Mussel inspired coating of a biocompatible cyclodextrin based polymer onto CoCr vascular stents

Limitation of the migration of plasticizers from medical devices through treatment with low-pressure cold plasma, polydopamine coating, and annealing

Poly(vinyl chloride) (PVC) is widely used in the manufacture of medical devices. The plasticizers added to PVC are potentially toxic for humans, likely to migrate, and thus unintentionally administered to patients. The objective of the present study was to reduce the migration of plasticizer (1,2-cyclohexanedicarboxylic acid, diisononylester (DINCH) or trioctyltrimellitate (TOTM)) from PVC by implementing a three-step surface treatment process: (i) pretreatment with low-pressure argon cold plasma, (ii) polydopamine coating, and (iii) post-treatment with cold plasma exposure or thermal treatment at 140 °C. Samples were then characterized in terms of the water contact angle (WCA) and the aspect in scanning electron microscopy. Plasticizer migration (n = 5) was measured using an HPLC technique with ultraviolet detection and found to depend on the treatment and the plasticizer. Plasticized PVC was hydrophobic, with a measured mean ± standard deviation WCA of 96.7 ± 3.6° for PVC-DINCH and 110.2 ± 5.8° for PVC-TOTM. Plasma post-treatment and thermal post-treatment were respectively associated with a mean decrease in migration of 38.3 ± 1.9% for DINCH and 61.5 ± 4.4% for TOTM. Our results are promising with regard to limiting the migration of plasticizers into the patient's blood and thus enabling the development of safer medical devices.

Multiple-ion Management of Perovskites by Regulating Spatial Distribution of Hydroxyls in Oligosaccharides

Suppressing migrations of intrinsic and extrinsic ions (e.g., Pb2+ , I- , FA+ /MA+ , and Li+ ) in organic-inorganic hybrid perovskites is critical for alleviating the hysteresis and degradation of perovskite solar cells (PSCs). However, various additives reported for that purpose usually interact with one or two types of those ions, not inhibiting multiple-ion migrations simultaneously. Two oligosaccharides (β-cyclodextrin (β-CD) and maltotetraose (G4)), containing 14 hydroxyls (-OH) with different spatial distributions, for the suppression of multiple-ion migrations in PSCs is herein employed. Compared to linear arrangement of -OH in G4, annular distribution of -OH around wide and narrow rims of β-CD can form supramolecular multi-site interactions in a focal manner with various ions, more effectively capturing and immobilizing these migrated ions. With this multiple-ion management strategy, β-CD-based PSCs exhibit an impressive efficiency of 24.22% with negligible hysteresis and excellent device stability. This work highlights the significances of multi-site interactions and molecular configuration of the additive for inhibiting multi-ion migrations in PSCs.

Improving Biocompatibility for Next Generation of Metallic Implants

The increasing need for joint replacement surgeries, musculoskeletal repairs, and orthodontics worldwide prompts emerging technologies to evolve with healthcare's changing landscape. Metallic orthopaedic materials have a shared application history with the aerospace industry, making them only partly efficient in the biomedical domain. However, suitability of metallic materials in bone tissue replacements and regenerative therapies remains unchallenged due to their superior mechanical properties, eventhough they are not perfectly biocompatible. Therefore, exploring ways to improve biocompatibility is the most critical step toward designing the next generation of metallic biomaterials. This review discusses methods of improving biocompatibility of metals used in biomedical devices using surface modification, bulk modification, and incorporation of biologics. Our investigation spans multiple length scales, from bulk metals to the effect of microporosities, surface nanoarchitecture, and biomolecules such as DNA incorporation for enhanced biological response in metallic materials. We examine recent technologies such as 3D printing in alloy design and storing surface charge on nanoarchitecture surfaces, metal-on-metal, and ceramic-on-metal coatings to present a coherent and comprehensive understanding of the subject. Finally, we consider the advantages and challenges of metallic biomaterials and identify future directions.

Coatings of Cyclodextrin/Citric-Acid Biopolymer as Drug Delivery Systems: A Review

In the early 2000s, a method for cross-linking cyclodextrins (CDs) with citric acid (CTR) was developed. This method was nontoxic, environmentally friendly, and inexpensive compared to the others previously proposed in the literature. Since then, the CD/CTR biopolymers have been widely used as a coating on implants and other materials for biomedical applications. The present review aims to cover the chemical properties of CDs, the synthesis routes of CD/CTR, and their applications as drug-delivery systems when coated on different substrates. Likewise, the molecules released and other pharmaceutical aspects involved are addressed. Moreover, the different methods of pretreatment applied on the substrates before the in situ polymerization of CD/CTR are also reviewed as a key element in the final functionality. This process is not trivial because it depends on the surface chemistry, geometry, and physical properties of the material to be coated. The biocompatibility of the polymer was also highlighted. Finally, the mechanisms of release generated in the CD/CTR coatings were analyzed, including the mathematical model of Korsmeyer-Peppas, which has been dominantly used to explain the release kinetics of drug-delivery systems based on these biopolymers. The flexibility of CD/CTR to host a wide variety of drugs, of the in situ polymerization to integrate with diverse implantable materials, and the controllable release kinetics provide a set of advantages, thereby ensuring a wide range of future uses.

