Surface characterizations of membranes and electrospun chitosan derivatives by optical speckle analysis

In this paper, we show that laser speckle pattern provides useful information toward revealing discrimination between nanofibers and membranes. Chitosan materials particularly organosoluble chitosan derivatives have a number of applications. The surface characteristics of these materials are very critical for specific applications. The analysis of laser speckles, both numerical and graphical, includes information about the surface structure. The development of digital electronics brought the ease of image processing and has opened new perspectives for a spectrum of laser speckle analysis (LASCA) applications. Our results show reasonable differences between the LASCA parameters of nanofibers and membranes. The methodology may be considered as a quantitative assessment tool for similar samples

Unveiling the potential of cellulose, chitosan and polylactic acid as precursors for the production of green carbon nanofibers with controlled morphology and diameter

Carbon nanofibers (CNFs) are very promising materials with application in many fields, such as sensors, filtration systems, and energy storage devices. This study aims to explore the use of eco-friendly biopolymers for CNF production, finding novel, suitable and sustainable precursors and thus prioritising environmentally conscious processes and ecological compatibility. Polymeric nanofibers (PNFs) using cellulose acetate, polylactic acid, and chitosan as precursors were successfully prepared via electrospinning. Rheological testing was performed to determine suitable solution concentrations for the production of PNFs with controlled diameter and appropriate morphology. Their dimensions and structure were found to be significantly influenced by the solution concentration and electrospinning flow rate. Subsequently, the electrospun green nanofibers were subject to stabilisation and carbonisation to convert them into CNFs. Thermal behaviour and chemical/structural changes of the nanofibers during stabilisation were investigated by means of thermogravimetric analysis and Fourier-transform infrared spectroscopy, while the final morphology of the fibers after stabilisation and carbonisation was examined through scanning electron microscopy to determine the optimal stabilisation parameters. The optimal fabrication parameters for cellulose and chitosan-based CNFs with excellent morphology and thermal stability were successfully established, providing valuable insight and methods for the sustainable and environmentally friendly synthesis of these promising materials

Neurodegenerative diseases and effective drug delivery: A review of challenges and novel therapeutics

The central nervous system (CNS) encompasses the brain and spinal cord and is considered the processing center and the most vital part of human body. The central nervous system (CNS) barriers are crucial interfaces between the CNS and the periphery. Among all these biological barriers, the blood-brain barrier (BBB) strongly impede hurdle for drug transport to brain. It is a semi-permeable diffusion barrier against the noxious chemicals and harmful substances present in the blood stream and regulates the nutrients delivery to the brain for its proper functioning. Neurological diseases owing to the existence of the BBB and the blood-spinal cord barrier have been terrible and threatening challenges all over the world and can rarely be directly mediated. In fact, drug delivery to brain remained a challenge in the treatment of neurodegenerative (ND) disorders, for these different approaches have been proposed. Nano-fabricated smart drug delivery systems and implantable drug loaded biomaterials for brain repair are among some of these latest approaches. In current review, modern approaches developed to deal with the challenges associated with transporting drugs to the CNS are included. Recent studies on neural drug discovery and injectable hydrogels provide a potential new treatment option for neurological disorders. Moreover, induced pluripotent stem cells used to model ND diseases are discussed to evaluate drug efficacy. These protocols and recent developments will enable discovery of more effective drug delivery systems for brain

Single-step, acid-based fabrication of homogeneous gelatin-polycaprolactone fibrillar scaffolds intended for skin tissue engineering

Blends of natural and synthetic polymers have recently attracted great attention as scaffolds for tissue engineering applications due to their favorable biological and mechanical properties. Nevertheless, phase-separation of blend components is an important challenge facing the development of electrospun homogeneous fibrillar natural-synthetic polymers scaffolds; phase-separation can produce significant detrimental effects for scaffolds fabricated by electrospinning. In the present study, blends of gelatin (Gel; natural polymer) and polycaprolactone (PCL; synthetic polymer), containing 30 and 45 wt.% Gel, were prepared using acetic acid as a "green" sole solvent to straightforwardly produce appropriate single-step Gel-PCL solutions for electrospinning. Miscibility of Gel and PCL in the scaffolds was assessed and the morphology, chemical composition and structural and solid-state properties of the scaffolds were thoroughly investigated. Results showed that the two polymers proved miscible under the single-step solution process used and that the electrospun scaffolds presented suitable properties for potential skin tissue engineering applications. Viability, metabolic activity and protein expression of human fibroblasts cultured on the Gel-PCL scaffolds were evaluated using LIVE/DEAD (calcein/ethidium homodimer), MTT-Formazan and immunocytochemistry assays, respectively. In vitro results showed that the electrospun Gel-PCL scaffolds enhanced cell viability and proliferation in comparison to PCL scaffolds. Furthermore, scaffolds allowed fibroblasts expression of extracellular matrix proteins, tropoelastin and collagen Type I, in a similar way to positive controls. Results indicated the feasibility of the single-step solution process used herein to obtain homogeneous electrospun Gel-PCL scaffolds with Gel content ≥ 30 wt.% and potential properties to be used as scaffolds for skin tissue engineering applications for wound healing

Antibacterial composite membranes of polycaprolactone/gelatin loaded with zinc oxide nanoparticles for guided tissue regeneration

