Functionalization of poly(ε-caprolactone) surface with lactose-modified chitosan via alkaline hydrolysis: ToF-SIMS characterization

Exploring chitosan-plant extract bilayer coatings: Advancements in active food packaging via polypropylene modification

UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.

Development of functionalized poly(lactide) films with chitosan via SI-SARA ATRP as scaffolds for neuronal cell growth

Polylactic acid (PLA), a polymer derived from renewable resources, is gaining increasing attention in the development of biomedical devices due to its cost-effectiveness, low immunogenicity, and biodegradability. However, its inherent hydrophobicity remains a problem, leading to poor cell adhesion features. On this basis, the aim of this work was to develop a method for functionalizing the surface of PLA films with a biopolymer, chitosan (CH), which was proved to be a material with intrinsic cell adhesive properties, but whose mechanical properties are insufficient to be used alone. The combination of the two polymers, PLA as a bulk scaffold and CH as a coating, could be a promising combination to develop a scaffold for cell growth. The modification of PLA films involved several steps: aminolysis followed by bromination to graft amino and then bromide groups, poly(glycidyl methacrylate) (PGMA) grafting by surface-initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA ATRP) and finally the CH grafting. To prove the effective adhesive properties, conjugated and non-conjugated films were tested in vitro as substrates for neuronal cell growth using differentiated neurons from human induced pluripotent stem cells. The results demonstrated enhanced cell growth in the presence of CH.

Poly(ε-caprolactone)-Based Graft Copolymers: Synthesis Methods and Applications in the Biomedical Field: A Review

Synthetic biopolymers are attractive alternatives to biobased polymers, especially because they rarely induce an immune response in a living organism. Poly ε-caprolactone (PCL) is a well-known synthetic aliphatic polyester universally used for many applications, including biomedical and environmental ones. Unlike poly lactic acid (PLA), PCL has no chiral atoms, and it is impossible to play with the stereochemistry to modify its properties. To expand the range of applications for PCL, researchers have investigated the possibility of grafting polymer chains onto the PCL backbone. As the PCL backbone is not functionalized, it must be first functionalized in order to be able to graft reactive groups onto the PCL chain. These reactive groups will then allow the grafting of new reagents and especially new polymer chains. Grafting of polymer chains is mainly carried out by "grafting from" or "grafting onto" methods. In this review we describe the main structures of the graft copolymers produced, their different synthesis methods, and their main characteristics and applications, mainly in the biomedical field.

Melimine-Modified 3D-Printed Polycaprolactone Scaffolds for the Prevention of Biofilm-Related Biomaterial Infections

Biomaterial-associated infections are one of the major causes of implant failure. These infections result from persistent bacteria that have adhered to the biomaterial surface before, during, or after surgery and have formed a biofilm on the implant's surface. It is estimated that 4 to 10% of implant surfaces are contaminated with bacteria; however, the infection rate can be as high as 30% in intensive care units in developed countries and as high as 45% in developing countries. To date, there is no clinical solution to prevent implant infection without relying on the use of high doses of antibiotics supplied systemically and/or removal of the infected device. In this study, melimine, a chimeric cationic peptide that has been tested in Phase I and II human clinical trials, was immobilized onto the surface of 3D-printed medical-grade polycaprolactone (mPCL) scaffolds via covalent binding and adsorption. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of melimine-treated surfaces confirmed immobilization of the peptide, as well as its homogeneous distribution throughout the scaffold surface. Amino acid analysis showed that melimine covalent and noncovalent immobilization resulted in a peptide density of ∼156 and ∼533 ng/cm², respectively. Furthermore, we demonstrated that the immobilization of melimine on mPCL scaffolds by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride (EDC) coupling and noncovalent interactions resulted in a reduction of Staphylococcus aureus colonization by 78.7% and 76.0%, respectively, in comparison with the nonmodified control specimens. Particularly, the modified surfaces maintained their antibacterial properties for 3 days, which resulted in the inhibition of biofilm formation in vitro. This system offers a biomaterial strategy to effectively prevent biofilm-related infections on implant surfaces without relying on the use of prophylactic antibiotic treatment.

