Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes

Enrofloxacin Pharmaceutical Formulations through the Polymer-Free Electrospinning of β-Cyclodextrin-oligolactide Derivatives

Enrofloxacin (ENR), a member of the fluoroquinolone class of antibiotics, is widely used in veterinary medicine to treat bacterial infections. Like many antibiotics, ENR has limited water solubility and low bioavailability. To address these challenges, drug formulations using solid dispersions, nanosuspensions, surfactants, cocrystal/salt formation, and inclusion complexes with cyclodextrins may be employed. The approach described herein proposes the development of ENR formulations by co-electrospinning ENR with custom-prepared cyclodextrin-oligolactide (CDLA) derivatives. This method benefits from the high solubility of these derivatives, enabling polymer-free electrospinning. The electrospinning parameters were optimized to incorporate significant amounts of ENR into the CDLA nanofibrous webs, reaching up to 15.6% by weight. The obtained formulations were characterized by FTIR and NMR spectroscopy methods and evaluated for their antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. This study indicates that the presence of CDLA derivative does not inhibit the antibacterial activity of ENR, recommending these formulations for further development.

Silica Aerogel-Polycaprolactone Scaffolds for Bone Tissue Engineering

Silica aerogel is a material composed of SiO₂ that has exceptional physical properties when utilized for tissue engineering applications. Poly-ε-caprolactone (PCL) is a biodegradable polyester that has been widely used for biomedical applications, namely as sutures, drug carriers, and implantable scaffolds. Herein, a hybrid composite of silica aerogel, prepared with two different silica precursors, tetraethoxysilane (TEOS) or methyltrimethoxysilane (MTMS), and PCL was synthesized to fulfil bone regeneration requirements. The developed porous hybrid biocomposite scaffolds were extensively characterized, regarding their physical, morphological, and mechanical features. The results showed that their properties were relevant, leading to composites with different properties. The water absorption capacity and mass loss were evaluated as well as the influence of the different hybrid scaffolds on osteoblasts' viability and morphology. Both hybrid scaffolds showed a hydrophobic character (with water contact angles higher than 90°), low swelling (maximum of 14%), and low mass loss (1-7%). hOB cells exposed to the different silica aerogel-PCL scaffolds remained highly viable, even for long periods of incubation (7 days). Considering the obtained results, the produced hybrid scaffolds may be good candidates for future application in bone tissue engineering.

In Vitro and In Vivo Evaluation of a Polycaprolactone (PCL)/Polylactic-Co-Glycolic Acid (PLGA) (80:20) Scaffold for Improved Treatment of Chondral (Cartilage) Injuries

Articular cartilage is a specialized tissue that provides a smooth surface for joint movement and load transmission. Unfortunately, it has limited regenerative capacity. Tissue engineering, combining different cell types, scaffolds, growth factors, and physical stimulation has become an alternative for repairing and regenerating articular cartilage. Dental Follicle Mesenchymal Stem Cells (DFMSCs) are attractive candidates for cartilage tissue engineering because of their ability to differentiate into chondrocytes, on the other hand, the polymers blend like Polycaprolactone (PCL) and Poly Lactic-co-Glycolic Acid (PLGA) have shown promise given their mechanical properties and biocompatibility. In this work, the physicochemical properties of polymer blends were evaluated by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and were positive for both techniques. The DFMSCs demonstrated stemness by flow cytometry. The scaffold showed to be a non-toxic effect when we evaluated it with Alamar blue, and the samples were analyzed using SEM and phalloidin staining to evaluate cell adhesion to the scaffold. The synthesis of glycosaminoglycans was positive on the construct in vitro. Finally, the PCL/PLGA scaffold showed a better repair capacity than two commercial compounds, when tested in a chondral defect rat model. These results suggest that the PCL/PLGA (80:20) scaffold may be suitable for applications in the tissue engineering of articular hyaline cartilage.

Cyclodextrin Derivatives as Promising Solubilizers to Enhance the Biological Activity of Rosmarinic Acid

