• Fluctuation scaling, the calibration of dispersion, and the detection of differences

      Holland, Rianne; Rebmann, Roman; Williams, Craig D.; Hanley, Quentin S. (ACS Publications, 2017-10-26)
      Fluctuation scaling describes the relationship between the mean and standard deviation of a set of measurements. An example is Horwitz scaling which has been reported from inter-laboratory studies. Horwitz and similar studies have reported simple exponential and segmented scaling laws with exponents (α) typically between 0.85 (Horwitz) and 1 when not operating near a detection limit. When approaching a detection limit the exponents change and approach an apparently Gaussian (α = 0) model. This behavior is generally presented as a property of inter-laboratory studies which makes controlled replication to understand the behavior costly to perform. To assess the contribution of instrumentation to larger scale fluctuation scaling, we measured the behavior of two inductively coupled plasma atomic emission spectrometry (ICP-AES) systems, in two laboratories measuring thulium using 2 emission lines. The standard deviation universally increased with the uncalibrated signal indicating the system was heteroscedastic. The response from all lines and both instruments was consistent with a single exponential dispersion model having parameters α = 1.09 and β = 0.0035. No evidence of Horwitz scaling was found and there was no evidence of Poisson noise limiting behavior. The “Gaussian” component was a consequence of background subtraction for all lines and both instruments. The observation of a simple exponential dispersion model in the data allows for the definition of a difference detection limit (DDL) with universal applicability to systems following known dispersion. The DDL is the minimum separation between two points along a dispersion model required to claim they are different according to a particular statistical test. The DDL scales transparently with the mean and works at any location in a response function.
    • Ni-ZSM-5 and Cu-ZSM-5 Synthesized Directly from Aqueous Fluoride Gels.

      Round, Catherine I.; Williams, Craig D.; Latham, Kay; Duke, Catherine V. A. (ACS Publications, 2001)
      Ni-ZSM-5 and Cu-ZSM-5 have been synthesized in a slightly acidic fluoride medium. A low water H-ZSM-5 formula was used to synthesize the metal-substituted systems using bis(tetraethylammonium) tetrachloronickelate(II) [N(CH2CH3)4]2[NiCl4] and bis(tetraethylammonium) tetrachlorocuprate(II) [N(CH2CH3)4]2[CuCl4] as the tetrahedrally coordinated metal species. X-ray diffraction analysis established the presence of highly crystalline and thermally stable material. Unit cell dimensions increased with increasing levels of metal substitution. X-ray fluorescence (XRF) bulk analysis showed increasing levels of metals in the material and corresponding decreases in the moles of silica. The maximum levels of substitution achieved were Ni 3.93 and Cu 4.38 (in wt %). Analysis by scanning electron microscopy (SEM) showed a crystal morphology similar to that of H-ZSM-5 but with smaller crystals having an increasing aspect ratio in the substituted materials. There was evidence of twinned crystals and the appearance of raised faces in all substituted samples. Thermogravimetric and derivative thermogravimetric analysis showed anomalous losses, which could be explained by Jahn-Teller distortions. Fourier transform infrared analysis of the materials showed an increasing level of distortion in significant regions of the spectra. Analysis of the filtrate, from EDTA-exchanged material, by atomic absorbance spectroscopy (AAS) showed that there were tetrahedrally coordinated M2+ species in the material and relatively small amounts were removed by ion exchange.
    • Synthesis of electroneutralized amphiphilic copolymers with peptide dendrons for intramuscular gene delivery

      Pu, Linyu; Wang, Jiali; Li, Na; Chai, Qiuxia; Irache, Juan M; Wang, Gang; Tang, James Z; Gu, Zhongwei (ACS Publications, 2016-06-08)
      Intramuscular gene delivery materials are of great importance in plasmid-based gene therapy system, but there is limited information so far on how to design and synthesize them. A previous study showed that the peptide dendron-based triblock copolymer with its components arranged in a reversed biomembrane architecture could significantly increase intramuscular gene delivery and expression. Herein, we wonder whether copolymers with biomembrane-mimicking arrangement may have similar function on intramuscular gene delivery. Meanwhile, it is of great significance to uncover the influence of electric charge and molecular structure on the function of the copolymers. To address the issues, amphiphilic triblock copolymers arranged in hydrophilic-hydrophobic-hydrophilic structure were constructed despite the paradoxical characteristics and difficulties in synthesizing such hydrophilic but electroneutral molecules. The as-prepared two copolymers, dendronG2(l-lysine-OH)-poly propylene glycol2k(PPG2k)-dendronG2(l-lysine-OH) (rL2PL2) and dendronG3(l-lysine-OH)-PPG2k-dendronG3(l-lysine-OH) (rL3PL3), were in similar structure but had different hydrophilic components and surface charges, thus leading to different capabilities in gene delivery and expression in skeletal muscle. rL2PL2 was more efficient than Pluronic L64 and rL3PL3 when mediating luciferase, β-galactosidase, and fluorescent protein expressions. Furthermore, rL2PL2-mediated growth-hormone-releasing hormone expression could significantly induce mouse body weight increase in the first 21 days after injection. In addition, both rL2PL2 and rL3PL3 showed good in vivo biosafety in local and systemic administration. Altogether, rL2PL2-mediated gene expression in skeletal muscle exhibited applicable potential for gene therapy. The study revealed that the molecular structure and electric charge were critical factors governing the function of the copolymers for intramuscular gene delivery. It can be concluded that, combined with the previous study, both structural arrangements either reverse or similar to the biomembrane are effective in designing such copolymers. It also provides an innovative way in designing and synthesizing new electroneutralized triblock copolymers, which could be used safely and efficiently for intramuscular gene delivery.
    • Tailoring the supramolecular structure of guanidinylated pullulan toward enhanced genetic photodynamic therapy

      Zhou, Jie; Mohamed Wali, Aisha Roshan; Ma, Shengnan; He, Yiyan; Yue, Dong; Tang, James Zhenggui; Gu, Zhongwei (ACS Publications, 2018-04-24)
      In the progress of designing a gene carrier system, what is urgently needed is a balance of excellent safety and satisfactory efficiency. Herein, a straightforward and versatile synthesis of a cationic guanidine-decorated dendronized pullulan (OGG3P) for efficient genetic photodynamic therapy was proposed. OGG3P was able to block the mobility of DNA from a weight ratio of 2. However, G3P lacking guanidine residues could not block DNA migration until at a weight ratio of 15, revealing guanidination could facilitate DNA condensation via specific guanidinium-phosphate interactions. A zeta potential plateau (∼+23 mV) of OGG3P complexes indicated the nonionic hydrophilic hydroxyl groups in pullulan might neutralize the excessive detrimental cationic charges. There was no obvious cytotoxicity and hemolysis, but also enhancement of transfection efficiency with regard to OGG3P in comparison with that of native G3P in Hela and HEK293T cells. More importantly, we found that the uptake efficiency in Hela cells between OGG3P and G3P complexes was not markedly different. However, guanidination caused changes in uptake pathway and led to macropinocytosis pathway, which may be a crucial reason for improved transfection efficiency. After introducing a therapeutic pKillerRed-mem plasmid, OGG3P complexes achieved significantly enhanced KillerRed protein expression and ROS production under irradiation. ROS-induced cancer cells proliferation suppression was also confirmed. This study highlights the guanidine-decorated dendronized pullulan could emerge as a reliable nonviral gene carrier to specifically deliver therapeutic genes.