Nanofibrous Scaffolds with Excellent Biocompatibility and Biodegradability

Recently, human hair keratin has been widely studied and applied in clinical fields due to its good histocompatibility, biocompatibility, and biodegradability. However, the regenerated keratin from human hair cannot be electrospun alone because of its low molecular weight. Herein, gamma polyglutamic acid (γ-PGA) was first selected to fabricate smooth and uniform γ-PGA/keratin composite scaffolds with excellent biocompatibility and biodegradability by electrospinning technology and a chemical cross-linking method in this study. The effect of electrospinning parameters on the structure and morphology, the mechanism of chemical cross-linking, biocompatibility in vitro cell culture experiments, and biodegradability in phosphate-buffered saline buffer solution and trypsin solution of the γ-PGA/keratin electrospun nanofibrous scaffolds (ENS) was studied. The results show that the cross-linked γ-PGA/keratin ENSs had excellent water stability and biodegradability. The γ-PGA/keratin ENSs showed better biocompatibility in promoting cell adhesion and cell growth compared with the γ-PGA ENSs. It is expected that γ-PGA/keratin ENSs will be easily and significantly used in tissue engineering to repair or regenerate materials.

Optimization of a cell surface vimentin binding peptoid to extract antagonist effect on lung cancer cells

Targeting cytoskeletal proteins that are uniquely translocated to cancer cell surface may provide an alternative path for conventional drug discovery. Vimentin is such a cell surface-translocated cytoskeletal protein (CSV) found in non small cell lung cancer (NSCLC). We previously reported the identification of CSV-binding peptoid, named JM3A. While JM3A had no antagonist effect, here we used multiple strategies to optimize the binding of JM3A on CSV and extract the antagonistic effect. We first performed minimum pharmacophore identification studies using alanine/sarcosine scans. These studies revealed that residues 1-4 and 8 (from the C-terminus) are not important and those residues 5-7 are important for JM3A binding to CSV. We then found that our previous N-terminal benzophenone (BP)-coupled JM3A (JM3A-BP), which was used for pull-down and target identification studies, displayed 3-fold binding enhancement. The molecular docking studies indicated that the BP moiety binds to a new binding pocket on the vimentin coil 2 fragment, and further studies using 12 benzophenone-like moieties indicated that at least two phenyl groups are needed to occupy this new binding site. Interestingly, the binding was improved when non-important and bulky residues at the 4th and 8th positions were replaced with methyl groups (JM3A-4,8-BP). We next dimerized JM3A-4,8-BP to enhance the binding via the "avidity effect," using a central lysine linker to develop JM3A-4,8-BPD1 (EC50 = 300 nM). This showed 27- and 63-fold-improvement in binding over JM3A-4,8-BP and JM3A monomers, respectively. JM3A4,8BPD1 also displayed binding comparable to vimentin antibody. Finally, we observed an antagonist effect on H1299 NSCLC cell proliferation and viability from this most improved dimeric JM3A-4,8BPD1, which was not shown by the monomeric versions.

Glycopolymer based LbL Multilayer Thin Films with Embedded Liposomes

Layer-by-layer (LbL) self-assembly emerged as an efficient technique for fabricating coating systems for, e.g., drug delivery systems with great versatility and control. In this work, we describe protecting group free and aqueous-based syntheses of bioinspired glycopolymer electrolytes. Thin films of the glycopolymers are fabricated by LbL self-assembly and function as scaffolds for liposomes, which potentially can encapsulate active substances. We investigate the adsorbed mass, pH stability and integrity of glycopolymer coatings as well as the embedded liposomes via whispering gallery mode (WGM) technology and quartz crystal microbalance with dissipation (QCM-D) monitoring, which enable label-free characterization. Glycopolymer thin films, with and without liposomes, are stable in the physiological pH range. QCM-D measurements verify the integrity of lipid vesicles. Thus, we present the fabrication of glycopolymer-based surface coatings with embedded and intact liposomes. This article is protected by copyright. All rights reserved.

