A biocompatible and functional adhesive amine-rich coating based on dopamine polymerization

Surface (bio)-functionalization of metallic materials: How to cope with real interfaces?

Metallic materials are an important class of biomaterials used in various medical devices, owing to a suitable combination of their mechanical properties. The (bio)-functionalization of their surfaces is frequently performed for biocompatibility requirements, as it offers a powerful way to control their interaction with biological systems. This is particularly important when physicochemical processes and biological events, mainly involving proteins and cells, are initiated at the host-material interface. This review addresses the state of "real interfaces" in the context of (bio)-functionalization of metallic materials, and the necessity to cope with it to avoid frequent improper evaluation of the procedure used. This issue is, indeed, well-recognized but often neglected and emerges from three main issues: (i) ubiquity of surface contamination with organic compounds, (ii) reactivity of metallic surfaces in biological medium, and (iii) discrepancy in (bio)-functionalization procedures between expectations and reality. These disturb the assessment of the strategies adopted for surface modifications and limit the possibilities to provide guidelines for their improvements. For this purpose, X-ray photoelectrons spectroscopy (XPS) comes to the rescue. Based on significant progresses made in methodological developments, and through a large amount of data compiled to generate statistically meaningful information, and to insure selectivity, precision and accuracy, the state of "real interfaces" is explored in depth, while looking after the two main constituents: (i) the bio-organic adlayer, in which the discrimination between the compounds of interest (anchoring molecules, coupling agents, proteins, etc) and organic contaminants can be made, and (ii) the metallic surface, which undergoes dynamic processes due to their reactivity. Moreover, through one of the widespread (bio)-functionalization strategy, given as a case study, a particular attention is devoted to describe the state of the interface at different stages (composition, depth distribution of contaminants and (bio)compounds of interest) and the mode of protein retention. It is highlighted, in particular, that the occurrence or improvement of bioactivity does not demonstrate that the chemical schemes worked in reality. These aspects are particularly essential to make progress on the way to choose the suitable (bio)-functionalization strategy and to provide guidelines to improve its efficiency.

Dual-functionalization of fluorescent carbon dots via cyclodextrin and aminosilane for visual detection of β-glucuronidase and bioimaging

A sensitive method for the detection of β-glucuronidase was established using functionalized carbon dots (β-CD-SiCDs) as fluorescent probes. The β-CD-SiCDs were found to be obtained through in situ autopolymerization by mixing the solutions of methyldopa, mono-6-ethylenediamine-β-cyclodextrin and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane at room temperature. The method has the characteristics of low energy consumption, simple and rapid. β-CD-SiCDs exhibited green fluorescence at 515 nm emission with a quantum yield of 7.9 %. 4-nitrophenyl-β-D-glucuronide was introduced as a substrate for β-glucuronidase to generate p-nitrophenol. Subsequently, p-nitrophenol self-assembled with β-CD-SiCDs through host-guest recognition to form a stable inclusion complex, resulting in the fluorescence quenching of β-CD-SiCDs. The linear range of β-CD-SiCDs for detecting β-glucuronidase activity was 0.5-60 U L-1 with a detection limit of 0.14 U L-1. For on-site detection, gel reagents were prepared by a simple method and the images were visualized and quantified by taking advantage of smartphones, avoiding the use of large instrumentation. The constructed fluorescence sensing platform has the benefits of easy operation and time saving, and has been successfully used for the detection of β-glucuronidase activity in serum and cell imaging.

Cell-Tissue Interaction: The Biomimetic Approach to Design Tissue Engineered Biomaterials

The advancement achieved in Tissue Engineering is based on a careful and in-depth study of cell-tissue interactions. The choice of a specific biomaterial in Tissue Engineering is fundamental, as it represents an interface for adherent cells in the creation of a microenvironment suitable for cell growth and differentiation. The knowledge of the biochemical and biophysical properties of the extracellular matrix is a useful tool for the optimization of polymeric scaffolds. This review aims to analyse the chemical, physical, and biological parameters on which are possible to act in Tissue Engineering for the optimization of polymeric scaffolds and the most recent progress presented in this field, including the novelty in the modification of the scaffolds' bulk and surface from a chemical and physical point of view to improve cell-biomaterial interaction. Moreover, we underline how understanding the impact of scaffolds on cell fate is of paramount importance for the successful advancement of Tissue Engineering. Finally, we conclude by reporting the future perspectives in this field in continuous development.

Eggshell membrane-incorporated cell friendly tough hydrogels with ultra-adhesive property

Adhesive and tough hydrogels have received increased attention for their potential biomedical applications. However, traditional hydrogels have limited utility in tissue engineering because they tend to exhibit low biocompatibility, low adhesiveness, and poor mechanical properties. Herein, the use of the eggshell membrane (ESM) for developing tough, cell-friendly, and ultra-adhesive hydrogels is described. The ESM enhances the performance of the hydrogel network in three ways. First, its covalent cross-linking with the polyacrylamide and alginate chains strengthens the hydrogel network. Second, it provides functional groups, such as amine and carboxyl moieties, which are well known for enhancing the surface adhesion of biomaterials, thereby increasing the adhesiveness of the hydrogel. Third, it is a bioactive agent and improves cell adhesion and proliferation on the constructed scaffold. In conclusion, this study proposes the unique design of ESM-incorporated hydrogels with high toughness, cell-friendly, and ultra-adhesive properties for various biomedical engineering applications.

Multi-functional plant flavonoids regulate pathological microenvironments for vascular stent surface engineering

In-stent restenosis (ISR) and late thrombosis, usually caused by excessive smooth muscle cell (SMC) proliferation and delayed endothelial layer repair, respectively, are the main risks for the failure of vascular stent implantation. For years, modification of stents with biomolecules that could selectively inhibit SMC proliferation and support endothelial cell (EC) growth had drawn extensive attention. However, the modulatory effect of these biomolecules faces the impact of oxidative stress, inflammation, and hyperlipidemia of the pathological vascular microenvironment, which is caused by the stent implantation injury and atherosclerosis lesions. Here, we modified stents with a natural and multi-functional flavonoid, baicalin (BCL), using poly-dopamine (PDA) coating technology to combat the harmful impact of the pathological microenvironment. Stent with an appropriate BCL immobilization density (approximately 2.03 μg/cm2) successfully supported ECs growth while inhibited SMC proliferation. Furthermore, baicalin-modified surfaces regulated the oxidative stress, inflammation, and high-lipid of the pathological microenvironment to inhibit endothelial dysfunction and the oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cells formation. In vivo results showed that baicalin-modified stents exhibited significant anti-ISR, anti-inflammatory, and endothelialization-promoting functions. Our study suggests that the multi-functional baicalin with pathological microenvironment-regulation (PMR) effect has potential use in the surface engineering of cardiovascular devices. STATEMENT OF SIGNIFICANCE: Empowering vascular stents with selective modulation of smooth muscle cells and endothelial cells by surface technology has become an important research direction for stent surface engineering. However, stent coatings that can furthermodulate the pathological microenvironment of blood vessels have been rarely reported. In this study, we constructed a multifunctional coating based on a flavonoid, baicalin, which can selectively modulate vascular wall cells and improve the pathological microenvironment. This study may provide a reference for developing advanced vascular stents.

