Reversible Self-Healing for Preserving Optical Transparency and Repairing Mechanical Damage in Composites

This research concentrates on the healing of optical properties, roughness, contact angle hysteresis, and shallow scratches in polymer/nanoparticle composites. A series of ternary composite blends [epoxy/halloysite nanotubes (HNTs)/cellulose acetate butyrate (CAB)] with various CAB concentrations were fabricated and subjected to a series of mechanical damages. The optimized concentration of a nanoparticle is 1.0 vol %, and the CAB concentration is 3.0 vol % based on the mechanical reinforcement and wear resistance. Nanoscale scratching, microlevel falling-sand test, and macrolevel Taber abrasions were utilized to damage the surfaces. The induced damage (roughness and surface scratch up to hundreds of nanometers in depth) healed upon heating. At any temperatures above the softening transition of the semi-interpenetrating network structure of the polymer composites, CAB migrates into the microcracks, and the essential mechanical parameters (modulus, strength, strain to failure) are recovered; in our particular epoxy/HNTs/CAB system, optical transparency is also recovered efficiently. CAB also moves to the macroscopic air/specimen interface and favorably modifies the surface properties, reducing the roll-off angles of water droplets from ∼90° to ∼20°. Through an appropriate choice of CAB additives with different molecular weights, the healing temperature can be tailored.

Macrophages with cellular backpacks for targeted drug delivery to the brain

Most potent therapeutics are unable to cross the blood-brain barrier following systemic administration, which necessitates the development of unconventional, clinically applicable drug delivery systems. With the given challenges, biologically active vehicles are crucial to accomplishing this task. We now report a new method for drug delivery that utilizes living cells as vehicles for drug carriage across the blood brain barrier. Cellular backpacks, 7-10 μm diameter polymer patches of a few hundred nanometers in thickness, are a potentially interesting approach, because they can act as drug depots that travel with the cell-carrier, without being phagocytized. Backpacks loaded with a potent antioxidant, catalase, were attached to autologous macrophages and systemically administered into mice with brain inflammation. Using inflammatory response cells enabled targeted drug transport to the inflamed brain. Furthermore, catalase-loaded backpacks demonstrated potent therapeutic effects deactivating free radicals released by activated microglia in vitro. This approach for drug carriage and release can accelerate the development of new drug formulations for all the neurodegenerative disorders.

Enhanced Wear Resistance of Transparent Epoxy Composite Coatings with Vertically Aligned Halloysite Nanotubes

The influence of nanoparticle orientation on wear resistance of transparent composite coatings has been studied. Using a nozzle spray coating method, halloysite nanotubes (HNTs) were aligned in the in-plane and out-of-plane directions and in various randomly oriented states. Nanoscratching, falling sand, and Taber Abrasion tests were used to characterize the wear resistance at different length scales. Composites consistently displayed better wear resistance than pure epoxy. Samples with out-of-plane particle orientations exhibited better wear-resistant behavior than those with in-plane particle distributions. In nanoscratching tests, the out-of-plane orientation decreases the normalized scratch volume by as much as 60% compared to pure epoxy. In the falling sand and Taber Abrasion tests, out-of-plane aligned halloysite particles resulted in surfaces with smaller roughness based on stylus profilometry and SEM observations. The decrease in roughness values after these wear tests can be as large as 67% from pure epoxy to composites. Composites with higher out-of-plane particle orientation factors exhibited better light transmittance after sand impingements and other wear tests. This study suggests a useful strategy for producing material systems with enhanced mechanical durability and more durable optical properties.

Spray-Coated Halloysite-Epoxy Composites: A Means To Create Mechanically Robust, Vertically Aligned Nanotube Composites

Halloysite nanotube-filled epoxy composites were fabricated using spray-coating methods. The halloysite nanotubes (HNTs) were aligned by the hydrodynamic flow conditions at the spray nozzle, and the polymer viscosity helped to preserve this preferential orientation in the final coatings on the target substrates. Electron microscopy demonstrated a consistent trend of higher orientation degree in the nanocomposite coatings as viscosity increased. The nanoindentation mechanical performances of these coatings were studied using a Hysitron TriboIndenter device. Composites showed improvements up to ∼50% in modulus and ∼100% in hardness as compared to pure epoxy, and the largest improvements in mechanical performance correlated with higher alignment of HNTs along the plane-normal direction. Achieving this nanotube alignment using a simple spray-coating method suggests potential for large-scale production of multifunctional anisotropic nanocomposite coatings on a variety of rigid and deformable substrates.

Liposome-Loaded Cell Backpacks

Cell backpacks, or micron-scale patches of a few hundred nanometers in thickness fabricated by layer-by-layer (LbL) assembly, are potentially useful vehicles for targeted drug delivery on the cellular level. In this work, echogenic liposomes (ELIPs) containing the anticancer drug doxorubicin (DOX) are embedded into backpacks through electrostatic interactions and LbL assembly. Poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA)n , and poly(diallyldimethylammonium chloride)/poly(styrene sulfonate) (PDAC/SPS)n film systems show the greatest ELIP incorporation of the films studied while maintaining the structural integrity of the vesicles. The use of ELIPs for drug encapsulation into backpacks facilitates up to three times greater DOX loading compared to backpacks without ELIPs. Cytotoxicity studies reveal that monocyte backpack conjugates remain viable even after 72 h, demonstrating promise as drug delivery vehicles. Because artificial vesicles can load many different types of drugs, ELIP containing backpacks offer a unique versatility for broadening the range of possible applications for cell backpacks.

