Biomaterials (v.32, #5)
Editorial board (IFC).
Immobilization of selenocystamine on TiO2 surfaces for in situ catalytic generation of nitric oxide and potential application in intravascular stents by Yajun Weng; Qiang Song; Yujuan Zhou; Liping Zhang; Jin Wang; Junying Chen; Yongxiang Leng; Suiyan Li; Nan Huang (1253-1263).
Immobilization of selenocystamine on TiO2 film deposited on silicon wafer and 316 stainless steel stents for catalytic generation of nitric oxide was described. Polydopamine was used as the linker for immobilization of selenocystamine to the TiO2 surface. In vitro stability of the immobilized selenocystamine was investigated and the result shows surface selenium loss occurs mostly in the first four weeks. The selenocystamine immobilized surface possesses glutathione peroxidase (GPx) activity, and the activity increases with the amount of grafted polydopamine. Such selenocystamine immobilized surfaces show the ability of catalytically decomposing endogenous S-nitrosothiols (RSNO), generating NO; thus the surface displays the ability to inhibit collagen-induced platelet acitivation and aggregation. Additionally, smooth muscle cells are inhibited from adhering to the selenocystamine immobilized sample when RSNO is added to the culture media. ELISA analysis reveals that cGMP in both platelets and smooth muscle cells significantly increases with NO release on selenocystamine immobilized samples. Two months in vivo results show that selenocystamine immobilized stents are endothelialized, and show significant anti-proliferation properties, indicating that this is a favorable method for potential application in vascular stents.
Keywords: Surface immobilization; Selenocystamine; Dopamine; Nitric oxide; Catalytic activity;
Hydrophilic surface coatings with embedded biocidal silver nanoparticles and sodium heparin for central venous catheters by Kris N.J. Stevens; Sander Croes; Rinske S. Boersma; Ellen E. Stobberingh; Cees van der Marel; Frederik H. van der Veen; Menno L.W. Knetsch; Leo H. Koole (1264-1269).
Central venous catheters (CVCs) have become indispensable in the treatment of neonates and patients undergoing chemotherapy or hemodialysis. A CVC provides easy access to the patient’s circulation, thus enabling facile monitoring of hemodynamic parameters, nutritional support, or administration of (cytostatic) medication. However, complications with CVCs, such as bacterial bloodstream infection or thromboembolism, are common. Bloodstream infections, predominantly caused by Staphylococcus aureus, are notoriously difficult to prevent and treat. Furthermore, patients receiving infusion therapy through a CVC are at risk for deep-vein thrombosis, especially of the upper limbs. Several recent clinical trials have shown that prophylactic anticoagulation (low-molecular-weight heparin or vitamin K antagonists) is not effective. Here, we report on the systematic development of a new bifunctional coating concept that can –uniquely– be applied to make CVC surfaces antimicrobial and antithrombogenic at the same time. The novel coating consists of a moderately hydrophilic synthetic copolymer of N-vinylpyrrollidinone (NVP) and n-butyl methacrylate (BMA), containing embedded silver nanoparticles (AgNPs) and sodium heparin. The work demonstrates that the AgNPs strongly inhibit adhesion of S. aureus (reference strain and clinical isolates). Surprisingly, heparin not only rendered our surfaces practically non-thrombogenic, but also contributed synergistically to their biocidal activity.
Keywords: Catheter infection; Thrombogenicity; Heparin; Silver; Surface analysis; Platelet activation;
The role of integrins in the recognition and response of dendritic cells to biomaterials by Todd H. Rogers; Julia E. Babensee (1270-1279).
Biomaterials have the potential to be utilized as immunostimulatory or immunosuppressive delivery agents for biologics. It is hypothesized that this is directed by the ability of a biomaterial to drive dendritic cells (DC) in situ toward an immunostimulatory or an immunosuppressive phenotype, respectively. However, the specific pattern recognition receptors (PRRs) that DCs use to recognize and respond to biomaterials are unknown. From among the many receptors that DCs use to recognize and respond to foreign entities, herein the focus is on integrins. A biomaterial that induces DC maturation, namely poly(lactic-co-glycolic) acid (PLGA), supported increased human monocyte-derived DC adhesion and up-regulation of integrin receptor gene expression, measured via RT-PCR, as compared to culture on tissue culture polystyrene (TCPS). This was not observed for a biomaterial that does not support DC maturation. Through antibody-blocking techniques, the adhesion to both TCPS and PLGA was found to be β2 integrin dependent and β1 independent. Significantly, inhibiting β2-mediated adhesion to biomaterials via blocking antibodies also lowered the level of maturation of DCs (CD86 expression). β2 integrins (but not β1) were found localized in biomaterial-adherent DC podosomes and also were found in direct contact with the PLGA surface. Therefore, it appeared that β2 integrin-mediated adhesion is involved in determining the state of DC maturation on the PLGA surface. DC adhesion to biomaterials may be engaged or avoided to manipulate an immune response to biological component delivered with a biomaterial carrier.