The bacterial colonization of absorbable membranes used for guided tissue regeneration (GTR), as well as their rapid degradation that can cause their rupture, are considered the major reasons for clinical failure. To address this, composite membranes of polycaprolactone (PCL) and gelatin (Gel) loaded with zinc oxide nanoparticles (ZnO-NPs; 1, 3 and 6 wt% relative to PCL content) were fabricated by electrospinning. To fabricate homogeneous fibrillar membranes, acetic acid was used as a sole common solvent to enhance the miscibility of PCL and Gel in the electrospinning solutions. The effects of ZnO-NPs in the physico-chemical, mechanical and in vitro biological properties of composite membranes were studied. The composite membranes showed adequate mechanical properties to offer a satisfactory clinical manipulation and an excellent conformability to the defect site while their degradation rate seemed to be appropriate to allow successful regeneration of periodontal defects. The presence of ZnO-NPs in the composite membranes significantly decreased the planktonic and the biofilm growth of the Staphylococcus aureus over time. Finally, the viability of human osteoblasts and human gingival fibroblasts exposed to the composite membranes with 1 and 3 wt% of ZnO-NPs indicated that those membranes are not expected to negatively influence the ability of periodontal cells to repopulate the defect site during GTR treatments. The results here obtained suggest that composite membranes of PCL and Gel loaded with ZnO-NPs have the potential to be used as structurally stable GTR membranes with local antibacterial properties intended for enhancing clinical treatments

1,2,4-Triazole and quinoxaline based polyimide reinforced with neat and epoxide-end capped modified SiC nanoparticles: Study thermal, mechanical and photophysical properties

In this paper, properties of nanocomposite films which were prepared from a new polyimide and SiC nanoparticles via two simple methods are reported: (1) SiC nanoparticles were firstly functionalized with epoxide-end groups (mSiC) and then solution blended with poly(triazole-imide) (PTAI) in DMAc. The homogeneous solution was heated in vacuum to give PTAI/mSiC film. (2) A new diamine containing 1,2,4-triazole ring and a commercial dianhydride was reacted in situ in the presence of native SiC nanoparticles to give a homogeneous poly(amic acid) PAA/SiC mixture which was then heated in vacuum under high temperature thermal process to give PTAI/SiC film. The nanocomposite films were tested for different properties including thermal using TGA and DMTA, mechanical and photophysical. The results showed that strong chemical bonding between SiC nanoparticles and the polymer matrix contributed to the enhanced Tg from 300 °C to >350 °C, tensile strength from 108 MPa to 165 MPa and temperature of 5% weight loss (T5%) from 380 °C to 500 °C. The photoluminescence intensity of the nanocomposites increased and the spectra showed blue shift with increasing SiC content

Novel fluorescent light-emitting polymer composites bearing 1,2,4-triazole and quinoxaline moieties: Reinforcement and thermal stabilization with silicon carbide nanoparticles by epoxide functionalization

New diamines bearing substituted 1,2,4-triazole and quinoxaline moieties with OCH3 or Br units were successfully synthesized and used for preparation of novel polyamides (PAs) by direct polycondensation with aromatic and aliphatic dicarboxylic acids. Chemical structure of the diamines as well as the resulting polymers was confirmed by elemental analysis, FT-IR and 1H NMR spectroscopic methods. Inherent viscosities of these PAs were in the range of 0.52–0.56 dL/g, they were readily soluble in a variety of organic solvents and formed low-coloured and tough thin films via solution casting. The aromatic PAs exhibited Tg between 284 °C and 300 °C, and their 10% weight loss temperatures were in excess of 420 °C with up to 70% char yield at 600 °C in N2. These PAs emitted green or blue fluorescence in dilute NMP solution and in the solid state. Silicon carbide (SiC) nanoparticles modified by silane coupling agent were used to prepare SiC/PA particle-reinforced composites by solution blending. Thermal properties of nanocomposites by using DMTA, DSC and TGA and also solubility and optical properties were investigated. The results show that both the uniform particle dispersion and the strong chemical bonding between the nanoparticles and the polymer–matrix contributed to the enhanced Tg, storage modulus and thermal stability

Curing of DGEBA/ZnO nanocomposite with new fluorinated curing agents: Study of kinetics, water absorption, thermal and photophysical properties

In this study, two new fluorinated curing agents bearing imidazole-bisphenol and imidazole-diamine groups in their structures, namely: 4,4′-(2-(4-(trifluoromethyl)phenyl)-1H-imidazole-4,5-diyl)diphenol (TFIDO) and 4,4′-(4,4′-(2-(4-(trifluoromethyl)phenyl)-1H-imidazole-4,5-diyl)bis(4,1-phenylene)bis(oxy)bis (3-(trifluoromethyl)aniline) (TFIA) were synthesized, fully characterized and used to cure diglycidylether of bisphenol-A (DGEBA)-based epoxy resin and blend of DGEBA with nano ZnO (NZ) particles. Two mechanisms were anticipated to play roles in the curing reactions based on adducts formation and ionic complexes. The DGEBA/TFIDO system was more reactive than the DGEBA/TFIA system, whereas the thermal stability of DGEBA/TFIA was higher than that of DGEBA/TFIDO. These results can be explained by the increase in cross-linking density and more CF3 groups in TFIA. The results indicated that cured materials showed red shift in absorption and fluorescence emission spectra and significant improvements in the water repellency and thermal stability. The NZ particles as catalyst increased the rate of cure reaction by decreasing the activation energy (Ea) and increasing the rate constant values