Cellulose/Zeolitic Imidazolate Framework (ZIF-8) Composites with Antibacterial Properties for the Management of Wound Infections

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with outstanding physical and chemical properties that make them suitable candidates in many fields, such as catalysis, sensing, energy production, and drug delivery. By combining MOFs with polymeric substrates, advanced functional materials are devised with excellent potential for biomedical applications. In this research, Zeolitic Imidazolate Framework 8 (ZIF-8), a zinc-based MOF, was selected together with cellulose, an almost inexhaustible polymeric raw material produced by nature, to prepare cellulose/ZIF-8 composite flat sheets via an in-situ growing single-step method in aqueous media. The composite materials were characterized by several techniques (IR, XRD, SEM, TGA, ICP, and BET) and their antibacterial activity as well as their biocompatibility in a mammalian model system were investigated. The cellulose/ZIF-8 samples remarkably inhibited the growth of Gram-positive and Gram-negative reference strains, and, notably, they proved to be effective against clinical isolates of Staphylococcus epidermidis and Pseudomonas aeruginosa presenting different antibiotic resistance profiles. As these pathogens are of primary importance in skin diseases and in the delayed healing of wounds, and the cellulose/ZIF-8 composites met the requirements of biological safety, the herein materials reveal a great potential for use as gauze pads in the management of wound infections.

Evaluation of the Immune Response to Chitosan-graft-poly(caprolactone) Biopolymer Scaffolds

Biomimetic scaffolds recreating key elements of the architecture and biological activity of the extracellular matrix have enormous potential for soft tissue engineering applications. Combining appropriate mechanical properties with select biological cues presents a challenge for bioengineering, as natural materials are most bioactive but can lack mechanical integrity, while synthetic polymers have strength but are often biologically inert. Blends of synthetic and natural materials, aiming to combine the benefits of each, have shown promise but inherently require a compromise, diluting down favorable properties in each polymer to accommodate the other. Here, we electrospun a material comprising chitosan, a natural polysaccharide, and polycaprolactone (PCL), one of the most widely studied synthetic polymers used in materials engineering. In contrast to a classical blend, here PCL was chemically grafted onto the chitosan backbone to create chitosan-graft-polycaprolactone (CS-g-PCL) and then combined further with unmodified PCL to generate scaffolds with discreet chitosan functionalization. These small amounts of chitosan led to significant changes in scaffold architecture and surface chemistry, reducing the fiber diameter, pore size, and hydrophobicity. Interestingly, all CS-g-PCL-containing blends were stronger than control PCL, though with reduced elongation. In in vitro assessments, increasing the CS-g-PCL content led to significant improvements in in vitro blood compatibility compared to PCL alone while increasing fibroblast attachment and proliferation. In a mouse subcutaneous implantation model, a higher CS-g-PCL content improved the immune response to the implants. Macrophages in tissues surrounding CS-g-PCL scaffolds decreased proportionately to the chitosan content by up to 65%, with a corresponding decrease in pro-inflammatory cytokines. These results suggest that CS-g-PCL is a promising hybrid material comprising natural and synthetic polymers with tailorable mechanical and biological properties, justifying further development and in vivo evaluation.

Cerium Ion-Incorporated Titanium Metal Implants of Enhanced Bioactivity for Biomedical Applications

The enhancement in the performance of metallic bone implants based on commercially pure titanium (CP-Ti) by incorporation of cerium (Ce) ions onto the surface was evaluated. The incorporation of Ce ions onto the CP-Ti surface was carried out by a simple two-step chemical treatment method, where an initial NaOH treatment and then a subsequent treatment with different molar concentrations of ceric nitrate solution followed by heat treatment at 600 °C were carried out. The modified surfaces were observed using field emission scanning electron microscopy (FE-SEM), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), X-ray photoelectron spectroscopy (XPS), the laser Raman spectroscopic technique, high-resolution transmission electron microscopy (HR-TEM), and atomic force microscopy (AFM). The formation of a nanonetwork structure by the initial NaOH treatment and the replacement of Na ions with Ce ions along with different phases of TiO₂ was evident from the surface characterization results. The transition of rutile TiO₂ to anatase TiO₂ in the modified surface is evident from the Raman spectra with respect to the treatment of higher to lower concentrations of ceric nitrate solution. The presence of two different oxidation states of Ce (Ce³⁺ and Ce⁴⁺) and improvement in the surface wettability were also distinct in the modified samples. Thus, the incorporated Ce ions over the nanostructured titania network showed low cytotoxicity, good cell adhesion, and enhanced extracellular mineralization on MG-63 cells with better protein adsorption in BSA medium. Taken together, the thus-improved nanostructured surface morphology with the anatase TiO₂ phase and distinct extracellular mineralization in the Ce-incorporated Ti metal with good biocompatibility make it a promising candidate for bone implant applications.