Keywords: Biomaterials; Dendritic cells; Immune response; Integrin; Adhesion;
Biodegradable collagen patch with covalently immobilized VEGF for myocardial repair by Yasuo Miyagi; Loraine L.Y. Chiu; Massimo Cimini; Richard D. Weisel; Milica Radisic; Ren-Ke Li (1280-1290).
Vascularization of engineered tissues in vitro and in vivo remains a key problem in translation of engineered tissues to clinical practice. Growth factor signalling can be prolonged by covalent tethering, thus we hypothesized that covalent immobilization of vascular endothelial growth factor (VEGF-165) to a porous collagen scaffold will enable rapid vascularization in vivo. Covalent immobilization may be preferred over controlled release or cell transfection if the effects are desired within the biomaterial rather than the surrounding tissue. Scaffolds were prepared with 14.5 ± 1.4 ng (Low) or 97.2 ± 8.0 ng (High) immobilized VEGF, or left untreated (control), and used to replace a full right ventricular free wall defect in rat hearts. In addition to rapid vascularization, an effective cardiac patch should exhibit neither thinning nor dilatation upon implantation. In vitro, VEGF enhanced the growth of endothelial and bone marrow cells seeded onto scaffolds. In vivo, High VEGF patches had greater blood vessel density (p < 0.01) than control at Day 7 and 28 due to increased cell recruitment and proliferation (p < 0.05 vs. control). At Day 28, VEGF-treated patches were significantly thicker (p < 0.05) than control, and thickness correlated positively with neovascularization (r = 0.67, p = 0.023). Importantly, angiogenesis in VEGF scaffolds contributed to improved cell survival and tissue formation.
Keywords: Angiogenesis; Cardiac tissue engineering; Collagen; Growth factors; Scaffold; Heart;
Hierarchical and non-hierarchical mineralisation of collagen by Yan Liu; Young-Kyung Kim; Lin Dai; Nan Li; Sara O. Khan; David H. Pashley; Franklin R. Tay (1291-1300).
Biomineralisation of collagen involves functional motifs incorporated in extracellular matrix protein molecules to accomplish the objectives of stabilising amorphous calcium phosphate into nanoprecursors and directing the nucleation and growth of apatite within collagen fibrils. Here we report the use of small inorganic polyphosphate molecules to template hierarchical intrafibrillar apatite assembly in reconstituted collagen in the presence of polyacrylic acid to sequester calcium and phosphate into transient amorphous nanophases. The use of polyphosphate without a sequestration analogue resulted only in randomly-oriented extrafibrillar precipitations along the fibrillar surface. Conversely, the use of polyacrylic acid without a templating analogue resulted only in non-hierarchical intrafibrillar mineralisation with continuous apatite strands instead of discrete crystallites. The ability of using simple non-protein molecules to recapitulate different levels of structural hierarchy in mineralised collagen signifies the ultimate simplicity in Nature’s biomineralisation design principles and challenges the need for using more complex recombinant matrix proteins in bioengineering applications.
Keywords: Biomineralisation; Non-protein molecules; Hierarchical intrafibrillar mineralisation; Crossbanding; Non-hierarchical intrafibrillar mineralisation; Extrafibrillar mineralisation;
SPARC-derived protease substrates to enhance the plasmin sensitivity of molecularly engineered PEG hydrogels by J. Patterson; J.A. Hubbell (1301-1310).
Bioactive hydrogels formed from the Michael-type addition reactions of end-functionalized poly (ethylene glycol) macromers with thiol-containing protease-sensitive peptide crosslinkers have previously been described as matrices for cell-induced enzymatic remodeling. In this study, we sought to develop materials formulations with different degradation profiles by evaluating peptides derived from secreted protein acidic and rich in cysteine (SPARC) as potential substrates for plasmin, matrix metalloproteinase (MMP)-1, and MMP-2. Michaelis–Menten analysis showed that different peptides could provide a range of k cat values for each enzyme. In most cases, hydrogels formed with crosslinker peptides that had higher k cat values degraded faster when exposed to the appropriate enzyme(s), and fibroblasts showed increased cell proliferation and cell spreading when cultured in the faster degrading hydrogels. Further, greater cell invasion was observed from aortic ring segments embedded in the faster degrading hydrogels. The addition of the SPARC-derived peptides to the repertoire of protease-sensitive crosslinkers increases the potential application of these materials by providing enhanced susceptibility to plasmin. Further, the graded increases in k cat and the differential responses for plasmin, MMP-1, and MMP-2 can be used to engineer hydrogels with degradation properties tuned to the enzymes produced by particular cell types, allowing for broader in vivo application.
