scholarly journals Unusual Enthalpy Driven Self Assembly at Room Temperature with Chitosan Amphiphiles

2019 ◽  
Vol 7 (1) ◽  
pp. 57-71 ◽  
Author(s):  
Uchechukwu Odunze ◽  
Fionn O'Brien ◽  
Lisa Godfrey ◽  
Andreas Schätzlein ◽  
Ijeoma Uchegbu
Keyword(s):  
Molecular Weight ◽  
Negative Correlation ◽  
Quaternary Ammonium ◽  
Self Assembly ◽  
Room Temperature ◽  
Isothermal Calorimetry ◽  
Relative Proportion ◽  
Polymer Molecular Weight ◽  
Self Assembling ◽  
Micellar Aggregates

Background: GCPQ (N-palmitoyl-N-monomethyl-N,N-dimethyl-N,N,N-trimethyl- 6-O-glycolchitosan) is a self-assembling polymer being investigated as a pharmaceutical nano-carrier. GCPQ nanoparticles shuttle drugs across biological barriers, improving drug performance. The exact chemistry of GCPQ is varied by the relative proportion of hydrophobic (N-palmitoyl) and hydrophilic (quaternary ammonium) groups and molecular weight. Objective: We hypothesised that the thermodynamics of self-assembly is controlled by the polymer molecular weight and hydrophobicity. Method: The thermodynamics of self-assembly was investigated using isothermal calorimetry. Results: GCPQs (Mw = 8-15 kDa) formed micellar aggregates at critical micellar concentrations of 1-2.4 µM at 25°C and micellisation was unusually enthalpy driven. There was a positive correlation between ΔHmic and mole% quaternary groups (Q): ΔHmic = 3.8 Q- 159 (r2 = 0.93) and a negative correlation between ΔHmic and molecular weight (Mw): ΔHmic = -13.5 Mw-26.3 (r2 = 0.99). Conclusion: These findings provide insights into the positive drivers of stable selfassemblies, namely hydrophobicity and molecular weight, as both hydrophobicity and molecular weight are associated with an increased enthalpy contribution to micellisation.

All-or-none switching of photon upconversion in self-assembled organogel systems

2017 ◽  
Vol 196 ◽  
pp. 305-316 ◽  
Author(s):  
Pengfei Duan ◽  
Deepak Asthana ◽  
Takuya Nakashima ◽  
Tsuyoshi Kawai ◽  
Nobuhiro Yanai ◽  
...  
Keyword(s):  
Self Assembly ◽  
Room Temperature ◽  
Stimuli Responsive ◽  
Molecular Systems ◽  
Controlled Assembly ◽  
Outstanding Problem ◽  
Self Assembling ◽  
New Strategy ◽  
Donor Acceptor

Aggregation-induced photon upconversion (iPUC) based on a triplet–triplet annihilation (TTA) process is successfully developed via controlled self-assembly of donor–acceptor pairs in organogel nanoassemblies. Although segregation of donor from acceptor assemblies has been an outstanding problem in TTA-based UC and iPUC, we resolved this issue by modifying both the triplet donor and aggregation induced emission (AIE)-type acceptor with glutamate-based self-assembling moieties. These donors and acceptors co-assemble to form organogels without segregation. Interestingly, these donor–acceptor binary gels show upconversion at room temperature but the upconversion phenomena were lost upon dissolution of the gels on heating. The observed changes in TTA-UC emission were thermally reversible, reflecting the controlled assembly/disassembly of the binary molecular systems. The observed on/off ratio of UC emission was much higher than that of the aggregation-induced fluorescence of the acceptor, which highlights the important role of iPUC, i.e., multi-exciton TTA for photoluminescence switching. This work bridges iPUC and supramolecular chemistry and provides a new strategy for designing stimuli-responsive upconversion systems.

scholarly journals Self-Assembling Quaternary Ammonium Sulfonamide Antimicrobials

2021 ◽  
Author(s):  
Kamlesh Mistry
Keyword(s):  
Stainless Steel ◽  
Quaternary Ammonium ◽  
Contact Time ◽  
Metal Surfaces ◽  
Room Temperature ◽  
Uv Curing ◽  
Water Soluble ◽  
Antimicrobial Coatings ◽  
Self Assembling ◽  
Plastic Surfaces