Polydopamine treatment of chitosan nanofibers for the conception of osteoinductive scaffolds for bone reconstruction

We report the influence of treatment time of electrospun chitosan nanofibers (CHT NFs) in dopamine hydrochloride bath (2 mg.mL^-1 in 10 mM Tris buffer, pH 8.5) on the extent of the polydopamine (pDA) coating on NFs surface. The reaction was characterized by FTIR and SEM analysis and the cytocompatibility of the scaffolds toward MT3C3-E1 cells was assessed. Biomimetic deposition of hydroxyapatite (HA) in 1.5xSBF batch was investigated by SEM-EDS and XRD. Samples treated in dopamine bath during 2 h promoted the structural stability of NFs in PBS, provided optimal cytocompatibility and induced the in vitro biomineralization from 6 days in 1.5xSBF. The XRD and SEM-EDS investigations confirmed formation of spherical-shaped particles composed of apatitic phase. Finally, this study shows that these NFs-pDA scaffolds prepared in the optimal experimental conditions defined here are promising candidates for application as osteoinductive scaffolds for bone regeneration applied to orthopedic and dental applications.

4D Printing of Shape Memory Vascular Stent Based on βCD-g-Polycaprolactone

The 4D-printing technology is applied to fabricate a shape memory peripheral stent with good biocompatibility, which sustains long-term drug release. The star polymer s-PCL is prepared by ring opening polymerization of ε-caprolactone with the -OH of β-cyclodextrin (βCD) as initiator, and then the s-PCL is modified with acrylate endgroup which allows the polymerization under UV light to form the crosslinking network c-PCL. Attributed to the feature of the high crosslinked structure and chemical nature of polycaprolactone (PCL) and βCD, the composite exhibits appropriate tensile strength and sufficient elasticity and bursting pressure, and it is comparable with great saphenous vein in human body. The radial support of the 4D-printed stent is 0.56 ± 0.11 N and is equivalent to that of commercial stent. The cell adhesion and proliferation results show a good biocompatibility of the stent with human umbilical vein endothelial cells. Due to the presence of βCD, the wettability and biocompatibility of the materials are improved, and the sustained paclitaxel release based on the host-guest complexion shows the potential of the drug-loaded stent for long-term release. This study provides a new strategy to solve the urgent need of small-diameter scaffolds to treat critical limb ischemia.

Polydopamine-coated curdlan hydrogel as a potential carrier of free amino group-containing molecules

Curdlan hydrogel obtained after thermal gelling exhibits elasticity and high water-absorbing capacity. However, its modifications leading to the increase of biofunctionality usually alter its solubility and reduce mechanical parameters. Therefore, curdlan hydrogel was modified by deposition of polydopamine to improve its capacity to bind biologically active molecules with free amino groups. It exhibited the unchanged structure, mechanical properties and increased soaking capacity. Aminoglycoside antibiotic (gentamicin) as a model molecule was effectively immobilized to such modified curdlan via quinone moiety (but not amino groups) of polydopamine. Approximately 50 % of the immobilized drug was released following Fickian diffusion and inhibited the bacterial growth in matrix-surrounding medium in prolonged manner. The remaining drug amount was stably attached and prevented the hydrogel against bacterial adhesion even when all the mobile drug has been released. Therefore, polydopamine-modified curdlan hydrogel shows the potential for fabrication of functional materials for different purposes, including drug-loaded biomaterials.

In vivo evaluation of a pro-healing polydopamine coated stent through an in-stent restenosis rat model

Drug-eluting stents have demonstrated efficiency in in-stent restenosis (ISR) but induced a risk of late acute thrombosis by delaying strut re-endothelialization. Polydopamine (PDA), a biocompatible polymer inspired from adhesive proteins of mussels, has been reported to promote endothelial cell (EC) proliferation while limiting SMC proliferation in vitro, thus suggesting the pro-healing potential. This study aimed at evaluating in vivo the impact of the pro-healing PDA-coated stent on ISR and on the quality of the strut re-endothelialization in a rat model. PDA-coated stents demonstrated a significant reduction in ISR in vivo compared to bare metal stents (ratio neointima/media = 0.48 (±0.26) versus 0.83 (±0.42), p < 0.001). Western blot analyses identified a trend towards an increased activation of p38 MAPK phosphorylation and its anti-proliferative effects on vascular SMC that could explain the results observed in morphological analyses. This bioinspired and biocompatible polydopamine layer could intrinsically limit ISR. In addition, according to its latent reactivity, PDA offers the possibility to immobilize some relevant drugs on the PDA-functionalized stent to provide potential synergistic effects.