Effects of semiquinone-rich surface on the behaviors of vascular cells

Dopamine has been widely used for surface modification of cardiovascular medical devices as it forms films on most substrates that provide functional groups for surface chemical modification. However, under oxidative stress, the phenolic hydroxyl group on dopamine can undergo reversible transformation into phenol-semiquinone-quinone, which can cause cytotoxicity and immunotoxicity. In this study, we measured the effects of semiquinone on the behavior of vascular wall cells and inflammatory cells under oxidative stress via ultraviolet irradiation with a hydrogen peroxide diluent. Na₂S₂O₃ was used as a stabilizer to obtain a semiquinone-rich poly-dopamine film, then phenol-semiquinone-quinone ratio on its surface was evaluated at three irradiation-oxidation time points. We found that the poly-dopamine film with ultraviolet irradiation in hydrogen peroxide solution for 15 min had the highest semiquinone occupancy of 19.18%. In the experimental group irradiated for 15 min, endothelial cells were cultured statically for 3 days and the number of surface adherent endothelial cells in the group with added semiquinone stabilizer was reduced to 73% of that in the group without stabilizer, indicating that semiquinone rich surface inhibits adhesion and proliferation of endothelial cells; Smooth muscle cells were cultured statically for 3 days, and the number of adherent smooth muscle on surfaces without stabilizer was reduced to 75% of that on surfaces with stabilizer added, indicating that semiquinone rich surfaces promote smooth muscle proliferation. These results demonstrate that semiquinone can adversely affect the repair effect after implantation of cardiovascular materials. Therefore, our study provides a reference for the application and optimization of dopamine in cardiovascular implant materials.

Patches as Polymeric Systems for Improved Delivery of Topical Corticosteroids: Advances and Future Perspectives

Mucoadhesive polymer patches are a promising alternative for prolonged and controlled delivery of topical corticosteroids (CS) to improve their biopharmaceutical properties (mainly increasing local bioavailability and reducing systemic toxicity). The main biopharmaceutical advantages of patches compared to traditional oral dosage forms are their excellent bioadhesive properties and their increased drug residence time, modified and unidirectional drug release, improved local bioavailability and safety profile, additional pain receptor protection, and patient friendliness. This review describes the main approaches that can be used for the pharmaceutical R&D of oromucosal patches with improved physicochemical, mechanical, and pharmacological properties. The review mainly focuses on ways to increase the bioadhesion of oromucosal patches and to modify drug release, as well as ways to improve local bioavailability and safety by developing unidirectional -release poly-layer patches. Various techniques for obtaining patches and their influence on the structure and properties of the resulting dosage forms are also presented.

Epicatechin-assembled nanoparticles against renal ischemia/reperfusion injury

Bioinspired and biosafety antioxidant nanoparticle assemblies from natural occurring molecules have been regarded as a class of effective therapeutic nanomaterials for addressing current inflammatory diseases such as acute kidney injury. In this study, a series of epicatechin-assembled nanoparticles have been developed via one-pot enzymatic polymerization of epicatechin. The prepared poly (epicatechin) (PEC) nanoparticles (NPs) showed excellent antioxidant capacity to scavenge multiple toxic free radicals, thus being able to effectively protect cells under oxidative stress conditions in vitro. Furthermore, in the renal ischemia/reperfusion model, blood renal function testing and renal tissue staining revealed a prominent therapeutic effect of PEC NPs. All these findings suggested that this class of bioinspired antioxidant nanoparticles provided a new therapeutic strategy for human ischemia/reperfusion-related diseases.

Biofouling-Resistant Ultrafiltration Membranes via Codeposition of Dopamine and Cetyltrimethylammonium Bromide with Retained Size Selectivity and Water Flux

Biofouling is a serious problem in ultrafiltration (UF) membrane applications. Modifying the surface of membranes with low molecular weight, commercially available antibacterial chemistries is an excellent strategy to mitigate biofouling. Herein, we report a new strategy to impart antibacterial and anti-biofouling behavior without changing the support membrane's size selectivity and pure water permeance (PWP). To this end, a strong antibacterial agent, cetyltrimethylammonium bromide (CTAB), was codeposited with dopamine onto commercial polyethersulfone (PES) UF membranes in the presence of nitrogen (N₂) gas backflow. The PWP and pore size of the support membrane did not change with codeposition, confirming the benefit of N₂ backflow in mitigating the solution intrusion phenomenon. X-ray photoelectron spectroscopy (XPS), surface ζ potentials, and contact angle measurements confirmed the successful codeposition of polydopamine (PDA) and CTAB onto the membrane. Among three different CTAB concentrations systematically investigated, the membrane functionalized with CTAB at the critical micelle concentration (CMC) provided the best anti-biofouling activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and retained its surface ζ potential after being stored in 1 M NaCl (pH = 6.8) for 3 months. Our results demonstrate the potential of using a facile, one-step approach to modify commercial UF membranes without compromising their pore size or flux, while simultaneously endowing antibacterial activity.

Novel chlorine-extending polymer coating with prolonged antiviral activity against SARS-CoV-2

We previously reported a novel polymeric surface coating, namely HaloFilm^TM , that can immobilize and extend the antimicrobial activity of chlorine on surfaces. In this study, we demonstrated the continuous antiviral efficacy of HaloFilm^TM when applied on stainless steel and cotton gauze as two representative models for non-porous and porous surfaces against SARS-CoV-2. Forty-eight hours post HaloFilm application and chlorination, and 2 hours post the viral challenge, the inoculum titer was reduced by 2.25±0.33 and ≥4.36±0.23 log₁₀ TCIDA₅₀ on non-porous and porous surfaces, respectively. The half-life of the virus was shorter (13.86 min) on a HaloFilm^TM -coated surface compared to what has been reported on copper (46.44 min).