A series of novel sulfonamide based quaternary ammonium (QUAT’s) antimicrobials containing a variety of chemical anchors R-SO2-NH-(CH2)3-N(CH3)2-(CH2)3-Y (where R = alkyl or aryl and Y = organosilane (Si(OMe)3), organophosphorus (P(O)(OR1)) and benzophenone (-OC6H4-C(O)-C6H5)) were used to immobilize them on different substrates. Sulfonamide organosilane QUAT’s were immobilized on to textiles substrates, whereas benzophenone QUAT’s were used to exclusively coat plastic surfaces (polyethylene (PE), and polyvinylchloride (PVC)), and organophosphorus QUAT’s were prepared for testing on metal surfaces (stainless steel). The covalently attached antimicrobial coatings were found to kill gram +ve and -ve bacteria on contact, hindering their attachment and colonization without any leachate. The partially water soluble sulfonamide QUAT’s presented are readily prepared, easy to apply and are relatively inexpensive. Textile samples were prepared by immersion in a MeOH:H2O (30:70) solution of organosilane QUAT’s followed by curing/drying at room temperature for 2 – 24 hours. Plastic samples were prepared by electrospraying an EtOH:H2O (10:90) solution containing benzophenone QUAT’s followed by UV curing using for 2 – 5 minutes. All samples showed a 100% reduction (107– 106 cells) of viable Arthrobacter, S. aureus, and E.coli after 3 hours of contact time and maintained their activity over 24 hours versus the control (untreated) samples.

scholarly journals Self-Assembling Quaternary Ammonium Sulfonamide Antimicrobials

2021 ◽  
Author(s):  
Kamlesh Mistry
Keyword(s):  
Stainless Steel ◽  
Quaternary Ammonium ◽  
Contact Time ◽  
Metal Surfaces ◽  
Room Temperature ◽  
Uv Curing ◽  
Water Soluble ◽  
Antimicrobial Coatings ◽  
Self Assembling ◽  
Plastic Surfaces

A series of novel sulfonamide based quaternary ammonium (QUAT’s) antimicrobials containing a variety of chemical anchors R-SO2-NH-(CH2)3-N(CH3)2-(CH2)3-Y (where R = alkyl or aryl and Y = organosilane (Si(OMe)3), organophosphorus (P(O)(OR1)) and benzophenone (-OC6H4-C(O)-C6H5)) were used to immobilize them on different substrates. Sulfonamide organosilane QUAT’s were immobilized on to textiles substrates, whereas benzophenone QUAT’s were used to exclusively coat plastic surfaces (polyethylene (PE), and polyvinylchloride (PVC)), and organophosphorus QUAT’s were prepared for testing on metal surfaces (stainless steel). The covalently attached antimicrobial coatings were found to kill gram +ve and -ve bacteria on contact, hindering their attachment and colonization without any leachate. The partially water soluble sulfonamide QUAT’s presented are readily prepared, easy to apply and are relatively inexpensive. Textile samples were prepared by immersion in a MeOH:H2O (30:70) solution of organosilane QUAT’s followed by curing/drying at room temperature for 2 – 24 hours. Plastic samples were prepared by electrospraying an EtOH:H2O (10:90) solution containing benzophenone QUAT’s followed by UV curing using for 2 – 5 minutes. All samples showed a 100% reduction (107– 106 cells) of viable Arthrobacter, S. aureus, and E.coli after 3 hours of contact time and maintained their activity over 24 hours versus the control (untreated) samples.

scholarly journals Mapping the Morphological Landscape of Oligomeric Di-block Peptide Polymer Amphiphiles

2021 ◽  
Author(s):  
Benjamin Allen ◽  
Zoe Wright ◽  
Hailey Taylor ◽  
Thomas Oweida ◽  
Sabila Kader-Pinky ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Self Assembly ◽  
Rational Design ◽  
Structural Diversity ◽  
Soft Materials ◽  
Ethyl Acrylate ◽  
Spherical Particles ◽  
Polymer Molecular Weight ◽  
Complex Protein ◽  
Critical Components

Peptide polymer amphiphiles (PPAs) are highly tunable hybrid materials that achieve complex, protein-like assembly landscapes by combining sequence-dependent properties of peptides with structural diversity of polymers. Despite their promise as functional biomimetic materials, determining how polymer and peptide properties simultaneously affect PPA self-assembly remains challenging. We herein present a systematic study of critical components within the PPA design space that dictate the self-assembled morphologies. PPAs containing hydrophobic oligo(ethyl acrylate) were used to interrogate the role of polymer molecular weight and dispersity in addition to peptide length and charge density on self-assembly. We observed that PPAs predominantly formed spherical particles (micelles and vesicles), with both polymer molecular weight and peptide hydrophilicity determining morphology. Additionally, peptide charge and polymer dispersity influence particle size. These key benchmarks will facilitate the rational design of PPAs that expand the scope of biomimetic and biocompatible functionality within assembled soft materials.

