Gelatin Porous Scaffolds as Delivery Systems of Calcium Alendronate

The systemic administration of bisphosphonates (BPs) for the treatment of metabolic diseases characterized by abnormal bone loss suffers from several adverse side effects, which can be reduced by implementation of alternative modes of administration. In this work, glutaraldehyde cross‐linked gelatin scaffolds are proposed as delivery systems of calcium alendronate monohydrate (CaAL•H₂O). The 3D highly porous scaffolds display a relevant interconnected porosity (>94%), independently from CaAL•H₂O content (0, 3, and 6 wt%). At variance, pore size varies with composition. The relative increase of the number of smaller pores on increasing BP content is in agreement with the parallel significant increase of the compressive modulus and collapse strength. The scaffolds exhibit a sustained CaAL•H₂O release profile, and a significant amount of the drug is retained in the scaffolds even after 14 d. In vitro tests are carried out using cocultures of osteoblast (OB) and osteoclast (OC). The evaluation of differentiation markers is performed both on the supernatants of cell culture and by means of quantitative polymerase chain reaction. The results indicate that BP containing scaffolds support osteoblast proliferation and differentiation, whereas they inhibit osteoclast viability and activity, displaying a promising beneficial role on bone repair processes.

     

明胶溶液中针状纳米HgS的仿生合成

以明胶为模板剂,制备出在明胶水溶液中稳定存在的HgS微晶.通过扫描电镜(SEM)图像表明,生长时间为2d的样品为微晶结构,生长15d的HgS微晶为针状,平均直径约87nm,长度约1.3μm.紫外可见吸收和荧光光谱的测试结果表明,所合成HgS具有量子限域效应.明胶分子的构象变化对HgS纳米颗粒的成核和形貌转化起到非常重要的作用.     

Crosslinked Silk Fibroin/Gelatin/Hyaluronan Blends as Scaffolds for Cell-Based Tissue Engineering

3D porous scaffolds fabricated from binary and ternary blends of silk fibroin (SF), gelatin (G), and hyaluronan (HA) and crosslinked by the carbodiimide coupling reaction were developed. Water-stable scaffolds can be obtained after crosslinking, and the SFG and SFGHA samples were stable in cell culture medium up to 10 days. The presence of HA in the scaffolds with appropriate crosslinking conditions greatly enhanced the swellability. The microarchitecture of the freeze-dried scaffolds showed high porosity and interconnectivity. In particular, the pore size was significantly larger with an addition of HA. Biological activities of NIH/3T3 fibroblasts seeded on SFG and SFGHA scaffolds revealed that both scaffolds were able to support cell adhesion and proliferation of a 7-day culture. Furthermore, cell penetration into the scaffolds can be observed due to the interconnected porous structure of the scaffolds and the presence of bioactive materials which could attract the cells and support cell functions. The higher cell number was noticed in the SFGHA samples, possibly due to the HA component and the larger pore size which could improve the microenvironment for fibroblast adhesion, proliferation, and motility. The developed scaffolds from ternary blends showed potential in their application as 3D cell culture substrates in fibroblast-based tissue engineering.     

Ionically Modified Gelatin Hydrogels Maintain Murine Myogenic Cell Viability and Fusion Capacity

For tissue engineering of skeletal muscles, there is a need for biomaterials which do not only allow cell attachment, proliferation, and differentiation, but also support the physiological conditions of the tissue. Next to the chemical nature and structure of the biomaterial, its response to the application of biophysical stimuli, such as mechanical deformation or application of electrical pulses, can impact in vitro tissue culture. In this study, gelatin methacryloyl (GelMA) is modified with hydrophilic 2-acryloxyethyltrimethylammonium chloride (AETA) and 3-sulfopropyl acrylate potassium (SPA) ionic comonomers to obtain a piezoionic hydrogel. Rheology, mass swelling, gel fraction, and mechanical characteristics are determined. The piezoionic properties of the SPA and AETA-modified GelMA are confirmed by a significant increase in ionic conductivity and an electrical response as a function of mechanical stress. Murine myoblasts display a viability of >95% after 1 week on the piezoionic hydrogels, confirming their biocompatibility. The GelMA modifications do not influence the fusion capacity of the seeded myoblasts or myotube width after myotube formation. These results describe a novel functionalization providing new possibilities to exploit piezo-effects in the tissue engineering field.     