Keywords: Biodegradation; Biomimetic material; Cell spreading; Hydrogel; Matrix metalloproteinase; Peptide;
Hyperbranched polyglycerols on the nanometer and micrometer scale by Dirk Steinhilber; Sebastian Seiffert; John A. Heyman; Florian Paulus; David A. Weitz; Rainer Haag (1311-1316).
We report the preparation of polyglycerol particles on different length scales by extending the size of hyperbranched polyglycerols (3 nm) to nanogels (32 nm) and microgels (140 and 220 μm). We use miniemulsion templating for the preparation of nanogels and microfluidic templating for the preparation of microgels, which we obtain through a free-radical polymerization of hyperbranched polyglycerol decaacrylate and polyethylene glycol-diacrylate. The use of mild polymerization conditions allows yeast cells to be encapsulated into the resultant microgels with cell viabilities of approximately 30%.
Keywords: Biocompatibility; Cell encapsulation; Hydrogel; Microsphere; Nanoparticle;
Human urine-derived stem cells seeded in a modified 3D porous small intestinal submucosa scaffold for urethral tissue engineering by Shaofeng Wu; Yan Liu; Shantaram Bharadwaj; Anthony Atala; Yuanyuan Zhang (1317-1326).
The goal of this study was to determine whether urothelial cells (UC) and smooth muscle cells (SMC) derived from the differentiation of urine-derived stem cells (USC) could be used to form engineered urethral tissue when seeded on a modified 3-D porous small intestinal submucosa (SIS) scaffold. Cells were obtained from 12 voided urine samples from 4 healthy individuals. USC were isolated, characterized and induced to differentiate into UC and SMC. Fresh SIS derived from pigs was decellularized with 5% peracetic acid (PAA). Differentiated UC and SMC derived from USC were seeded onto SIS scaffolds with highly porous microstructure in a layered co-culture fashion and cultured under dynamic conditions for one week. The seeded cells formed multiple uniform layers on the SIS and penetrated deeper into the porous matrix during dynamic culture. USC that were induced to differentiate also expressed UC markers (Uroplakin-III and AE1/AE3) or SMC markers (α-SM actin, desmin, and myosin) after implantation into athymic mice for one month, and the resulting tissues were similar to those formed when UC and SMC derived from native ureter were used. In conclusion, UC and SMC derived from USC could be maintained on 3-D porous SIS scaffold. The dynamic culture system promoted 3-D cell–matrix ingrowth and development of a multilayer mucosal structure similar to that of native urinary tract tissue. USC may serve as an alternative cell source in cell-based tissue engineering for urethral reconstruction or other urological tissue repair.
Keywords: Urine; Stem cells; Biomaterial; Urethral stricture; Tissue engineering;
Unique biomaterial compositions direct bone marrow stem cells into specific chondrocytic phenotypes corresponding to the various zones of articular cartilage by Lonnissa H. Nguyen; Abhijit K. Kudva; Nicole L. Guckert; Klaus D. Linse; Krishnendu Roy (1327-1338).
Numerous studies have reported generation of cartilage-like tissue from chondrocytes and stem cells, using pellet cultures, bioreactors and various biomaterials, especially hydrogels. However, one of the primary unsolved challenges in the field has been the inability to produce tissue that mimics the highly organized zonal architecture of articular cartilage; specifically its spatially varying mechanical properties and extra-cellular matrix (ECM) composition. Here we show that different combinations of synthetic and natural biopolymers create unique niches that can “direct” a single marrow stem cell (MSC) population to differentiate into the superficial, transitional, or deep zones of articular cartilage. Specifically, incorporating chondroitin sulfate (CS) and matrix metalloproteinase-sensitive peptides (MMP-pep) into PEG hydrogels (PEG:CS:MMP-pep) induced high levels of collagen II and low levels of proteoglycan expression resulting in a low compressive modulus, similar to the superficial zone. PEG:CS hydrogels produced intermediate-levels of both collagen II and proteoglycans, like the transitional zone, while PEG:hyaluronic acid (HA) hydrogels induced high proteoglycan and low collagen II levels leading to high compressive modulus, similar to the deep zone. Additionally, the compressive moduli of these zone-specific matrices following cartilage generation showed similar trend as the corresponding zones of articular cartilage, with PEG:CS:MMP-pep having the lowest compressive modulus, followed by PEG:CS while PEG:HA had the highest modulus. These results underscore the potential for composite scaffold structures incorporating these biomaterial compositions such that a single stem-progenitor cell population can give rise to zonally-organized, functional articular cartilage-like tissue.