Silica Mesoporous Structures: Effective Nanocarriers in Drug Delivery and Nanocatalysts

The application of silica mesoporous structures in drug delivery and the removal of pollutants and organic compounds through catalytic reactions is increasing due to their unique characteristics, including high loading capacities, tunable pores, large surface areas, sustainability, and so on. This review focuses on very well-studied class of different construction mesoporous silica nano(particles), such as MCM-41, SBA-15, and SBA-16. We discuss the essential parameters involved in the synthesis of these materials with providing a diverse set of examples. In addition, the recent advances in silica mesoporous structures for drug delivery and catalytic applications are presented to fill the existing gap in the literature with providing some promising examples on this topic for the scientists in both industry and academia active in the field. Regarding the catalytic applications, mesoporous silica particles have shown some promises to remove the organic pollutants and to synthesize final products with high yields due to the ease with which their surfaces can be modified with various ligands to create appropriate interactions with target molecules. In the drug delivery process, as nanocarriers, they have also shown very good performance thanks to the easy surface functionalization but also adjustability of their porosities to providing in-vivo and in-vitro cargo delivery at the target site with appropriate rate.

Cyclodextrin Cationic Polymer-Based Nanoassemblies to Manage Inflammation by Intra-Articular Delivery Strategies

Injectable nanobioplatforms capable of locally fighting the inflammation in osteoarticular diseases, by reducing the number of administrations and prolonging the therapeutic effect is highly challenging. β-Cyclodextrin cationic polymers are promising cartilage-penetrating candidates by intra-articular injection due to the high biocompatibility and ability to entrap multiple therapeutic and diagnostic agents, thus monitoring and mitigating inflammation. In this study, nanoassemblies based on poly-β-amino-cyclodextrin (PolyCD) loaded with the non-steroidal anti-inflammatory drug diclofenac (DCF) and linked by supramolecular interactions with a fluorescent probe (adamantanyl-Rhodamine conjugate, Ada-Rhod) were developed to manage inflammation in osteoarticular diseases. PolyCD@Ada-Rhod/DCF supramolecular nanoassemblies were characterized by complementary spectroscopic techniques including UV-Vis, steady-state and time-resolved fluorescence, DLS and ζ-potential measurement. Stability and DCF release kinetics were investigated in medium mimicking the physiological conditions to ensure control over time and efficacy. Biological experiments evidenced the efficient cellular internalization of PolyCD@Ada-Rhod/DCF (within two hours) without significant cytotoxicity in primary human bone marrow-derived mesenchymal stromal cells (hMSCs). Finally, polyCD@Ada-Rhod/DCF significantly suppressed IL-1β production in hMSCs, revealing the anti-inflammatory properties of these nanoassemblies. With these premises, this study might open novel routes to exploit original CD-based nanobiomaterials for the treatment of osteoarticular diseases.

Immobilisation of an anti-platelet adhesion and anti-thrombotic drug (EP224283) on polydopamine coated vascular stent promoting anti-thrombogenic properties

Current vascular drug-eluting stents based on immuno-proliferative drugs would reduce the rate of in-stent restenosis (ISR) but may be associated with a higher risk of acute stent thrombosis due to non-selective activity. In this paper, we aimed to develop a polydopamine (PDA) coated chromium‑cobalt (CoCr) stent functionalised with EP224283 (Endotis Pharma SA), which combines both a GPIIbIIIa antagonist (tirofiban moiety) and a factor Xa inhibitor (idraparinux moiety) to reduce acute stent thrombosis. PDA-coated chromium‑cobalt (CoCr) samples were first immersed in a polyethylenimine (PEI, pH 8.5) solution to increase amine function density (36.0 ± 0.1 nmol/cm²) on the CoCr surface. In a second step, avidin was grafted onto CoCr-PDA-PEI through the biotin linkage (strategy 1) or directly by coupling reactions (strategy 2). The HABA titration proved the fixation of biotin onto CoCr-PDA-PEI surface with a density of 0.74 nmol/cm². The fixation of avidin was demonstrated by water contact angle (WCA) and surface plasmon resonance (SPR). SEM micrograph shows the flexibility of the thin layer coated onto the stent after balloon inflation. Independently of the strategy, a qualitative SEM analysis showed a reduction in platelet activation when the molecule EP224283 was immobilised on avidin. In parallel, the measurement of anticoagulant activity (anti-Xa) revealed a higher anti-factor Xa activity (2.24 IU/mL vs. 0.09 IU/mL in control) when EP224283 was immobilised on avidin. Interestingly, after seven days of degradation, the anticoagulant activity was persistent in both strategies and looked more important with the strategy 2 than in strategy 1. Throughout this work, we developed an innovative vascular stent through the immobilisation of EP224283 onto CoCr-PDA-PEI-(avidin) system, which provides a promising solution to reduce ISR and thrombosis after stent implantation.