Step-wise CAG@PLys@PDA-Cu2+ modification on micropatterned nanofibers for programmed endothelial healing

Native-like endothelium regeneration is a prerequisite for material-guided small-diameter vascular regeneration. In this study, a novel strategy is proposed to achieve phase-adjusted endothelial healing by step-wise modification of parallel-microgroove-patterned (i.e., micropatterned) nanofibers with polydopamine-copper ion (PDA-Cu²⁺) complexes, polylysine (PLys) molecules, and Cys-Ala-Gly (CAG) peptides (CAG@PLys@PDA-Cu²⁺). Using electrospun poly(l-lactide-co-caprolactone) random nanofibers as the demonstrating biomaterial, step-wise modification of CAG@PLys@PDA-Cu²⁺ significantly enhanced substrate wettability and protein adsorption, exhibited an excellent antithrombotic surface and outstanding phase-adjusted capacity of endothelium regeneration involving cell adhesion, endothelial monolayer formation, and the regenerated endothelium maturation. Upon in vivo implantation for segmental replacement of rabbit carotid arteries, CAG@PLys@PDA-Cu²⁺ modified grafts (2 mm inner diameter) with micropatterns on inner surface effectively accelerated native-like endothelium regeneration within 1 week, with less platelet aggregates and inflammatory response compared to those on non-modified grafts. Prolonged observations at 6- and 12-weeks post-implantation demonstrated a positive vascular remodeling with almost fully covered endothelium and mature smooth muscle layer in the modified vascular grafts, accompanied with well-organized extracellular matrix. By contrast, non-modified vascular grafts induced a disorganized tissue formation with a high risk of thrombogenesis. In summary, step-wise modification of CAG@PLys@PDA-Cu²⁺ on micropatterned nanofibers can significantly promote endothelial healing without inflicting thrombosis, thus confirming a novel strategy for developing functional vascular grafts or other blood-contacting materials/devices.

Synthesis of soluble melanin nanoparticles under acidic conditions using Burkholderia cepacia tyrosinase and their characterization

Melanin nanoparticles (MNPs) used for biomedical applications are often synthesized via the chemical auto-oxidation of catecholic monomers such as dopamine and 3,4-dihydroxyphenylalanine (DOPA) under alkaline conditions. However, the synthetic method for the chemical synthesis of MNP (cMNP) is relatively straightforward and more robust to control their homogenous particle size and morphology than the corresponding enzymatic synthetic methods. In this study, we demonstrated that the simple enzymatic synthesis of MNPs (eMNPs) with homogenous and soluble (<20 nm diameter) properties is possible using dopamine and Burkholderia cepacia tyrosinase (BcTy) under acidic conditions (i.e., pH 3.0). BcTy was highly reactive under pH 5.0, where the natural and chemical oxidation of catechol is complex, and thus melanin was synthesized via the hydroxylation of phenolic substrates. The detailed chemical analysis and characterization of the physical properties of the eMNPs confirmed the higher preservation of the catechol and primary amine moieties in the monomer substrate such as dopamine under acidic conditions. The eMNPs showed enhanced antioxidant activity and conferred stickiness to the formed hydrogel compared to the chemical auto-oxidation method owing to the large number of hydroxyl groups remaining such as catechol and quinone moieties. Because of these advantages and characteristics, the synthesis of MNPs using BcTy under acidic conditions can open a new path for their biomedical applications.

Melanin nanoparticles (MNPs) used for biomedical applications are often synthesized via the chemical auto-oxidation of catecholic monomers such as dopamine and 3,4-dihydroxyphenylalanine (DOPA) under alkaline conditions.

Artificial Nonenzymatic Antioxidant MXene Nanosheet-Anchored Injectable Hydrogel as a Mild Photothermal-Controlled Oxygen Release Platform for Diabetic Wound Healing

Hypoxia, excessive reactive oxygen species (ROS), impaired angiogenesis, lasting inflammation, and bacterial infection, are key problems impeding diabetic wound healing. Particularly, controllable oxygen release and ROS scavenging capacities are critical during the wound healing process. Here, an injectable hydrogel based on hyaluronic acid-graft-dopamine (HA-DA) and polydopamine (PDA) coated Ti₃C₂ MXene nanosheets is developed catalytically cross-linked by an oxyhemoglobin/hydrogen (HbO₂/H₂O₂) system combined with mild photothermal stimulation for diabetic wound healing. HbO₂ not only acts as a horseradish peroxidase-like to catalyze the hydrogel formation but also as an oxygen carrier to controllably release oxygen when activated by the mild heat produced from near-infrared (NIR) irradiation. Specifically, HbO₂ can provide oxygen repeatedly by binding oxygen in the air when the NIR is off. The stable photoresponsive heating behavior of MXene ensures the repeatable oxygen release. Additionally, artificial nonenzymatic antioxidant MXene nanosheets are proposed to scavenge excessive reactive nitrogen species and ROS including H₂O₂, O₂^•-, and ^•OH, keeping the intracellular redox homeostasis and alleviating oxidative stress, and eradicate bacteria to avoid infection. The antioxidant and antibacterial abilities of MXene are further improved by PDA coating, which also promotes the MXene nanosheets cross-linking into the network of the hydrogel. HA-DA molecules endow the hydrogel with the capacity to regulate macrophage polarization from M1 to M2 to achieve anti-inflammation. More importantly, the MXene-anchored hydrogel with multifunctions including tissue adhesion, self-healing, injectability, and hemostasis, combined with mild photothermal stimulation, greatly promotes human umbilical vein endothelial cell proliferation and migration and notably facilitates infected diabetic wound healing.

Novel and Sustainable Colorants Developed via Incorporating Azo Chromophores into Dopamine Molecules

Inspired by the application of dopamine as an "anchor" and UV absorber, novel sustainable colorants with biscatecholic structure were synthesized through a simple incorporation of simple azo chromophores with dopamine. Their structures were confirmed using MS and NMR analyses, and their application on textile materials was investigated. Compared to the simple azo chromophores with almost no coloring ability on fabrics, the biscatecholic colorants could color different fabrics effectively, mainly through self-polymerization only in the presence of a trace amount of organic base at room temperature, which is environmentally friendly in terms of saving resources and alleviating chemical pollution. Meanwhile, the UV resistance of colored fabrics was enhanced significantly, showing the advantage of protecting wearers from UV damage.

Co-immobilized bienzyme of horseradish peroxidase and glucose oxidase on dopamine-modified cellulose–chitosan composite beads as a high-efficiency biocatalyst for degradation of acridine

Co-immobilized bienzyme biocatalysts are attracting increasing interest in the field of wastewater treatment due to their widespread application.

Highly Stretchable and Sensitive Single-Walled Carbon Nanotube-Based Sensor Decorated on a Polyether Ester Urethane Substrate by a Low Hydrothermal Process

We report a highly stretchable sensor with low-concentration (1.5 wt %) single-walled carbon nanotubes (SWCNTs) on flexible polyether ester urethane (PEEU) yarn, fabricated using a low hydrothermal process at 90 °C. Although SWCNTs restrict the PEEU polymer chain mobility, the resulting ductility of our nanocomposites reduces only by 16.5% on average, initially from 667.3% elongation at break to 557.2%. The resulting electrical resistivity of our nanocomposites can be controlled systematically by the number of hydrothermal cycles. A high gauge factor value of 4.84 is achieved at a tensile strain below 100%, and it increases up to 28.5 with applying a tensile strain above 450%. We find that the piezoresistivity of our nanocomposite is sensitive to temperature variations of 25-85 °C due to the hopping effect, which promotes more charge transport at elevated temperatures. Our nanocomposites offer both a high sensitivity and a large strain sensing range, which is achieved with a relatively simple fabrication technique and low concentration of SWCNTs.