Vimentin Targeted Nano-gene Carrier for Treatment of Renal Diseases

BACKGROUND

Chronic kidney disease (CKD) is a global health problem, and there is no permanent treatment for reversing kidney failure; thus, early diagnosis and effective treatment are required. Gene therapy has outstanding potential; however, the lack of safe gene delivery vectors, a reasonable transfection rate, and kidney targeting ability limit its application. Nanoparticles can offer innovative ways to diagnose and treat kidney diseases as they facilitate targetability and therapeutic efficacy.

METHODS

Herein, we developed a proximal renal tubule-targeting gene delivery system based on alternative copolymer (PS) of sorbitol and polyethyleneimine (PEI), modified with vimentin-specific chitobionic acid (CA), producing PS-conjugated CA (PSC) for targeting toward vimentin-expressing cells in the kidneys. In vitro studies were used to determine cell viability, transfection efficiency, serum influence, and specific uptake in the human proximal renal tubular epithelial cell line (HK-2). Finally, the targeting efficiency of the prepared PSC gene carriers was checked in a murine model of Alport syndrome.

RESULTS

Our results suggested that the prepared polyplex showed low cytotoxicity, enhanced transfection efficiency, specific uptake toward HK-2 cells, and excellent targeting efficiency toward the kidneys.

CONCLUSION

Collectively, from these results it can be inferred that the PSC can be further evaluated as a potential gene carrier for the kidney-targeted delivery of therapeutic genes for treating diseases.

Surface-modified polymeric nanoparticles for drug delivery to cancer cells

INTRODUCTION

The utilization of polymeric nanoparticles, as drug payloads, has been extensively prevailed in cancer therapy. However, the precise distribution of these nanocarriers is restrained by various physiological and cellular obstacles. Nanoparticles must avoid nonspecific interactions with healthy cells and in vivo compartments to circumvent these barriers. Since in vivo interactions of nanoparticles are mainly dependent on surface properties of nanoparticles, efficient control on surface constituents is necessary for the determination of nanoparticles' fate in the body.

AREAS COVERED

In this review, the surface-modified polymeric nanoparticles and their utilization in cancer treatment were elaborated. First, the interaction of nanoparticles with numerous in vivo barriers was highlighted. Second, different strategies to overcome these obstacles were described. Third, some inspiring examples of surface-modified nanoparticles were presented. Later, fabrication and characterization methods of surface-modified nanoparticles were discussed. Finally, the applications of these nanoparticles in different routes of treatments were explored.

EXPERT OPINION

Surface modification of anticancer drug-loaded polymeric nanoparticles can enhance the efficacy, selective targeting, and biodistribution of the anticancer drug at the tumor site.

Progress in drug delivery system for fibrosis therapy

Fibrosis is a necessary process in the progression of chronic disease to cirrhosis or even cancer, which is a serious disease threatening human health. Recent studies have shown that the early treatment of fibrosis is turning point and particularly important. Therefore, how to reverse fibrosis has become the focus and research hotspot in recent years. So far, the considerable progress has been made in the development of effective anti-fibrosis drugs and targeted drug delivery. Moreover, the existing research results will lay the foundation for more breakthrough delivery systems to achieve better anti-fibrosis effects. Herein, this review summaries anti-fibrosis delivery systems focused on three major organ fibrotic diseases such as liver, pulmonary, and renal fibrosis accompanied by the elaboration of relevant pathological mechanisms, which will provide inspiration and guidance for the design of fibrosis drugs and therapeutic systems in the future.

