Nanocarrier of α-Tocopheryl Succinate Based on a Copolymer Derivative of (4,7-dichloroquinolin-2-yl)methanol and Its Cytotoxicity against a Breast Cancer Cell Line

In order to improve the water solubility and, therefore, bioavailability and therapeutic activity of anticancer hydrophobic drug α-tocopherol succinate (α-TOS), in this work, copolymers were synthesized via free radicals from QMES (1-[4,7-dichloroquinolin-2-ylmethyl]-4-methacryloyloxyethyl succinate) and VP (N-vinyl-2-pirrolidone) using different molar ratios, and were used to nanoencapsulate and deliver α-TOS into cancer cells MCF-7. QMES monomer was chosen because the QMES pendant group in the polymer tends to hydrolyze to form free 4,7-dichloro-2-quinolinemethanol (QOH), which also, like α-TOS, exhibit anti-proliferative effects on cancerous cells. From the QMES-VP 30:70 (QMES-30) and 40:60 (QMES-40) copolymers obtained, it was possible to prepare aqueous suspensions of empty nanoparticles (NPs) loaded with α-TOS by nanoprecipitation. The diameter and encapsulation efficiency (%EE) of the QMES-30 NPs loaded with α-TOS were 128.6 nm and 52%; while for the QMES-40 NPs loaded with α-TOS, they were 148.8 nm and 65%. The results of the AlamarBlue assay at 72 h of treatment show that empty QMES-30 NPs (without α-TOS) produced a marked cytotoxic effect on MCF-7 breast cancer cells, corresponding to an IC50 value of 0.043 mg mL-1, and importantly, they did not exhibit cytotoxicity against healthy HUVEC cells. Furthermore, NP-QMES-40 loaded with α-TOS were cytotoxic with an IC50 value of 0.076 mg mL-1, demonstrating a progressive release of α-TOS; however, the latter nanoparticles were also cytotoxic to healthy cells in the range of the assayed concentrations. These results contribute to the search for a new polymeric nanocarrier of QOH, α-TOS or other hydrophobic drugs for the treatment of cancer or others diseases treatable with these drugs.

Challenges and advances in materials and fabrication technologies of small-diameter vascular grafts

The arterial occlusive disease is one of the leading causes of cardiovascular diseases, often requiring revascularization. Lack of suitable small-diameter vascular grafts (SDVGs), infection, thrombosis, and intimal hyperplasia associated with synthetic vascular grafts lead to a low success rate of SDVGs (< 6 mm) transplantation in the clinical treatment of cardiovascular diseases. The development of fabrication technology along with vascular tissue engineering and regenerative medicine technology allows biological tissue-engineered vascular grafts to become living grafts, which can integrate, remodel, and repair the host vessels as well as respond to the surrounding mechanical and biochemical stimuli. Hence, they potentially alleviate the shortage of existing vascular grafts. This paper evaluates the current advanced fabrication technologies for SDVGs, including electrospinning, molding, 3D printing, decellularization, and so on. Various characteristics of synthetic polymers and surface modification methods are also introduced. In addition, it also provides interdisciplinary insights into the future of small-diameter prostheses and discusses vital factors and perspectives for developing such prostheses in clinical applications. We propose that the performance of SDVGs can be improved by integrating various technologies in the near future.

Heparin-Modified Collagen Gels for Controlled Release of Pleiotrophin: Potential for Vascular Applications

A fast re-endothelialization, along with the inhibition of neointima hyperplasia, are crucial to reduce the failure of vascular bypass grafts. Implants modifications with molecules capable of speeding up the re-endothelialization process have been proposed over the last years. However, clinical trials of angiogenic factor delivery have been mostly disappointing, underscoring the need to investigate a wider array of angiogenic factors. In this work, a drug release system based on a type I collagen hydrogel has been proposed for the controlled release of Pleiotrophin (PTN), a cytokine known for its pro-angiogenetic effects. Heparin, in virtue of its ability to sequester, protect and release growth factors, has been used to better control the release of PTN. Performances of the PTN drug delivery system on endothelial (ECs) and smooth muscle cells (SMCs) have been investigated. Structural characterization (mechanical tests and immunofluorescent analyses of the collagen fibers) was performed on the gels to assess if heparin caused changes in their mechanical behavior. The release of PTN from the different gel formulations has been analyzed using a PTN-specific ELISA assay. Cell viability was evaluated with the Alamar Blue Cell Viability Assay on cells directly seeded on the gels (direct test) and on cells incubated with supernatant, containing the released PTN, obtained from the gels (indirect test). The effects of the different gels on the migration of both ECs and SMCs have been evaluated using a Transwell migration assay. Hemocompatibility of the gel has been assessed with a clotting/hemolysis test. Structural analyses showed that heparin did not change the structural behavior of the collagen gels. ELISA quantification demonstrated that heparin induced a constant release of PTN over time compared to other conditions. Both direct and indirect viability assays showed an increase in ECs viability while no effects were noted on SMCs. Cell migration results evidenced that the heparin/PTN-modified gels significantly increased ECs migration and decreased the SMCs one. Finally, heparin significantly increased the hemocompatibility of the collagen gels. In conclusion, the PTN-heparin-modified collagen here proposed can represent an added value for vascular medicine, able to ameliorate the biological performance, and integration of vascular grafts.