Keywords: Bone marrow stromal cells; Degradable hydrogel; Chondroitin sulfate; Hyaluronic acid; MMP (matrix metalloproteinase); Articular cartilage tissue engineering;
The role of collagen receptors Endo180 and DDR-2 in the foreign body reaction against non-crosslinked collagen and gelatin by Qingsong Ye; Martin C. Harmsen; Yijin Ren; Ruud A. Bank (1339-1350).
Despite the use of collagen-derived scaffolds in regenerative medicine, little is known about the degradation mechanisms of these scaffolds in vivo. Non-crosslinked dermal sheep (NDSC) and gelatin disks were implanted subcutaneously in mice. NDSC disks showed a very low degradation rate, despite the presence of high numbers of macrophages and the influx of neutrophils. This was attributed to the presence of the matrix metalloproteinase inhibitor TIMP-1. The limited degradation occurred mainly in the later stages of the foreign body reaction, and could be attributed to (1) phagocytosis by macrophages due to a co-expression of Endo180 and MT1-MMP on these cells (intracellular degradation) and (2) the presence of MMP-13 due to an upregulation of the expression of the DDR-2 receptor (extracellular degradation). In contrast, gelatin disks degraded quickly, due to the efficient formation of large giant cells as well as the presence of MMP-13; the inhibitor TIMP-1 was absent. The DDR-2 receptor was not expressed in the gelatin disks. Endo180 and MT1-MMP were expressed, but at most times no co-expression was seen. We conclude that the physical state of collagen (native or denatured) had a dramatic outcome on the degradation rate and provoked a completely different foreign body reaction.
Keywords: Collagen; Gelatin; Endo180; DDR-2; Foreign body reaction; Giant cells;
Surface patterning using plasma-deposited fluorocarbon thin films for single-cell positioning and neural circuit arrangement by Amanda M. Leclair; Stephen S.G. Ferguson; François Lagugné-Labarthet (1351-1360).
Micropatterning glass substrates with a plasma-deposited fluoropolymer thin film was shown to be an efficient approach to manipulate cell positioning. The glass windows promoted cell adhesion, whereas the surrounding fluoropolymer displays a cell-repelling character. Herein, multiple micropatterned substrates were developed with pattern dimensions sufficient to host solely single-cells. These single-cell arrays would allow analysis of individual cell response to stimulation without interference from cell–cell interactions. Mouse myoblast C2C12 cells and cortical neurons from mice were examined, both for amenability to patterning, as well as success of cell adhesion and cell morphology. Both cell types were found to have optimal adherence and growth on the glass surface, while cell adhesion and function was inhibited on the fluoropolymer. The C2C12 cells conformed to the shape of the pattern, while maintaining a healthy structure. Moreover, the neuron cells followed the hexagonal grid patterns and formed circuits, wherein the complexity of the connections depended on incubation time.
Keywords: Cell spreading; Fluorocarbon; Micropatterning; Neural networks; Plasma polymerization; Wettability;
Combinatorial screening of osteoblast response to 3D calcium phosphate/poly(ε-caprolactone) scaffolds using gradients and arrays by Kaushik Chatterjee; Limin Sun; Laurence C. Chow; Marian F. Young; Carl G. Simon (1361-1369).
There is a need for combinatorial and high-throughput methods for screening cell–biomaterial interactions to maximize tissue generation in scaffolds. Current methods employ a flat two-dimensional (2D) format even though three-dimensional (3D) scaffolds are more representative of the tissue environment in vivo and cells are responsive to topographical differences of 2D substrates and 3D scaffolds. Thus, combinatorial libraries of 3D porous scaffolds were developed and used to screen the effect of nano-amorphous calcium phosphate (nACP) particles on osteoblast response. Increasing nACP content in poly(ε-caprolactone) (PCL) scaffolds promoted osteoblast adhesion and proliferation. The nACP-containing scaffolds released calcium and phosphate ions which are known to activate osteoblast function. Scaffold libraries were fabricated in two formats, gradients and arrays, and the magnitude of the effect of nACP on osteoblast proliferation was greater for arrays than gradients. The enhanced response in arrays can be explained by differences in cell culture designs, diffusional effects and differences in the ratio of “scaffold mass to culture medium”. These results introduce a gradient library approach for screening large pore 3D scaffolds and demonstrate that inclusion of the nACP particles enhances osteoblast proliferation in 3D scaffolds. Further, comparison of gradients and arrays suggests that gradients were more sensitive for detecting effects of scaffold composition on cell adhesion (short time points, 1 day) whereas arrays were more sensitive at detecting effects on cell proliferation (longer time points, 14 day).
