Chitosan-based films grafted with citrus waste-derived antifungal agents: An innovative and sustainable approach to enhance post-harvest preservation of citrus fruit

This paper reports the synthesis, characterization, and properties of chitosan films (CHI) grafted with a natural antifungal agent with the aim of developing active films of natural origin to prevent post-harvest losses of citrus fruit. The antifungal agent was prepared by fermentation using lemon peel (AntiFun-LM), a citrus waste, and grafted on chitosan using different coupling agents (CHI/AntiFun-LM). Bioactive films were prepared by solvent casting. FTIR-ATR and ToF-SIMS analyses provided compelling evidence of the successful grafting process. TGA-DSC demonstrated that the films are stable after grafting. SEM studies showed the continuous and compact surface of the films. WCA measurements proved that CHI/AntiFun-LM films are more hydrophilic than CHI films. Moreover, the CHI/AntiFun-LM films showed stronger UV shielding effect when compared to CHI. The biological evaluation demonstrated that CHI/AntiFun-LM films gained considerable antifungal properties against most fungi responsible for post-harvest decay. Cytotoxicity tests showed that CHI/AntiFun-LM films did not cause any toxic effect against L929 fibroblasts. This study highlights the great potential of chemical grafting of antifungal agents produced from citrus waste to chitosan and preparation of natural-based films to act as a powerful alternative in post-harvest protection of citrus fruit in a perspective of circular economy.

In vivo behavior of a collagen-coated nano-hydroxyapatite enriched polycaprolactone membrane in rat mandibular defects

BACKGROUND

This research investigated the ability of fabricated collagen (COL) coated nano-hydroxyapatite (nHA) enriched polycaprolactone (PCL) membrane to facilitate new bone formation (NBF) and its biocompatibility.

METHODS

Unilateral mandibular angulus defects of 28 female 12-week-old long Evans rats were created with a trephine bur with 5 mm in diameter and divided into two groups. While the test group was treated with the membrane (M-1, M-2), the control was left as self-healing (C-1, C-2) and sacrificed at 2nd (M-1, C-1) and 8th week (M-2, C-2) postoperatively. The mandibular bone of the rats was evaluated histopathologically. Density of the regenerated bone was evaluated with PET/CT.

RESULTS

Histopathologically, NBF which started from the periphery of the defect had rich cellular character in M-1. Significantly higher NBF was found in M-2 when compared to M-1 (P=0.003). Furthermore, significantly lesser degree of inflammation was found in M-2 when compared to M-1 (P<0.05).

CONCLUSION

This study suggests that the novel COL-coated nHA-enriched PCL membrane can serve a promising design for tissue engineering as guided bone regeneration in alveolar defects.

Optimizing Chitosan/Collagen Type I/Nanohydroxyapatite Cross-linked Porous Scaffolds for Bone Tissue Engineering

Bio-composite scaffolds mimicking the natural microenvironment of bone tissue offer striking advantages in material-guided bone regeneration. The combination of biodegradable natural polymers and bioactive ceramics that leverage potent bio-mimicking cues has been an active strategy to achieve success in bone tissue engineering. Herein, a competitive approach was followed to point out an optimized bio-composite scaffold in terms of scaffold properties and stimulation of osteoblast differentiation. The scaffolds, composed of chitosan/collagen type I/nanohydroxyapatite (Chi/Coll/nHA) as the most attractive components in bone tissue engineering, were analyzed. The scaffolds were prepared by freeze-drying method and cross-linked using different types of cross-linkers. Based on the physicochemical and mechanical characterization, the scaffolds were eliminated comparatively. All types of scaffolds displayed highly porous structures. The cross-linker type and collagen content had prominent effects on mechanical strength. Glyoxal cross-linked structures displayed optimum mechanical and structural properties. The MC3T3-E1 proliferation, osteogenic-related gene expression, and matrix mineralization were better pronounced in collagen presence and triggered as collagen type I amount was increased. The results highlighted that glyoxal cross-linked scaffolds containing equal amounts of Chi and Coll by mass and 1% (w/v) nHA are the best candidates for osteoblast differentiation and matrix mineralization.