Stent coating by electrospinning with chitosan/poly-cyclodextrin based nanofibers loaded with simvastatin for restenosis prevention

The main cause of failure of angioplasty stenting is restenosis due to neointimal hyperplasia, a too high proliferation of smooth muscle cells (SMC). The local and sustained delivery of selective pleiotropic drugs to limit SMC proliferation seems to be the hopeful solution to minimize this post surgery complication. The aim of this study is to develop a stent covered by nanofibers (NFs) produced by electrospinning, loaded with simvastatin (SV), a drug commonly used for restenosis prevention. NFs were prepared from the electrospinning of a solution containing SV and a mixture of chitosan (cationic) and β-cyclodextrin (CD) polymer (anionic) which form together a polyelectrolyte complex that makes up the NFs matrix. First, the SV/CD interactions were studied by phase solubility diagram, DRX and DSC. The electrospinning process was then optimized to cover a self-expandable NiTiNOL stent and the mechanical resistance of the NFs sheath upon its introduction inside the delivery catheter was considered, using a crimper apparatus. The morphology, coating thicknesses and diameters of nanofibers were studied by scanning electron microscopy. The SV loading rates on the stents were controlled by the electrospinning time, and the presence of SV in the NFs was confirmed by FTIR. NFs stability in PBS pH 7.4 buffer could be improved after thermal post-treatment of NFs and in vitro release of SV in dynamic conditions demonstrated that the release profiles were influenced by the presence of CD polymer in NFs and by the thickness of the NFs sheath. Finally, a covered stent delivering 3 µg/mm² of SV within 6 h was obtained, whose efficiency will be investigated in a further in vivo study.

Fabrication of Curcumin-Modified TiO2 Nanoarrays via Cyclodextrin Based Polymer Functional Coatings for Osteosarcoma Therapy

The incomplete removal of bone tumors leads to increased local recurrence and poor prognosis. To prevent ostoperative tumor recurrence and simultaneously repair surgery-caused bone defects, there is a need of great significance to develop implantable biomaterials possessing both cancer cell-killing ability and excellent bioactivity. In this work, a functionalized titanium-based implant is successfully fabricated by loading curcumin (CUR) onto cyclodextrin based polymer (pCD) modified titanium dioxide (TiO₂ ) nanorod arrays. Herein, a polydopamine (pDA) assisted film is implemented as a first coating layer onto the surface of the TiO₂ nanoarrays to guarantee the robust anchorage of the pCD. The pCD coating acts as a reservoir for CUR, allowing for efficient drug loading and sustained release of anticancer drugs. Studies show that the CUR-modified surfaces (TiO₂ /pDA/pCD/CUR) can significantly promote apoptosis of osteosarcoma cells in vitro by inducing mitochondrial dysfunction caused by the ROS overproduction, and meanwhile, effectively inhibit the tumor growth in vivo. Moreover, such functionalized implants with surface density of loaded CUR at 22.48 µg cm^-2 or lower support the attachment and proliferation of osteoblasts in vitro. These results successfully demonstrate that as-prepared TiO₂ /pDA/pCD/CUR constructs have combined anticancer performance and good biocompatibility, which has great promise for the surgical therapy of bone tumors.

Antifouling amphiphilic silicone coatings for dairy fouling mitigation on stainless steel

Pasteurization of dairy products is plagued by fouling, which induces significant economic, environmental and microbiological safety concerns. Herein, an amphiphilic silicone coating was evaluated for its efficacy against fouling by a model dairy fluid in a pilot pasteurizer and against foodborne bacterial adhesion. The coating was formed by modifying an RTV silicone with a PEO-silane amphiphile comprised of a PEO segment and flexible siloxane tether ([(EtO)₃Si-(CH₂)₂-oligodimethylsiloxane_m-block-(OCH₂CH₂)_n-OCH₃]). Contact angle analysis of the coating revealed that the PEO segments were able to migrate to the aqueous interface. The PEO-modified silicone coating applied to pretreated stainless steel was exceptionally resistant to fouling. After five cycles of pasteurization, these coated substrata were subjected to a standard clean-in-place process and exhibited a minor reduction in fouling resistance in subsequent tests. However, the lack of fouling prior to cleaning indicates that harsh cleaning is not necessary. PEO-modified silicone coatings also showed exceptional resistance to adhesion by foodborne pathogenic bacteria.