Keywords: 3D scaffolds; Calcium phosphate; Combinatorial screening; Nanoparticles; Osteoblast; Tissue engineering;
Integrin-targeted nanocomplexes for tumour specific delivery and therapy by systemic administration by Aristides D. Tagalakis; Stephanie M. Grosse; Qing-Hai Meng; M. Firouz Mohd Mustapa; Albert Kwok; Shahla E. Salehi; Alethea B. Tabor; Helen C. Hailes; Stephen L. Hart (1370-1376).
Nanoparticle formulations offer opportunities for tumour delivery of therapeutic reagents. The Receptor-Targeted Nanocomplex (RTN) formulation consists of a PEGylated, endosomally-cleavable lipid and an RGD integrin-targeting, endosomally-cleavable peptide. Nancomplexes self-assemble on mixing with plasmid DNA to produce nanoparticles of about 100 nm. The environmentally-sensitive linkers promote intracellular disassembly and release of the DNA. RTNs carrying luciferase genes were administered intravenously to mice carrying subcutaneous neuroblastoma tumours. Luciferase expression was much higher in tumours than in liver, spleen and lungs while plasmid biodistribution studies supported the expression data. Transfection in tumours was enhanced two-fold by integrin-targeting peptides compared to non-targeted nanocomplexes. RTNs containing the interleukin-2 (IL-2) and IL-12 genes were administered intravenously with seven doses at 48 h intervals and tumour growth monitored. Tumours from treated animals were approximately 75% smaller on day 11 compared with RTNs containing control plasmids with one third of treated mice surviving long-term. Extensive leukocyte infiltration, decreased vascularization and increased necrotic areas were observed in the tumours from IL2/IL12 treated animals. Splenocytes from re-challenged mice displayed enhanced IL-2 production following Neuro-2A co-culture, which, combined with infiltration studies, suggested a cytotoxic T cell-mediated9 tumour-rejection process. The integrin-targeted RTN formulation may have broader applications in the further development of cancer therapeutics.
Keywords: Cancer; Integrin; Gene therapy; Immunotherapy; Nanoparticle; Neuroblastoma;
Light induced drug delivery into cancer cells by Yosi Shamay; Lily Adar; Gonen Ashkenasy; Ayelet David (1377-1386).
Cell-penetrating peptides (CPPs) can be used for intracellular delivery of a broad variety of cargoes, including various nanoparticulate pharmaceutical carriers. However, the cationic nature of all CPP sequences, and thus lack of cell specificity, limits their in vivo use for drug delivery applications. Here, we have devised and tested a strategy for site-specific delivery of dyes and drugs into cancer cells by using polymers bearing a light activated caged CPP (cCPP). The positive charge of Lys residues on the minimum sequence of the CPP penetratin (52RRMKWKK58) was masked with photo-cleavable groups to minimize non-specific adsorption and cellular uptake. Once illuminated by UV light, these protecting groups were cleaved, the positively charged CPP regained its activity and facilitated rapid intracellular delivery of the polymer–dye or polymer–drug conjugates into cancer cells. We have found that a 10-min light illumination time was sufficient to enhance the penetration of the polymer–CPP conjugates bearing the proapoptotic peptide, d (KLAKLAK)2, into 80% of the target cells, and to promote a ‘switch’ like cytotoxic activity resulting a shift from 100% to 10% in cell viability after 2 h. This report provides an example for tumor targeting by means of light activation of cell-penetrating peptides for intracellular drug delivery.
Keywords: HPMA copolymers; Drug delivery; Cell-penetrating peptides; Caged peptides; Light activation;
Multi-functional liposomes having temperature-triggered release and magnetic resonance imaging for tumor-specific chemotherapy by Kenji Kono; Seiji Nakashima; Daisuke Kokuryo; Ichio Aoki; Hiroaki Shimomoto; Sadahito Aoshima; Kazuo Maruyama; Eiji Yuba; Chie Kojima; Atsushi Harada; Yukihito Ishizaka (1387-1395).
