Light-responsive smart nanocarriers for wirelessly controlled photodynamic therapy for prostate cancers.

Photodynamic therapy (PDT) is an effective non-invasive or minimally invasive treatment method against different tumors. Loading photosensitizers in nanocarriers can potentially increase their accumulation in tumor sites. However, the PDT efficacy may be hindered because of self-quenching of the encapsulated photosensitizer and the small diffusion radii of the generated reactive oxygen species (ROS). Herein, light responsive nano assemblies composed of (Polyethylene glycol)-block-poly(4,5-dimethoxy-2-nitrobenzylmethacrylate) (PEG-b-PNBMA) were designed and loaded with the photosensitizer, Rose Bengal lactone (RB), to act as a smart nanocarrier (RB-M) for the delivery of the photosensitizer. A wirelessly activated light-emitting diode (LED) implant was designed to programmatically induce the release of the loaded RB first, followed by activating PDT after diffusion of RB into the cytoplasm. The results showed that sequential '405-580 nm' irradiation of the RB-M treated 22RV1 cells resulted in the highest PDT outcome among different irradiation protocols. The combination of this smart nanocarrier and sequential '405-580 nm' irradiation strategy exhibited good PDT efficacy against 2D 22RV1 prostate cancer cells as well as 3D cancer cell spheroids. This platform overcomes the light penetration limitations in PDT, and can potentially be applied in cancer bearing patients who are unfit for chemotherapy. STATEMENT OF SIGNIFICANCE: Nanocarriers for the delivery of photosensitizer in photodynamic therapy may result in relatively low therapeutic efficacy because of self-quenching of the encapsulated photosensitizer and the small diffusion radii of the generated reactive oxygen species (ROS). Light responsive smart nanocarriers can potentially overcome this challenge. In this study, a light responsive polymer (Polyethylene glycol)-block-poly(4,5-dimethoxy-2-nitrobenzylmethacrylate) (PEG-b-PNBMA) was synthesized and utilized to fabricate the smart nanocarrier. A wirelessly activated light-emitting diode (LED) implant was designed for light delivery in deep tissue. This new approach permits wirelessly and programmatically control of photosensitizer release and PDT activation under deep tissue, thus significantly enhancing PDT efficacy against prostate cancer cells as well as 3D cancer cell spheroids. This design should have a significant impact on controllable PDT under deep tissue.

Tumor-targeting albumin nanoparticles as an efficacious drug delivery system and potential diagnostic tool in non-muscle-invasive bladder cancer therapy.

Current intravesical chemotherapy for non-muscle invasive bladder cancer (NMIBC) has limited efficacy due to loss of the instilled agent from urine voiding and the agent's lack of specificity for the tumors. We developed a nanocarrier (txCD47-HNP, ∼100 nm) based on human serum albumin conjugated with a peptide that targets the cluster of differentiation 47 receptor overexpressed on bladder cancer (BC) cells. The IC50 of gemcitabine elaidate (GEM) loaded in the txCD47-HNP was almost an order of magnitude lower than that of free GEM. In a mouse orthotopic BC model, GEM loaded in txCD47-HNP effectively reduced the tumor burden. Tumor cells in BC patients' urine can also be targeted by fluorescence-labeled txCD47-HNP resulting in >83 % of the cells exhibiting fluorescence. Thus, txCD47-HNP can potentially be a theranostic agent in NMIBC management by serving as a targeted drug delivery vehicle as well as an alternative to urine cytology.

Glycosylated phospholipid-coated upconversion nanoparticles for bioimaging of non-muscle invasive bladder cancers.