Optimization of amine-rich multilayer thin films for the capture and quantification of prostate-specific antigen

It is demonstrated that poly(allylamine hydrochloride)/poly(styrenesulfonate) (PAH/SPS) multilayer films can be successfully tailored for the capture and detection of small biomolecules in dilute concentrations. Based on in vitro results, these films could be potentially applied for rapid and high-throughput diagnosis of dilute biomarkers in serum or tissue. PAH presents functional amino groups that can be further reacted with desired chemistries in order to create customizable and specific surfaces for biomolecule capture. A variety of film assembly characteristics were tested (pH, molecular weight of PAH, and ionic strength) to tune the biotinylation and swelling behavior of these films to maximize detection capabilities. The resultant optimized biotinylated PAH/SPS 9.3/9.3 system was utilized in conjunction with quantum dots (Qdots) to capture and detect a dilute biomarker for prostate cancer, prostate-specific antigen (PSA). Compared to previous work, our system presents a good sensitivity for PSA detection within the clinically relevant range of 0.4-100 ng/mL.

Sugar-mediated disassembly of mucin/lectin multilayers and their use as pH-Tolerant, on-demand sacrificial layers

The layer-by-layer (LbL) assembly of thin films on surfaces has proven to be an extremely useful technology for uses ranging from optics to biomedical applications. Releasing these films from the substrate to generate so-called free-standing multilayer films opens a new set of applications. Current approaches to generating such materials are limited because they can be cytotoxic, difficult to scale up, or have undesirable side reactions on the material. In this work, a new sacrificial thin film system capable of chemically triggered dissolution at physiological pH of 7.4 is described. The film was created through LbL assembly of bovine submaxillary mucin (BSM) and the lectin jacalin (JAC) for a (BSM/JAC) multilayer system, which remains stable over a wide pH range (pH 3-9) and at high ionic strength (up to 5 M NaCl). This stability allows for subsequent LbL assembly of additional films in a variety of conditions, which could be released from the substrate by incubation in the presence of a competitive inhibitor sugar, melibiose, which selectively disassembles the (BSM/JAC) section of the film. This novel multilayer system was then applied to generate free-standing, 7 μm diameter, circular ultrathin films, which can be attached to a cell surface as a "backpack". A critical thickness of about 100 nm for the (BSM/JAC) film was required to release the backpacks from the glass substrate, after incubation in melibiose solution at 37 °C for 1 h. Upon their release, backpacks were subsequently attached to murine monocytes without cytotoxicity, thereby demonstrating the compatibility of this mucin-based release system with living cells.

Spurious hypokalaemia and hypophosphataemia due to extreme hyperleukocytosis in a patient with a haematological malignancy

Serious hyperleukocytosis can strongly affect laboratory results of potassium, phosphate and arterial oxygen tension. A 40-year-old woman is presented with an acute myeloid leukaemia and a strongly elevated leukocyte count (310 × 109/L). Apart from this hyperleukocytosis, initial blood tests showed hypokalaemia, hypophosphataemia and serious hypoxaemia without any corresponding complaints. Blood sampled and transported on ice or directly analysed showed no electrolyte abnormalities and hypoxaemia. The observed discrepancy in laboratory results is probably due to the metabolic activity of the leukocytes in vitro. Spurious laboratory results can be a reason for incorrect decisions concerning additional diagnostics and treatment. In conclusion, hyperleukocytosis can cause pseudohypokalaemia, pseudohypophosphataemia and pseudohypoxaemia, which can be prevented by correct sampling and immediate analysis.

High-dose intravenous isosorbide-dinitrate is safer and better than Bi-PAP ventilation combined with conventional treatment for severe pulmonary edema

OBJECTIVE

To determine the feasibility, safety and efficacy of bilevel positive airway ventilation (BiPAP) in the treatment of severe pulmonary edema compared to high dose nitrate therapy.

BACKGROUND

Although noninvasive ventilation is increasingly used in the treatment of pulmonary edema, its efficacy has not been compared prospectively with newer treatment modalities.

METHODS

We enrolled 40 consecutive patients with severe pulmonary edema (oxygen saturation <90% on room air prior to treatment). All patients received oxygen at a rate of 10 liter/min, intravenous (IV) furosemide 80 mg and IV morphine 3 mg. Thereafter patients were randomly allocated to receive 1) repeated boluses of IV isosorbide-dinitrate (ISDN) 4 mg every 4 min (n = 20), and 2) BiPAP ventilation and standard dose nitrate therapy (n = 20). Treatment was administered until oxygen saturation increased above 96% or systolic blood pressure decreased to below 110 mm Hg or by more than 30%. Patients whose conditions deteriorated despite therapy were intubated and mechanically ventilated. All treatment was delivered by mobile intensive care units prior to hospital arrival.

RESULTS

Patients treated by BiPAP had significantly more adverse events. Two BiPAP treated patients died versus zero in the high dose ISDN group. Sixteen BiPAP treated patients (80%) required intubation and mechanical ventilation compared to four (20%) in the high dose ISDN group (p = 0.0004). Myocardial infarction (MI) occurred in 11 (55%) and 2 (10%) patients, respectively (p = 0.006). The combined primary end point (death, mechanical ventilation or MI) was observed in 17 (85%) versus 5 (25%) patients, respectively (p = 0.0003). After 1 h of treatment, oxygen saturation increased to 96 +/- 4% in the high dose ISDN group as compared to 89 +/- 7% in the BiPAP group (p = 0.017). Due to the significant deterioration observed in patients enrolled in the BiPAP arm, the study was prematurely terminated by the safety committee.

CONCLUSIONS

High dose ISDN is safer and better than BiPAP ventilation combined with conventional therapy in patients with severe pulmonary edema.