UiO-66 metal-organic framework as a double actor in chitosan scaffolds: Antibiotic carrier and osteogenesis promoter

Metal-organic frameworks (MOFs) have recently emerged as a useful class of nanostructures with well-suited characteristics for drug delivery applications, due to the high surface area and pore size for efficient loading. Despite their use as a nano-carrier for controlled delivery of various types of drugs, the inherent osteo-conductive properties have stolen a great attention as a growing area of investigation. Here, we evaluated the double function of UiO-66 MOF structure as a carrier for fosfomycin antibiotic and also as an osteogenic differentiation promoter when introduced in 3D chitosan scaffolds, for the first time. Our results revealed that the wet-spun chitosan scaffolds containing fosfomycin loaded UiO-66 nanocrystals (CHI/UiO-66/FOS) possessed fiber mesh structure with integrated micro-scale fibers and increased mechanical strength. In vitro antibacterial studies indicated that CHI/UiO-66/FOS scaffolds showed bactericidal activity against Staphylococcus aureus. Moreover, the scaffolds were biocompatible to MC3T3-E1 pre-osteoblasts and significantly up-regulated the expression of osteogenesis-related genes and facilitated the extracellular matrix mineralization, in vitro. Taken together, our results demonstrate UiO-66 MOFs can present double functionality and CHI/UiO-66/FOS scaffolds hold a significant potential to be further explored as an alternative approach in treating infected bone defects like osteomyelitis.

Design of Zr-based metal organic framework as an efficient fosfomycin carrier: a combined experimental and DFT study

Biomolecule carrier systems based on metal-organic frameworks (MOFs) are highly promising owing to a high degree of structural tunability, high surface area, porosity, and higher chemical/thermal stability. UiO-66, one of...

Chitosan and silver nanoparticles are attractive auxin carriers: A comparative study on the adventitious rooting of microcuttings in apple rootstocks

Nanocarriers for encapsulation and sustained release of agrochemicals such as auxins have emerged as an attractive strategy to provide enhanced bioavailability and efficacy for improved crop yields and nutrition quality. Here, a comparative study was conducted on the effectiveness of chitosan-as a biopolymeric nanocarrier- and silver-as a metallic nanocarrier- on in vitro adventitious rooting potential of microcuttings in apple rootstocks, for the first time. Auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) loaded silver (nAg) or chitosan nanoparticles (nChi) were synthesized. Scanning electron microscopy and transmission electron microscopy studies showed the spherical shape of the nanoparticles. The average particle size of IAA-nChi was 167.5 ± 0.1 nm while that of IBA-nChi was 123.2 ± 2.6 nm. The hydrodynamic diameter of the nAg-IAA and nAg-IBA particles were measured as 93.66 ± 5 nm and 71.41 ± 3 nm, respectively. Fourier transform infrared spectroscopy analyses confirmed the encapsulation of IAA or IBA in the chitosan nanoparticles. Meanwhile, the characteristic peaks of IAA or IBA were detected on silver nanoparticles. In-vitro adventitious rooting of microcuttings of Malling Merton 106 (MM 106) was significantly higher both in chitosan and silver nanoparticles loaded with IAA or IBA (91.7%-62.5%) compared to free IAA or IBA applications (50.0%-33.3%), except for 2.0 mg L^-1 IBA (66.7%). However, the application of 2 mg L^-1 IBA and IBA-nChi at all concentrations caused an undesirable large callus development.

BMP-6 carrying metal organic framework-embedded in bioresorbable electrospun fibers for enhanced bone regeneration

Biomolecule carrier structures have attracted substantial interest owing to their potential utilizations in the field of bone tissue engineering. In this study, MOF-embedded electrospun fiber scaffold for the controlled release of BMP-6 was developed for the first time, to enrich bone regeneration efficacy. The scaffolds were achieved by first, one-pot rapid crystallization of BMP-6 encapsulated ZIF-8 nanocrystals-as a novel carrier for growth factor molecules- and then electrospinning of the blending solution composed of poly (ε-caprolactone) and BMP-6 encapsulated ZIF-8 nanocrystals. BMP-6 molecule encapsulation efficiency for ZIF-8 nanocrystals was calculated as 98%. The in-vitro studies showed that, the bioactivity of BMP-6 was preserved and the release lasted up to 30 days. The release kinetics fitted the Korsmeyer-Peppas model exhibiting a pseudo-Fickian behavior. The in-vitro osteogenesis studies revealed the superior effect of sustained release of BMP-6 towards osteogenic differentiation of MC3T3-E1 pre-osteoblasts. In-vivo studies also revealed that the sustained slow release of BMP-6 was responsible for the generation of well-mineralized, new bone formation in a rat cranial defect. Our results proved that; MOF-carriers embedded in electrospun scaffolds can be used as an effective platform for bone regeneration in bone tissue engineering applications. The proposed approach can easily be adapted for various growth factor molecules for different tissue engineering applications.