Detection of non-muscle invasive bladder cancer (NMIBC) is crucial to facilitate complete tumor resection, thus improving the survival rate as well as reducing the recurrence frequency and treatment expense. Fluorescence imaging cystoscopy is an effective method for the detection of NMIBC. However, its application is limited as the commonly applied fluorescent agents such as dyes and photosensitizers usually lack specific tumor accumulation and are vulnerable to photobleaching. Furthermore, the broad emission band of conventional fluorescent agents limits their imaging and detection efficacy. To overcome these limitations, upconversion nanoparticles (UCNPs) have been selected as the fluorescent agent, due to their resistance to photobleaching, less background auto-fluorescence, and narrow emission bands. In order to achieve active tumor targeting, the UCNPs are coated with a glycosylated phospholipid layer. The glycosylated phospholipid-coated UCNPs exhibited high selective accumulation in cancer cells over normal cells and enhanced the upconversion luminescence (UCL) (at 540 nm and 660 nm) from bladder cancer cells under 980 nm laser irradiation. Glycosylated phospholipid coating that promotes uptake of UCNPs by cancer cells, and UCL emitted from UCNPs under NIR (980 nm) laser irradiation for cancer cell imaging.

Wirelessly Activated Nanotherapeutics for In Vivo Programmable Photodynamic-Chemotherapy of Orthotopic Bladder Cancer.

Photochemical internalization (PCI) is a promising intervention using photodynamic therapy (PDT) to enhance the activity of chemotherapeutic drugs. However, current bladder cancer treatments involve high-dose chemotherapy and high-irradiance PDT which cause debilitating side effects. Moreover, low penetration of light and drugs in target tissues and cumbersome light delivery procedures hinder the clinical utility of PDT and chemotherapy combination for PCI. To circumvent these challenges, a photodynamic-chemotherapy approach is developed comprising tumor-targeting glycosylated nanocarriers, coloaded with chlorin e6 (Ce6) and gemcitabine elaidate (GemE), and a miniaturized implantable wirelessly powered light-emitting diode (LED) as a light source. The device successfully delivers four weekly light doses to the bladder while the nanocarrier promoted the specific accumulation of drugs in tumors. This approach facilitates the combination of low-irradiance PDT (1 mW cm-2 ) and low-dose chemotherapy (≈1500× lower than clinical dose) which significantly cures and controls orthotopic disease burden (90% treated vs control, 35%) in mice, demonstrating a potential new bladder cancer treatment option.

Emerging pharmaceutical and organic contaminants removal using carbonaceous waste from oil refineries.

The occurrence of emerging organic contaminants (EOCs) such as chemicals in personal care products, pharmaceuticals, plasticizers, etc. in surface waters is a growing global concern. The discharge of most EOCs is not regulated, and EOCs have been shown to be toxic to both human and aquatic life even at low concentrations. In this work, acid-leached carbon black waste (LCBW), a carbonaceous residue from petroleum refineries, was investigated as a potential waste-derived adsorbent for the removal of EOCs. Ciprofloxacin hydrochloride, (CIPRO, antibiotic), sulfamethoxazole (SULFA, antibiotic), acetaminophen (ACET, pharmaceutical), bisphenol A (BPA, plasticizer) and N,N-diethyl-3-methylbenzamide (DEET, insect repellent) were chosen as the target EOCs owing to their presence in relatively high concentrations in surface waters as well as in the influent and effluent of wastewater treatment plants. LCBW, with a specific surface area of 409 m2/g, demonstrated 90-99% removal of 10 ppm CIPRO, BPA, and ACET and 70-80% removal of 10 ppm SULFA and DEET in tap water. Adsorption was rapid, particularly for CIPRO, BPA, and ACET, wherein >85% of the adsorption occurred within 1 h of contact time. To illustrate the potential of LCBW as an adsorbent in different physical forms, ∼3 mm spherical beads of LCBW encapsulated within carboxymethyl cellulose matrix were prepared by a facile ionic gelation method and their adsorption performance was demonstrated.

Antimicrobial Copper-Based Materials and Coatings: Potential Multifaceted Biomedical Applications.

Surface contamination by microbes leads to several detrimental consequences like hospital- and device-associated infections. One measure to inhibit surface contamination is to confer the surfaces with antimicrobial properties. Copper's antimicrobial properties have been known since ancient times, and the recent resurgence in exploiting copper for application as antimicrobial materials or coatings is motivated by the growing concern about antibiotic resistance and the pressure to reduce antibiotic use. Copper, unlike silver, demonstrates rapid and high microbicidal efficacy against pathogens that are in close contact under ambient indoor conditions, which enhances its range of applicability. This review highlights the mechanisms behind copper's potent antimicrobial property, the design and fabrication of different copper-based antimicrobial materials and coatings comprising metallic copper/copper alloys, copper nanoparticles or ions, and their potential for practical applications. Finally, as the antimicrobial coatings market is expected to grow, we offer our perspectives on the implications of increased copper release into the environment and the potential ecotoxicity effects and possibility of development of resistant genes in pathogens.