Development of a Gene Delivery System of Oligonucleotides for Fibroses by Targeting Cell-Surface Vimentin-Expressing Cells with N-Acetylglucosamine-Bearing Polymer-Conjugated Polyethyleneimine

Targeting myofibroblasts and activated stellate cells in lesion sites of fibrotic tissues is an important approach to treat fibroses. Herein, we focused on targeting the cytoskeletal proteins vimentin, which are reportedly highly expressed on the surface of these cells and have N-acetylglucosamine (GlcNAc)-binding activity. A GlcNAc-bearing polymer synthesized via radical polymerization with a reversible addition-fragmentation chain transfer reagent has been previously found to interact with cell-surface vimentin-expressing cells. We designed a GlcNAc-bearing polymer-conjugated polyethyleneimine (PEI), as the gene carrier to target cell-surface vimentin-expressing cells and specifically deliver nuclear factor-κB decoy oligonucleotides (ODNs) and heat shock protein 47 (HSP47)-small interfering RNA (siRNA) to normal human dermal fibroblasts (NHDFs) that express cell-surface vimentin. The results showed that the expression of tumor necrosis factor-α in lipopolysaccharide-stimulated NHDFs and HSP47 in transforming growth factor-β1-stimulated NHDFs was suppressed by cellular uptake of the GlcNAc-bearing polymer-conjugated PEI/nuclear factor (NF)-κB decoy ODNs and HSP47-siRNA complexes through cell-surface vimentin, respectively. These findings suggest that the effective and specific delivery of ODNs and siRNA for cell-surface vimentin-expressing cells such as myofibroblasts and activated stellate cells can be achieved using GlcNAc-bearing polymer-conjugated PEI. This therapeutic approach could prove advantageous to prevent the promotion of various fibroses.

Improved Isolation of Mesenchymal Stem Cells Based on Interactions between N-Acetylglucosamine-Bearing Polymers and Cell-Surface Vimentin

Mesenchymal stem cells (MSCs) in bone marrow and adipose tissues are expected to be effective tools for regenerative medicine to treat various diseases. To obtain MSCs that possess both high differentiation and tissue regenerative potential, it is necessary to establish an isolation system that does not require long-term culture. It has previously been reported that the cytoskeletal protein vimentin, expressed on the surfaces of multiple cell types, possesses N-acetylglucosamine- (GlcNAc-) binding activity. Therefore, we tried to exploit this interaction to efficiently isolate MSCs from rat bone marrow cells using GlcNAc-bearing polymer-coated dishes. Cells isolated by this method were identified as MSCs because they were CD34-, CD45-, and CD11b/c-negative and CD90-, CD29-, CD44-, CD54-, CD73-, and CD105-positive. Osteoblast, adipocyte, and chondrocyte differentiation was observed in these cells. In total, yields of rat MSCs were threefold to fourfold higher using GlcNAc-bearing polymer-coated dishes than yields using conventional tissue-culture dishes. Interestingly, MSCs isolated with GlcNAc-bearing polymer-coated dishes strongly expressed CD106, whereas those isolated with conventional tissue-culture dishes had low CD106 expression. Moreover, senescence-associated β-galactosidase activity in MSCs from GlcNAc-bearing polymer-coated dishes was lower than that in MSCs from tissue-culture dishes. These results establish an improved isolation method for high-quality MSCs.

Discovery of cell surface vimentin targeting mAb for direct disruption of GBM tumor initiating cells

Intracellular vimentin overexpression has been associated with epithelial–mesenchymal transition, metastasis, invasion, and proliferation, but cell surface vimentin (CSV) is less understood. Furthermore, it remains unknown whether CSV can serve as a therapeutic target in CSV-expressing tumor cells. We found that CSV was present on glioblastoma multiforme (GBM) cancer stem cells and that CSV expression was associated with spheroid formation in those cells. A newly developed monoclonal antibody against CSV, 86C, specifically and significantly induced apoptosis and inhibited spheroid formation in GBM cells in vitro. The addition of 86C to GBM cells in vitro also led to rapid internalization of vimentin and decreased GBM cell viability. These findings were associated with an increase in caspase-3 activity, indicating activation of apoptosis. Finally, treatment with 86C inhibited GBM progression in vivo. In conclusion, CSV-expressing GBM cells have properties of tumor initiating cells, and targeting CSV with the monoclonal antibody 86C is a promising approach in the treatment of GBM.