Water-Dispersible Polydopamine-Coated Nanofibers for Stimulation of Neuronal Growth and Adhesion

Hybrid nanomaterials have shown great potential in regenerative medicine due to the unique opportunities to customize materials properties for effectively controlling cellular growth. The peptide nanofiber-mediated auto-oxidative polymerization of dopamine, resulting in stable aqueous dispersions of polydopamine-coated peptide hybrid nanofibers, is demonstrated. The catechol residues of the polydopamine coating on the hybrid nanofibers are accessible and provide a platform for introducing functionalities in a pH-responsive polymer analogous reaction, which is demonstrated using a boronic acid modified fluorophore. The resulting hybrid nanofibers exhibit attractive properties in their cellular interactions: they enhance neuronal cell adhesion, nerve fiber growth, and growth cone area, thus providing great potential in regenerative medicine. Furthermore, the facile modification by pH-responsive supramolecular polymer analog reactions allows tailoring the functional properties of the hybrid nanofibers in a reversible fashion.

Current Options and Emerging Biomaterials for Periprosthetic Joint Infection

PURPOSE OF REVIEW

Infection in the setting of total joint arthroplasty, referred to as periprosthetic joint infection (PJI), is a devastating complication requiring prolonged and costly treatment. The unique environment around an artificial joint and ability of surrounding tissues to sequester bacteria collectively make prevention, diagnosis, and treatment of this condition challenging. In light of the unique pathogenesis of PJI, this review explores the limitations of contemporary treatments and discusses novel treatment options.

RECENT FINDINGS

Recent advancements in local antibiotic delivery platforms for preventing and treating PJI include titanium nanotube arrays, synthetic polymers, resorbable hydrogels, and cyclodextrin-based drug delivery options. In particular, cyclodextrins have facilitated great advancements in other clinical disorders and have demonstrated early promise as a future option in the arena of PJI. Novel treatment modalities for PJI optimize the implant surfaces to prevent bacterial biofilm formation or provide prolonged intra-articular antibiotic dosing to eradicate bacteria.

Embedding Well-Defined Responsive Hydrogels with Nanocontainers: Tunable Materials from Telechelic Polymers and Cyclodextrins

Design, synthesis, and application of cyclodextrin (CD) containing thermoresponsive hydrogels fabricated from thiol-reactive telechelic polymers are reported. Hydrophilic polymers containing 2-hydroxyethyl methacrylate and/or di(ethylene glycol)methylether methacrylate monomers as side chains and thiol-reactive groups at chain ends were synthesized. A series of hydrogels was fabricated using thiol-ene conjugation of these thiol-reactive polymers with multivalent thiol-containing CDs as crosslinkers. Clear and transparent hydrogels were obtained with good conversion (79-89%) by utilizing the "nucleophilic" and "radical" thiol-ene "click" reactions. Analysis of the amount of residual thiol groups in these hydrogels using Ellman's reagent suggested that gels with a moderately well-defined network structure were obtained. Hydrogels fabricated using different telechelic polymers were examined for their properties such as morphology, equilibrium water uptake, and rheological characteristics. Cytocompatibility of these hydrogels was ascertained by a cell viability assay that demonstrated low toxicity toward fibroblast cells. Thereafter, the CD-containing hydrogels were evaluated for the loading and controlled release of puerarin, an antiglaucoma drug. Utilization of thermoresponsive polymers as the matrix for these hydrogels allows use of temperature as a stimulus to modulate the drug release. A slower and more sustained drug release was observed at physiological temperatures compared to ambient conditions. The effect of temperature on the elasticity of the hydrogel was investigated rheologically to demonstrate that the collapse of the network structure occurs near physiological temperatures. The increased hydrophobicity and compactness of the gel matrix at higher temperatures results in a slower drug release. The strategy employed here demonstrates that tuning the matrix composition of hydrogels with well-defined network structures through appropriate choice of responsive copolymers allows design of materials with control of their physical properties and drug-release behavior.

Specific Binding of Liposomal Nanoparticles through Inverse Electron-Demand Diels-Alder Click Chemistry

Here, we report a method to specifically bind liposomal radiopharmaceuticals to a CoCrMo alloy, which can be used in arterial stents, via an irreversible inverse electron‐demand Diels–Alder reaction. Inspired by recent accomplishments in pre‐targeted imaging using tetrazine‐trans‐cyclooctene click chemistry, we synthesized ⁸⁹Zr‐labeled trans‐cyclooctene‐functionalized liposomal nanoparticles, which were validated on a tetrazine‐appended polydopamine‐coated CoCrMo surface. In efforts to ultimately translate this new material to biomedical applications, we compared the ability of ⁸⁹Zr‐TCO–liposomal nanoparticles (⁸⁹Zr‐TCO‐LNP) to be immobilized on the tetrazine surface to the control suspensions of non‐TCO functionalized ⁸⁹Zr‐liposomal nanoparticles. Ultimately, this platform technology could result in a systemic decrease of the radiotherapeutic dose deposited in non‐targeted tissues by specific removal of long‐circulating liposomal radiopharmaceuticals from the blood pool.

