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Supplemental Material, sj-docx-1-gsj-10.1177_21925682211022290 for Racial Disparities in Perioperative Morbidity Following Oncological Spine Surgery by Rafael De la Garza Ramos, Jong Hyun Choi, Ishan Naidu, Joshua A. Benton, Murray Echt, Vijay Yanamadala, Peter G. Passias, John H. Shin, David J. Altschul, C. Rory Goodwin, Daniel M. Sciubba and Reza Yassari in Global Spine Journal

Two dimensional (2D) van der Waals heterostructures from transition metal dichalcogenide (TMDC) semiconductors show a new class of spatially separate excitons with extraordinary properties. The interlayer excitons (XI) have been studied extensively, yet the mechanisms that modulate XI are still not well understood. Here, we introduce several organic-layer-embedded hybrid heterostructures, MoS2/organic/WSe2, to study the binding energy of XI. We discover that the dielectric screening of the quasi-particle is reduced with organic molecules due to decreased dielectric constant and greater separation distance between the TMDC layers. As a result, a distinct blueshift is observed in interlayer emission. We also find that the band alignment at the heterointerface is critical. When the organic layer provides a staggered energy state, interlayer charge transfer can transition from tunneling to band-assisted transfer, further increasing XI emission energies due to a stronger dipolar interaction. The formation of XI may also be significantly suppressed with electron or hole trapping molecules. These findings should be useful in realizing XI-based optoelectronics.

Motor proteins, like kinesin, transport cargo within biological cells by transforming chemical energy into mechanical energy through the hydrolysis of adenosine triphosphate (ATP). Kinesins walk across small tracks called microtubules. Recent studies have found that these concepts can be applied in vitro by attaching the motors to a glass substrate, on which microtubules can then glide across. These systems could be useful for many applications, such as targeted drug delivery and efficient, easy medical diagnosis. However, the motion of traveling microtubules is randomly ordered, and methods for controlling it are often hard to implement and recreate. One promising approach is to use depletants, or unreactive macromolecules, that can align microtubules in the same direction by forcing them to move together. This study aims to improve control of microtubule collective motion by using DNA as a signal to increase the effect that depletants have on the microtubule system. This is done by attaching bulky DNA molecules to the filaments, thus increasing their volumes. By comparing the organization of the system before and after the modification of the microtubules, the effects can be analyzed at many concentrations. This study provides an assessment of the relationship between the use of altered microtubules and the concentration of depletants within a gliding assay to induce an ordered collective motion.

Limitations to current solar cells include the high cost of pure silicon and poor current transfer within cells. An emerging alternative is single-walled carbon nanotubes (SWCNTs), which when combined with DNA and porphyrin chromophores can generate a current when absorbing light. We sought to find a chromophore and conditions that would promote bonding to the SWCNTs and improve light harvesting, while being able to regenerate on the film after being damaged. This was experimentally tested by first making SWCNT films on conducting glass slides. These were then functionalized in solutions of chromophore and spectra were measured to determine the bonding and absorbtion changes. Samples were also tested on an electrode system to measure photocurrents. Key shifts were noted for functionalization in porphyrin and defunctionalization in buffer solution, which caused the release of chromophore by DNA conformation change. The films consistently generated an electric current when exposed to light, with increased current from assembled SWCNT-DNA-porphyrin complexes. Through this testing we found that the regeneration was feasible with the solutions tested on the SWNT films and chromophore solutions. Further research can be done regarding DNA bonding interactions with porphryin and SWCNTs to promote functionality of the light-harvesting donor-acceptor complex.