Immobilization of Glycogen Synthase Kinase-3β Inhibitor on 316L Stainless Steel via Polydopamine to Accelerate Endothelialization

The coverage of stents with healthy endothelium is crucial to the success of cardiovascular stent implantation. Immobilizing bioactive molecules on stents is an effective strategy to generate such stents. Glycogen synthase kinase-3β inhibitor (GSKi) is a bioactive molecule that can effectively accelerate vascular endothelialization. In this work, GSKi was covalently conjugated on 316L stainless steel through polydopamine to develop a stable bioactive surface. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and water contact angle results revealed the successful introduction of GSKi onto 316L stainless steel. The GSKi coating did not obviously affect the hemocompatibility of plates. The adhesion and proliferation of human coronary artery endothelial cells (HCAECs) on stainless steel was significantly promoted by the addition of GSKi. In summary, this work provides a universal and stable strategy of immobilizing GSKi on the stent surface. This method has the potential for widespread application in the modification of vascular stents.

A tough nitric oxide-eluting hydrogel coating suppresses neointimal hyperplasia on vascular stent

Vascular stent is viewed as one of the greatest advancements in interventional cardiology. However, current approved stents suffer from in-stent restenosis associated with neointimal hyperplasia or stent thrombosis. Herein, we develop a nitric oxide-eluting (NOE) hydrogel coating for vascular stents inspired by the biological functions of nitric oxide for cardiovascular system. Our NOE hydrogel is mechanically tough and could selectively facilitate the adhesion of endothelial cells. Besides, it is non-thrombotic and capable of inhibiting smooth muscle cells. Transcriptome analysis unravels the NOE hydrogel could modulate the inflammatory response and induce the relaxation of smooth muscle cells. In vivo study further demonstrates vascular stents coated with it promote rapid restoration of native endothelium, and persistently suppress inflammation and neointimal hyperplasia in both leporine and swine models. We expect such NOE hydrogel will open an avenue to the surface engineering of vascular implants for better clinical outcomes.

Neointimal hyperplasia and stent thrombosis remain issues with vascular stents. Here, the authors report on the development of a nitric oxide releasing hydrogel which allows for endothelialisation of the stent surface and prevents smooth muscle cell growth reducing hyperplasia and thrombosis in in vivo models.

Bioactive Plasma Coatings on Orthodontic Brackets: In Vitro Metal Ion Release and Cytotoxicity

The metal ion release characteristics and biocompatibility of meta-based materials are key factors that influence their use in orthodontics. Although stainless steel-based alloys have gained much interest and use due to their mechanical properties and cost, they are prone to localised attack after prolonged exposure to the hostile oral environment. Metal ions may induce cellular toxicity at high dosages. To circumvent these issues, orthodontic brackets were coated with a functional nano-thin layer of plasma polymer and further immobilised with enantiomers of tryptophan. Analysis of the physicochemical properties confirmed the presence of functional coatings on the surface of the brackets. The quantification of metal ion release using mass spectrometry proved that plasma functionalisation could minimise metal ion release from orthodontic brackets. Furthermore, the biocompatibility of the brackets has been improved after functionalisation. These findings demonstrate that plasma polymer facilitated surface functionalisation of orthodontic brackets is a promising approach to reducing metal toxicity without impacting their bulk properties.

Controlling the Morphology of Dynamic Thia-Michael Networks to Target Pressure-Sensitive and Hot Melt Adhesives

A series of multistage (pressure-sensitive/hot melt) adhesives utilizing dynamic thia-Michael bonding motifs are reported. The benzalcyanoacetate Michael acceptors used in this work undergo bond exchange under ambient conditions without external catalysis, facilitating pressure-sensitive adhesion. A key feature of this system is the dynamic reaction-induced phase separation that lends reinforcement to the otherwise weakly bonded materials, enabling weak, repeatable pressure-sensitive adhesion under ambient conditions and strong adhesion when processed as a hot melt adhesive. By using different pairs of benzalcyanoacetate cross-linking units, the phase separation characteristics of the adhesives can be directly manipulated, allowing for a tailored adhesive response.

Durable endothelium-mimicking coating for surface bioengineering cardiovascular stents

Mimicking the nitric oxide (NO)-release and glycocalyx functions of native vascular endothelium on cardiovascular stent surfaces has been demonstrated to reduce in-stent restenosis (ISR) effectively. However, the practical performance of such an endothelium-mimicking surfaces is strictly limited by the durability of both NO release and bioactivity of the glycocalyx component. Herein, we present a mussel-inspired amine-bearing adhesive coating able to firmly tether the NO-generating species (e.g., Cu-DOTA coordination complex) and glycocalyx-like component (e.g., heparin) to create a durable endothelium-mimicking surface. The stent surface was firstly coated with polydopamine (pDA), followed by a surface chemical cross-link with polyamine (pAM) to form a durable pAMDA coating. Using a stepwise grafting strategy, Cu-DOTA and heparin were covalently grafted on the pAMDA-coated stent based on carbodiimide chemistry. Owing to both the high chemical stability of the pAMDA coating and covalent immobilization manner of the molecules, this proposed strategy could provide 62.4% bioactivity retention ratio of heparin, meanwhile persistently generate NO at physiological level from 5.9 ± 0.3 to 4.8 ± 0.4 × 10⁻¹⁰ mol cm⁻² min⁻¹ in 1 month. As a result, the functionalized vascular stent showed long-term endothelium-mimicking physiological effects on inhibition of thrombosis, inflammation, and intimal hyperplasia, enhanced re-endothelialization, and hence efficiently reduced ISR.

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A durable endothelium-mimicking coating was developed for surface bioengineering of cardiovascular stents.

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The durable endothelium-mimicking surface was realized by stepwise grafting of Cu-DOTA and heparin on a robust coating.

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The durable endothelium-mimicking coating endows the vascular stents with ability to dramatically reduce restenosis.