Regulation of chondrocyte hypertrophy in an osteochondral interface mimicking gel matrix

Calcified cartilage extracellular matrix (ECM) is a critical interface at the osteochondral junction which plays an important role in maintaining the structural continuity between articular cartilage and subchondral bone. This mineralized network is primarily composed of glycosaminoglycans (GAGs) and collagen type II (col II) and hosts hypertrophic chondrocytes. This work aimed to investigate the effect of gel composition and collagen II content on the behavior and hypertrophic differentiation of ATDC5 cells for regeneration of calcified cartilage tissue. For this purpose, chitosan/collagen type II/nanohydroxyapatite (chi/col II/nHA) composite hydrogels were prepared to mimic the calcified cartilage ECM. ATDC5 cells were encapsulated within the composite gels and the viability, ECM production and hypertrophic gene expression were assessed during culture. All composites were favorable for ATDC5 viability and proliferation, whereas specific ECM production and hypertrophic differentiation were dependent on gel composition. Chitosan: collagen II ratio had an impact on ATDC5 cell fate. Hypertrophic differentiation was best pronounced in chi/col II/nHA 70:30 composition. The results obtained from this study offers a scaffold-based approach for calcified cartilage regeneration and provide an insight for biomimetic design and preparation of more complicated gradient osteochondral units.

Chitosan/collagen based biomimetic osteochondral tissue constructs: A growth factor-free approach

Tissue engineering approach offers alternative strategies to develop multi-layered/multi-component osteochondral mimetic constructs to meet the requirements of the heterogeneous and layered structure of native osteochondral tissue. Herein, an iterative overlaying process to fabricate a multi-layered scaffold with a gradient composition and layer specific structure have been developed by combining the natural extracellular matrix (ECM) components-chitosan, type I collagen, type II collagen, nanohydroxyapatite- of the osteochondral tissue in biomimetic compositions. Subchondral bone layer was prepared by using freeze-drying method to obtain 3D porous scaffolds. The calcified cartilage and cartilage layers were prepared by thermal gelation method in the hydrogel form. Osteochondral scaffolds fabricated by iterative overlaying of each distinct layer exhibited a porous, continuous gradient structure and supported cell proliferation in a co-culture of MC3T3-E1 preosteoblasts and ATDC5 chondrocytes. Histology and biochemical analysis showed enhanced extracellular matrix production and demonstrated collagen and glycosaminoglycan deposition. Expression of genes specific for bone, calcified cartilage and cartilage were improved in the osteochondral scaffold. Overall, these findings suggest that iterative overlaying of freeze-dried scaffolds and hydrogel matrices prepared by using ECM components in biomimetic ratios to fabricate gradient, multi-layered structures can be a promising strategy without the need for growth factors.

Fabrication and Process Optimization of Poly(2-hydroxyethyl methacrylate) Nanofibers by Response Surface Methodology

In this study, Response Surface Methodology (RSM) was used to model and optimize the electrospinning parameters to obtain poly(2-hydroxylethyl methacrylate) (pHEMA) nanofibers which is challenging in terms of evaluating the optimum conditions in nanofiber production. A second order (quadratic model) polynomial function was used for correlation between electrospinning parameters (flow rate, applied voltage, polymer/ethanol concentration) and average fiber diameter. An electro-spinning set-up was used to fabricate nanofibers and scanning electron microscopy (SEM) was used to determine the morphology and the size of the nanofibers with diameter ranging from 211 nm to 1661 nm. Results concluded that the concentration of polymer solution played an important role in distribution of fiber diameter. Based on RSM, the optimum pHEMA fibers with 245±35 nm diameter were collected at 13 μL/min flow rate, 12 kV applied voltage at an ethanol:pHEMA ratio of 1.76.