Concurrent Tissue Engineering for Wound Healing in Diabetic Rats Utilizing Dual Actions of Green Synthesized CuO NPs Prepared from Two Plants Grown in Egypt

Purpose

Diabetes mellitus is among the disrupting factors of orchestrated events in wound healing. This necessitates the urge for tailored medications, which are continually offered by nano-sized materials. Herein, we present greenly synthesized copper oxide nanoparticles (CuO NPs), obtained from either Punica granatum L. (PG) or Pisidium guajava L. (GV) extract, to function as potent bactericidal and fungicidal materials that promote regeneration and healing of the targeted diabetic wounded tissues.

Methods

PG or GV plant extracts were compared as source of reducing agents for CuO NPs synthesis process. The yield and photocatalytic degradation potential were compared. NPs obtained from the superior extract, PG, were characterized using particles size, zeta potential, XRD, TEM, SEM, and EDX. The antimicrobial effects were evaluated on multidrug-resistant human pathogens and then the percentage biofilm inhibitory concentration was determined. The cytotoxicity and wound scratch study were conducted on a normal human skin cell line. In-vivo wound healing activity in diabetic rats was assessed along with histopathological and immunohistochemical examination of CD45 and α-SMA.

Results

The greenly synthesized CuO NPs are spherical in shape having a diameter of 233nm. CuO NPs (250µg/mL) acted as promising biocontrol agent against a variety of multidrug-resistant human pathogens. They significantly exhibited 29.460±0.811% healing of the scratched wound compared to only 2.001±0.155% for the control. Wound healing experiments revealed the safety of a low CuO NPs concentration in a diabetic animal model as well as on human normal skin fibroblast cell line. The treated group with a dose of 2mg/cm2 showed superior results with a WC50 value of 7.2 days, and 92% wound contraction after 13-days. Immunohistochemical investigation of the same group demonstrated well-established fibrous tissue (5.7±3.7/HPF), and an amplified granulation tissue of recently developed blood vessels (70±1.5/HPF).

Conclusion

Green synthesized CuO NPs could overcome drug resistance and promote wound healing process effectively.

Modification and evaluation of diatrizoate sodium containing polymethyl methacrylate bone cement

Polymethyl methacrylate (PMMA) bone cement is now widely used in percutaneous vertebro plasty (PVP) and percutaneous kyphoplasty (PKP). However, studies showed that the radiopacifiers (zirconia, barium sulfate, etc.) added to PMMA will have a negative impact on its use, e.g. barium sulfate will weaken the mechanical properties of bone cement and lead to bone absorption and aseptic loosening. Iodine is an element existing in the human body and has good imaging performance. Iodine contrast agent has been used in clinic for many years and has abundant clinical data. Therefore, using iodine instead of barium sulfate may be a promising choice. In this paper, the effect of different content of diatrizoate sodium (DTA, C₁₁H₈I₃N₂NaO₄) on the properties of PMMA was studied and compared with the traditional PMMA bone cement containing 30 wt% barium sulfate. The mechanical properties, setting properties, radiopacity, and biocompatibility of bone cement were evaluated. The compressive strength of PMMA bone cement with 20 wt% DTA can reach 76.38 MPa. DTA released from bone cement up to 14 days accounted for only 2.3% of its dosage. The water contact angle was 62.3°. The contrast of bone cement on X-ray film was comparable to that of bone cement containing 30 wt% barium. The hemolysis rate was lower than 4%, and there was no obvious hemolysis. PMMA with 20 wt% DTA can maintain the relative growth rate of MC3T3-E1 and L929 cells above 80%. The results show that adding 20 wt% DTA into PMMA can obtain good radiopacity while maintaining its mechanical properties, setting properties, and biocompatibility. DTA can be used as a promising candidate material for PMMA bone cement radiopacifier.