Single-wall carbon nanotubes (SWCNTs) are a promising material for future biological applications such as imaging and targeted drug delivery. SWCNTs can be made soluble in water through surface functionalization, a priority for their use in biology. By studying the surface chemistry of SWCNTs, various functionalization methods can be accomplished without perturbing their electronic structure. This study probes the use of pyrene derivatives and phospholipids to non-covalently functionalize SWCNTs, maintaining useful surface properties. Phospholipids cross-linked to polyethylene glycol (PEG) or 1-pyrenebutyric acid conjugated to DNA is anchored onto the sidewalls of SWCNTs by hydrophobic interactions or π-stacking. The PEG/DNA portion is water soluble and biocompatible, thus solubilizing the SWCNTs. Biofunctional materials such as DNA or proteins can be attached to the functionalized nanotubes and used for biological applications. Functionalization is characterized by optical methods and atomic force microscopy (AFM). Length sorting of SWCNTs fit for use in bio-functionalization is also explored. By functionalizing SWCNTs with groups that are cytologically compatible, allowing for their dispersion in water, they show greater promise in future biological applications.

Motor proteins such as kinesin move along microtubules in order to transport cellular cargos throughout the cell by obtaining energy from RNA hydrolysis which allows the cell to complete the tasks needed to stay alive. In this work, we developed synthetic molecular motors using DNA enzymes (DNAzyme) and fluorescent nanomaterials which mimic the functions and structures of motor proteins. A DNAzyme-capped CdS nanoparticle and a RNA-functionalized single-walled carbon nanotube (SWCNT) were used as a walker and a track in the motor platform, respectively. As a walking mechanism, the DNAzyme cleaved the RNA substrates in the presence of metal cations. The RNA molecules were functionalized with SWCNTs using pi-pi stacking. Due to their fluorescent properties under specific light excitations, they were visualized to track the position of our motor. In addition, we studied the kinetics of molecular motors in different environments. As a result, the fastest translocation velocity was found to be 1nm min-1 and the maximum displacement was 3µm. A turnover rate of 0.025s-1 was determined by making a kinetic model based on the density of the single motor reactions. We demonstrated that the cation concentration, type of metal cation, pH, and temperature all modify the kinetics of the molecular motor. In conclusion, we developed the bio-inspired synthetic motors using DNA nanotechnology and showed how to control their movements using design of structures and modification of chemical environments. In the future, we will develop the kinetic model to analyze their kinetics and design the optimized molecular motors on purpose.

In the search to improve solar cells, scientists are exploring new materials that will provide better current transfer. One material that has emerged as a strong contender is the single walled carbon nanotube (SWNT). Current DNA-SWNT based films combined with chromophores have poor operational lifetimes compared to commercial solar cells. Once exposed to light the chromophore begins to degrade, eventually rendering the solar cell unusable. To solve this problem, we used a method involving multiple steps. First we found which DNA sequences formed structures around the SWNT that could hold the most chromophores by using a spectrophotometer to test the concentration of chromophores on each film. Secondly we determined which chromophores generated the strongest current when exposed to light by testing the photocurrent of each film. Finally we searched for a chemical, or solution, that would remove damaged chromophores without damaging or removing the DNA or SWNTs from the film. Currently it has been found that DNA sequences high in guanine, which form G-quadruplexes, are ideal for holding chromophores. Through testing, we found that zinc porphyrin created the strongest current of the chromophores tried. Research still needs to be done to find an ideal solution for removing damaged chromophores, but progress has been made into making organic solar cells viable. Eventually automating this process, a solar cell could be repeatedly refunctionalized, thus extending the life of the solar cells indefinitely.

Naturally occurring photosynthetic systems in plants are supported by elaborate pathways of self-repair that limit the impact of photo-damage. Herein, we demonstrate a complex consisting of two recombinant proteins, phospholipids and a carbon nanotube that reversibly assembles into a particular configuration, forming an array of 4 nm lipid bilayers housing light-converting proteins. The system can reversibly self-assemble into this configuration, and disassemble upon the addn. of sodium cholate, over an indefinite no. of cycles. The assembly is thermodynamically meta-stable and can only transition reversibly between free components and assembled state if the rate of surfactant removal exceeds about 10-5 sec-1. Only in the assembled state, do the complexes exhibit photoelectrochem. activity. We demonstrate a regeneration cycle that utilizes only surfactant to signal between assembly and disassembly with the result that photo-conversion efficiency is increased more than 300% over 168 h, and the useable lifetime extended indefinitely. [on SciFinder(R)]