Effect of anti-TGF-β2 surface modification of polydimethylsiloxane on lens epithelial cell markers of posterior capsule opacification

Posterior capsule opacification is the most common complication of cataract surgery. Lens epithelial cells remaining in the capsular bag following surgery can undergo epithelial-to-mesenchymal transition and migrate from the anterior to the posterior capsule, leading to fibrosis, capsular wrinkling, and ultimately vision loss. Transforming growth factor-beta 2 has been shown to play a major role in epithelial-to-mesenchymal transition. Covalent tethering of anti-transforming growth factor-beta 2 to the surface of the intraocular lens material may inhibit epithelial-to-mesenchymal transition and the subsequent events, thus leading to a reduction in posterior capsule opacification. In this work, the antibody was tethered to the surface of polydimethylsiloxane as a model lens material via a poly(ethylene) glycol spacer. Surface characterization using a variety of methods demonstrated successful modification. The surface density of the anti-transforming growth factor-beta 2 was approximately 0.5 µg/cm2. The presence of transforming growth factor-beta 2 in cell culture medium stimulated production of extracellular matrix components such as collagen, fibronectin, laminin, and the fibrotic marker α-smooth muscle actin, by HLE-B3 cells. These effects were decreased but not completely eradicated by the presence of the anti-transforming growth factor-beta 2 antibody on the polydimethylsiloxane surface. These results suggest that surface modification with appropriate antifibrotic molecules has the potential to modulate cellular changes following cataract surgery and lead to a reduction in posterior capsule opacification.

Preparation of an adipose-derived stem cell/fibrin–poly(d,l-lactic-co-glycolic acid) construct based on a rapid prototyping technique

Currently, large, thick, and complex tissue vascularization is one of the research focuses of tissue engineering. Numerous studies have proven that microvascular systems can be developed by cultivating endothelial cells in a hydrogel/scaffold structure. As the sources of adult endothelial cells are very limited and very easily degraded, it is better to induce stem cells into endothelial cells. In this article, a grid poly(d,l-lactic- co-glycolic acid) structure with defined internal channels was fabricated using a low-temperature deposition manufacturing technique under computer direction. In a fibrinogen mixture, an aqueous adipose-derived stem cell fibrinogen mixture was incorporated into the internal walls of the poly(d,l-lactic- co-glycolic acid) scaffold and stabilized with thrombin solution. After several days of in vitro culture, the adipose-derived stem cells immobilized in the fibrin hydrogel were induced into endothelial-like cells with endothelial growth factor and basic fibroblast growth factor. Morphological and biological properties of the composite cell/fibrin–poly(d,l-lactic- co-glycolic acid) construct were characterized.

Angiogenic therapy for cardiac repair based on protein delivery systems

Cardiovascular diseases remain the first cause of morbidity and mortality in the developed countries and are a major problem not only in the western nations but also in developing countries. Current standard approaches for treating patients with ischemic heart disease include angioplasty or bypass surgery. However, a large number of patients cannot be treated using these procedures. Novel curative approaches under investigation include gene, cell, and protein therapy. This review focuses on potential growth factors for cardiac repair. The role of these growth factors in the angiogenic process and the therapeutic implications are reviewed. Issues including aspects of growth factor delivery are presented in relation to protein stability, dosage, routes, and safety matters. Finally, different approaches for controlled growth factor delivery are discussed as novel protein delivery platforms for cardiac regeneration.