For development of tumor-specific chemotherapy, we designed liposomes with temperature-triggered drug release and magnetic resonance imaging (MRI) functions. We prepared multi-functional liposomes by incorporating thermosensitive poly(2-ethoxy(ethoxyethyl)vinyl ether) chains with a lower critical solution temperatures around 40 °C and polyamidoamine G3 dendron-based lipids having Gd3+ chelate residues into pegylated liposomes. These stable doxorubicin (DOX)-loaded liposomes retained DOX in their interior below physiological temperature but released DOX immediately at temperatures greater than 40 °C. They exhibited excellent ability to shorten the longitudinal proton relaxation time. When administered intravenously into colon 26 tumor-bearing mice, accumulated liposomes in tumors increased with time, reaching a constant level 8 h after administration by following T 1-weighted MRI signal intensity in tumors. Liposome size affected the liposome accumulation efficiency in tumors: liposomes of about 100 nm diameter were accumulated more efficiently than those with about 50 nm diameter. Tumor size also affected accumulation: more efficient accumulation occurred in larger tumors. Tumor growth was strongly suppressed when liposomes loaded with DOX were administered intravenously into tumor-bearing mice and the tumor was heated mildly at 44 °C for 10 min at 8 h after administration. Multi-functional liposomes having temperature-triggered drug release and MRI functions might engender personalized chemotherapy, providing efficient patient-optimized chemotherapy.
Keywords: Drug delivery; Temperature-responsive; Doxorubicin; Chemotherapy; Thermosensitive polymer; MRI;
Quantitative proteomic profiling of breast cancers using a multiplexed microfluidic platform for immunohistochemistry and immunocytochemistry by Minseok S. Kim; Seyong Kwon; Taemin Kim; Eun Sook Lee; Je-Kyun Park (1396-1403).
This paper describes a multiplexed microfluidic immunohistochemistry (IHC)/immunocytochemistry (ICC) platform for quantitative proteomic profiling in breast cancer samples. Proteomic profiling via ICC was examined for four breast cancer cell lines (AU-565, HCC70, MCF-7, and SK-BR-3). The microfluidic device enabled 20 ICC assays on a biological specimen at the same time and a 16-fold decrease in time consumption, and could be used to quantitatively compare the expression level of each biomarker. The immunohistochemical staining from the microfluidic system showed an accurate localization of protein and comparable quality to that of the conventional IHC method. Although AU-565 and SK-BR-3 cell lines were classified by luminal subtype and adenocarcinomas and were derived from the same patient, weak p63 expression was seen only in SK-BR-3. The HCC70 cell line showed a triple-negative (estrogen receptor-negative/progesterone receptor-negative/human epidermal growth factor receptor 2-negative) phenotype and showed only cytokeratin 5 expression, a representative basal/myoepithelial cell marker. To demonstrate the applicability of the system to clinical samples for proteomic profiling, we were also able to apply this platform to human breast cancer tissue. This result indicates that the microfluidic IHC/ICC platform is useful for accurate histopathological diagnoses using numerous specific biomarkers simultaneously, facilitating the individualization of cancer therapy.
Keywords: Polydimethylsiloxane; Micropatterning; Immunochemistry; In vitro test; Fluorescence; Microfluidics;
The modification of siRNA with 3′ cholesterol to increase nuclease protection and suppression of native mRNA by select siRNA polyplexes by Vishakha V. Ambardekar; Huai-Yun Han; Michelle L. Varney; Serguei V. Vinogradov; Rakesh K. Singh; Joseph A. Vetro (1404-1411).
Polymer-siRNA complexes (siRNA polyplexes) are being actively developed to improve the therapeutic application of siRNA. A major limitation for many siRNA polyplexes, however, is insufficient mRNA suppression. Given that modifying the sense strand of siRNA with 3′ cholesterol (chol-siRNA) increases the activity of free nuclease-resistant siRNA in vitro and in vivo, we hypothesized that complexation of chol-siRNA can increase mRNA suppression by siRNA polyplexes. In this study, the characteristics and siRNA activity of self assembled polyplexes formed with chol-siRNA or unmodified siRNA were compared using three types of conventional, positively charged polymers: (i) biodegradable, cross-linked nanogels (BDNG) (ii) graft copolymers (PEI-PEG), and (iii) linear block copolymers (PLL10-PEG, and PLL50-PEG). Chol-siRNA did not alter complex formation or the resistance of polyplexes to siRNA displacement by heparin but increased nuclease protection by BDNG, PLL10-PEG, and PLL50-PEG polyplexes over polyplexes with unmodified siRNA. Chol-CYPB siRNA increased suppression of native CYPB mRNA in mammary microvascular endothelial cells (MVEC) by BDNG polyplexes (35%) and PLL10-PEG polyplexes (69%) over comparable CYPB siRNA polyplexes but had no effect on PEI-PEG or PLL50-PEG polyplexes. Overall, these results indicate that complexation of chol-siRNA increases nuclease protection and mRNA suppression by select siRNA polyplexes. These results also suggest that polycationic block length is an important factor in increasing mRNA suppression by PLL-PEG chol-siRNA polyplexes in mammary MVEC.