Sugar-powered nanoantimicrobials for combating bacterial biofilms.

Bacterial biofilms cause chronic infections due to their inherent tolerance to antimicrobial therapies. We describe and compare the efficacy of two types of sugar (d-glucose and d-mannose)-modified cyclodextrin nanocarriers (CD-GLU and CD-MAN) loaded with antibacterial agents for preventing and eradicating bacterial biofilm. The antibacterial agents comprise a quorum sensing inhibitor (5,6-dimethyl-2-aminobenzimidazole, DMABI) and two antibiotics (erythromycin and rifampicin), and the cyclodextrin nanocarriers were tested on Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive). DMABI loaded in the CD-GLU carrier was significantly more effective at inhibiting the development of Pseudomonas aeruginosa biofilm when compared to either its free form or when it is loaded in CD without grafted sugar moieties. Antibiotics loaded in CD-GLU and CD-MAN carriers were similarly more effective at dispersing pre-formed Pseudomonas aeruginosa biofilms. These antibacterial compounds loaded in the CD-GLU and CD-MAN carriers were somewhat less effective in eradicating Staphylococcus aureus biofilm as compared to Pseudomonas aeruginosa biofilm. This difference is attributed to the different extent of penetration of the sugar-grafted carriers into the biofilms of these two species of bacterial cells. Although the sugar-grafted carrier-antibacterial agent complexes exhibit potent effects against bacterial biofilms, they are not cytotoxic to mammalian cells.

Mucopenetration and biocompatibility of polydopamine surfaces for delivery in an Ex Vivo porcine bladder.

Urine voiding and the presence of a mucus layer on the apical surface of the urothelium are two major challenges towards an effective intravesical drug delivery for bladder malignancies. Improved bioavailability to the underlying bladder tissue could be achieved with delivery vectors that diffuse efficiently through the bladder mucus. Pegylation of delivery vectors remains the existing "gold standard" to enhance mucosal delivery despite known poor cell uptake and reported PEG sensitivity. Here, we showed improved mucopenetration of carboxylated polystyrene (PS) nanoparticles (NPs) passivated with a polydopamine (PDA) surface, at similar level as PEG. While the diffusion of PS NPs in mucus was retarded by ~1000-fold, PS-PDA diffused only 6-fold slower in mucus than water. This enabled faster and deeper penetration of PS-PDA into porcine bladder tissue beneath the mucus layer. The same PDA surface also conferred biocompatibility and enabled photothermal therapy (PTT) with significant surface disruption on an ex vivo porcine bladder model upon localized laser irradiation, which was not possible with PEG. Our outcomes suggested the facile and versatile PDA surface passivation of nanoparticles as an enabler for dual purposes of enhancing mucopenetration and allowing photothermal therapy on bladder tissue, which has not been demonstrated to date.

Polydopamine Coating Enhances Mucopenetration and Cell Uptake of Nanoparticles.

Mucus is an endogenous viscoelastic biopolymer barrier that limits the entry of foreign pathogens and therapeutic carriers to the underlying mucosal cells. This could be overcome with a hydrophilic and nonpositively charged carrier surface that minimizes interactions with the mucin glycoprotein fibers. Although PEGylation remains an attractive surface strategy to enhance mucopenetration, cell uptake of PEGylated nanoparticles (NPs) often remains poor. Here, we demonstrated polydopamine (PDA) coating to enhance both mucopenetration and cell uptake of NPs. PDA was polymerized on carboxylated polystyrene (PS) NPs to form a PDA coating, and the resulting PS-PDA achieved a similar level of mucopenetration as our PEGylated PS (PS-PEG) positive control in three separate studies: NP-mucin interaction test, transwell assay, and multiple particle tracking. Compared to water, the diffusions of PS-PDA and PS-PEG in reconstituted mucus solution were only 3.5 and 2.4 times slower, respectively, whereas the diffusion of bare PS was slowed by up to 250 times. However, the uptake of PS-PDA (61.2 ± 6.1%) was almost three times higher than PS-PEG (24.6 ± 5.4%) in T24 cells, which were used as a model for underlying mucosal cells. Our results showed a novel unreported functionality of PDA coating in enhancing both mucopenetration and cell uptake of NPs for mucosal drug delivery applications, not possible with conventional PEGylation strategies.