Micropatterned angiogenesis induced by poly(d,l-lactic-co-glycolic acid) mesh-structured scaffolds

Angiogenesis is an important process used to guide the regeneration of functional tissues and organs. The incorporation of inductive cues into scaffolds to control angiogenesis is an attractive strategy for scaffold preparation. Four mesh-type scaffolds, including a vascular endothelial growth factor-embedded poly(d,l-lactic- co-glycolic acid) mesh, a vascular endothelial growth factor-coated poly(d,l-lactic- co-glycolic acid) mesh, a collagen-coated poly(d,l-lactic- co-glycolic acid) mesh, and a poly(d,l-lactic- co-glycolic acid) mesh, were compared for their inductive effects on the formation of a micropatterned capillary network. Following subcutaneous implantation, all of the scaffolds induced the formation of micropatterned capillary networks, as observed at 2 and 6 weeks after implantation. The vascular endothelial growth factor-embedded mesh and the vascular endothelial growth factor-coated mesh promoted a higher degree of blood vessel formation than the collagen-coated mesh and the poly(d,l-lactic- co-glycolic acid) mesh. The capillary density in the vascular endothelial growth factor-embedded mesh and the vascular endothelial growth factor-coated mesh increased with time following implantation. The macrophages that surrounded the scaffolds were similar for all the meshes. The microstructure of the poly(d,l-lactic- co-glycolic acid) mesh determined the micropattern of the capillary network, and vascular endothelial growth factor provided a synergistic effect on the micropatterned angiogenesis process.

Design concepts and strategies for tissue engineering scaffolds

In the emerging field of tissue engineering and regenerative medicine, new viable and functional tissue is fabricated from living cells cultured on an artificial matrix in a simulated biological environment. It is evident that the specific requirements for the three main components, cells, scaffold materials, and the culture environment, are very different, depending on the type of cells and the organ-specific application. Identifying the variables within each of these components is a complex and challenging assignment, but there do exist general requirements for designing and fabricating tissue engineering scaffolds. Therefore, this review explores one of the three main components, namely, the key concepts, important parameters, and required characteristics related to the development and evaluation of tissue engineering scaffolds. An array of different design strategies will be discussed, which include mimicking the extra cellular matrix, responding to the need for mass transport, predicting the structural architecture, ensuring adequate initial mechanical integrity, modifying the surface chemistry and topography to provide cell signaling, and anticipating the material selection so as to predict the required rate of bioresorption. In addition, this review considers the major challenge of achieving adequate vascularization in tissue engineering constructs, without which no three-dimensional thick tissue such as the heart, liver, and kidney can remain viable.

Nanomaterials for cancer therapy and imaging

A variety of organic and inorganic nanomaterials with dimensions below several hundred nanometers are recently emerging as promising tools for cancer therapeutic and diagnostic applications due to their unique characteristics of passive tumor targeting. A wide range of nanomedicine platforms such as polymeric micelles, liposomes, dendrimers, and polymeric nanoparticles have been extensively explored for targeted delivery of anti-cancer agents, because they can accumulate in the solid tumor site via leaky tumor vascular structures, thereby selectively delivering therapeutic payloads into the desired tumor tissue. In recent years, nanoscale delivery vehicles for small interfering RNA (siRNA) have been also developed as effective therapeutic approaches to treat cancer. Furthermore, rationally designed multi-functional surface modification of these nanomaterials with cancer targeting moieties, protective polymers, and imaging agents can lead to fabrication versatile theragnostic nanosystems that allow simultaneous cancer therapy and diagnosis. This review highlights the current state and future prospects of diverse biomedical nanomaterials for cancer therapy and imaging.

Bioactive scaffolds for engineering vascularized cardiac tissues

Functional vascularization is a key requirement for the development and function of most tissues, and most critically cardiac muscle. Rapid and irreversible loss of cardiomyocytes during cardiac infarction directly results from the lack of blood supply. Contractile cardiac grafts, engineered using cardiovascular cells in conjunction with biomaterial scaffolds, are an actively studied method for cardiac repair. In this article, we focus on biomaterial scaffolds designed to mediate the development and maturation of vascular networks, by immobilized growth factors. The interactive effects of multiple vasculogenic factors are discussed in the context of cardiac tissue engineering.