Cellular Response to Reagent‐Free Electron‐Irradiated Gelatin Hydrogels

As a biomaterial, it is well established that gelatin exhibits low cytotoxicity and can promote cellular growth. However, to circumvent the potential toxicity of chemical crosslinkers, reagent‐free crosslinking methods such as electron irradiation are highly desirable. While high energy irradiation has been shown to exhibit precise control over the degree of crosslinking, these hydrogels have not been thoroughly investigated for biocompatibility and degradability. Here, NIH 3T3 murine fibroblasts are seeded onto irradiated gelatin hydrogels to examine the hydrogel's influence on cellular viability and morphology. The average projected area of cells seeded onto the hydrogels increases with irradiation dose, which correlates with an increase in the hydrogel's shear modulus up to 10 kPa. Cells on these hydrogels are highly viable and exhibits normal cell cycles, particularly when compared to those grown on glutaraldehyde crosslinked gelatin hydrogels. However, proliferation is reduced on both types of crosslinked samples. To mimic the response of the hydrogels in physiological conditions, degradability is monitored in simulated body fluid to reveal strongly dose‐dependent degradation times. Overall, given the low cytotoxicity, influence on cellular morphology and variability in degradation times of the electron irradiated gelatin hydrogels, there is significant potential for application in areas ranging from regenerative medicine to mechanobiology.

     

Strontium‐based initiator system for ring‐opening polymerization of cyclic esters

An amino isopropoxyl strontium (Sr‐PO) initiator, which was prepared by the reaction of propylene oxide with liquid strontium ammoniate solution, was used to carry out the ring‐opening polymerization (ROP) of cyclic esters to obtain aliphatic polyesters, such as poly(ε‐caprolactone) (PCL) and poly(L ‐lactide) (PLLA). The Sr‐PO initiator demonstrated an effective initiating activity for the ROP of ε‐caprolactone (ε‐CL) and L‐lactide (LLA) under mild conditions and adjusted the molecular weight by the ratio of monomer to Sr‐PO initiator. Block copolymer PCL‐b‐PLLA was prepared by sequential polymerization of ε‐CL and LLA, which was demonstrated by ¹H NMR, ¹³C NMR, and gel permeation chromatography. The chemical structure of Sr‐PO initiator was confirmed by elemental analysis of Sr and N, ¹H NMR analysis of the end groups in ε‐CL oligomer, and Fourier transform infrared (FTIR) spectroscopy. The end groups of PCL were hydroxyl and isopropoxycarbonyl, and FTIR spectroscopy showed the coordination between Sr‐PO initiator and model monomer γ‐butyrolactone. These experimental facts indicated that the ROP of cyclic esters followed a coordination‐insertion mechanism, and cyclic esters exclusively inserted into the Sr–O bond. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1934–1941, 2003     

Injectable,Interconnected, High‐Porosity Macroporous Biocompatible Gelatin Scaffolds Made by Surfactant‐Free Emulsion Templating

High‐porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil‐in‐water high internal phase emulsions (HIPEs) stabilized by gelatin‐graft‐poly(N‐isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell‐laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.

     

明胶基质作用下碳酸钙的仿生合成

依据生物矿化的基本原理, 以明胶为基质, 在动态条件下, 仿生合成碳酸钙/明胶复合材料. 扫描电子显微镜和能量分散X射线(SEM-EDAX)分析表明, 明胶基质中形成的碳酸钙完全不同于纯水中形成的碳酸钙, 具有独特的微观结构形态和取向. 明胶浓度不同, 晶体的形态、取向以及主要元素Ca, O和N的含量相差较大.     

Gelatin scaffolds functionalized by silver nanoparticle‐containing calcium alginate beads for wound care applications

The embedding of silver nanoparticle (nAg)‐containing calcium alginate (CaAlg) beads in gelatin scaffolds was aimed to reduce the burst release and prolong the release of silver (Ag⁺) ions for a long period of time. The reduced sizes of the nAg‐containing CaAlg beads were prepared by an emulsification/external gelation method. The diameter of these beads was ~2 µm. The nAg‐containing CaAlg beads were then embedded into gelatin scaffolds by a freeze‐drying method for evaluating the potential of these scaffolds as wound dressings. The compressive modulus of these scaffolds embedded with nAg‐containing CaAlg beads ranged between 7 and 9 kPa. For release study, the cumulative released amounts of Ag⁺ ions from the nAg‐containing CaAlg beads embedded in gelatin scaffolds were lower than those from the nAg‐containing CaAlg beads. Moreover, the nAg‐containing CaAlg beads embedded in gelatin scaffolds had great antibacterial activity and low cytotoxicity. Thus, these scaffolds had potential for sustaining the release and use in wound care applications, especially chronic wound. Copyright © 2016 John Wiley & Sons, Ltd.     

