Polymer multilayer tattooing for enhanced DNA vaccination

DNA vaccines have many potential benefits but have failed to generate robust immune responses in humans. Recently, methods such as in vivo electroporation have demonstrated improved performance, but an optimal strategy for safe, reproducible, and pain-free DNA vaccination remains elusive. Here we report an approach for rapid implantation of vaccine-loaded polymer films carrying DNA, immune-stimulatory RNA, and biodegradable polycations into the immune-cell-rich epidermis, using microneedles coated with releasable polyelectrolyte multilayers. Films transferred into the skin following brief microneedle application promoted local transfection and controlled the persistence of DNA and adjuvants in the skin from days to weeks, with kinetics determined by the film composition. These ‘multilayer tattoo’ DNA vaccines induced immune responses against a model HIV antigen comparable to electroporation in mice, enhanced memory T-cell generation, and elicited 140-fold higher gene expression in non-human primate skin than intradermal DNA injection, indicating the potential of this strategy for enhancing DNA vaccination.Howard Hughes Medical Institute (Investigator)Ragon Institute of MGH, MIT, and HarvardNational Institutes of Health (U.S.) (NIH AI095109)United States. Dept. of Defense. Institute for Soldier Nanotechnologies (contract W911NF-07-D-0004)United States. Dept. of Defense. Institute for Soldier Nanotechnologies (contract W911NF-07-0004

Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers

We fit the size distribution of liquid-ordered (Lo) domains measured from fluorescence images of model cytoplasmic myelin monolayers with an equilibrium thermodynamic expression that includes the competing effects of line tension, λ, dipole density difference, Δm, and the mixing entropy. From these fits, we extract the line tension, λ, and dipole density difference, Δm, between the Lo and liquid-disordered (Ld) phases. Both λ and Δm decrease with increasing surface pressure, Graphic, although λ/Δm2 remains roughly constant as the monolayer approaches the miscibility surface pressure. As a result, the mean domain size changed little with surface pressure, although the polydispersity increased significantly. The most probable domain radius was significantly smaller than that predicted by the energy alone, showing that the mixing entropy promotes a greater number of smaller domains. Our results also explain why domain shapes are stable; at equilibrium, only a small fraction of the domains are large enough to undergo theoretically predicted shape fluctuations. Monolayers based on the composition of myelin from animals with experimental allergic encephalomyelitis had slightly lower values of λ and Δm, and a higher area fraction of domains, than control monolayers at all Graphic. While it is premature to generalize these results to myelin bilayers, our results show that the domain distribution in myelin may be an equilibrium effect and that subtle changes in surface pressure and composition can alter the distribution of material in the monolayer, which will likely also alter the interactions between monolayers important to the adhesion of the myelin sheath.National Institutes of Health (U.S.) (Grant GM076709)National Institutes of Health (U.S.) (Grant HL051177

Deposition Kinetics of Graphene Oxide on Charged Self-Assembled Monolayers

Numerous applications of graphene oxide (GO) thin films have emerged after the discovery of their intriguing electrical, mechanical, and thermal properties. Function and performance of such GO films tend to depend on their homogeneity, morphology, and nanostructure, which are influenced by their deposition kinetics. This study investigates the kinetics of GO deposition on substrates of systematically varying surface potentials via systematic quartz crystal microbalance with dissipation and atomic force microscopy techniques. While the substrates with a positive surface potential yielded high deposition rates but wrinkled GO films, the substrates with a negative surface potential lead to low deposition rates but smooth GO films. For the repulsive interactions, the deposition rate was found to roughly exponentially decay with the product of surface potentials of GO and the substrate. Also, building upon the Gouy–Chapman theory and the additivity of van der Waals interactions, expressions for electrostatic double-layer and van der Waals interactions between a nanoplatelet (e.g., GO) and a planar wall under parallel, perpendicular, and inclined configurations were derived to explain the observed deposition trends. We anticipate that these findings will provide useful guidelines for manipulating and controlling the aqueous deposition of GO and structural properties of resultant GO films

Adsorption mechanism of myelin basic protein on model substrates and its bridging interaction between the two surfaces

Myelin basic protein (MBP) is an intrinsically disordered (unstructured) protein known to play an important role in the stability of myelin's multilamellar membrane structure in the central nervous system. The adsorption of MBP and its capacity to interact with and bridge solid substrates has been studied using a surface forces apparatus (SFA) and a quartz crystal microbalance with dissipation (QCM-D). Adsorption experiments show that MBP molecules adsorb to the surfaces in a swollen state before undergoing a conformational change into a more compact structure with a thickness of similar to 3 nm. Moreover, this compact structure is able to interact with nearby mica surfaces to form adhesive bridges. The measured adhesion force (energy) between two bridged surfaces is 1.0 +/- 0.1 mN/m, (E-ad = 0.21 +/- 0.02 mJ/m(2)), which is slightly smaller than our previously reported adhesion force of 1.7 mN/m (E-ad = 0.36 mJ/m(2)) for MBP adsorbed on two supported lipid bilayers (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775). The saturated surface concentration of compact MBP on a single SiO2 surface reaches a stable value of 310 +/- 10 ng/cm(2) regardless of the bulk MBP concentration. A kinetic three-step adsorption model was developed that accurately fits the adsorption data. The developed model is a general model, not limited to intrinsically disordered proteins, that can be extended to the adsorption of various chemical compounds that undergo chemical reactions and/or conformational changes upon adsorbing to surfaces. Taken together with our previously published data (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775), the present results confirm that conformational changes of MBP upon adsorption are a key for strong adhesion, and that such conformational changes are strongly dependent on the nature of the surfaces.close1