Receptor-Targeting Drug and Drug Carrier for Enhanced Killing Efficacy against Non-Muscle-Invasive Bladder Cancer.

Intravesical chemotherapy for bladder cancer has limited efficacy due to the lack of specificity of drugs/drug carriers toward the cancer cells as well as inadequate drug residence time in the bladder due to urine voiding. From analyses of surface receptor expression of UMUC3 bladder cancer cells and the targeting efficacy of different peptides, we selected a peptide (txCD47) that targets the cluster of differentiation 47 (CD47) surface protein overexpressed on these cells as a targeting ligand for docetaxel (DTX) and an albumin nanocarrier of DTX. The IC50 of DTX conjugated to txCD47 (txCD47-DTX) in a 1:1 molar ratio was lowered by a factor of 3 from that of free DTX. By using the albumin molecule (txCD47-BSA) as a delivery vehicle, different amounts of txCD47 can be conjugated to investigate the effects of peptide concentration on targeting efficacy. The IC50 of DTX loaded in txCD47-BSA with 14 txCD47 per albumin molecule was 1 order of magnitude lower than that of free DTX, and a factor of 4 lower than that of txCD47-BSA with 8 txCD47 per albumin molecule. DTX was released from the albumin nanocarrier at a controlled rate, and the endocytosed carrier will release most of its payload inside the cells within 72 h. Thus, txCD47 promotes delivery of the drug/drug carrier, and the resultant enhanced killing efficacy of the drug can potentially alleviate some of the limitations of intravesical chemotherapy against bladder cancer.

Transparent Copper-Based Antibacterial Coatings with Enhanced Efficacy against Pseudomonas aeruginosa.

Bacterial surface contamination is a major cause of hospital-associated infections. Antibacterial coatings can play an important role in reducing bacterial transmission via inanimate surfaces in healthcare settings. In this work, transparent copper-based antibacterial coatings were fabricated on commercial poly(vinyl fluoride) and stainless steel. Acrylated quaternized chitosan and ethylenediaminetetraacetic acid were covalently grafted on the substrate for complexation with copper ions. The number of viable Staphylococcus aureus in a droplet [containing ∼104 colony forming units (CFU)], deposited on the copper-containing coating decreased by ∼96% within 60 min at 25 °C. With Pseudomonas aeruginosa, one of the most virulent and hardest to kill bacteria, no CFU could be observed within the same time span (killing efficacy >99.8% based on the detection limit). An increase in copper release from the coating was observed in the presence of P. aeruginosa, which was postulated to be due to the proteolytic activity of P. aeruginosa. The higher efficacy of the coating against P. aeruginosa compared to S. aureus is thus attributed to this increased copper release from the coating, which resulted in extensive bacterial membrane damage and death. The copper-containing coating on poly(vinyl fluoride) retained its antibacterial efficacy after 100 wipes with a water-wetted cloth or isopropanol wipes, demonstrating its durability and long-term efficacy. The coating did not exhibit significant cytotoxicity toward mammalian fibroblasts, further demonstrating its potential for mitigating bacterial transmission in a clinical setting.

Restriction of in vivo infection by antifouling coating on urinary catheter with controllable and sustained silver release: a proof of concept study.