Fabrication and Evaluation of Alginate/Bacterial Cellulose Nanocrystals–Chitosan–Gelatin Composite Scaffolds

It is common knowledge that pure alginate hydrogel is more likely to have weak mechanical strength, a lack of cell recognition sites, extensive swelling and uncontrolled degradation, and thus be unable to satisfy the demands of the ideal scaffold. To address these problems, we attempted to fabricate alginate/bacterial cellulose nanocrystals-chitosan-gelatin (Alg/BCNs-CS-GT) composite scaffolds using the combined method involving the incorporation of BCNs in the alginate matrix, internal gelation through the hydroxyapatite-d-glucono-δ-lactone (HAP-GDL) complex, and layer-by-layer (LBL) electrostatic assembly of polyelectrolytes. Meanwhile, the effect of various contents of BCNs on the scaffold morphology, porosity, mechanical properties, and swelling and degradation behavior was investigated. The experimental results showed that the fabricated Alg/BCNs-CS-GT composite scaffolds exhibited regular 3D morphologies and well-developed pore structures. With the increase in BCNs content, the pore size of Alg/BCNs-CS-GT composite scaffolds was gradually reduced from 200 μm to 70 μm. Furthermore, BCNs were fully embedded in the alginate matrix through the intermolecular hydrogen bond with alginate. Moreover, the addition of BCNs could effectively control the swelling and biodegradation of the Alg/BCNs-CS-GT composite scaffolds. Furthermore, the in vitro cytotoxicity studies indicated that the porous fiber network of BCNs could fully mimic the extracellular matrix structure, which promoted the adhesion and spreading of MG63 cells and MC3T3-E1 cells on the Alg/BCNs-CS-GT composite scaffolds. In addition, these cells could grow in the 3D-porous structure of composite scaffolds, which exhibited good proliferative viability. Based on the effect of BCNs on the cytocompatibility of composite scaffolds, the optimum BCNs content for the Alg/BCNs-CS-GT composite scaffolds was 0.2% (w/v). On the basis of good merits, such as regular 3D morphology, well-developed pore structure, controlled swelling and biodegradation behavior, and good cytocompatibility, the Alg/BCNs-CS-GT composite scaffolds may exhibit great potential as the ideal scaffold in the bone tissue engineering field.     

Biomimetic Macroporous PCL Scaffolds for Ex Vivo Expansion of Cord Blood‐Derived CD34+ Cells with Feeder Cells Support

Ex vivo expansion of hematopoietic stem cells (HSCs) with most current methods can hardly satisfy clinical application requirement. While in vivo, HSCs efficiently self‐renew in niche where they interact with 3D extracellular matrix and stromal cells. Therefore, co‐cultures of CD34⁺ cells and mesenchyme stem cells derived from human amniotic membrane (hAMSCs) on the basis of biomimetic macroporous three‐dimensional (3D) poly(ε‐caprolactone) (PCL) scaffolds are developed, where scaffolds and hAMSCs are applied to mimic structural and cellular microenvironment of HSCs. The influence of scaffolds, feeder cells, and contact manners on expansion and stemness maintenance of CD34⁺ cells is investigated in this protocol. Biomimetic scaffolds‐dependent co‐cultures of CD34⁺ cells and hAMSCs can effectively promote the expansion of CD34⁺ cells; meanwhile, indirect contact is superior to direct contact. The combination of biomimetic scaffolds and hAMSCs represents a new strategy for achieving clinical‐scale ex vivo expansion of CD34⁺ cells.

     

Fabrication of Biomimetic Superhydrophobic Coating with a Micro‐Nano‐Binary Structure

Summary: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor‐induced phase separation occurred during the solidifying process and a rough surface with a micro‐nano‐binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.

SEM image of a single micro‐flower.     

Bifunctional Diaminoterephthalate Scaffolds as Fluorescence Turn‐On Probes for Thiols

The fluorescent diaminoterephthalate scaffold was equipped by amidation with three types of reactive functions: thiols for metal‐surface binding, alkynes for click reactions, and maleimides for ligation with proteins. Starting from a succinyl succinate derivative with two orthogonally cleavable ester functions, three monoamides (38–57 % yield over three steps) and two bisamides (19 and 25 % yield over five steps) were prepared. Although alkyne and thiol derivatized compounds showed reasonable luminescence behavior (Φ≈1–4 %), the fluorescence was quenched by the maleimide moiety. It was turned on (10‐ to 20‐fold increase of fluorescence quantum yield) by conjugate addition of thiols.     

Biomimetic Dopamine‐Diels–Alder Switches

Mussel adhesives function as tools for surface modifications of a wide variety of materials due to their remarkable adhesion properties. Herein, a combination of bioinspired mussel adhesives based on a dopamine derivative, polymer chemistry, and well‐established Diels–Alder (DA) chemistry leads to a bioinspired switchable surface system that possesses the capability of attaching and detaching specific polymers on demand. A dopaminemaleimide compound, which has been attached to a gold surface under maritime conditions undergoes DA‐ and retro‐DA‐click‐conjugations with cyclopentadiene‐carrying PEG chains. The surface attachment and the subsequent DA/rDA cycles are evidenced via XPS analysis.