The construction of tissue-engineered blood vessels crosslinked with adenosine-loaded chitosan/β-cyclodextrin nanoparticles using a layer-by-layer assembly method

Adenosine Encapsulation and Characterization through Layer-by-Layer Assembly of Hydroxypropyl-β-Cyclodextrin and Whey Protein Isolate as Wall Materials

Adenosine, as a water-soluble active substance, has various pharmacological effects. This study proposes a layer-by-layer assembly method of composite wall materials, using hydroxypropyl-β-cyclodextrin as the inner wall and whey protein isolate as the outer wall, to encapsulate adenosine within the core material, aiming to enhance adenosine microcapsules' stability through intermolecular interactions. By combining isothermal titration calorimetry with molecular modeling analysis, it was determined that the core material and the inner wall and the inner wall and the outer wall interact through intermolecular forces. Adenosine and hydroxypropyl-β-cyclodextrin form an optimal 1:1 complex through hydrophobic interactions, while hydroxypropyl-β-cyclodextrin and whey protein isolate interact through hydrogen bonds. The embedding rate of AD/Hp-β-CD/WPI microcapsules was 36.80%, and the 24 h retention rate under the release behavior test was 76.09%. The method of preparing adenosine microcapsules using composite wall materials is environmentally friendly and shows broad application prospects in storage and delivery systems with sustained release properties.

Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering, and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Coordinated encapsulation by β-cyclodextrin and chitosan derivatives improves the stability of anthocyanins

To improve the stability of anthocyanins (ACNs), ACNs were loaded into dual-encapsulated nanocomposite particles by self-assembly using β-cyclodextrin (β-CD) and two different water-soluble chitosan derivatives, namely, chitosan hydrochloride (CHC) and carboxymethyl chitosan (CMC). The ACN-loaded β-CD-CHC/CMC nanocomplexes with small diameters (333.86 nm) and had a desirable zeta potential (+45.97 mV). Transmission electron microscopy (TEM) showed that the ACN-loaded β-CD-CHC/CMC nanocomplexes had a spherical structure. Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (¹H NMR) and X-ray diffraction (XRD) confirmed that the ACNs in the dual nanocomplexes were encapsulated in the cavity of the β-CD and that the CHC/CMC covered the outer layer of β-CD through noncovalent hydrogen bonding. The ACNs from the dual-encapsulated nanocomplexes improved stability of ACNs under adverse environmental conditions or in a simulated gastrointestinal environment. Further, the nanocomplexes exhibited good storage stability and thermal stability over a wide pH range when added into simulated electrolyte drinks (pH = 3.5) and milk tea (pH = 6.8). This study provides a new option for the preparation of stable ACNs nanocomplexes and expands the applications for ACNs in functional foods.

Construction of enzyme-laden vascular scaffolds based on hyaluronic acid oligosaccharides-modified collagen nanofibers for antithrombosis and in-situ endothelialization of tissue-engineered blood vessels

The current use of synthetic grafts often yields low patency in the reconstruction of small-diameter blood vessels owing to the deposition of thrombi and imperfect coverage of the endothelium on the graft lumen. Therefore, the design of vascular scaffolds with antithrombotic performance and endothelialization is greatly required. Herein, we developed an enzyme-laden scaffold based on hyaluronic acid oligosaccharides-modified collagen nanofibers (labeled HA-COL) to improve the anti-platelet capacity and endothelialization of vascular grafts. In this study, HA-COL nanofibers not only encouraged the endothelialization of vascular scaffolds, but acted as an antiplatelet enzyme-laden platform. Apyrase (Apy) and 5'-nucleotidase (5'-NT) were covalently grafted onto the nanofibers, which in turn converted the platelet-sensitive substance: adenosine diphosphate (ADP) into adenosine monophosphate (AMP) and adenosine, thereby, improving the antithrombotic performance of the scaffolds. Notably, the catalytic end-product: adenosine would work in coordination with HA-COL to synergistically enhance the endothelialization of the vascular scaffolds. The results demonstrated that the enzyme-laden scaffolds maintained catalytic performance, reduced platelet adhesion and aggregation, and guaranteed higher patency after 1-month in situ transplantation. Moreover, these scaffolds showed optimal cytocompatibility, tissue compatibility, scaffold biodegradability and tissue regenerative capability during in vivo implantation. Overall, these engineered vascular scaffolds demonstrated their capacity for endothelialization and antithrombotic performance, suggesting their potential for small-diameter vascular tissue engineering applications. STATEMENT OF SIGNIFICANCE: Considering the critical problems in small-diameter vascular reconstruction, the enzyme-laden vascular scaffolds were prepared for improving in-situ endothelialization and antithrombotic performances of artificial blood vessels. The electrospun HA-COL nanofibers were used as the main matrix materials, which provided favorable structural templates for the regeneration of vasculature and functioned as a platform for the loading of enzymes. The enzyme-laden scaffolds with the biomimetic cascading reaction would convert ADP into adenosine, thereby, decreasing the sensitivity of platelets and improving the antithrombotic performance of tissue-engineered blood vessels (TEBVs). The nanofibrous scaffolds exhibited optimal cytocompatibility, tissue compatibility and regenerative capability, working together with catalytic products of dual-enzyme reaction that would synergistically contribute to TEBVs endothelialization. This study provides a new method for the improvement of in-situ endothelialization of small-diameter TEBVs while qualified with antithrombotic performance.