Scaffolds with covalently immobilized VEGF and Angiopoietin-1 for vascularization of engineered tissues

The aim of this study was to engineer a biomaterial capable of supporting vascularization in vitro and in vivo. We covalently immobilized vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang1) onto three-dimensional porous collagen scaffolds using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) chemistry. Over both 3 and 7 days in vitro, seeded endothelial cells (ECs) had increased proliferation on scaffolds with immobilized VEGF and/or Ang1 compared to unmodified scaffolds and soluble growth factor controls. Notably, the group with co-immobilized VEGF and Ang1 showed significantly higher cell number (P=0.0079), higher overall lactate production rate (P=0.0044) and higher overall glucose consumption rate (P=0.0034) at Day 3, compared to its corresponding soluble control for which growth factors were added to culture medium. By Day 7, hematoxylin and eosin, live/dead, CD31, and von Willebrand factor staining all showed improved tube formation by ECs when cultivated on scaffolds with co-immobilized growth factors. Interestingly, scaffolds with co-immobilized VEGF and Ang1 showed increased EC infiltration in the chorioallantoic membrane (CAM) assay, compared to scaffolds with independently immobilized VEGF/Ang1. This study presents an alternative method for promoting the formation of vascular structures, via covalent immobilization of angiogenic growth factors that are more stable than soluble ones and have a localized effect.

Surface Engineered Polymeric Biomaterials with Improved Biocontact Properties

We present many examples of surface engineered polymeric biomaterials with nanosize modified layers, controlled protein adsorption, and cellular interactions potentially applicable for tissue and/or blood contacting devices, scaffolds for cell culture and tissue engineering, biosensors, biological microchips as well as approaches to their preparation.

Controlled release of substances bound to fibrin-anchors or of DNA

Fibrin sealants have been proposed as depot matrices for substances due to their biocompatibility, advantageous biological properties, and widespread use in wound healing. This study showed possibilities for a continuous and controlled release of pharmaceutically active substances out of a fibrin matrix. Substances of interest were linked to naturally occuring fibrin-anchors, (i) thrombin, (ii) fibronectin, and (iii) DNA. Fibronectin and thrombin bind fibrin by a specific binding moiety and DNA by charge. Fibrin clots were prepared from Tisseel Fibrin Sealant (Baxter AG, Vienna) by mixing 100 mg/ml fibrinogen, the substance of interest, and 4 U/ml of thrombin. Chemical crosslinking of proteins was performed with EDC using standard reaction conditions. Modification of proteins with biotin and PPACK was performed with N-hydroxysuccinimid activated compounds. With fibrin-anchors pharmaceutically active substances, i.e., tumor necrosis factor (TNF), albumin, and plasmid-DNA, were continously released over 10 days. In conclusion, the naturally occuring proteins fibronectin and thrombin with a fibrin binding moiety or DNA can be used as fibrin-anchors.

Fabrication of Repairing Skull Bone Defects Based on the Rapid Prototyping

The Rapid Prototyping (RP) manufacture technology, computer tomography (CT) image processing, and mechanical analyses were adopted to repair a skull defect injury. After the patient was inspected by spiral CT the data was exported to Digital Imaging and Communications in Medicine (DICOM) format. The data was processed with Mimics software to eliminate noise and gray-level registration. The processing filtered out the parenchyma data and preserved the bone data. The STL files were analyzed and processed by the Magics and put into the RP equipment. The RP equipment is one type of Stereo Lithography Apparatus (SLA) with laser light spot diameter that is <0. 2mm The 3D models were analyzed to comply with the patients’ requirements. The stereo lithography model emulated the mechanical properties and shape with the patient's bone. The titanium-alloy plate matched the anatomy well. The 3D reconstructed freeform model was accurate to within 0.2 mm.

Syntheses and Evaluations of Antitumor and Antiangiogenic Compounds Conjugated with 5-Fluorouracil and Ascorbic Acid

The new multifunctional antitumor conjugates containing ascorbic acid and 5-fluorouracil (5-FU) were synthesized from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, ascorbic acid and/or a chain spacer, followed by condensation with 5-FU. The synthesized conjugates were identified by 1H and 13C NMR spectroscopies and elemental analysis. The in vitro cytotoxicities of these conjugates were determined and their antitumor activity was evaluated. The IC50 values (drug concentration for 50% inhibition of tumor growth) indicated that the synthesized conjugates were better inhibitors against cancer cells and were lower in cytotoxicity than the free 5-FU. The in vivo antitumor activity of the conjugates was examined against mice bearing the sarcoma 180 tumor cells. The life spans (T/C) of mice treated with the conjugates were higher than for the free 5-FU. In addition, the synthesized conjugates showed excellent antiangiogenic activity, based on the embryo chorioallantoic membrane assay.