Desmin- and vimentin-mediated hepatic stellate cell-targeting radiotracer 99mTc-GlcNAc-PEI for liver fibrosis imaging with SPECT

Extracellular matrix (ECM) accumulation in liver fibrosis is caused by the activation of hepatic stellate cells (HSCs). The goal of this study was to develop a ^99mTc-labeled N-acetylglucosamine (GlcNAc) that specifically interacts with desmin and vimentin expressed on activated HSCs to monitor the progression and prognosis of liver fibrosis using single-photon emission computed tomography (SPECT) imaging.

Methods: GlcNAc-conjugated polyethylenimine (PEI) was first prepared and radiolabeled with ^99mTc. Noninvasive SPECT imaging with ^99mTc-GlcNAc-PEI was used to assess liver fibrosis in a carbon tetrachloride (CCl₄) mouse model. The liver uptake value (LUV) of ^99mTc-GlcNAc-PEI was measured by drawing the region of interest (ROI) of the whole liver as previously suggested. The LUV of the CCl₄ groups was compared with that of the olive oil group. Next, we estimated the correlation between the results of SPECT imaging and physiological indexes. After treatment with clodronate liposome, the LUV of ^99mTc-GlcNAc-PEI in fibrotic mice was compared with that in control mice.

Results:^99mTc-GlcNAc-PEI is a hydrophilic compound with high radiochemical purity (>98%) and good stability. It could specifically target desmin and vimentin on the surface of activated HSCs with high affinity (the K_d values were 53.75 ± 9.50 nM and 20.98 ± 3.56 nM, respectively). The LUV of ^99mTc-GlcNAc-PEI was significantly different between the CCl₄ and control groups as early as 4 weeks of CCl₄ administration (3.30 ± 0.160 vs 2.34 ± 0.114%/cc; P ˂ 0.05). There was a strong correlation between the LUV and Sirius Red quantification (R = 0.92, P ˂ 0.001). Compared with control, clodronate liposome treatment reduced the LUV of ^99mTc-GlcNAc-PEI (4.62 ± 0.352 vs 2.133 ± 0.414%/cc; P ˂ 0.05).

Conclusion:^99mTc-GlcNAc-PEI SPECT/CT was useful in assessing liver fibrosis and monitoring the treatment response.

Elucidation of GlcNAc-binding properties of type III intermediate filament proteins, using GlcNAc-bearing polymers

Vimentin, desmin, glial fibrillary acidic protein (GFAP) and peripherin belong to type III intermediate filament family and are expressed in mesenchymal cells, skeletal muscle cells, astrocytes and peripheral neurons, respectively. Vimentin and desmin possess N-acetyl-d-glucosamine (GlcNAc)-binding properties on cell surfaces. The rod II domain of these proteins is a GlcNAc-binding site, which also exists in GFAP and peripherin. However, the GlcNAc-binding activities and behaviors of these proteins remain unclear. Here, we characterized the interaction and binding behaviors of these proteins, using various well-defined GlcNAc-bearing polymers synthesized by radical polymerization with a reversible addition-fragmentation chain transfer reagent. The small GlcNAc-bearing polymers strongly interacted with HeLa cells through vimentin expressed on the cell surface and interacted with vimentin-, desmin-, GFAP- and peripherin-transfected vimentin-deficient HeLa cells. These proteins present high affinity to GlcNAc-bearing polymers, as shown by surface plasmon resonance. These results show that type III intermediate filament proteins possess GlcNAc-binding activities on cell surfaces. These findings provide important insights into novel cellular functions and physiological significance of type III intermediate filaments.