Coaxial-printed small-diameter polyelectrolyte-based tubes with an electrostatic self-assembly of heparin and YIGSR peptide for antithrombogenicity and endothelialization

Low patency ratio of small-diameter vascular grafts remains a major challenge due to the occurrence of thrombosis formation and intimal hyperplasia after transplantation. Although developing the functional coating with release of bioactive molecules on the surface of small-diameter vascular grafts are reported as an effective strategy to improve their patency ratios, it is still difficult for current functional coatings cooperating with spatiotemporal control of bioactive molecules release to mimic the sequential requirements for antithrombogenicity and endothelialization. Herein, on basis of 3D-printed polyelectrolyte-based vascular grafts, a biologically inspired release system with sequential release in spatiotemporal coordination of dual molecules through an electrostatic self-assembly was first described. A series of tubes with tunable diameters were initially fabricated by a coaxial extrusion printing method with customized nozzles, in which a polyelectrolyte ink containing of ε-polylysine and sodium alginate was used. Further, dual bioactive molecules, heparin with negative charges and Tyr-Ile-Gly-Ser-Arg (YIGSR) peptide with positive charges were layer-by-layer assembled onto the surface of these 3D-printed tubes. Due to the electrostatic interaction, the sequential release of heparin and YIGSR was demonstrated and could construct a dynamic microenvironment that was thus conducive to the antithrombogenicity and endothelialization. This study opens a new avenue to fabricate a small-diameter vascular graft with a biologically inspired release system based on electrostatic interaction, revealing a huge potential for development of small-diameter artificial vascular grafts with good patency.

Fabrication and assessment of chondroitin sulfate-modified collagen nanofibers for small-diameter vascular tissue engineering applications

Chondroitin sulfate (ChS) has shown promising results in promoting cell proliferation and antithrombogenic activity. To engineered develop a dual-function vascular scaffold with antithrombosis and endothelialization, ChS was tethered to collagen to accelerate the growth of endothelial cells and prevent platelet activation. First, ChS was used to conjugate with collagen to generate glycosylated products (ChS-COL) via reductive amination. Then, the fabricated ChS-COL conjugates were electrospun into nanofibers and their morphologies and physicochemical characteristics, cell-scaffold responses and platelet behaviors upon ChS-COL nanofibers were comprehensively characterized to evaluate their potential use for small-diameter vascular tissue-engineered scaffolds. The experimental results demonstrated that the ChS modified collagen electrospun nanofibers were stimulatory of endothelial cell behavior, alleviated thrombocyte activation and maintained an antithrombotic effect in vivo in 10-day post-transplantation. The ChS-COL scaffolds encouraged rapid endothelialization, thus probably ensuring the antithrombotic function in long-term implantation, suggesting their promise for small-diameter vascular tissue engineering applications.

Neurotrophin-3 accelerates reendothelialization through inducing EPC mobilization and homing

Rapid endothelialization is an effective way to treat intimal hyperplasia after intravascular stent implantation. Blood vessels and nerves coordinate with each other in function, while neurotrophin-3 (NT-3) is an important class of nerve growth factors. Our study found that NT-3 promoted endothelial progenitor cell (EPC) mobilization, and the proportion of EPCs in peripheral blood was increased by 1.774 times compared with the control group. Besides, NT-3 promoted the expression of stromal cell-derived factor-1α (SDF-1α), matrix metalloproteinase-9 (MMP9), and chemokine (C-X-C motif) receptor 4 (CXCR4) in EPCs, which increased by 59.89%, 74.46%, and 107.7%, respectively, compared with the control group. Transwell experiments showed that NT-3 enhanced the migration of EPCs by 1.31 times. Flow chamber experiments demonstrated that NT-3 captured more circulating EPCs. As shown by ELISA results, NT-3 can promote the paracrine of vascular endothelial growth factor, interleukin-8, MMP-9, and SDF-1 from EPCs. Such increased angiogenic growth factors further accelerated the closure of endothelial cell scratches. Additionally, EPC-conditioned medium in the NT-3 group significantly inhibited the proliferation of vascular smooth muscle cells. Then animal experiments also illustrated that NT-3 prominently accelerated the endothelialization of injured carotid artery. In short, NT-3 accelerated rapid reendothelialization of injured carotid artery through promoting EPC mobilization and homing.