Distinctive Stress-Stiffening Responses of Regenerated Silk Fibroin Protein Polymers under Nanoscale Gap Geometries: Effect of Shear on Silk Fibroin-Based Materials

Interfacial dynamics, assembly processes, and changes in nanostructures and mechanical properties of Bombyx mori silk fibroin (SF) proteins under varying degrees of nanoconfinement without and with lateral shear are investigated. When only compressive confinement forces were applied, SF proteins adsorbed on the surfaces experienced conformational changes following the Alexander-de Gennes theory of polymer brushes. By contrast, when SF proteins were exposed to a simultaneous nanoconfinement and shear, remarkable changes in interaction forces were observed, displaying the second order phase transitions, which are attributed to the formation of SF micelles and globular superstructural aggregates via hierarchical assembly processes. The resultant nanostructured SF aggregates show several folds greater elastic moduli than those of SF films prepared by drop-casting and compression-only and even degummed SF fibers. Such a striking improvement in mechanical strength is ascribed to a directional organization of β-sheet nanocrystals, effectively driven by nanoconfinement and shear stress-induced stiffing and ordering mechanisms

Adsorption mechanism of myelin basic protein on model substrates and its bridging interaction between the two surfaces.

Myelin basic protein (MBP) is an intrinsically disordered (unstructured) protein known to play an important role in the stability of myelin's multilamellar membrane structure in the central nervous system. The adsorption of MBP and its capacity to interact with and bridge solid substrates has been studied using a surface forces apparatus (SFA) and a quartz crystal microbalance with dissipation (QCM-D). Adsorption experiments show that MBP molecules adsorb to the surfaces in a swollen state before undergoing a conformational change into a more compact structure with a thickness of ∼3 nm. Moreover, this compact structure is able to interact with nearby mica surfaces to form adhesive bridges. The measured adhesion force (energy) between two bridged surfaces is 1.0 ± 0.1 mN/m, (Ead = 0.21 ± 0.02 mJ/m(2)), which is slightly smaller than our previously reported adhesion force of 1.7 mN/m (Ead = 0.36 mJ/m(2)) for MBP adsorbed on two supported lipid bilayers (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775). The saturated surface concentration of compact MBP on a single SiO2 surface reaches a stable value of 310 ± 10 ng/cm(2) regardless of the bulk MBP concentration. A kinetic three-step adsorption model was developed that accurately fits the adsorption data. The developed model is a general model, not limited to intrinsically disordered proteins, that can be extended to the adsorption of various chemical compounds that undergo chemical reactions and/or conformational changes upon adsorbing to surfaces. Taken together with our previously published data (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775), the present results confirm that conformational changes of MBP upon adsorption are a key for strong adhesion, and that such conformational changes are strongly dependent on the nature of the surfaces

Bacterial Antifouling Characteristics of Helicene-Graphene Films.

Herein, we describe interfacially-assembled [7]helicene films that were deposited on graphene monolayer using the Langmuir-Schaefer deposition by utilizing the interactions of nonplanar (helicene) and planar (graphene) π-π interactions as functional antifouling coatings. Bacterial adhesion of Staphylococcus aureus on helicene-graphene films was noticeably lower than that on bare graphene, up to 96.8% reductions in bacterial adhesion. The promising bacterial antifouling characteristics of helicene films was attributed to the unique molecular geometry of helicene, i.e., nano-helix, which can hinder the nanoscale bacterial docking processes on a surface. We envision that helicene-graphene films may eventually be used as protective coatings against bacterial antifouling on the electronic components of clinical and biomedical devices

Bacterially Antiadhesive, Optically Transparent Surfaces Inspired from Rice Leaves

Because of the growing prevalence of antimicrobial resistance strains, there is an increasing need to develop material surfaces that prevent bacterial attachment and contamination in the absence of antibiotic agents. Herein, we present bacterial antiadhesive materials inspired from rice leaves. “Rice leaf-like surfaces” (RLLS) were fabricated by a templateless, self-masking reactive-ion etching approach. Bacterial attachment on RLLS was characterized under both static and dynamic conditions using Gram-negative <i>Escherichia coli</i> O157:H7 and Gram-positive <i>Staphylococcus aureus</i>. RLLS surfaces showed exceptional bacterial antiadhesion properties with a >99.9% adhesion inhibition efficiency. Furthermore, the optical properties of RLLS were investigated using UV–vis–NIR spectrophotometry. In contrast to most other bacterial antiadhesive surfaces, RLLS demonstrated optical-grade transparency (i.e., ≥92% transmission). We anticipate that the combination of bacterial antiadhesion efficiency, optical grade transparency, and the convenient single-step method of preparation makes RLLS a very attractive candidate for the surfaces of biosensors; endoscopes; and microfluidic, bio-optical, lab-on-a-chip, and touchscreen devices