Bio-Functionalized Chitosan for Bone Tissue Engineering

Hybrid biomaterials allow for the improvement of the biological properties of materials and have been successfully used for implantology in medical applications. The covalent and selective functionalization of materials with bioactive peptides provides favorable results in tissue engineering by supporting cell attachment to the biomaterial through biochemical cues and interaction with membrane receptors. Since the functionalization with bioactive peptides may alter the chemical and physical properties of the biomaterials, in this study we characterized the biological responses of differently functionalized chitosan analogs. Chitosan analogs were produced through the reaction of GRGDSPK (RGD) or FRHRNRKGY (HVP) sequences, both carrying an aldehyde-terminal group, to chitosan. The bio-functionalized polysaccharides, pure or "diluted" with chitosan, were chemically characterized in depth and evaluated for their antimicrobial activities and biocompatibility toward human primary osteoblast cells. The results obtained indicate that the bio-functionalization of chitosan increases human-osteoblast adhesion (p < 0.005) and proliferation (p < 0.005) as compared with chitosan. Overall, the 1:1 mixture of HVP functionalized-chitosan:chitosan is the best compromise between preserving the antibacterial properties of the material and supporting osteoblast differentiation and calcium deposition (p < 0.005 vs. RGD). In conclusion, our results reported that a selected concentration of HVP supported the biomimetic potential of functionalized chitosan better than RGD and preserved the antibacterial properties of chitosan.

Antibacterial Electrospun Polycaprolactone Membranes Coated with Polysaccharides and Silver Nanoparticles for Guided Bone and Tissue Regeneration

Electrospun polycaprolactone (PCL) membranes have been widely explored in the literature as a solution for several applications in tissue engineering and regenerative medicine. PCL hydrophobicity and its lack of bioactivity drastically limit its use in the medical field. To overcome these drawbacks, many promising strategies have been developed and proposed in the literature. In order to increase the bioactivity of electrospun PCL membranes designed for guided bone and tissue regeneration purposes, in the present work, the membranes were functionalized with a coating of bioactive lactose-modified chitosan (CTL). Since CTL can be used for the synthesis and stabilization of silver nanoparticles, a coating of this compound was employed here to provide antibacterial properties to the membranes. Scanning electron microscopy imaging revealed that the electrospinning process adopted here allowed us to obtain membranes with homogeneous fibers and without defects. Also, PCL membranes retained their mechanical properties after several weeks of aging in simulated body fluid, representing a valid support for cell growth and tissue development. CTL adsorption on membranes was investigated by fluorescence microscopy using fluorescein-labeled CTL, resulting in a homogeneous and slow release over time. Inductively coupled plasma-mass spectrometry was used to analyze the release of silver, which was shown to be stably bonded to the CTL coating and to be slowly released over time. The CTL coating improved MG63 osteoblast adhesion and proliferation on membranes. On the other hand, the presence of silver nanoparticles discouraged biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus without being cytotoxic. Overall, the stability and the biological and antibacterial properties make these membranes a valid and versatile material for applications in guided tissue regeneration and in other biomedical fields like wound healing.

Cysteine-Modified Self-Assembling Peptides on Gold: The Role of the Head and Tail

Molecular self-assembly consists of the spontaneous aggregation of molecules into a well-defined structure guided by noncovalent bonds. The self-assembly strategy is ubiquitous in nature and recently has been proposed as a nature-mimetic strategy in polymer science and biomaterial engineering. In this context, we aim at designing and testing innovative but simple chemical strategies to efficiently modify surfaces by exploiting minor modifications in the bioactive molecule functionalities, for example, introducing cysteine (Cys) as a terminal residue in self-assembling peptides (SAPs). In this work, we report the attenuated total reflection-Fourier transform infrared spectroscopy, synchrotron radiation-induced X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and time-of-flight secondary ion mass spectrometry investigation of self-assembled layers of oligopeptides anchored onto gold surfaces through cysteine residues, opportunely inserted in an SAP (EAK16-II) main chain in three different positions: at the amine end group, at the carboxyl end group, and at both terminal groups (i.e., a bidentate SAP). This study, which allowed us to individuate in the bidentate SAP the best candidate for the controlled production of ordered SAP layers on the gold substrate surface, is envisaged to open wide perspectives for efficient chemical modification of surfaces with biomolecules, leading to obtaining innovative bioactive materials for applications in the field of tissue engineering.