The Contact Phase of Blood Coagulation in Diabetes Mellitus and in Patients with Vasculopathy

1984 ◽  
Vol 52 (03) ◽  
pp. 221-223 ◽  
Author(s):  
M Christe ◽  
P Gattlen ◽  
J Fritschi ◽  
B Lämmle ◽  
W Berger ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Molecular Weight ◽  
Blood Coagulation ◽  
High Molecular Weight ◽  
Negative Correlation ◽  
Factor Xii ◽  
C1 Inhibitor ◽  
High Molecular Weight Kininogen ◽  
Contact Phase ◽  
Α2 Macroglobulin

SummaryThe contact phase has been studied in diabetics and patients with macroangiopathy. Factor XII and high molecular weight kininogen (HMWK) are normal. C1-inhibitor and also α2-macroglobulin are significantly elevated in diabetics with complications, for α1-macroglobulin especially in patients with nephropathy, 137.5% ± 36.0 (p <0.001). C1-inhibitor is also increased in vasculopathy without diabetes 113.2 ± 22.1 (p <0.01).Prekallikrein (PK) is increased in all patients’ groups (Table 2) as compared to normals. PK is particularly high (134% ± 32) in 5 diabetics without macroangiopathy but with sensomotor neuropathy. This difference is remarkable because of the older age of diabetics and the negative correlation of PK with age in normals.

Degradation in a Methyl-phenyl Co-Polymeric Polysilane for LED Applications

2003 ◽  
Vol 769 ◽  
Author(s):  
Asha Sharma ◽  
Deepak ◽  
Monica Katiyar ◽  
Satyendra Kumar ◽  
V. Chandrasekhar ◽  
...  
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Light Source ◽  
Room Temperature ◽  
Light Exposure ◽  
Room Temperature Photoluminescence ◽  
Pl Spectrum ◽  
Pl Intensity ◽  
Methyl Phenyl

AbstractThe optical degradation of polysilane copolymer has been studied in spin cast thin films and solutions using light source of 325 nm wavelength. The room temperature photoluminescence (PL) spectrum of these films show a sharp emission at 368 nm when excited with a source of 325 nm. However, the PL intensity deteriorates with time upon light exposure. Further the causes of this degradation have been examined by characterizing the material for its transmission behaviour and changes occurring in molecular weight as analysed by GPC data.

Factors Affecting Molecular Self-Assembly and Its Mechanism

2012 ◽  
Vol 9 (1) ◽  
pp. 43 ◽  
Author(s):  
Hueyling Tan
Keyword(s):  
Self Assembly ◽  
Building Blocks ◽  
Molecular Engineering ◽  
Molecular Structures ◽  
Polymer Science ◽  
New Approach ◽  
Factors Affecting ◽  
Dna Structures ◽  
Self Assembling ◽  
Wide Range

Molecular self-assembly is ubiquitous in nature and has emerged as a new approach to produce new materials in chemistry, engineering, nanotechnology, polymer science and materials. Molecular self-assembly has been attracting increasing interest from the scientific community in recent years due to its importance in understanding biology and a variety of diseases at the molecular level. In the last few years, considerable advances have been made in the use ofpeptides as building blocks to produce biological materials for wide range of applications, including fabricating novel supra-molecular structures and scaffolding for tissue repair. The study ofbiological self-assembly systems represents a significant advancement in molecular engineering and is a rapidly growing scientific and engineering field that crosses the boundaries ofexisting disciplines. Many self-assembling systems are rangefrom bi- andtri-block copolymers to DNA structures as well as simple and complex proteins andpeptides. The ultimate goal is to harness molecular self-assembly such that design andcontrol ofbottom-up processes is achieved thereby enabling exploitation of structures developed at the meso- and macro-scopic scale for the purposes oflife and non-life science applications. Such aspirations can be achievedthrough understanding thefundamental principles behind the selforganisation and self-synthesis processes exhibited by biological systems.