Poly(amidoamine) dendrimer-enabled simultaneous stabilization and functionalization of electrospun poly(γ-glutamic acid) nanofibers

We report a facile and general approach to using generation 2 (G2) poly(amidoamine) (PAMAM) dendrimers for simultaneous stabilization and functionalization of electrospun poly(γ-glutamic acid) nanofibers (γ-PGA NFs). In this study, uniform γ-PGA NFs with a smooth morphology were generated using electrospinning technology. In order to endow the NFs with good water stability, amine-terminated G2.NH2 PAMAM dendrimers were utilized to crosslink the γ-PGA NFs via 1-ethyl-3-(3-dimethylami-nopropyl) carbodiimide coupling chemistry. Under the optimized crosslinking conditions, G2.NH2 dendrimers partially modified with fluorescein isothiocyanate (FI) or folic acid (FA) were used to crosslink γ-PGA NFs. Our results reveal that G2.NH2-FI is able to simultaneously render the NFs with good water stability and fluorescence property, while G2.NH2-FA is able to simultaneously endow the NFs with water stability and the ability to capture FA receptor-overexpressing cancer cells in vitro via ligand-receptor interaction. With the tunable dendrimer surface chemistry, multifunctional water-stable γ-PGA-based NFs may be generated via a dendrimer crosslinking approach, thereby providing diverse applications in the areas of biosensing, tissue engineering, drug delivery, and environmental sciences.

Functional and biodegradable dendritic macromolecules with controlled architectures as nontoxic and efficient nanoscale gene vectors

Gene therapy has provided great potential to revolutionize the treatment of many diseases. This therapy is strongly relied on whether a delivery vector efficiently and safely directs the therapeutic genes into the target tissue/cells. Nonviral gene delivery vectors have been emerging as a realistic alternative to the use of viral analogs with the potential of a clinically relevant output. Dendritic polymers were employed as nonviral vectors due to their branched and layered architectures, globular shape and multivalent groups on their surface, showing promise in gene delivery. In the present review, we try to bring out the recent trend of studies on functional and biodegradable dendritic polymers as nontoxic and efficient gene delivery vectors. By regulating dendritic polymer design and preparation, together with recent progress in the design of biodegradable polymers, it is possible to precisely manipulate their architectures, molecular weight and chemical composition, resulting in predictable tuning of their biocompatibility as well as gene transfection activities. The multifunctional and biodegradable dendritic polymers possessing the desirable characteristics are expected to overcome extra- and intracellular obstacles, and as efficient and nontoxic gene delivery vectors to move into the clinical arena.

Imaging and therapy of liver fibrosis using bioreducible polyethylenimine/siRNA complexes conjugated with N-acetylglucosamine as a targeting moiety

Diagnosis and therapy of early stage liver fibrosis is very important for the treatment of fatal liver diseases. Here, we report on the targeted imaging and therapy of activated hepatic stellate cells (HSCs) and fibrotic liver tissue using N-acetylglucosamine (GlcNAc)- and indocyanine green (ICG)-conjugated PEI/siRNA complexes. The conjugation of a disulfide bond to PEI (PEI-D) was achieved by Michael addition. We modified PEI with N-acetylglucosamine (PEI-D-GlcNAc), which can specifically interact with desmin on activated HSCs, using the EDC coupling method. Confocal microscopic analysis showed that the PEI-D-GlcNAc/siRNA was internalized by HSCs upon interaction with surface desmin. In vitro western blot analysis confirmed that PEI-D-GlcNAc provided strong protein knock-down after transfection with TGFβ1siRNA into HSCs. After a tail vein injection of ICG-conjugated complexes, the PEI-D-GlcNAc-ICG/siRNA complex accumulated to a greater extent in the livers of fibrotic mice than in normal mice over an extended duration. Moreover, immunohistofluorescence analysis confirmed that the PEI-D-GlcNAc-ICG/siRNA complex specifically colocalized with HSCs, which are desmin-positive cells, in fibrotic liver tissues. In vivo TGFβ1siRNA delivery also resulted in superior protein knock-down when using the PEI-D-GlcNAc complex. These results demonstrate that the PEI-D-GlcNAc-ICG/TGFβ1siRNA complex is a useful tool for imaging and treatment of liver fibrosis.