Keywords: Immortomouse; H-2Kb-ts-A58; Mammary fat pad; PEGylated cationic polymers; PEGss; PPIB;
Transfection efficiency and intracellular fate of polycation liposomes combined with protamine by Jinliang Chen; Zhenwei Yu; Hailiang Chen; Jianqing Gao; Wenquan Liang (1412-1418).
Endosomal escape and nuclear entry are the two main barriers for successful non-viral gene delivery. To overcome these barriers, polyethylenimine (PEI) with a molecular weight of 800, conjugated to cholesterol (PEI 800-Chol) was synthesized to prepare polycation liposomes (PCLs). The effect of cationic polymers on transfection was investigated by pre-condensing DNA with these before using PCLs. The complexes of PCLs and protamine/DNA nanoparticles (PLPD) were introduced as efficient gene transfer vectors, and displayed obviously higher transfection efficiency (approximately 39-fold) than PCLs/DNA complexes. Kinetics of transgene expression indicated PLPD complexes could be maintained at a relatively high level over 72 h. The order of protamine addition affected the transfection of PLPD complexes. Pre-mixed and post-mixed PLPD complexes improved transfection, although the former was preferred. Distribution of FAM-labeled oligonucleotides (FAM-ODN) in cells mediated by PCLs were throughout the whole cell, while most FAM-ODN were nuclear when transfected with PLPD. These results suggest that the protonation of PEI and membrane destabilization of 1, 2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) increases the endosomal escape ability of vectors. The addition of protamine, containing nuclear localization signals, improved nuclear entry of DNA. The internalization pathways for PCLs involved multiple processes and were possibly dependent on cell lines.
Keywords: Polycation liposomes; Protamine; Synergistic effect; Nuclear targeting; Clathrin; Gene transfer;
Multivalent niacin nanoconjugates for delivery to cytoplasmic lipid droplets by Anjali Sharma; Armen Khatchadourian; Kunal Khanna; Rishi Sharma; Ashok Kakkar; Dusica Maysinger (1419-1429).
We report here the design, synthesis, and properties, of multifunctional niacin nanoconjugates based on dendritic, miktoarm and linear backbone nanocarriers, using “click” chemistry. The conjugates were in this instance used to deliver the therapeutic agent niacin to lipid droplets. The desired combination of niacin, a lipophilic fluorescent dye (BODIPY), and polyethylene glycol (PEG), was achieved by covalently linking the desired agents to the selected carrier. The nanocarriers containing niacin and BODIPY were found almost exclusively within cytoplasmic lipid droplets in the cells used in this study (living hepatocytes and microglia), whereas the trifunctional carrier containing niacin, BODIPY and PEG was partially localized within these organelles but also elsewhere in the cytoplasmic compartment. Spectrofluorometric analyses, confocal microscopy and fluorescence cell sorting revealed different rates and extent of multifunctional conjugate(s) internalization in the two cell types. Even micromolar concentrations of the internalized multifunctional conjugates did not cause significant cell death or mitochondrial functional impairment, suggesting that they are suitable candidate nanostructures for lipid droplet imaging and for targeting drugs to these cellular organelles. These studies provide an efficient and easy way to synthesize multifunctional nanocarriers by click chemistry, applicable to the synthesis of related multifunctional nanostructures and to their use in the targeting of cellular organelles, including lipid droplets.
Keywords: Multifunctional nanocarriers; Dendrimers; Drug delivery; Niacin; Targeting lipid droplets;
Human ferritin cages for imaging vascular macrophages by Masahiro Terashima; Masaki Uchida; Hisanori Kosuge; Philip S. Tsao; Mark J. Young; Steven M. Conolly; Trevor Douglas; Michael V. McConnell (1430-1437).