Mussel Inspired Chemistry and Bacteria Derived Polymers for Oral Mucosal Adhesion and Drug Delivery

Ulceration of the oral mucosa is common, can arise at any age and as a consequence of the pain lessens enjoyment and quality of life. Current treatment options often involve the use of topical corticosteroids with poor drug delivery systems and inadequate contact time. In order to achieve local controlled delivery to the lesion with optimal adhesion, we utilized a simple polydopamine chemistry technique inspired by mussels to replicate their adhesive functionality. This was coupled with production of a group of naturally produced polymers, known as polyhydroxyalkanoates (PHA) as the delivery system. Initial work focused on the synthesis of PHA using Pseudomonas mendocina CH50; once synthesized and extracted from the bacteria, the PHAs were solvent processed into films. Polydopamine coating was subsequently achieved by immersing the solvent cast film in a polymerized dopamine solution. Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy confirmed functionalization of the PHA films via the presence of amine groups. Further characterization of the samples was carried out via surface energy measurements and Scanning Electron Microscopy (SEM) micrographs for surface topography. An adhesion test via reverse compression testing directly assessed adhesive properties and revealed an increase in polydopamine coated samples. To further identify the effect of surface coating, LIVE/DEAD imaging and Alamar Blue metabolic activity evaluated attachment and proliferation of fibroblasts on the biofilm surfaces, with higher cell growth in favor of the coated samples. Finally, in vivo biocompatibility was investigated in a rat model where the polydopamine coated PHA showed less inflammatory response over time compared to uncoated samples with sign of neovascularization. In conclusion, this simple mussel inspired polydopamine chemistry introduces a step change in bio-surface functionalization and holds great promise for the treatment of oral conditions.

Hybrid Metal-Phenol Nanoparticles with Polydopamine-like Coating for PET/SPECT/CT Imaging

The validation of metal-phenolic nanoparticles (MPNs) in preclinical imaging studies represents a growing field of interest due to their versatility in forming predesigned structures with unique properties. Before MPNs can be used in medicine, their pharmacokinetics must be optimized so that accumulation in nontargeted organs is prevented and toxicity is minimized. Here, we report the fabrication of MPNs made of a coordination polymer core that combines In(III), Cu(II), and a mixture of the imidazole 1,4-bis(imidazole-1-ylmethyl)-benzene and the catechol 3,4-dihydroxycinnamic acid ligands. Furthermore, a phenolic-based coating was used as an anchoring platform to attach poly(ethylene glycol) (PEG). The resulting MPNs, with effective hydrodynamic diameters of around 120 nm, could be further derivatized with surface-embedded molecules, such as folic acid, to facilitate in vivo targeting and multifunctionality. The prepared MPNs were evaluated for in vitro plasma stability, cytotoxicity, and cell internalization and found to be biocompatible under physiological conditions. First, biomedical evaluations were then performed by intrinsically incorporating trace amounts of the radioactive metals 111In or 64Cu during the MPN synthesis directly into their polymeric matrix. The resulting particles, which had identical physicochemical properties to their nonradioactive counterparts, were used to perform in vivo single-photon emission computed tomography (SPECT) and positron emission tomography (PET) in tumor-bearing mice. The ability to incorporate multiple metals and radiometals into MPNs illustrates the diverse range of functional nanoparticles that can be prepared with this approach and broadens the scope of these nanoconstructs as multimodal preclinical imaging agents.

Influence of interaction between surface-modified magnetic nanoparticles with infectious biofilm components in artificial channel digging and biofilm eradication by antibiotics in vitro and in vivo

Magnetic targeting of antimicrobial-loaded magnetic nanoparticles to micrometer-sized infectious biofilms is challenging. Bacterial biofilms possess water channels that facilitate transport of nutrient and metabolic waste products, but are insufficient to allow deep penetration of antimicrobials and bacterial killing. Artificial channel digging in infectious biofilms involves magnetically propelling nanoparticles through a biofilm to dig additional channels to enhance antimicrobial penetration. This does not require precise targeting. However, it is not known whether interaction of magnetic nanoparticles with biofilm components impacts the efficacy of antibiotics after artificial channel digging. Here, we functionalized magnetic-iron-oxide-nanoparticles (MIONPs) with polydopamine (PDA) to modify their interaction with staphylococcal pathogens and extracellular-polymeric-substances (EPS) and relate the interaction with in vitro biofilm eradication by gentamicin after magnetic channel digging. PDA-modified MIONPs had less negative zeta potentials than unmodified MIONPs due to the presence of amino groups and accordingly more interaction with negatively charged staphylococcal cell surfaces than unmodified MIONPs. Neither unmodified nor PDA-modified MIONPs interacted with EPS. Concurrently, use of non-interacting unmodified MIONPs for artificial channel digging in in vitro grown staphylococcal biofilms enhanced the efficacy of gentamicin more than the use of interacting, PDA-modified MIONPs. In vivo experiments in mice using a sub-cutaneous infection model confirmed that non-interacting, unmodified MIONPs enhanced eradication by gentamicin of Staphylococcus aureus Xen36 biofilms about 10 fold. Combined with the high biocompatibility of magnetic nanoparticles, these results form an important step in understanding the mechanism of artificial channel digging in infectious biofilms for enhancing antibiotic efficacy in hard-to-treat infectious biofilms in patients.

Poly-dopamine, poly-levodopa, and poly-norepinephrine coatings: Comparison of physico-chemical and biological properties with focus on the application for blood-contacting devices

Thanks to its simplicity, versatility, and secondary reactivity, dopamine self-polymerized coatings (pDA) have been widely used in surface modification of biomaterials, but the limitation in secondary molecular grafting and the high roughness restrain their application in some special scenarios. Therefore, some other catecholamine coatings analog to pDA have attracted more and more attention, including the smoother poly-norepinephrine coating (pNE), and the poly-levodopa coating (pLD) containing additional carboxyl groups. However, the lack of a systematic comparison of the properties, especially the biological properties of the above three catecholamine coatings, makes it difficult to give a guiding opinion on the application scenarios of different coatings. Herein, we systematically studied the physical, chemical, and biological properties of the three catecholamine coatings, and explored the feasibility of their application for the modification of biomaterials, especially cardiovascular materials. Among them, the pDA coating was the roughest, with the largest amount of amino and phenolic hydroxyl groups for molecule grafting, and induced the strongest platelet adhesion and activation. The pLD coating was the thinnest and most hydrophilic but triggered the strongest inflammatory response. The pNE coating was the smoothest, with the best hemocompatibility and histocompatibility, and with the strongest cell selectivity of promoting the proliferation of endothelial cells while inhibiting the proliferation of smooth muscle cells. To sum up, the pNE coating may be a better choice for the surface modification of cardiovascular materials, especially those for vascular stents and grafts, but it is still not widely recognized.

Behaviour of Vascular Smooth Muscle Cells on Amine Plasma-Coated Materials with Various Chemical Structures and Morphologies

Amine-coated biodegradable materials based on synthetic polymers have a great potential for tissue remodeling and regeneration because of their excellent processability and bioactivity. In the present study, we have investigated the influence of various chemical compositions of amine plasma polymer (PP) coatings and the influence of the substrate morphology, represented by polystyrene culture dishes and polycaprolactone nanofibers (PCL NFs), on the behavior of vascular smooth muscle cells (VSMCs). Although all amine-PP coatings improved the initial adhesion of VSMCs, 7-day long cultivation revealed a clear preference for the coating containing about 15 at.% of nitrogen (CPA-33). The CPA-33 coating demonstrated the ideal combination of good water stability, a sufficient amine group content, and favorable surface wettability and morphology. The nanostructured morphology of amine-PP-coated PCL NFs successfully slowed the proliferation rate of VSMCs, which is essential in preventing restenosis of vascular replacements in vivo. At the same time, CPA-33-coated PCL NFs supported the continuous proliferation of VSMCs during 7-day long cultivation, with no significant increase in cytokine secretion by RAW 264.7 macrophages. The CPA-33 coating deposited on biodegradable PCL NFs therefore seems to be a promising material for manufacturing small-diameter vascular grafts, which are still lacking on the current market.