Effect of Poly(Oxanorbonene)- and Poly(Methacrylate)-Based Polyzwitterionic Surface Coatings on Cell Adhesion and Gene Expression of Human Keratinocytes

Polyzwitterions are generally known for their anti-adhesive properties, including resistance to protein and cell adhesion, and overall high bio-inertness. Yet there are a few polyzwitterions to which mammalian cells do adhere. To understand the structural features of this behavior, a panel of polyzwitterions with different functional groups and overall degrees of hydrophobicity is analyzed here, and their physical and biological properties are correlated to these structural differences. Cell adhesion is focused on, which is the basic requirement for cell viability, proliferation, and growth. With the here presented polyzwitterion panel, three different types of cell-surface interactions are observed: adhesion, slight attachment, and cell repellency. Using immunofluorescence methods, it is found that human keratinocytes (HaCaT) form focal adhesions on the cell-adhesive polyzwitterions, but not on the sample that has only slight cell attachment. Gene expression analysis indicates that HaCaT cells cultivated in the presence of a non-adhesive polyzwitterion have up-regulated inflammatory and apoptosis-related cell signaling pathways, while the gene expression of HaCaT cells grown on a cell-adhesive polyzwitterion does not differ from the gene expression of the growth control, and thus can be defined as fully cell-compatible.

Biocompatibility of Zinc Matrix Biodegradable Composites Reinforced by Graphene Nanosheets

As a new type of biodegradable implant material, zinc matrix composites have excellent potential in the application of biodegradable implants because of their better corrosion resistance than magnesium matrix materials. Our previous studies have shown that graphene nanosheet reinforced zinc matrix composites (Zn-GNS) prepared by spark plasma sintering (SPS) have good mechanical properties and suitable degradation rate. However, the biocompatibility of zinc matrix composites is still a problem of concern. The cytocompatibility and blood compatibility of pure zinc and Zn-GNS composites in vitro were studied. The results showed that Zn-GNS composites had acceptable toxicity to MG-63 human osteosarcoma cells. In addition, the hemolysis rate of pure zinc and its composites were less than 3%, which has no adverse effect on adhered platelets, and has good antithrombotic and antiadhesion platelets properties. In conclusion, the addition of GNS did not adversely affect the biocompatibility of Zn-GNS composites, which indicated that Zn-GNS composites are a promising candidate for bone implantation.

Preliminary Study on Fish Scale Collagen Lamellar Matrix as Artificial Cornea

To construct a novel artificial cornea biomaterial, a method to prepare collagen lamellar matrix was developed in this study using grass carp scales as raw materials. The relationship between the structure of fish scale collagen lamellar matrix and the optical and mechanical properties was analyzed, and co-culture of it and rat bone marrow mesenchymal stem cells (BMSCs) was performed to preliminarily analyze the cellular compatibility of fish scale collagen lamellar matrix. The results show that the grass carp scales could be divided into base region, lateral region and parietal region according to the surface morphology. The inorganic calcium in the surface layer could be effectively removed by decalcification, and the decalcification rate could reach 99%. After etching treatment, homogeneous collagen lamellar matrix could be obtained. With the decalcification and etching treatment, the water content of the sample increased gradually, but the cross-linking treatment had no obvious effect on the water content of fish scale collagen lamellar matrix. Fish scale collagen lamellar matrix has good transparency, refractive index, mechanical properties and cellular compatibility, which may represent a prospect for the construction of cornea tissue engineering products.