Preparation and Characterization of Triamcinolone Acetonide-loaded Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx) Microspheres

Triamcinolone acetonide loaded in poly(3-hydroxybutyrate-co-3 hydroxyhexanoate) (PHBHx) microspheres were prepared to treat cystoid macular oedema (CMO) and acute posterior segment inflammation associated with uveitis. The PHBHx microspheres were prepared by solvent evaporation technique using methylene chloride as the solvent and aqueous poly(vinyl alcohol) emulsifier as the dispersion medium. The PHBHx microspheres obtained were well formed with narrow size distribution; the average size prepared ranged from 40—200 μm depending on the formulation used. The stirring rate of the dispersion medium, emulsifier concentration, and polymer/solvent ratio parameters were varied to determine their effect on the size and size distribution of the PHBHx microspheres. Increasing the stirring rate and emulsifier concentration decreased the size and the size distribution of the microspheres, while increasing the polymer/solvent ratio caused the opposite effect. The polymer/drug ratio was the most effective parameter for controlling drug loading and release properties. More than 90% of the loaded drug was released within the first 24 h; after that, the release rate was slower for all formulations.

In Vitro Osteogenic Differentiation of Rat Mesenchymal Stem Cells in a Microgravity Bioreactor

Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the ability to differentiate into osteoblasts, chondroblasts, myocytes, and adipocytes. They have potential for bone tissue engineering by the utilization of in vitro expanded cells with osteogenic capacity and their delivery to the appropriate sites via biomaterial scaffolds. The objective was to evaluate the potential of rat bone marrow MSCs to form 3D bone-like tissue by the use of mineralized poly(DL-lactic-co-glycolic acid) (PLGA) foam and osteoinductive medium under rotating culture conditions. PLGA foams were prepared by solvent casting and particulate leaching, then mineralized by incubating in simulated body fluid. MSCs isolated from the bone marrow of young Wistar rats were expanded and seeded on the mineralized scaffolds. The cell-polymer constructs were then cultured in a slow turning lateral vessel-type rotating bioreactor for 4 weeks under the effect of osteogenic inducers, β-glycerophosphate, ascorbic acid and dexamethasone. Mineralization was evaluated using FT-IR and increases in dry mass; morphology changes of the mineralized foams and cell adhesion was characterized by SEM; cell viability was monitored by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide). Osteogenic differentiation was determined by using immunohistochemistry (anti-osteopontin). Results indicate the feasibility of bone tissue engineering with MSCs and mineralized PLGA scaffolds supporting cell adhesion, viability and osteogenic differentiation properties of cells in hybrid structures under appropriate bioreactor conditions.

Dynamic Co-Seeding of Osteoblast and Endothelial Cells on 3D Polycaprolactone Scaffolds for Enhanced Bone Tissue Engineering

Tissue engineered scaffolds must have an organized and repeatable microstructure which enables cells to assemble in an ordered matrix that allows adequate nutriental perfusion. In this work, to evaluate the reciprocal cell interactions of endothelial and osteoblast-like cells, human osteoblast-like cells (MG63) and Human Umbilical Vein Endothelial Cells (HUVEC) were co-seeded onto 3D geometrically controlled porous poly(ε-caprolactone) (PCL) and cultured by means of a rotary cell culture system (RCCS-4DQ). In our dynamic co-culture system, the lack of significant enhancement of osteoblast ALP activity and ECM production indicated that the microgravity conditions of the rotary system affected the cells by favoring their proliferation and cellular cross-talk. These results emphasize how osteoblasts increase endothelial cell proliferate and endothelial cells amplify the growth of osteoblasts but decrease their differentiation. This dynamic seeding of osteoblasts and endothelial cells onto a 3D polymeric scaffold may represent a unique approach for studying the mechanisms of interaction of endothelial and osteoblast cells as well as achieve a functional hybrid in which angiogenesis, furnished by neo-vascular organization of endothelial cells may further support osteoblasts growth. Furthermore, this in vitro model may be useful in examining the applicability of novel material structures for tissue engineering.

Surface engineered and drug releasing pre-fabricated scaffolds for tissue engineering

A wide range of polymeric scaffolds have been intensively studied for use as implantable and temporal devices in tissue engineering. Biodegradable and biocompatible scaffolds having a highly open porous structure and good mechanical strength are needed to provide an optimal microenvironment for cell proliferation, migration, and differentiation, and guidance for cellular in-growth from host tissue. A variety of natural and synthetic polymeric scaffolds can be fabricated in the form of a solid foam, nanofibrous matrix, microsphere, or hydrogel. Biodegradable porous scaffolds can be surface engineered to provide an extracellular matrix mimicking environment for better cell adhesion and tissue in-growth. Furthermore, scaffolds can be designed to release bioactive molecules, such as growth factors, DNA, or drugs, in a sustained manner to facilitate tissue regeneration. This paper reviews the current status of surface engineered and drug releasing scaffolds for tissue engineering.