Biological responses to physicochemical properties of biomaterial surface

Biomedical scientists use chemistry-driven processes found in nature as an inspiration to design biomaterials as promising diagnostic tools, therapeutic solutions, or tissue substitutes. While substantial consideration is devoted to the design and validation of biomaterials, the nature of their interactions with the surrounding biological microenvironment is commonly neglected. This gap of knowledge could be owing to our poor understanding of biochemical signaling pathways, lack of reliable techniques for designing biomaterials with optimal physicochemical properties, and/or poor stability of biomaterial properties after implantation. The success of host responses to biomaterials, known as biocompatibility, depends on chemical principles as the root of both cell signaling pathways in the body and how the biomaterial surface is designed. Most of the current review papers have discussed chemical engineering and biological principles of designing biomaterials as separate topics, which has resulted in neglecting the main role of chemistry in this field. In this review, we discuss biocompatibility in the context of chemistry, what it is and how to assess it, while describing contributions from both biochemical cues and biomaterials as well as the means of harmonizing them. We address both biochemical signal-transduction pathways and engineering principles of designing a biomaterial with an emphasis on its surface physicochemistry. As we aim to show the role of chemistry in the crosstalk between the surface physicochemical properties and body responses, we concisely highlight the main biochemical signal-transduction pathways involved in the biocompatibility complex. Finally, we discuss the progress and challenges associated with the current strategies used for improving the chemical and physical interactions between cells and biomaterial surface.

Layered hydroxide/polydopamine/hyaluronic acid functionalized magnesium alloys for enhanced anticorrosion, biocompatibility and antithrombogenicity in vascular stents

Magnesium alloys are promising cardiovascular stent materials due to the favourable physical properties and complete biodegradability in vivo. However, the rapid degradation, poor cytocompatibility and tendency of thrombogenesis hinder practical clinical applications. In order to solve these problems, a facile and highly efficient strategy of alkali treatment combined with subsequent layer-by-layer assembly was used to fabricate a multifunctional coating. A bottom layer hydroxyl (–OH) with negative charge after alkali treatment first formed a solid bond with magnesium matrix to provide a rough outer surface for the further immobilization of functional biomolecules. Afterwards, polydopamine and hyaluronic acid were successively immobilized on alkali-treated magnesium surface via strong electrostatic adsorption and covalent bonding between carboxyl group of hyaluronic acid and amine or hydroxyl of polydopamine to form magnesium/OH/polydopamine/hyaluronic acid. Hydroxyl significantly improves the corrosion resistance while polydopamine and hyaluronic acid layers act as a further barrier to provide better anticorrosion. A balance between biocompatibility and antithrombogenicity has been achieved by adjusting the content of hyaluronic acid on polydopamine surface. The multifunctional magnesium/OH/polydopamine/hyaluronic acid coating with lower hyaluronic acid concentrations expose more active sites of polydopamine molecules to promote endothelial cell proliferation while retaining the intrinsic antithrombogenic function of hyaluronic acid to offer a potential application for vascular stents.

Hexamethylenediamine-Mediated Polydopamine Film Deposition: Inhibition by Resorcinol as a Strategy for Mapping Quinone Targeting Mechanisms

Hexamethylenediamine (HMDA) and other long chain aliphatic diamines can induce substrate-independent polymer film deposition from dopamine and several other catechols substrates at relatively low concentrations, however the mechanism of the diamine-promoted effect has remained little understood. Herein, we report data indicating that: (a) film deposition from 1 mM HMDA and dopamine is not affected by chemical oxidation with periodate but is markedly inhibited by resorcinol, which also prevents PDA film formation at 10 mM monomer concentration in the absence of HMDA; (b) N-acetylation of HMDA completely inhibits the effect on PDA film formation; (c) HMDA enables surface functionalization with 1 mM 5,6-dihydroxyindole (DHI) polymerization at pH 9.0 in a resorcinol-inhibitable manner. Structural investigation of the polymers produced from dopamine and DHI in the presence of HMDA using solid state 13C and 15N NMR and MALDI-MS suggested formation of covalent cross linked structures. It is concluded that HMDA enhances polydopamine adhesion by acting both on dopamine quinone and downstream, e.g., via covalent coupling with DHI. These results provide new insights into the mechanisms of PDA adhesion and disclose resorcinol as a new potent tool for targeting/mapping quinone intermediates and for controlling polymer growth.

Polydopamine-mediated covalent functionalization of collagen on a titanium alloy to promote biocompatibility with soft tissues

The clinical success of a titanium (Ti) percutaneous implant requires the integration with soft tissues to form a biological seal, which effectively combats marsupialization, premigration and infection after implantation. However, the bioinert surface of Ti or its alloys prevents the material from sufficient biological sealing and limits the application of Ti or its alloys as percutaneous implants. In this study, we achieved a collagen coating to bioactivate the surface of Ti-6Al-4V. In order to enable covalent functionalization, we first deposited a polydopamine (PDA) coating on Ti-6Al-4V based on dopamine self-polymerization and then immobilized collagen chains on PDA. Compared with physical absorption, such a chemical bonding method through mussel-inspired chemistry showed better stability of the coating. Meanwhile, the cellular tests in vitro indicated that collagen functionalization on the Ti-6Al-4V surface showed better adhesion of human foreskin fibroblasts (HFFs) and human immortal keratinocytes (HaCaTs). The subcutaneous implantation tests in rats indicated that the collagen modification attenuated soft tissue response and improved tissue compatibility compared with either pure Ti-6Al-4V or merely PDA coated samples. The facile bioinspired approach enables a persistent modification of metals by macromolecules under aqueous environments, and the PDA-collagen coated titanium alloy is worthy of further investigation as a percutaneous implant.