Atherosclerosis is a leading cause of death worldwide. Macrophages are key components of vascular inflammation, which contributes to the development and complications of atherosclerosis. Ferritin, an iron storage and transport protein, has been found to accumulate in macrophages in human atherosclerotic plaques. We hypothesized that ferritin could serve as an intrinsic nano-platform to target delivery of imaging agents to vascular macrophages to detect high-risk atherosclerotic plaques. Here we show that engineered human ferritin protein cages, either conjugated to the fluorescent Cy5.5 molecule or encapsulating a magnetite nanoparticle, are taken up in vivo by macrophages in murine atherosclerotic carotid arteries and can be imaged by fluorescence and magnetic resonance imaging. These results indicate that human ferritin can serve as a nanoparticle platform to image vascular inflammation in vivo.
Keywords: Nanoparticle; Inflammation; Macrophage; Ferritin; Atherosclerosis; Molecular imaging;
The use of low molecular weight heparin–pluronic nanogels to impede liver fibrosis by inhibition the TGF-β/Smad signaling pathway by Ju-Hee Lee; Hyunseung Lee; Yoon Ki Joung; Kyung Hee Jung; Jong-Hoon Choi; Don-Haeng Lee; Ki Dong Park; Soon-Sun Hong (1438-1445).
Low molecular weight heparin (LH) has been reported to have anti-fibrotic and anti-cancer effects. To enhance the efficacy and minimize adverse effects of LH, a low molecular weight heparin–pluronic nanogel (LHP) was synthesized by conjugating carboxylated pluronic F127 to LH. The LHP reduced anti-coagulant activity by about 33% of the innate activity. Liver fibrosis was induced by the injection of 1% dimethylnitrosamine (DMN) in rats, and LH or LHP (1000 IU/kg body weight) was treated once daily for 4 weeks. LHP administration prevented DMN-mediated liver weight loss and decreased the values of aspartate transaminase, alanine transaminase, total bilirubin, and direct bilirubin. LHP markedly reduced the fibrotic area compared to LH. Also, LHP potently inhibited mRNA or protein expression of alpha-smooth muscle actin, collagen type I, matrix metalloproteinase-2, and tissue inhibitor of metalloproteinase-1 compared to LH, in DMN-induced liver fibrosis. In addition, LHP decreased the expression of transforming growth factor-β1 (TGF-β1), p-Smad 2, and p-Smad 3, which are all important molecules of the TGF-β/Smad signaling pathway. The results support an LHP shows anti-fibrotic effect in the liver via inhibition of the TGF-β/Smad pathway as well as by the elimination of the extracellular matrix.
Keywords: Low molecular weight heparin–pluronic nanogel (LHP); DMN; Liver fibrosis; TGF-β/Smad; anti-Fibrotic agent;
Tissue integration of growth factor-eluting layer-by-layer polyelectrolyte multilayer coated implants by Mara L. Macdonald; Raymond E. Samuel; Nisarg J. Shah; Robert F. Padera; Yvette M. Beben; Paula T. Hammond (1446-1453).
Drug eluting coatings that can direct the host tissue response to implanted medical devices have the potential to ameliorate both the medical and financial burden of complications from implantation. However, because many drugs useful in this arena are biologic in nature, a paucity of delivery strategies for biologics, including growth factors, currently limits the control that can be exerted on the implantation environment. Layer-by-Layer (LbL) polyelectrolyte multilayer films are highly attractive as ultrathin biologic reservoirs, due to the capability to conformally coat difficult geometries, the use of aqueous processing likely to preserve fragile protein function, and the tunability of incorporation and release profiles. Herein, we describe the first LbL films capable of microgram-scale release of the biologic Bone Morphogenetic Protein 2 (BMP-2), which is capable of directing the host tissue response to create bone from native progenitor cells. Ten micrograms of BMP-2 are released over a period of two weeks in vitro; less than 1% is released in the first 3 h (compared with commercial collagen matrices which can release up to 60% of BMP-2, too quickly to induce differentiation). BMP-2 released from LbL films retains its ability to induce bone differentiation in MC3T3 E1S4 pre-osteoblasts, as measured by induction of alkaline phosphatase and stains for calcium (via Alizarin Red) and calcium matrix (via Von Kossa). In vivo, BMP-2 film coated scaffolds were compared with film coated scaffolds lacking BMP-2. BMP-2 coatings implanted intramuscularly were able to initiate host progenitor cells to differentiate into bone, which matured and expanded from four to 9 weeks as measured by MicroCT and histology. Such LbL films represent new steps towards controlling and tuning host response to implanted medical devices, which may ultimately increase the success of implanted devices, provide alternative new approaches toward bone wound healing, and lay the foundation for development of a multi-therapeutic release coating.
Keywords: Bone morphogenetic protein 2 (BMP-2); Polyelectrolyte multilayer; Bone tissue engineering; Coating; Layer-by-Layer; Controlled drug release;