Enzymatically Forming Cell Compatible Supramolecular Assemblies of Tryptophan-Rich Short Peptides

Here we report a new type of tryptophan-rich short peptides, which act as hydrogelators, form supramolecular assemblies via enzymatic dephosphorylation, and exhibit cell compatibility. The facile synthesis of the peptides starts with the production of phosphotyrosine, then uses solid phase peptide synthesis (SPPS) to build the phosphopeptides that contain multiple tryptophan residues. Besides exhibiting excellent solubility, these phosphopeptides, unlike the previously reported cytotoxic phenylalanine-rich phosphopeptides, are largely compatible toward mammalian cells. Our preliminary mechanistic study suggests that the tryptophan-rich peptides, instead of forming pericellular assemblies, largely accumulate in lysosomes. Such lysosomal localization may account for their cell compatibility. Moreover, these tryptophan-rich peptides are able to transiently reduce the cytotoxicity of phenylalanine-rich peptide assemblies. This rather unexpected result implies that tryptophan may act as a useful aromatic building block for developing cell compatible supramolecular assemblies for soft materials and find applications for protecting cells from cytotoxic peptide assemblies.

Mechanical Rupture-Based Antibacterial and Cell-Compatible ZnO/SiO2 Nanowire Structures Formed by Bottom-Up Approaches

There are growing interests in mechanical rupture-based antibacterial surfaces with nanostructures that have little toxicity to cells around the surfaces; however, current surfaces are fabricated via top-down nanotechnologies, which presents difficulties to apply for bio-surfaces with hierarchal three-dimensional structures. Herein, we developed ZnO/SiO2 nanowire structures by using bottom-up approaches and demonstrated to show mechanical rupture-based antibacterial activity and compatibility with human cells. When Escherichia coli were cultured on the surface for 24 h, over 99% of the bacteria were inactivated, while more than 80% of HeLa cells that were cultured on the surface for 24 h were still alive. This is the first demonstration of mechanical rupture-based bacterial rupture via the hydrothermally synthesized nanowire structures with antibacterial activity and cell compatibility.

Comparison of SB-SDS and other decellularization methods for the acellular nerve graft: Biological evaluation and nerve repair in vitro and in vivo

We aimed to compare the performance of acellular nerves prepared by different decellularization methods, screening out the optimal decellularization protocol, repairing the sciatic nerve defects in rats by the allogeneic transplantation, and evaluating the effect of regenerative nerve on the function reconstruction. The Sondell, SB-SDS, TnBP, and the high/low permeation methods were used to decellularize donor nerves. Nerves without any treatment were as the control group. The histological results were evaluated by HE staining and toluidine blue (TB) staining. The proliferation activity of L929 cells was detected by CCK-8 assay. The adhesion of Schwann cells was observed and quantified by SEM. Balb/c mice were used to evaluate the cellular and humoral immunogenicity of the nerve scaffolds. The rat sciatic nerve defect model was applied to observe the repair effect of acellular nerve scaffold in vivo. To SB-SDS group, it remained the original state of the nerves, with no observed nucleus and axons, the neurotoxicity grade detected by CCK-8 being almost 0, and it kept the largest number of Schwann cells adhered to the acellular nerve and the better morphology. Further, it showed that the selected SB-SDS rats acellular nerve scaffold could promote the nerve repair of the rats by HE staining and TB staining. We could conclude that the acellular nerve matrix prepared by the SB-SDS method effectively removes the cellular components in the nerve tissue and retains the main components of the extracellular matrix of the nerve tissue, whose rats decellularized nerve scaffold could promote the sciatic nerve repair better.

α-Bisabolol-Loaded Cross-Linked Zein Nanofibrous 3D-Scaffolds For Accelerating Wound Healing And Tissue Regeneration In Rats

Objectives

Novel α-bisabolol (BIS)-loaded citric acid cross-linked zein nanofibrous scaffolds (C-ZNFs) were proposed to serve as safe platforms for promoting wound repair in rats.

Methods

ZNFs were synthesized using electrospinning technique, then NFs, with adequate water resistance, were produced using citric acid as a safe cross-linker.