Assembly of Metal-Phenolic/Catecholamine Networks for Synergistically Anti-Inflammatory, Antimicrobial, and Anticoagulant Coatings

The development of a facile and versatile strategy to endow surfaces with synergistically anti-inflammatory, antimicrobial, and anticoagulant functions is of particular significance for blood-contacting biomaterials and medical devices. In this work, we report a simple and environmentally friendly "one-pot" method inspired by byssal cuticle chemistry, namely, [Fe(dopa)₃] coordination chemistry for assembly of copper ions (Cu²⁺) and plant polyphenol (tannic acid)/catecholamine (dopamine or norepinephrine) to form metal-phenolic/catecholamine network-based coatings. This one-pot method enabled us to easily develop a multifunctional surface based on the combination of the characteristic functions of metal ions and plant polyphenol or catecholamine. The residual phenolic hydroxyl groups on the coatings imparted the modified surface with excellent antioxidant and anti-inflammatory functions. The robust chelation of copper ions to the metal-phenolic/catecholamine networks provided not only durable antibacterial property but also glutathione peroxidase like catalytic capability to continuously and controllably produce antithrombotic nitric oxide by catalyzing endogenous S-nitrothiol. The biological functions of such coatings could be well regulated by adjusting the ratios of the feed concentration of Cu²⁺ ions to plant polyphenol or catecholamine. We envision that our simple, multifunctional, and bioinspired coating strategy can hold great application promise for bioengineering blood-contacting devices.

Polymethyldopa Nanoparticles-Based Fluorescent Sensor for Detection of Tyrosinase Activity

Being a typical copper-containing oxidase, tyrosinase plays critical roles in biological activity, and its aberrant expression might cause diverse skin diseases. Herein, we, for the first time, have found an interesting green fluorogenic reaction between methyldopa and ethanolamine. By combining transmission electron microscopy, UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and MALDI-TOF mass spectrum analysis, we have confirmed that there is a reliable method for preparing the bright green fluorescent polymethyldopa nanoparticles (PMNPs) by simply mixing methyldopa and ethanolamine at room temperature. Inspired by such a simple and convenient fluorogenic reaction, a novel polymethyldopa nanoparticles-based fluorescent sensor for detection of tyrosinase activity was developed by using the commercially available metyrosine as a substrate, accompanied by the tyrosinase-catalyzed specific conversion of metyrosine into methyldopa. According to the intrinsic sensitivity/selectivity of fluorescence technology and unambiguous response mechanism, our fluorescent sensor exhibits excellent sensing performance and can be utilized in the determination of the tyrosinase activity in real biological samples and inhibitor screening.

The Chemistry of Polydopamine Film Formation: The Amine-Quinone Interplay

Despite extensive investigations over the past decade, the chemical basis of the extraordinary underwater adhesion properties of polydopamine (PDA) has remained not entirely understood. The bulk of evidence points to PDA wet adhesion as a complex process based on film deposition, and growth in which primary amine groups, besides catechol moieties, play a central role. However, the detailed interplay of chemical interactions underlying the dynamics of film formation has not yet been elucidated. Herein, we report the results of a series of experiments showing that coating formation from dopamine at pH 9.0 in carbonate buffer: (a) Requires high dopamine concentrations (>1 mM); (b) is due to species produced in the early stages of dopamine autoxidation; (c) is accelerated by equimolar amounts of periodate causing fast conversion to the o-quinone; and (d) is enhanced by the addition of hexamethylenediamine (HMDA) and other long chain aliphatic amines even at low dopamine concentrations (<1 mM). It is proposed that concentration-dependent PDA film formation reflects the competition between intermolecular amine-quinone condensation processes, leading to adhesive cross-linked oligomer structures, and the intramolecular cyclization route forming little adhesive 5,6-dihydroxyindole (DHI) units. Film growth would then be sustained by dopamine and other soluble species that can be adsorbed on the surface.

Cardiovascular stents: overview, evolution, and next generation

Compared to bare-metal stents (BMSs), drug-eluting stents (DESs) have been regarded as a revolutionary change in coronary artery diseases (CADs). Releasing pharmaceutical agents from the stent surface was a promising progress in the realm of cardiovascular stents. Despite supreme advantages over BMSs, in-stent restenosis (ISR) and long-term safety of DESs are still deemed ongoing concerns over clinically application of DESs. The failure of DESs for long-term clinical use is associated with following factors including permanent polymeric coating materials, metallic stent platforms, non-optimal drug releasing condition, and factors that have recently been supposed as contributory factors such as degradation products of polymers, metal ions due to erosion and degradation of metals and their alloys utilizing in some stents as metal frameworks. Discovering the direct relation between stent materials and associating adverse effects is a complicated process, and yet it has not been resolved. For clinical success it is of significant importance to optimize DES design and explore novel strategies to overcome all problems including inflammatory response, delay endothelialization, and sub-acute stent thrombosis (ST) simultaneously. In this work, scientific reports are reviewed particularly focusing on recent advancements in DES design which covers both potential improvements of existing and recently novel prototype stent fabrications. Covering a wide range of information from the BMSs to recent advancement, this study mostly sheds light on DES's concepts, namely stent composition, drug release mechanism, and coating techniques. This review further reports different forms of DES including fully biodegradable DESs, shape-memory ones, and polymer-free DESs.

Surface modification of stainless steel for biomedical applications: Revisiting a century-old material

Stainless steel (SS) has been widely used as a material for fabricating cardiovascular stents/valves, orthopedic prosthesis, and other devices and implants used in biomedicine due to its malleability and resistance to corrosion and fatigue. Despite its good mechanical properties, SS (as other metals) lacks biofunctionality. To be successfully used as a biomaterial, SS must be made resistant to the biological environment by increasing its anti-fouling properties, preventing biofilm formation (passive surface modification), and imparting functionality for eluting a specific drug or capturing selected cells (active surface modification); these features depend on the final application. Various physico-chemical techniques, including plasma vapor deposition, electrochemical treatment, and attachment of different linkers that add functional groups, are used to obtain SS with increased corrosion resistance, improved osseointegration capabilities, added hemocompatibility, and enhanced antibacterial properties. Existing literature on this topic is extensive and has not been covered in an integrated way in previous reviews. This review aims to fill this gap, by surveying the literature on SS surface modification methods, as well as modification routes tailored for specific biomedical applications.

STATEMENT OF SIGNIFICANCE

Stainless steel (SS) is widely used in many biomedical applications including bone implants and cardiovascular stents due to its good mechanical properties, biocompatibility and low price. Surface modification allows improving its characteristics without compromising its important bulk properties. SS with improved blood compatibility (blood contacting implants), enhanced ability to resist bacterial infection (long-term devices), better integration with a tissue (bone implants) are examples of successful SS surface modifications. Existing literature on this topic is extensive and has not been covered in an integrated way in previous reviews. This review paper aims to fill this gap, by surveying the literature on SS surface modification methods, as well as to provide guidance for selecting appropriate modification routes tailored for specific biomedical applications.