Green synthesis of mixed metallic nanoparticles using room temperature self-assembly

2017 ◽  
Vol 13 (2) ◽  
pp. 4671-4677 ◽  
Author(s):  
A. M. Abdelghany ◽  
A.H. Oraby ◽  
Awatif A Hindi ◽  
Doaa M El-Nagar ◽  
Fathia S Alhakami
Keyword(s):  
Self Assembly ◽  
Metallic Nanoparticles ◽  
Room Temperature ◽  
Bimetallic Nanoparticles ◽  
Reduction Process ◽  
Nano Particles ◽  
Nano Structure ◽  
Small Shift ◽  
Molar Ratios ◽  
Vis Spectroscopy

Bimetallic nanoparticles of silver (Ag) and gold (Au) were synthesized at room temperature using Curcumin. Reduction process of silver and gold ions with different molar ratios leads to production of different nanostructures including alloys and core-shells. Produced nanoparticles were characterized simultaneously with FTIR, UV/vis. spectroscopy, transmission electron microscopy (TEM), and Energy-dispersive X-ray (EDAX). UV/vis. optical absorption spectra of as synthesized nanoparticles reveals presence of surface palsmon resonance (SPR) of both silver at (425 nm) and gold at (540 nm) with small shift and broadness of gold band after mixing with resucing and capping agent in natural extract which suggest presence of bimetallic nano structure (Au/Ag). FTIR and EDAX data approve the presence of bimetallic nano structure combined with curcumin extract. TEM micrographs shows that silver and gold can be synthesized separately in the form of nano particles using curcumin extract. Synthesis of gold nano particles in presence of silver effectively enhance and control formation of bi-metallic structure.

Directive Effect of Chain Length in Modulating Peptide Nano-assemblies

2020 ◽  
Vol 27 (9) ◽  
pp. 923-929
Author(s):  
Gaurav Pandey ◽  
Prem Prakash Das ◽  
Vibin Ramakrishnan
Keyword(s):  
Electron Microscopy ◽  
Amino Acids ◽  
Light Scattering ◽  
Chain Length ◽  
Self Assembly ◽  
The Self ◽  
Ionic Charge ◽  
Self Assembling ◽  
Biophysical Techniques

Background: RADA-4 (Ac-RADARADARADARADA-NH2) is the most extensively studied and marketed self-assembling peptide, forming hydrogel, used to create defined threedimensional microenvironments for cell culture applications. Objectives: In this work, we use various biophysical techniques to investigate the length dependency of RADA aggregation and assembly. Methods: We synthesized a series of RADA-N peptides, N ranging from 1 to 4, resulting in four peptides having 4, 8, 12, and 16 amino acids in their sequence. Through a combination of various biophysical methods including thioflavin T fluorescence assay, static right angle light scattering assay, Dynamic Light Scattering (DLS), electron microscopy, CD, and IR spectroscopy, we have examined the role of chain-length on the self-assembly of RADA peptide. Results: Our observations show that the aggregation of ionic, charge-complementary RADA motifcontaining peptides is length-dependent, with N less than 3 are not forming spontaneous selfassemblies. Conclusion: The six biophysical experiments discussed in this paper validate the significance of chain-length on the epitaxial growth of RADA peptide self-assembly.

Crystallization of Isotactic Poly(propylene) in Solution as Followed by Slow Calorimetry

1995 ◽  
Vol 60 (11) ◽  
pp. 1905-1924 ◽  
Author(s):  
Hong Phuong-Nguyen ◽  
Geneviève Delmas
Keyword(s):  
Molecular Weight ◽  
Crystal Growth ◽  
High Temperature ◽  
Heat Of Fusion ◽  
Complete Dissolution ◽  
Polymer Molecular Weight ◽  
Solvent Quality ◽  
Temperature Ramp ◽  
Poly Propylene

Dissolution, crystallization and second dissolution traces of isotactic poly(propylene) have been obtained in a slow temperature ramp (3 K h-1) with the C80 Setaram calorimeter. Traces of phase-change, in presence of solvent, are comparable to traces without solvent. The change of enthalpy on heating or cooling, ∆Htotal, over the 40-170 °C temperature range, is the sum of two contributions, ∆HDSC and ∆Hnetwork. The change ∆HDSC is the usual heat obtained in a fast temperature ramp and ∆Hnetwork is associated with a physical network whose disordering is slow and subject to superheating due to strain. When dissolution is complete, ∆Htotal is equal to ∆H0, the heat of fusion of perfect crystals. The values of ∆Htota for nascent and recrystallized samples are compared. Dissolution is the tool to evaluate the quality of the crystals. The repartition of ∆Htotal, into the two endotherms, reflects the quality of crystals. The crystals grown more rapidly have a higher fraction of network crystals which are stable at high T in the solvents. A complete dissolution, i.e. a high temperature (170 °C or more) is necessary to obtain good crystals. The effect of concentration, polymer molecular weight and solvent quality on crystal growth is analyzed.

Sign in / Sign up

Export Citation Format

Share Document