BACKGROUND: Catheter Associated Urinary Tract Infections are among the most common urological infections world-wide. Bacterial biofilms and encrustation cause significant complications in patients with urinary catheters. The objective of the study is to demonstrate the efficacy and safety of an anti-microbial and anti-encrustation silver nanoparticle (AgNP) coating on silicone urinary catheter in two different animal models. METHODS: Antifouling coating (P3) was prepared with alternate layers of polydopamine and AgNP and an outermost antifouling layer. Sixteen C57BL/6 female mice and two female PWG Micropigs® were used to perform the experiments. In mice, a 5 mm long silicone catheter with or without P3 was transurethrally placed into the urinary bladder. Micropigs were transurethrally implanted - one with P3 silicone catheter and the other with commercially available silver coated silicone catheter. Both models were challenged with E. coli. Bacteriuria was evaluated routinely and upon end of study (2 weeks for mice, 3 weeks for micropigs), blood, catheters and bladders were harvested and analysed for bacterial colonization and encrustation as well as for toxicity. RESULTS: Lower bacterial colonization was seen on P3 catheters as well as in bladders of animals with P3 catheter. Bacteriuria was consistently less in mice with P3 catheter than with uncoated catheters. Encrustation was lower on P3 catheter and in bladder of micropig with P3 catheter. No significant toxicity of P3 was observed in mice or in micropig as compared to controls. The numbers were small in this proof of concept study and technical issues were noted especially with the porcine model. CONCLUSIONS: Antifouling P3 coating reduces bacterial colonization on catheter and in animal bladders without causing any considerable toxicity for 2 to 3 weeks. This novel coating could potentially reduce the complications of indwelling urethral catheters.

Polydopamine Nanoparticles Enhance Drug Release for Combined Photodynamic and Photothermal Therapy.

Our study shows a facile two-step method which does not require the use of core templates to load a hydrophobic photosensitizer drug chlorin e6 (Ce6) within polydopamine (PDA) nanoparticles (NPs) while maintaining the intrinsic surface properties of PDA NPs. This structure is significantly different from hollow nanocapsules which are less stiff as they do not possess a core. To our knowledge, there exist no similar studies in the literature on drug loading within the polymer matrix of PDA NPs. We characterized the drug loading and release behavior of the photosensitizer Ce6 and demonstrated the therapeutic efficacy of the combined photodynamic (PDT) and photothermal therapy (PTT) from Ce6 and PDA, respectively, under a single wavelength of 665 nm irradiation on bladder cancer cells. We obtained a saturated loading amount of 14.2 ± 0.85 µM Ce6 in 1 nM PDA NPs by incubating 1 mg/mL dopamine solution with 140 µM of Ce6 for 20 h. The PDA NPs maintained colloidal stability in biological media, whereas the pi-pi (π-π) interaction between PDA and Ce6 enabled a release profile of the photosensitizer until day 5. Interestingly, loading of Ce6 in the polymer matrix of PDA NPs significantly enhanced the cell uptake because of endocytosis. An increased cell kill was observed with the combined PDT + PTT from 1 nM PDA-Ce6 compared to that with PTT alone with 1 nM PDA and PDT alone with 15 µM equivalent concentration of free Ce6. PDA-Ce6 NPs could be a promising PDT/PTT therapeutic agent for cancer therapy.

Extraction and quantification of biofilm bacteria: Method optimized for urinary catheters.

Bacterial biofilms are responsible for the failure of many medical devices such as urinary catheters and are associated with many infectious and non-infectious complications. Preclinical and clinical evaluation of novel catheter coatings to prevent these infections needs to accurately quantify the bacterial load in the biofilm in vitro and ex vivo. There is currently no uniform gold standard for biofilm quantification for different surfaces and established biofilms. We have tried to establish a simple, accurate and reproducible method for extraction and measurement of biofilm bacteria on indwelling catheters, using a combination of vortexing and sonication. We demonstrate the usefulness of this method for catheters of different sizes - 3 Fr to 14 Fr - in vitro, in murine and porcine models, and indwelling in human clinical subjects. We also demonstrate consistent results with complex and polymicrobial biofilms. We believe that this standardized reproducible method will assist the assessment of biofilms in general and urological devices in particular in efforts to harness novel technologies to prevent healthcare associated infections.

Tailoring Polyelectrolyte Architecture To Promote Cell Growth and Inhibit Bacterial Adhesion.