Cyclodextrin modified PLLA parietal reinforcement implant with prolonged antibacterial activity

The use of textile meshes in hernia repair is widespread in visceral surgery. Though, mesh infection is a complication that may prolong the patient recovery period and consequently presents an impact on public health economy. Such concern can be avoided thanks to a local and extended antibiotic release on the operative site. In recent developments, poly-l-lactic acid (PLLA) has been used in complement of polyethyleneterephthalate (Dacron®) (PET) or polypropylene (PP) yarns in the manufacture of semi-resorbable parietal implants. The goal of the present study consisted in assigning drug reservoir properties and prolonged antibacterial effect to a 100% PLLA knit through its functionalization with a cyclodextrin polymer (polyCD) and activation with ciprofloxacin. The study focused i) on the control of degree of polyCD functionalization of the PLLA support and on its physical and biological characterization by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and cell viability, ii) on the understanding of drug/meshes interaction using mathematic model and iii) on the correlation between drug release studies in phosphate buffer saline (PBS) and microbiological evaluation of meshes and release medium against E. coli and S. aureus. All above mentioned tests highlighted the contribution of polyCD on the improved performances of the resulting antibacterial implantable material.

STATEMENT OF SIGNIFICANCE

1. We managed for the first time, with well-defined parameters in terms of temperature and time of treatment, to functionalize a bio-absorbable synthetic material to improve drug sorption and drug release properties without affecting its mechanical properties. 2. We analyzed for the first time the degradation of our coating products by mass spectroscopy to show that only citrate and cyclodextrin residues (and glucose units) without any cytotoxicity are formed. 3. We managed to improve the mechanical properties of the PLA with the cyclodextrin polymer to form a composite. The assembly (cyclodextrin polymer and PLLA) remains biodegradable.

Reversible Tethering of Polymers onto Catechol-Based Titanium Platforms

In this article, we report on the reversible tethering of end-functionalized polymers onto catechol-based titanium platforms by exploiting the reversible Diels-Alder (DA) cycloaddition reaction. For this purpose, furan and maleimide end-functionalized polymers, prepared via reversible addition-fragmentation chain transfer polymerization, were covalently grafted through a DA reaction onto reactive titanium platforms elaborated from catechol-based anchors incorporating either the furan or the maleimide moiety. As a proof of concept, a hydrophilic poly(oligo(ethylene glycol)acrylate) (POEGA) and a hydrophobic poly(2,2,2-trifluoroethyl acrylate) (PTFEA) were grafted onto titanium surfaces and subsequently detached by exploiting the thermoreversible nature of the DA reaction [i.e., retro Diels-Alder (rDA)]. These polymers were interchanged by performing a second DA reaction, thereby allowing the titanium surface wettability to be switched from hydrophobic to hydrophilic on demand. The grafting of furan/maleimide end-functionalized polymers onto functionalized (maleimide/furan, respectively) catechol-based titanium platforms and the subsequent rDA/DA sequence used for switching the titanium surface were evidenced by attenuated total reflectance-Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements.

Poly(carboxylic acid)-Cyclodextrin/Anionic Porphyrin Finished Fabrics as Photosensitizer Releasers for Antimicrobial Photodynamic Therapy

In the development of new antibacterial therapeutic approaches to fight multidrug-resistant bacteria, antimicrobial photodynamic therapy (aPDT) represents a well-known alternative to treat local infections caused by different microorganisms. Here we present a polypropylene (PP) fabric finished with citrate-hydroxypropyl-βCD polymer (PP-CD) entrapping the tetra-anionic 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine (TPPS) as photosensitizer-eluting scaffold (PP-CD/TPPS) for aPDT. The concept is based on host-guest complexation of porphyrin in the cavities of CDs immobilized on the PP fibers, followed by its sustained and controlled delivery in release medium and simultaneous photoinactivation of microorganisms. Morphology of fabric was characterized by optical (OM) and scanning electron microscopies (SEM). Optical properties were investigated by UV-vis absorption, steady- and time-resolved fluorescence emission spectroscopy. X-ray photoelectron spectroscopy (XPS) and FT-IR revealed the surface chemical composition and the distribution map of the molecular components on the fabric, respectively. Direct ¹O₂ determination allowed to assess the potential photodynamic activity of the fabric. Release kinetics of TPPS in physiological conditions pointed out the role of the CD cavity to control the TPPS elution. Photoantimicrobial activity of the porphyrin-loaded textile was investigated against both Gram-positive Staphylococcus aureus ATCC 29213 (S. aureus) and Gram-negative Pseudomonas aeruginosa ATCC 27853 (P. aeruginosa). Optical microscopy coupled with UV-vis extinction and fluorescence spectra aim to ascertain the uptake of TPPS to S. aureus bacterial cells. Finally, PP-CD/TPPS fabric-treated S. aureus cells were photokilled of 99.98%. Moreover, low adhesion of S. aureus cells on textile was established. Conversely, no photodamage of fabric-treated P. aeruginosa cells was observed, together with their satisfying adhesion.