Rosmarinic acid (RA) is a natural antioxidant with neuroprotective properties; however, its preventive and therapeutic use is limited due to its slight solubility and poor permeability. This study aimed to improve RA physicochemical properties by systems formation with cyclodextrins (CDs): hydroxypropyl-α-CD (HP-α-CD), HP-β-CD, and HP-γ-CD, which were prepared by the solvent evaporation (s.e.) method. The interactions between components were determined by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and Fourier Transform infrared spectroscopy (FTIR). The sites of interaction between RA and CDs were suggested as a result of in silico studies focused on assessing the interaction between molecules. The impact of amorphous systems formation on water solubility, dissolution rate, gastrointestinal (GIT) permeability, and biological activity was studied. RA solubility was increased from 5.869 mg/mL to 113.027 mg/mL, 179.840 mg/mL, and 194.354 mg/mL by systems formation with HP-α-CD, HP-β-CD, and HP-γ-CD, respectively. During apparent solubility studies, the systems provided an acceleration of RA dissolution. Poor RA GIT permeability at pH 4.5 and 5.8, determined by parallel artificial membrane permeability assay (PAMPA system), was increased; RA–HP-γ-CD s.e. indicated the greatest improvement (at pH 4.5 from P_app 6.901 × 10⁻⁷ cm/s to 1.085 × 10⁻⁶ cm/s and at pH 5.8 from 5.019 × 10⁻⁷ cm/s to 9.680 × 10⁻⁷ cm/s). Antioxidant activity, which was determined by DPPH, ABTS, CUPRAC, and FRAP methods, was ameliorated by systems; the greatest results were obtained for RA–HP-γ-CD s.e. The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was increased from 36.876% for AChE and 13.68% for BChE to a maximum inhibition of the enzyme (plateau), and enabled reaching IC₅₀ values for both enzymes by all systems. CDs are efficient excipients for improving RA physicochemical and biological properties. HP-γ-CD was the greatest one with potential for future food or dietary supplement applications.

Electrospinning of Biomedical Nanofibers/Nanomembranes: Effects of Process Parameters

Nanotechnology has attracted great attention from researchers in modern science because nanomaterials have innovative and superior physical, chemical, and biological properties, and they can be altered and modified accordingly. As particles get smaller, their surface area increases compared to their volume. Electrospinning is one of the advanced techniques to produce ultrathin nanofibers and membranes, and it is one of the best ways to create continuous nanomaterials with variable biological, chemical, and physical properties. The produced fibers can be utilized in various domains such as wound dressing, drug release, enzyme immobilization, etc. This review examines the biomedical nanofibers/membranes produced by electrospinning techniques to investigate the effects of process parameters (e.g., solution characteristics, applied voltage, and ambient conditions) on nanofiber characteristics (physical, chemical, and mechanical properties). The solution parameters like (i) optimum concentration, (ii) higher molecular weight, and (iii) higher conductivity produce uniform nanofibers, smoother nanofibers, and a smaller and more uniform fiber diameter, respectively. In addition, process parameters such as (i) higher voltage and (ii) slower flow rate produce more polymer ejection from the nozzle and enhance the smoother fiber production, respectively. The optimum tip-to-collector distance is considered to be 13-15 cm. The ambient conditions such as (i) higher humidity and (ii) higher temperature produce thicker and thinner nanofibers, respectively. The controlled parameters through optimization process determine the size and quality of the fibers. The effects of each parameter are discussed in this review. The applications of nanofibers are also discussed.

Electrospun Polymer-Free Nanofibers Incorporating Hydroxypropyl-β-cyclodextrin/Difenoconazole via Supramolecular Assembly for Antifungal Activity

In this study, flexible and self-standing hydroxypropyl-β-cyclodextrin/difenoconazole inclusion complex (HPβCD/DZ-IC) nanofibers were prepared by polymer-free electrospinning, which exhibited potential to be a new fast-dissolving pesticide formulation. Scanning electron microscopy and optical microscopy were applied to evaluate the morphology of nanofibers, which showed that the resulting HPβCD/DZ-IC nanofibers were bead-free and uniform. In addition, the proton nuclear magnetic resonance (¹H NMR) spectrum suggested a stoichiometric ratio of 1:0.9 (HPβCD/DZ). Other characterization methods, such as UV-vis absorption, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), were applied in this study. On the one hand, UV-vis absorption, fluorescence spectroscopy, FT-IR, XRD, and TGA provided useful information for the successful formation of an inclusion complex; on the other hand, the results of TGA indicated the thermal stability of DZ was enhanced after the formation of inclusion complexes. Besides, the phase solubility test could explain the increased water solubility of the nanofibers of inclusion complexes formed by DZ and HPβCD. The results of molecular docking studies demonstrated the most favorable binding interactions when HPβCD combined with DZ. The dissolution test and the antifungal performance test exhibited the characteristics of fast dissolution and the excellent antifungal performance of HPβCD/DZ-IC nanofibers, respectively.

Fabrication of Poly(Ethylene-glycol 1,4-Cyclohexane Dimethylene-Isosorbide-Terephthalate) Electrospun Nanofiber Mats for Potential Infiltration of Fibroblast Cells

Recently, bio-based electrospun nanofiber mats (ENMs) have gained substantial attention for preparing polymer-based biomaterials intended for use in cell culture. Herein, we prepared poly(ethylene-glycol 1,4-Cyclohexane dimethylene-isosorbide-terephthalate) (PEICT) ENMs using the electrospinning technique. Cell adhesion and cell viability of PEICT ENMs were checked by fibroblast cell culture. Field emission electron microscope (FE-SEM) image showed a randomly interconnected fiber network, smooth morphology, and cell adhesion on PEICT ENM. Fibroblasts were cultured in an adopted cell culturing environment on the surface of PEICT ENMs to confirm their biocompatibility and cell viability. Additionally, the chemical structure of PEICT ENM was checked under Fourier-transform infrared (FTIR) spectroscopy and the results were supported by -ray photoelectron (XPS) spectroscopy. The water contact angle (WCA) test showed the hydrophobic behavior of PEICT ENMs in parallel to good fibroblast cell adhesion. Hence, the results confirmed that PEICT ENMs can be potentially utilized as a biomaterial.