Nanogels for regenerative medicine

Nanogels have been widely explored for drug delivery, but their applications in the tissue engineering field are still quite recent. Regenerative medicine also demands controlled delivery of growth factors and other active substances able to promote cell adhesion and guide cell differentiation and tissue formation. Moreover, nanogels could be added to tissue scaffolds for modifying their inner architecture, texture and mechanical properties, which are critical for regulating cell behavior. This review aims to provide an insight into the different roles that nanogels may play for improving tissue regeneration. Last decade literature has been carefully analyzed with a focus on in vivo outcomes. After an introductory section to nanogels, relevant examples of their performance for skin and bone tissue regeneration applications are discussed. Healing of chronic wounds and critical size bone fractures may significantly improve thanks to the use of nanogels solely or in combination with scaffolds. Nanogel roles in regenerating vessels, cardiac tissue, urothelium and urethral muscle tissue are also presented. Overall, the information gathered in the review clearly highlights the relevance of multidisciplinary approaches to design nanogels that can face up to the needs of the regenerative medicine. Nanogels may help bring together researchers working in active ingredient formulation, controlled release, nanomechanics, tissue engineering and scaffolding with the common purpose of developing clinically relevant tools for the complete regeneration of complex tissues.

Construction of a small-caliber tissue-engineered blood vessel using icariin-loaded β-cyclodextrin sulfate for in situ anticoagulation and endothelialization

The rapid endothelialization of tissue-engineered blood vessels (TEBVs) can effectively prevent thrombosis and inhibit intimal hyperplasia. The traditional Chinese medicine ingredient icariin is highly promising for the treatment of cardiovascular diseases. β-cyclodextrin sulfate is a type of hollow molecule that has good biocompatibility and anticoagulation properties and exhibits a sustained release of icariin. We studied whether icariin-loaded β-cyclodextrin sulfate can promote the endothelialization of TEBVs. The experimental results showed that icariin could significantly promote the proliferation and migration of endothelial progenitor cells; at the same time, icariin could promote the migration of rat vascular endothelial cells (RAVECs). Subsequently, we used an electrostatic force to modify the surface of the TEBVs with icariin-loaded β-cyclodextrin sulfate, and these vessels were implanted into the rat common carotid artery. After 3 months, micro-CT results showed that the TEBVs modified using icariin-loaded β-cyclodextrin sulfate had a greater patency rate. Scanning electron microscopy (SEM) and CD31 immunofluorescence results showed a better degree of endothelialization. Taken together, icariin-loaded β-cyclodextrin sulfate can achieve anticoagulation and rapid endothelialization of TEBVs to ensure their long-term patency.

Cyclodextrins as versatile building blocks for regenerative medicine

Cyclodextrins (CDs) are one of the most versatile substances produced by nature, and it is in the aqueous biological environment where the multifaceted potential of CDs can be completely unveiled. CDs form inclusion complexes with a variety of guest molecules, including polymers, producing very diverse biocompatible supramolecular structures. Additionally, CDs themselves can trigger cell differentiation to distinct lineages depending on the substituent groups and also promote salt nucleation. These features together with the affinity-driven regulated release of therapeutic molecules, growth factors and gene vectors explain the rising interest for CDs as building blocks in regenerative medicine. Supramolecular poly(pseudo)rotaxane structures and zipper-like assemblies exhibit outstanding viscoelastic properties, performing as syringeable implants. The sharp shear-responsiveness of the supramolecular assemblies is opening new avenues for the design of bioinks for 3D printing and also of electrospun fibers. CDs can also be transformed into polymerizable monomers to prepare alternative nanostructured materials. The aim of this review is to analyze the role that CDs may play in regenerative medicine through the analysis of the last decade research. Most applications of CD-based scaffolds are focussed on non-healing bone fractures, cartilage reparation and skin recovery, but also on even more challenging demands such as neural grafts. For the sake of clarity, main sections of this review are organized according to the architecture of the CD-based scaffolds, mainly syringeable supramolecular hydrogels, 3D printed scaffolds, electrospun fibers, and composites, since the same scaffold type may find application in different tissues.