Dynamic behaviors of vimentin induced by interaction with GlcNAc molecules

The cytoskeleton protein vimentin is dramatically altered following pathological events such as fibrosis and tumorigenesis. Vimentin binds to multivalent N-acetylglucosamine (GlcNAc) molecules at the cell surface and interacts with O-linked β-GlcNAc proteins. Moreover, dying cells can be engulfed by neighboring cells through surface interactions between vimentin and many O-GlcNAc proteins in cell debris. Here, we show that vimentin was altered by its interaction with GlcNAc-bearing molecules such as GlcNAc-bearing polymers. The interaction with GlcNAc-bearing polymers promoted the cell surface recruitment of vimentin followed by the phosphorylation of vimentin serine 71 and the increase in tetrameric vimentin disassembled from vimentin filaments in HeLa cells. Moreover, it was found that GlcNAc-bearing polymers and O-GlcNAc proteins from dying cells promoted vimentin expression and cell migration in the Madin-Darby canine kidney and Michigan Cancer Foundation-7 cells. These results suggest that interactions between surface vimentin and GlcNAc molecules, including the O-GlcNAc proteins from dying cells, may play a pivotal role in vimentin expression and the migration of cancer cells. We propose new mechanisms of vimentin expression in cancer cells.

Strategies in biomimetic surface engineering of nanoparticles for biomedical applications

Engineered nanoparticles (NPs) play an increasingly important role in biomedical sciences and in nanomedicine. Yet, in spite of significant advances, it remains difficult to construct drug-loaded NPs with precisely defined therapeutic effects, in terms of release time and spatial targeting. The body is a highly complex system that imposes multiple physiological and cellular barriers to foreign objects. Upon injection in the blood stream or following oral administation, NPs have to bypass numerous barriers prior to reaching their intended target. A particularly successful design strategy consists in masking the NP to the biological environment by covering it with an outer surface mimicking the composition and functionality of the cell's external membrane. This review describes this biomimetic approach. First, we outline key features of the composition and function of the cell membrane. Then, we present recent developments in the fabrication of molecules that mimic biomolecules present on the cell membrane, such as proteins, peptides, and carbohydrates. We present effective strategies to link such bioactive molecules to the NPs surface and we highlight the power of this approach by presenting some exciting examples of biomimetically engineered NPs useful for multimodal diagnostics and for target-specific drug/gene delivery applications. Finally, critical directions for future research and applications of biomimetic NPs are suggested to the readers.

Interactions of vimentin- or desmin-expressing liver cells with N-acetylglucosamine-bearing polymers

It is necessary to develop highly functionalized liver cell culture systems for liver tissue engineering such as bioartificial livers and liver cell chips. To maintain a high level of hepatocyte function, well-organized patterning culture systems of hepatocytes and nonparenchymal cells would be advantageous. To design the patterning culture system using these cells, cell-recognizable polymers should be useful to regulate not only the hepatocytes, but also the nonparenchymal cells. Here, we report that N-acetylglucosamine (GlcNAc)-bearing polymers are useful as nonparenchymal cell-recognizable polymers. It has previously been reported that mesenchymal cells adhered to GlcNAc-bearing polymer-coated dishes through surface vimentin. It was also observed that nonparenchymal cells expressing vimentin or desmin specifically adhered to GlcNAc-bearing polymer-coated dishes. Especially, in hepatic stellate cells (HSCs) cultured on GlcNAc-bearing polymer-coated dishes, the expression of α-smooth muscle actin as an activated HSCs marker was suppressed in long-term. Therefore, HSCs were shown to maintain a quiescent state on PVGlcNAc-coated dishes during a long-term culture. These results demonstrated that GlcNAc-bearing polymers could be beneficial to culture nonparenchymal cells such as HSCs. Our findings suggest that galactose- and GlcNAc-bearing polymers can regulate the culture of all liver cells and may be useful tools for the establishment of liver tissue engineering.