[Implants for drug substance delivery]

Implants for controlled drug delivery can be very helpful to improve the therapeutic efficacy of a medical treatment, and at the same time reduce the risk of toxic side effects. In this article, four different strategies are exemplarily presented: hybrid bone substitutes combining hydroxyapatite and chitosan hydrogels; vascular stents coated with a bio-inspired polymer; cochlear implants for local dexamethasone delivery; and in-situ forming implants for periodontitis treatment. But this is only a restricted selection, and numerous other approaches and applications based on implants releasing a drug (or a combination of drugs) exist. Compared to conventional implants or pharmaceutical dosage forms, they might offer decisive advantages.

New multifunctional pharmaceutical excipient in tablet formulation based on citric acid-cyclodextrin polymer

A β-cyclodextrin (β-CD) polymer obtained by crosslinking β-CD with citric acid in its water-insoluble (PCD-I) and soluble (PCD-S) forms was used as a multifunctional direct compression excipient for tablet designing. PCD-I powder was obtained after grinding the solid fraction through a 200μm grid. PCD-S powder was recovered after lyophilization or spray drying of the PCD-S aqueous solutions, eventually followed by a wet granulation step. Both PCD-I and PCD-S powders were characterized, separately and mixed in variable ratios, based on dynamic water vapor sorption, SEM, particle size distribution, tapped density, compressibility, and flowability. PCD-I and spray dried and lyophilized/wet granulated PCD-S, as well as the mixture PCD-I/PCD-S=90/10, presented optimal free flowing characteristics. Then, PCD-I or PCD-S powders - separately or mixed in variable ratios - were used for tablets preparation by direct compression without adding any other excipient (e.g. binder, lubricant, disintegrant etc). As PCD-I decreased, tablets resistance to crushing and disintegration time increased from 15s to 15min (against 30min for β-CD), showing the improved disintegrant functionality of PCD-I, that rapidly swelled once in contact with water. Finally, PCD was force-fed to Sprague-Dawley rats (2g/kg) which were then observed during 14days for any clinical signs of toxicity.

Recent developments in poly(dopamine)-based coatings for biomedical applications

The success of polymer coatings for biomedical applications is undeniable. Among the very successful examples are poly(dopamine) (PDA) films due to their simplicity in deposition and beneficial interaction with biomolecules and cells. The aim of this review is to highlight the findings and achievement of PDA in nanomedicine since 2011. We discuss the progress that has been made to elucidate the structure of PDA and novel aspects considering the assembly of PDA-based films on diverse substrates. We highlight the newest results considering the biological evaluation PDA-based coatings to control cell behavior and the use of PDA in biosensing. The popularity of PDA remains unchanged, but the research efforts start to be consolidated toward more specific aims and clinical applications.

EDTA-Cross-Linked β-Cyclodextrin: An Environmentally Friendly Bifunctional Adsorbent for Simultaneous Adsorption of Metals and Cationic Dyes

The discharge of metals and dyes poses a serious threat to public health and the environment. What is worse, these two hazardous pollutants are often found to coexist in industrial wastewaters, making the treatment more challenging. Herein, we report an EDTA-cross-linked β-cyclodextrin (EDTA-β-CD) bifunctional adsorbent, which was fabricated by an easy and green approach through the polycondensation reaction of β-cyclodextrin with EDTA as a cross-linker, for simultaneous adsorption of metals and dyes. In this setting, cyclodextrin cavities are expected to capture dye molecules through the formation of inclusion complexes and EDTA units as the adsorption sites for metals. The adsorbent was characterized by FT-IR, elemental analysis, SEM, EDX, ζ-potential, and TGA. In a monocomponent system, the adsorption behaviors showed a monolayer adsorption capacity of 1.241 and 1.106 mmol g(-1) for Cu(II) and Cd(II), respectively, and a heterogeneous adsorption capacity of 0.262, 0.169, and 0.280 mmol g(-1) for Methylene Blue, Safranin O, and Crystal Violet, respectively. Interestingly, the Cu(II)-dye binary experiments showed adsorption enhancement of Cu(II), but no significant effect on dyes. The simultaneous adsorption mechanism was further confirmed by FT-IR, thermodynamic study, and elemental mapping. Overall, its facile and green fabrication, efficient sorption performance, and excellent reusability indicate that EDTA-β-CD has potential for practical applications in integrative and efficient treatment of coexistenting toxic pollutants.