Promoting Endothelial Cell Affinity and Antithrombogenicity of Polytetrafluoroethylene (PTFE) by Mussel-Inspired Modification and RGD/Heparin Grafting

When used as small-diameter vascular grafts (SDVGs), synthetic biomedical materials like polytetrafluoroethylene (PTFE) may induce thrombosis and intimal hyperplasia due to the lack of an endothelial cell layer. Modification of the PTFE in an aqueous solution is difficult because of its hydrophobicity. Herein, aiming to simultaneously promote endothelial cell affinity and antithrombogenicity, a mussel-inspired modification approach was employed to enable the grafting of various bioactive molecules like RGD and heparin. This approach involves a series of pragmatic steps including oxygen plasma treatment, dopamine (DA) coating, polyethylenimine (PEI) grafting, and RGD or RGD/heparin immobilization. Successful modification in each step was verified via Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Plasma treatment increased the hydrophilicity of PTFE, thereby allowing it to be efficiently coated with dopamine. Grafting of dopamine, RGD, and heparin led to an increase in surface roughness and a decrease in water contact angle due to increased surface energy. Platelet adhesion increased after dopamine and RGD modification, but it dramatically decreased when heparin was introduced. All of these modifications, especially the incorporation of RGD, showed favorable effects on endothelial cell attachment, viability, and proliferation. Due to strong cell-substrate interactions between endothelial cells and RGD, the RGD/heparin-grafted PTFE demonstrated high endothelial cell affinity. This facile modification method is highly suitable for all hydrophobic surfaces and provides a promising technique for SDVG modification to stimulate fast endothelialization and effective antithrombosis.

Layer-by-layer siRNA/poly(L-lysine) Multilayers on Polydopamine-coated Surface for Efficient Cell Adhesion and Gene Silencing

For tissue engineering applications, small interfering RNA (siRNA) is an attractive agent for controlling cellular functions and differentiation. Although polyionic condensation of nucleic acids with polycations has been widely used for gene delivery, siRNA is not strongly associated with cationic carriers due to its low charge density and rigid molecular structures. The use of an excess amount of cationic carriers is often used for siRNA condensation, though they can induce severe cytotoxicity. Here we introduce the self-assembly of siRNA with mild polyelectrolytes into multilayers for efficient gene silencing during cell proliferation. The multilayers were prepared through the sequential layer-by-layer deposition of siRNA and poly-L-lysine (PLL) on a polydopamine-coated substrate. The cells, grown on the siRNA/PLL multilayers, exhibited a remarkable inhibition of the expression of target genes as compared to the use of scrambled siRNA. The gene silencing efficiency depends on the number of siRNA layers within a multilayer. This result indicates that siRNA/PLL multilayers can be potentially utilized for efficient surface-mediated siRNA delivery.

Barbaloin loaded polydopamine-polylactide-TPGS (PLA-TPGS) nanoparticles against gastric cancer as a targeted drug delivery system: Studies in vitro and in vivo

Gastric cancer is the third leading cause of cancer-associated death worldwide. Although a decrease in its incidence is observed, gastric cancer still poses a major clinical challenge due to poor prognosis and limited treatments. Barbaloin (BBL) is a main medicinal composition of the Chinese traditional medicine aloe vera. BBL has various bioactivities, including anti-oxidant, anti-inflammatory and anti-tumor properties. Polydopamine (pD)-based surface modification is easy to functionalize polymeric nanoparticles (NPs) surfaces with ligands and/or additional polymeric layers. In the present study, BBL-loaded formulations was developed with pD-modified NPs, which was synthesized by polylactide-TPGS (PLA-TPGS) (pD-PLA-TPGS/NPs). And galactosamine (Gal) was conjugated on the prepared NPs (Gal-pD-PLA-TPGS/NPs) for targeting the gastric cancer cells. Here, we found that BBL-loaded Gal-pD-PLA-TPGS/NPs showed the highest cellular uptake efficacy in gastric cancer cells. Gal-pD-PLA-TPGS/NPs more significantly reduced the gastric cancer cell viability. Further, greater apoptosis, autophagy and ROS generation was induced by Gal-pD-PLA-TPGS/NPs in gastric cancer cells. Additionally, compared to the other two NPs, Gal-pD-PLA-TPGS/NPs most markedly decreased ATP levels in gastric cancer cells. In vivo, Gal-pD-PLA-TPGS/NPs were specifically targeted to tumor site. Moreover, Gal-pD-PLA-TPGS/NPs exhibited the most anti-tumor effects, as evidenced by the lowest tumor volume and tumor weight. Of note, there was no significant difference was observed in body and liver weight, as well as the histological changes in major organs isolated from each group of mice. Together, the findings indicated that BBL-loaded Gal-pD-PLA-TPGS/NPs could be targeted to gastric cancer cells to suppress tumor progression without toxicity.

Polydopamine Modified TiO2 Nanotube Arrays for Long-Term Controlled Elution of Bivalirudin and Improved Hemocompatibility

Sustained and controllable release characteristics are pivotal factors for novel drug delivery technologies. TiO₂ nanotube arrays prepared by self-ordering electrochemical anodization are attractive for the development of biomedical devices for local drug delivery applications. In this work, several layers of polydopamine (PDA) were deposited to functionalize TiO₂ nanotube arrays. The anticoagulant drug bivalirudin (BVLD) was used as a model drug. PDA extended the release period of BVLD and maintained a sustained release kinetic. Depending on the number of PDA layers, the release characteristics of BVLD improved, as there was a reduced burst release (from 45% to 11%) and extended overall release period from 40 days to more than 300 days in the case of 5 layers. Besides, the BVLD loaded 5-layer PDA coating maintained the high bioactivity of BVLD and effectively reduced the thrombosis formation by inhibition of the adhesion and denaturation of fibrinogen, platelets, and other blood components. Both in vitro and ex vivo blood evaluation results demonstrated that this coating significantly improved the hemocompatibility. These results confirmed the capability of PDA fitted TiO₂ nanotube systems to be applied for local drug delivery over an extended period with well retained bioactivity and predictable release kinetics.

Surface Modification of Poly(dimethylsiloxane) with Polydopamine and Hyaluronic Acid To Enhance Hemocompatibility for Potential Applications in Medical Implants or Devices

Poly(dimethylsiloxane) (PDMS) has been widely utilized in micro-electromechanical systems (MEMS) and implantable devices. To improve the hemocompatibility of a PDMS-based implant, a facile technique was developed by modifying PDMS with a hyaluronic acid (HA) and polydopamine (PDA) composite (HA/PDA). Under appropriate ratio of HA to PDA, platelet adhesion and activation were considerably reduced on modified PDMS substrates, indicating an enhanced hemocompatibility compared to native PDMS or those coated with HA or PDA solely. HA/PDA coating also posed minimal cytotoxicity on the adhesion and proliferation of endothelial cells (HUVECs). The anti-inflammation effect of the modified PDMS surface was characterized based on the expression of critical cytokines in adherent macrophages. This study revealed that the hemocompatibility, cytotoxicity, and anti-inflammation properties could be tailored conveniently by adjusting the ratio of HA and PDA composite on the modified PDMS surface, which has an exceptional potential as the core or packaging material for constructing implantable devices in biomedical applications.