Results

Compared to the uncross-linked ZNFs, cross-linking with 7% w/w citric acid decreased swelling index by 3 folds, while the tensile strength and the contact angle were enhanced to 2.5 and 3.8 folds, respectively. SEM images showed beads-free homogeneous NFs with a fully inter-connected 3D-network, where the average diameter of optimized C-ZNFs was 181.7±50 nm. After 24 h, C-ZNFs exhibited a decreased BIS release rate (45.6%), compared to uncross-linked mats (84.9%). By increasing BIS concentration, the cell adhesion (WI38 fibroblasts) was improved which can be attributed mainly to BIS activation of transforming growth factor-beta (TGF-β1). The MTT-OD obtained values indicated that all tested zein scaffolds significantly enhanced the viability of WI38 fibroblasts, compared to the control after 48h of incubation which can be referred to the proliferative potential of zein by provoking cell spreading process. The scratch wound assay demonstrated that BIS-loaded ZNF scaffolds showed accelerated migration and proliferation of fibroblasts expressed by significantly higher wound closure rates compared to the control sample. BIS-loaded-C-ZNFs prominently accelerated tissue regeneration for wound closure demonstrated by entirely grown epithelium with normal keratinization and rapid wound contraction, compared to the control. Immunohistochemical results confirmed the superiority of BIS-loaded-C-ZNFs, where the observed reduced NF-κB and the elevated cytokeratin expressions confirmed the anti-inflammatory and proliferative effects of the scaffolds, respectively.

Conclusion

In-vitro, optimized C-ZNFs offered a satisfactory cytocompatibility, adhesion and healing which were consistent with the in-vivo results. BIS-loaded-C-ZNFs could be regarded as a promising and effective biomaterial for tissue regeneration and for accelerating the wound healing process.

Glancing-Angle Deposition of Nanostructures on an Implant Material Surface

Cell-compatible and antibacterial surfaces are needed for implants, which frequently have complex and rough surfaces. Bio-inspired columnar nanostructures can be grown on flat substrates; however, the application of these nanostructures on clinically relevant, complex, and rough surfaces was pending. Therefore, a titanium plasma spray (TPS) implant surface was coated with titanium nano-spikes via glancing angle magnetron sputter deposition (GLAD) at room temperature. Using GLAD, it was possible to cover the three-dimensional, highly structured macroscopic surface (including cavities, niches, clefts, and curved areas) of the TPS homogeneously with nano-spikes (TPS+), creating a cell-compatible and antibacterial surface. The adherence and spreading of mesenchymal stem cells (MSC) were similar for TPS and TPS+ surfaces. However, MSC adherent to TPS+ expressed less and shorter pseudopodia. The induced osteogenic response of MSC was significantly increased in cells cultivated on TPS+ compared with TPS. In addition, Gram-negative bacteria (E. coli) adherent to the nano-spikes were partly destructed by a physico-mechanical mechanism; however, Gram-positive bacteria (S. aureus) were not significantly damaged.

Facile Synthesis of Lipid-Perfluorocarbon Nanoemulsion Coated with Silica Shell as an Ultrasound Imaging Agent

A novel organic/inorganic hybrid nanovesicle as an ultrasound imaging agent is synthesized via facile emulsion and silica deposition methods. This nanovesicle, hyaluronate (HA)-docetaxel (DTX)/perfluoro-n-pentane (PFP)@SNC, consists of an encapsulated liquid PFP core, loaded DTX, and an HA-decorated silica shell. The HA-DTX/PFP@SNC has a narrow size distribution of 274.5 ± 3.25 nm, a negative zeta potential of -11.6 ± 0.47 mV, and an entrapment efficiency of 86.70% ± 1.42%. HA-DTX/PFP@SNC possesses an ultrasound (US)-triggered drug release and a temperature-dependent size change behavior. Compared with DTX/PFP@soybean phosphatidylcholine (SPC), which has no silica shell, the HA-DTX/PFP@SNC is more stable under various conditions. The MTT assay indicates that the blank HA-PFP@SNC vehicle has no cytotoxicity to A549 cells. Furthermore, due to the HA-mediated tumor-targeting ability, the HA-DTX/PFP@SNC shows obvious cytotoxicity to A549 cells. In vitro and in vivo US imaging results indicate that HA-DTX/PFP@SNC has a stronger and more durable echo signal than DTX/PFP@SPC. Moreover, the in vivo echo signal of HA-DTX/PFP@SNC is stronger than that of DTX/PFP@SNC due to the HA-mediated tumor targeting. Therefore, this novel organic/inorganic hybrid vesicle is a US contrast agent candidate.