Bioinspired Titanium Drug Eluting Platforms Based on a Poly-β-cyclodextrin-Chitosan Layer-by-Layer Self-Assembly Targeting Infections

In the field of implantable titanium-based biomaterials, infections and inflammations are the most common forms of postoperative complications. The controlled local delivery of therapeutics from implants through polyelectrolyte multilayers (PEMs) has recently emerged as a versatile technique that has shown great promise in the transformation of a classical medical implant into a drug delivery system. Herein, we report the design and the elaboration of new biodegradable multidrug-eluting titanium platforms based on a polyelectrolyte multilayer bioactive coating that target infections. These systems were built up in mild conditions according to the layer-by-layer (L-b-L) assembly and incorporate two biocompatible polysaccharides held together through electrostatic interactions. A synthetic, negatively charged β-cyclodextrin-based polymer (PCD), well-known for forming stable and reversible complexes with hydrophobic therapeutic agents, was exploited as a multidrug reservoir, and chitosan (CHT), a naturally occurring, positively charged polyelectrolyte, was used as a barrier for controlling the drug delivery rate. These polyelectrolyte multilayer films were strongly attached to the titanium surface through a bioinspired polydopamine (PDA) film acting as an adhesive first layer and promoting the robust anchorage of PEMs onto the biomaterials. Prior to the multilayer film deposition, the interactions between both oppositely charged polyelectrolytes, as well the multilayer growth, were monitored by employing surface plasmon resonance (SPR). Several PEMs integrating 5, 10, and 15 bilayers were engineered using the dip coating strategy, and the polyelectrolyte surface densities were estimated by colorimetric titrations and gravimetric analyses. The morphologies of these multilayer systems, as well as their naturally occurring degradation in a physiological medium, were investigated by scanning electron microscopy (SEM), and their thicknesses were measured by means of profilometry and ellipsometry studies. Finally, the ability of the coated titanium multilayer devices to act as a drug-eluting system and to treat infections was validated with gentamicin, a relevant water-soluble antibiotic commonly used in medicine due to its broad bactericidal spectrum.

Improving osteointegration and osteogenesis of three-dimensional porous Ti6Al4V scaffolds by polydopamine-assisted biomimetic hydroxyapatite coating

Titanium alloys with various porous structures can be fabricated by advanced additive manufacturing techniques, which are attractive for use as scaffolds for bone defect repair. However, modification of the scaffold surfaces, particularly inner surfaces, is critical to improve the osteointegration of these scaffolds. In this study, a biomimetic approach was employed to construct polydopamine-assisted hydroxyapatite coating (HA/pDA) onto porous Ti6Al4V scaffolds fabricated by the electron beam melting method. The surface modification was characterized with the field emission scanning electron microscopy, energy dispersive spectroscopy, water contact angle measurement, and confocal laser scanning microscopy. Attachment and proliferation of MC3T3-E1 cells on the scaffold surface were significantly enhanced by the HA/pDA coating compared to the unmodified surfaces. Additionally, MC3T3-E1 cells grown on the HA/pDA-coated Ti6Al4V scaffolds displayed significantly higher expression of runt-related transcription factor-2, alkaline phosphatase, osteocalcin, osteopontin, and collagen type-1 compared with bare Ti6Al4V scaffolds after culture for 14 days. Moreover, microcomputed tomography analysis and Van-Gieson staining of histological sections showed that HA/pDA coating on surfaces of porous Ti6Al4V scaffolds enhanced osteointegration and significantly promoted bone regeneration after implantation in rabbit femoral condylar defects for 4 and 12 weeks. Therefore, this study provides an alternative to biofunctionalized porous Ti6Al4V scaffolds with improved osteointegration and osteogenesis functions for orthopedic applications.

Nonfouling tunable βCD dextran polymer films for protein applications

Polymeric β-cyclodextrin (βCD) films tunable with respect to thickness and βCD content were prepared in order to develop a suitable platform, allowing for inclusion of nonpolar guest molecules in the βCD cavity, while suppressing nonspecific protein adsorption. The βCD films were synthesized from linear βCD dextran polymers, and grafted onto silicon oxide surfaces by "click" chemistry. Topographic and morphological characteristics are controllable by reaction conditions and polymer type, with average film heights from 2.5 to 12.5 nm. Reversible introduction of electrostatic charges in the βCD dextran by complex formation with 1-adamantanecarboxylic acid prior to surface grafting resulted in a thinner and denser film, presumably by decompaction of the polymers. Total internal reflection fluorescence spectroscopy (TIRF) was employed to evaluate the accessibility of βCD cavities to the fluorescent probe 2-anilinonaphthalene-6-sulfonic acid. Only a minor fraction of the βCD cavities was accessible in the thicker and less dense films; however, accessibility was largely improved with increased ionic strength using NaCl up to 1 M. Antifouling properties of the βCD dextran polymer films were assessed by TIRF real-time monitoring, using bovine serum albumin as a model protein, and showed a 5- to 10-fold reduction in nonspecific adsorption as compared to a bare quartz surface with the degree of reduction reflecting film thickness and interfacial polymer density.