Preparation of bioactive and antimicrobial PLGA membranes by magainin II/EGF functionalization

Development of dual functional materials that are capable of both reducing bacterial interaction and encouraging host tissue integration has gained importance in design of biomaterials. In this study, we prepared a bilayer poly (lactide co-glycolide) fibrous membrane with antibacterial and bioactive properties by electrospinning. The antibacterial layer was produced by covalent immobilization of antimicrobial peptide, Magainin II. The bioactive layer incorporating epidermal growth factor (EGF) molecules was subsequently electrospun on the antibacterial layer. The membranes were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and fluorescence microscopy. EGF release was detected by enzyme-linked immunosorbent assay. The antibacterial activity was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The ability to support tissue cell integration was detected by using L-929 mouse fibroblasts. The dual functional membranes established enhanced antibacterial properties and increased tissue cell compatibility. This combined approach suggests a promising strategy for wound dressings, vascular grafts and dental membranes as well as catheters and fixation devices.

Combined delivery of PDGF-BB and BMP-6 for enhanced osteoblastic differentiation

Natural microenvironment during bone tissue regeneration involves integration of multiple biological growth factors which regulate mitogenic activities and differentiation to induce bone repair. Among them platelet derived growth factor (PDGF-BB) and bone morphogenic protein-6 (BMP-6) are known to play a prominent role. The aim of this study was to investigate the benefits of combined delivery of PDGF-BB and BMP-6 on proliferation and osteoblastic differentiation of MC3T3-E1 preosteoblastic cells. PDGF-BB and BMP-6 were loaded in gelatin and poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) particles, respectively. The carrier particles were then loaded into 3D chitosan matrix fabricated by freeze drying. The fast release of PDGF-BB during 7 days was accompanied by slower and prolonged release of BMP-6. The premising release of mitogenic factor PDGF-BB resulted in an increased MC3T3-E1 cell population seeded on chitosan scaffolds. Osteogenic markers of RunX2, Col 1, OPN were higher on chitosan scaffolds loaded with growth factors either individually or in combination. However, OCN expression and bone mineral formation were prominent on chitosan scaffolds incorporating PDGF-BB and BMP-6 as a combination.

Antibacterial activity on electrospun poly(lactide-co-glycolide) based membranes via Magainin II grafting

An antimicrobial peptide (AMP), Magainin II (Mag II) was covalently immobilized on poly(lactide-co-glycolide) (PLGA) and PLGA/gelatin electrospun fibrous membranes. The surface immobilization was characterized by X-ray Photoelectron Spectroscopy (XPS). Scanning Electron Microscopy (SEM) and Atomic Force Microscopy studies showed that the surface morphology of the fibers at micron scale was not affected by the immobilization process. The antibacterial activity of the bound Mag II was tested against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Bacterial adhesion tests, SEM and confocal analyses revealed that the attachment and survival of bacteria were inhibited on Mag II functionalized membranes. AMP immobilization strategy was introduced as a new perspective for the modulation of antibacterial properties on PLGA based materials prepared by electrospinning.

In vitro characterization of chitosan scaffolds: influence of composition and deacetylation degree

In this study, the influence of degree of deacetylation (DD) and composition on some structural and biological properties of chitosan scaffolds were examined in vitro. 3D chitosan scaffolds of 2% (w/v) and 3% (w/v) composition in different DDs i.e. 75-85% and >85% were prepared by freeze-drying method at -80 degrees C. We noticed that >85% deacetylated chitosan scaffolds of 2% (w/v) composition has a highly interconnected morphological structure having approximately 100 mum pore size with 0.0917 N/mm(2) compression modulus. L929 fibroblastic cells were cultured on chitosan scaffolds in order to evaluate their biocompatibilities. Cell culture studies demonstrated that fibroblastic cell attachment and proliferation is affected by DD. The higher deacetylated chitosan scaffolds strongly supported the attachment and proliferation when compared with the lower deacetylated scaffolds. MTT assay indicated that >85% deacetylated chitosan scaffolds of 2% (w/v) composition, having the highest specific growth rate 0.017 h(-1) of all, was found to be the most suitable for cell culture studies and a potential candidate for tissue engineering with enhanced biostability and good biocompatibility.