Construction of physical crosslink-based chitosan/liquid crystal composite hydrogel and evaluation on their cytocompatibility

In order to provide a novel biomimetic composite substrate for tissue engineering and explore the interaction between cells and this type of material, we developed chitosan/liquid crystal (CS/LC) composite hydrogel with embedded LC phases by composing of cholesterol hydroxypropyl cellulose ester liquid crystalline material and CS. The micromorphology of CS/LC composite hydrogels exhibited ‘islands-sea’ phase separation structures similar to the ‘fluid mosaic model’ of biomembrane. In vitro cell compatibility study suggested that 3T3 is fibroblasts exhibited better initial cell adhesions and higher proliferation rates on the composite hydrogel than on the polystyrene control plate and the pure LC membrane. This novel CS/LC composite hydrogel provides more favorable interface for cell growth and proliferation and may serve as potentially active substrate for engineering interfaces to live cells.

Highly enhanced compatibility of human brain vascular pericyte cells on monolayer graphene

We introduce a method for increasing the compatibility of human brain vascular pericyte (HBVP) cells on a glass substrate, based on wet transferred monolayer graphene without any treatment. As a novel material, graphene has key properties for incubating cells, such as chemical stability, transparency, appropriate roughness, hydrophobicity and high electrical conductivity. These outstanding properties of graphene were examined by Raman spectroscopy, water contact angle measurements and atomic force microscopy. The performance of this graphene-based implant was investigated by a cell compatibility test, comparing the growth rate of cells on the graphene surface and that on a bare glass substrate. After an incubation period of 72 h, the number of live HBVP cells on a graphene surface with an area of 1×1 mm² was 1.83 times greater than that on the glass substrate.

Synthesis of novel conjugates of a saccharide, amino acids, nucleobase and the evaluation of their cell compatibility

This article reports the synthesis of a novel type of conjugate of three fundamental biological build blocks (i.e., saccharide, amino acids, and nucleobase) and their cell compatibility. The facile synthesis starts with the synthesis of nucleobase and saccharide derivatives, then uses solid-phase peptide synthesis (SPPS) to build the peptide segment (Phe-Arg-Gly-Asp or naphthAla-Phe-Arg-Gly-Asp with fully protected groups), and later, an amidation reaction in liquid phase connects these three parts together. The overall yield of these multiple step synthesis is about 34%. Besides exhibiting excellent solubility, these conjugates of saccharide-amino acids-nucleobase (SAN), like the previously reported conjugates of nucleobase-amino acids-saccharide (NAS) and nucleobase-saccharide-amino acids (NSA), are mammalian cell compatible.

Genipin-cross-linked thermosensitive silk sericin/poly(N-isopropylacrylamide) hydrogels for cell proliferation and rapid detachment

To overcome release of silk sericin (SS) from semi-interpenetrating polymer network (semi-IPN) SS/poly(N-isopropylacrylamide) (PNIPAm) hydrogels, natural biocompatible genipin (GNP) was adopted as cross-linking agent of SS. The GNP/SS/PNIPAm hydrogels with various GNP contents were prepared by radical polymerization. Depending on GNP content, the resultant hydrogels present white, yellow, or dark blue. Required time of color change for GNP/SS mixture solution shortened with increasing GNP ratio. The GNP/SS/PNIPAm hydrogels present good oscillatory shrinking-swelling behavior between 20 and 37°C. The behaviors of L929 cell proliferation, desorption, and transshipment on the surface of hydrogels and tissue culture polystyrene were investigated by 3-(4,5-dimethy thioazol-2-yl)-2,5-di-phenytetrazoliumromide and scanning electron microscopy method. In comparison with pure SS/PNIPAm hydrogels, the introduction of certain GNP can accelerate cell adhesion and proliferation. Due to reversible change between hydrophobicity and hydrophilicity, by lowering temperature to 4°C from 37°C, L929 cells could spontaneously detach from the surface of hydrogels without the need for trypsin or ethylenediaminetetraacetic acid. The detached cells could subsequently be recultured. The prepared hydrogel and detached cells have potential applications in biomedical fields, such as organs or tissue regeneration and cancer or disease therapy.