5-Aminoimidazole-4-carboxamide 1-β-D-ribofuranoside reduces intimal hyperplasia of tissue engineering blood vessel by inhibiting phenotype switch of vascular smooth muscle cell

Intimal hyperplasia (IH) is the cause of clinical failure in patients with vascular transplants and intravascular stents. The proliferation and phenotype switching of vascular smooth muscle cells (VSMCs) play important roles in IH. Inhibiting the proliferation of VSMCs and maintaining the differentiated phenotype of VSMCs is one way to reduce IH. In this article, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) was used in experiments after drug screening. We found that the metabolism, autophagy, and differentiation of VSMCs were enhanced which were important to the normal function of VSMCs, but the secretion of VSMCs was reduced after AICAR treatment. AICAR induces G1 phase arrest and inhibits the proliferation of VSMCs using the MTT and EdU assays and cell cycle analysis. Then, the rat carotid artery vessel transplantation model was used to evaluate the function of AICAR in vivo. AICAR-modified tissue-engineered blood vessels (TEBVs) had a higher patency rate and less IH than the control TEBVs. In conclusion, AICAR can improve the normal function of VSMCs by increasing the metabolism and autophagy of VSMCs but inhibit the proliferation, paracrine, and phenotypes switching of VSMCs, further contribute the reducing of IH in TEBVs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 744-752, 2017.

Construction of an Aptamer-SiRNA Chimera-Modified Tissue-Engineered Blood Vessel for Cell-Type-Specific Capture and Delivery

The application of tissue-engineered blood vessels (TEBVs) is the main developmental direction of vascular replacement therapy. Due to few and/or dysfunctional endothelial progenitor cells (EPCs), it is difficult to successfully construct EPC capture TEBVs in diabetes. RNA has a potential application in cell protection and diabetes treatment, but poor specificity and low efficiency of RNA transfection in vivo limit the application of RNA. On the basis of an acellular vascular matrix, we propose an aptamer-siRNA chimera-modified TEBV that can maintain a satisfactory patency in diabetes. This TEBV consists of two parts, CD133-adenosine kinase (ADK) chimeras and a TEBV scaffold. Our results showed that CD133-ADK chimeras could selectively capture the CD133-positive cells in vivo, and then captured cells can internalize the bound chimeras to achieve RNA self-transfection. Subsequently, CD133-ADK chimeras were cut into ADK siRNA by a dicer, resulting in depletion of ADK. An ADK-deficient cell may act as a bioreactor that sustainably releases adenosine. To reduce nonspecific RNA transfection, we increased the proportion of HAuCl4 during the material preparation, through which the transfection capacity of polyethylenimine (PEI)/polyethylene glycol (PEG)-capped gold nanoparticles (PEI/PEG-AuNPs) was significantly decreased and the ability of TEBV to resist tensile and liquid shear stress was greatly enhanced. PEG and 2'-O-methyl modification was used to enhance the in vivo stability of RNA chimeras. At day 30 postgrafting, the patency rate of CD133-ADK chimera-modified TEBVs reached 90% in diabetic rats and good endothelialization was observed.

Immobilization of DNA aptamers via plasma polymerized allylamine film to construct an endothelial progenitor cell-capture surface

The endothelial progenitor cells (EPCs) capture stent has drawn increasing attentions and become one of the most promising concepts for the next generation vascular stent. In this regard, it is of great significance to immobilize a molecule with the ability to bind EPC for rapid in vivo endothelialization with high specificity. In this work, a facile two-step method aimed at constructing a coating with specific EPC capturing aptamers is reported. The processes involves as the first-step deposition of plasma polymerized allylamine (PPAam) on a substrate to introduce amine groups, followed by the electrostatic adsorption of a 34 bases single strand DNA sequence to the PPAam surface as a second step (PPAam-DNA). Grazing incidence attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the aptamers. Quartz crystal microbalance with dissipation (QCM-D) real time monitoring result shows that about 175 ng/cm(2) aptamers were conjugated onto the PPAam surface. The interactions between the modified surfaces and human umbilical vein endothelial cells (ECs), smooth muscle cells (SMCs), and murine induced EPCs derived from mesenchymal stem cells (MSCs) were also investigated. It was demonstrated that PPAam-DNA samples could capture more EPCs, and present a cellular friendly surface for the proliferation of both EPCs and ECs but no effect on the hyperplasia of SMCs. Also, the co-culture results of 3 types of cells confirmed that the aptamer could specifically bond EPCs rather than ECs and SMCs, suggesting the competitive adhesion advantage of EPCs to ECs and SMCs. These data demonstrate that the EPC aptamer has large potential for designing an EPC captured stent and other vascular grafts with targeted in situ endothelialization.