Fibronectin Functionalized Electrospun Fibers by Using Benign Solvents: Best Way to Achieve Effective Functionalization

The aim of this study is to demonstrate the feasibility of different functionalization methods for electrospun fibers developed using benign solvents. In particular three different approaches were investigated to achieve the functionalization of poly(epsilon caprolactone) (PCL) electrospun fibers with fibronectin. Protein surface entrapment, chemical functionalization and coaxial electrospinning were performed and compared. Moreover, bilayered scaffolds, with a top patterned and functionalized layer with fibronectin and a randomly oriented not functionalized layer were fabricated, demonstrating the versatility of the use of benign solvents for electrospinning also for the fabrication of complex graded structures. Besides the characterization of the morphology of the obtained scaffolds, ATR-FTIR and ToF-SIMS were used for the surface characterization of the functionalized fibers. Cell adhesion and proliferation were also investigated by using ST-2 cells. Positive results were obtained from all functionalized scaffolds and the most promising results were obtained with bilayered scaffolds, in terms of cells infiltration inside the fibrous structure.

Chitosan functionalization of titanium and Ti6Al4V alloy with chloroacetic acid as linker agent

In this work, a new covalent grafting of chitosan on titanium and Ti6Al4V alloy surfaces is reported using chloroacetic acid as linker agent. Good results were obtained both on titanium and on Ti6Al4V alloy. The effect of the surface acid pretreatments on the subsequent functionalization with chitosan is evaluated. The morphological aspect of acid etched metal surfaces before chitosan grafting has been characterized by scanning electron microscopy (SEM). The presence of carboxylic groups on metal surfaces and then the efficiency of chitosan covalent immobilization were detected by Fourier transformed infrared-Attenuated Total Reflectance (FTIR-ATR) and X-Ray photoelectron spectroscopy (XPS). Cyclic voltammetry tests, using the functionalized titanium and Ti6Al4V samples as electrodes, were conducted in different aqueous solutions, to detect the presence of the homogeneous overlayer of chitosan on the surface, and to evaluate the importance of the carboxyl groups as linker agent.

Hydrophobization of chitosan films by surface grafting with fluorinated polymer brushes

Chitosan with its surface-properties and biodegradability is a promising biomaterial for green packaging applications. Till now, this application is still limited due to chitosan high sensitivity to water. Some existing studies deal with the incorporation of hydrophobic additives to enhance water-proof performances of chitosan films. As these additives may impair the film properties, our study focuses on chitosan efficient hydrophobization by means of simple and successful surface grafting reactions. Chitosan films prepared by solvent casting were modified by means of surface-initiated activators regenerated by electron transfer atom radical polymerization (SI-ARGET-ATRP) of 2-hydroxyethyl methacrylate (HEMA) followed by esterification reaction with fluorinated acyl compound. X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) highlighted the surface chemical changes after each step. Surface properties were investigated by contact angle measurements and surface energy calculations. Hydrophobic surfaces with low surface energy and good water-repellent properties were obtained using a simple handling polymerization procedure. This is the first study in applying ARGET ATRP to prepare hydrophobic biopolymer films offering potential applications in packaging.

Incorporation of bioactive glass nanoparticles in electrospun PCL/chitosan fibers by using benign solvents

The use of bioactive glass (BG) particles as a filler for the development of composite electrospun fibers has already been widely reported and investigated. The novelty of the present research work is represented by the use of benign solvents (like acetic acid and formic acid) for electrospinning of composite fibers containing BG particles, by using a blend of PCL and chitosan. In this work, different BG particle sizes were investigated, namely nanosized and micron-sized. A preliminary investigation about the possible alteration of BG particles in the electrospinning solvents was performed using SEM analysis. The obtained composite fibers were investigated in terms of morphological, chemical and mechanical properties. An in vitro mineralization assay in simulated body fluid (SBF) was performed to investigate the capability of the composite electrospun fibers to induce the formation of hydroxycarbonate apatite (HCA).