An important challenge facing the application of implanted biomaterials for tissue engineering is the need to facilitate desirable tissue interactions with the implant while simultaneously inhibiting bacterial colonization, which can lead to implant-associated infection. In this study, we explore the relevance of the physical parameters of polyelectrolyte multilayers, such as surface charge, wettability, and stiffness, in tissue cell/surface and bacteria/surface interactions, and investigate the tuning of the multilayer architecture to differentially control such interactions. Polyions with different side-chain chemical structures were paired with polyethylenimine to assemble multilayers with parallel control over surface charge and wettability under controlled conditions. The multilayers can be successfully cross-linked to yield stiffer (the apparent Young's modulus was increased more than three times its original value) and more stable films while maintaining parallel control over surface charge and wettability. The initial adhesion and proliferation of 3T3 fibroblast cells were found to be strongly affected by surface charge and wettability on the non-cross-linked multilayers. On the other hand, these cells adhered and proliferated in a manner similar to those on the cross-linked multilayers (apparent Young's modulus ∼2 MPa), regardless of surface charge and wettability. In contrast, Staphylococcus aureus ( S. aureus) and Escherichia coli ( E. coli) adhesion was primarily controlled by surface charge and wettability on both cross-linked and non-cross-linked multilayers. In both cases, negative charge and hydrophilicity inhibited their adhesion. Thus, a surface coating with a relatively high degree of stiffness from covalent cross-linking coupled with negative surface charge and high wettability can serve as an efficient strategy to enhance host cell growth while resisting bacterial colonization.

Dominant Albumin-Surface Interactions under Independent Control of Surface Charge and Wettability.

Understanding protein adsorption behaviors on solid surfaces constitutes an important step toward development of efficacious and biocompatible medical devices. Both surface charge and wettability have been shown to influence protein adsorption attributes, including kinetics, quantities, deformation, and reversibility. However, determining the dominant interaction in these surface-induced phenomena is challenging because of the complexity of inter-related mechanisms at the liquid/solid interface. Herein, we reveal the dominant interfacial forces in these essential protein adsorption attributes under the influence of a combination of surface charge and wettability, using quartz crystal microbalance with dissipation monitoring and atomic force microscopy-based force spectroscopy on a series of model surfaces. These surfaces were fabricated via layer-by-layer assembly, which allowed two-dimensional control of surface charge and wettability with minimal cross-parameter dependency. We focused on a soft globular protein, bovine serum albumin (BSA), which is prone to conformational changes during adsorption. The information obtained from the two techniques shows that both surface charge and hydrophobicity can increase the protein-surface interaction forces and the adsorbed amount. However, surface hydrophobicity triggered a greater extent of deformation in the adsorbed BSA molecules, leading to more dehydration, spreading, and resistance to elution by ionic strength changes regardless of the surface charge. The role played by the surface charge in the adsorbed protein conformation and extent of desorption induced by changes in the ionic strength is secondary to that of surface hydrophobicity. These findings advance the understanding of how surface chemistry and properties can be tailored for directing protein-substrate interactions.

pH-Sensitive Zwitterionic Polymer as an Antimicrobial Agent with Effective Bacterial Targeting.

It is highly desirable to develop new and more potent biocompatible antimicrobial agents to reduce the increasing risk of bacterial infection worldwide. To address this problem, we prepared a smart pH-sensitive polymer, poly(N'-citraconyl-2-(3-aminopropyl-N,N-dimethylammonium)ethyl methacrylate), or P(CitAPDMAEMA), which can undergo change in functionality from a biocompatible zwitterionic polymer to an antimicrobial cationic polymer at acidic bacterial infection sites. The precursor polymer, poly(2-(3-aminopropyl-N,N-dimethylammonium)ethyl methacrylate) (P(APDMAEMA)), was first prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization, and then modified with citraconic anhydride to obtain the zwitterionic P(CitAPDMAEMA). P(CitAPDMAEMA) is zwitterionic at physiological pH and exhibits low hemotoxicity and good biocompatibility. However, P(CitAPDMAEMA) can change from neutral to cationic with decreasing pH because of the hydrolysis of citraconic amide under low pH conditions. This switch leads to pronounced bacteria binding of cationic P(CitAPDMAEMA) under acidic conditions of the infection sites and significantly inhibits the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). These results indicate that P(CitAPDMAEMA) is potentially a new on-demand antimicrobial agent.