Biocompatible Polymers Combined with Cyclodextrins: Fascinating Materials for Drug Delivery Applications

Cyclodextrins (CD) are a group of cyclic oligosaccharides with a cavity/specific structure that enables to form inclusion complexes (IC) with a variety of molecules through non-covalent host-guest interactions. By an elegant combination of CD with biocompatible, synthetic and natural polymers, different types of universal drug delivery systems with dynamic/reversible properties have been generated. This review presents the design of nano- and micro-carriers, hydrogels, and fibres based on the polymer/CD supramolecular systems highlighting their possible biomedical applications. Application of the most prominent hydrophobic aliphatic polyesters that exhibit biodegradability, represented by polylactide and polycaprolactone, is described first. Subsequently, particular attention is focused on materials obtained from hydrophilic polyethylene oxide. Moreover, examples are also presented for grafting of CD on polysaccharides. In summary, we show the application of host-guest interactions in multi-component functional biomaterials for controlled drug delivery.

Electrospun Bioresorbable Membrane Eluting Chlorhexidine for Dental Implants

To prevent the uncontrolled development of a pathogenic biofilm around a dental implant, an antimicrobial drug-release electrospun membrane, set up between the implant and the gingival tissue, was developed by taking several technical, industrial and regulatory specifications into account. The membrane formulation is made of a blend of poly(l-lactic–co–gycolic acid) (PLGA, 85:15) and poly(l-lactic acide–co–ɛ-caprolactone) (PLC, 70:30) copolymers with chlorhexidine diacetate (CHX) complexed with β-cyclodextrin (CD). The amount of residual solvent, the mechanical properties and the drug release kinetics were tuned by the copolymers’ ratio, between 30% and 100% of PLC, and a CHX loading up to 20% w/w. The membranes were sterilized by γ-irradiation without significant property changes. The fiber′s diameter was between 600 nm and 3 µm, depending on the membrane composition and the electrospinning parameters. CHX was released in vitro over 10 days and the bacterial inhibitory concentration, 80 µg·mL⁻¹, was reached within eight days. The optimal membrane, PGLA/PLC/CHX-CD (60%/40%/4%), exhibited a breaking strain of 50%, allowing its safe handling. This membrane and a membrane without CHX-CD were implanted subcutaneous in a rat model. The cell penetration remained low. The next step will be to increase the porosity of the membrane to improve the dynamic cell penetration and tissue remodeling.

Nanostructured and Photochromic Material for Environmental Detection of Metal Ions

Compared to conventional spectroscopy or chromatography analysis, chemical sensing based on colorimetric changes offers an alternative to monitor potential metal hazards in aqueous environment through rapid and low-cost colorimetric changes which can be easily interpreted. In this work poly(ethylene glycol) (PEG 2000) was modified with a carboxylic acid spiropyran (SPCOOH) derivate by Steglich esterification (PEGSP2). PEGSP2 was incorporated into a poly(ε-caprolactone) (PCL) polymer matrix by electrospinning technique to produce nanofibers with photochromic properties. Spectroscopic analysis, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to characterize PEGSP2. Drop shape analysis (DSA) and scanning electronic microscopy (SEM) were used to characterize the electrospun (ES) nanofibers morphology. Several metal ions solutions relevant to environmental hazards were prepared to be spotted on the surface of ES nanofibers for photochromatic sensing. Among them, Mg²⁺, Ca²⁺, Zn²⁺, Cd²⁺, La³⁺, and Er³⁺ demonstrated orange fluorescence when exposed to UV light. ES nanofibers also presented higher wettability when compared to a pure PCL polymer matrix, which is critical for sensitivity. Eighteen metals ions could be detected on the electrospun material. Additionally, among all metal ions Fe³⁺ was the most sensitive one in solution, in a µmol L⁻¹ range.

Complex systems that incorporate cyclodextrins to get materials for some specific applications

Cyclodextrins (CDs) are a family of biodegradable cyclic hydrocarbons composed of α-(1,4) linked glucopyranose subunits, the more common containing 6, 7 or 8 glucose units are named α, β and γ-cyclodextrins respectively. Since the discovery of CDs, they have attracted interest among scientists and the first studies were about the properties of the native compounds and in particular their use as catalysts of organic reactions. Characteristics features of different types of cyclodextrins stimulated investigation in different areas of research, due to its non-toxic and non-inmunogenic properties and also to the development of an improved industrial production. In this way, many materials with important properties have been developed. This mini-review will focus on chemical systems that use cyclodextrins, whatever linked covalently or mediated by the non covalent interactions, to build complex systems developed mainly during the last five years.

Host⁻Guest Polymer Complexes

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