Electrical stimulation of adipose-derived mesenchymal stem cells and endothelial cells co-cultured in a conductive scaffold for potential orthopaedic applications.

Electrical stimulation (ES) has emerged as a useful tool to regulate cell behaviour, but the effect of ES on mesenchymal stem cell (MSC)/vasculogenic cell co-culture has not been investigated. Herein, human adipose-derived MSCs (AD-MSCs) and umbilical vein endothelial cells (HUVECs) were co-cultured in an electrically conductive polypyrrole/chitosan scaffold. Compared with AD-MSC monoculture, calcium deposition in the co-culture without and with ES (200 µA for 4 h/day) was 139% and 346% higher, respectively, after 7 days. As the application of ES to AD-MSC monoculture only increased calcium deposition by 56% compared with that without ES after 7 days, these results indicate that ES and co-culture with HUVECs have synergistic effects on AD-MSCs' osteogenic differentiation. ES application also significantly enhanced CD31 expression of HUVECs. In HUVEC monoculture, application of ES increased CD31 expression by 224%, whereas the corresponding increase in AD-MSC/HUVEC co-culture with ES application was 62%. The gene expression results indicate that ES enhanced the cellular functions in AD-MSC and HUVEC monoculture via autocrine bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF), respectively. In co-culture, crosstalk between AD-MSCs and HUVECs due to paracrine BMP-2 and VEGF enhanced the cellular functions compared with the respective monoculture. With application of ES to the AD-MSC/HUVEC co-culture, autocrine signalling was enhanced, resulting in further promotion of cellular functions. These findings illustrate that co-culturing AD-MSC/HUVEC in a conductive scaffold with ES offers potential benefits for bone defect therapy.

Transparent Copper-Loaded Chitosan/Silica Antibacterial Coatings with Long-Term Efficacy.

Bacteria-contaminated inanimate surfaces within hospitals and clinics result in transmission of pathogens via direct or indirect contact, leading to increased risk of healthcare-associated infections (HAI). The use of antibacterial coatings is a potential way of reducing the bacterial burden, but many surfaces such as instrument panels and monitors necessitate the coatings to be transparent while being highly antibacterial. In this work, silica nanoparticles (SiO2 NPs) were first grown over a layer of acrylated quaternized chitosan (AQCS) covalently immobilized on commercially available transparent poly(vinyl fluoride) (PVF) films. The SiO2 NPs then served as nanoreservoirs for adsorption of copper ions. The coated PVF films were transparent and reduced viable bacterial count by ∼99% and 100%, when incubated with a bacteria-loaded droplet for 60 and 120 min, respectively. The killing efficacy of these coatings, after wiping 100 times, with a deionized water-wetted cloth was reduced slightly to 97-98%. The stability of these coatings can be further improved with the deposition of another layer of cationic quaternized chitosan (QCS) over the negatively charged SiO2 NP layer, wherein the coatings maintained ∼99% killing efficacy even after 100 wipes. These coatings showed no significant toxicity to mammalian cells and, hence, can potentially be used in a clinical setting for reducing HAI.

A one step method for the functional and property modification of DOPA based nanocoatings.

Biomimetic poly(catecholamine) coatings have gained much attention in recent years due to their versatility as functional materials. Despite this, only limited methods are available to modify the function and property of poly(catecholamine) coatings, primarily through post-modification methods. Our approach reported herein provides a simple approach to the fabrication of novel functionalized poly(catecholamine) coatings. The strategy employs the copolymerization of N-Ac-3,4-dihydroxyphenylalanine methyl ester (NADOPAMe) with nucleophilic additives, giving rise to nano-coatings on various surfaces including plastic, metal, glass and polymers. With the appropriate choice of nucleophilic additives, coatings with desired properties can be achieved. This is demonstrated through the fabrication of a redox responsive coating based on NADOPAMe with cysteamine as additive, which shows a concentration-dependent glutathione (GSH) responsive behavior. The ability to utilize this as a controlled release system is also demonstrated.