Poly(colloid)s: “Polymerization” of Poly(l‑tyrosine)-silica Composite Particles through the Photoinduced Cross-Linking of Unmodified Proteins Method

Photoinduced cross-linking of unmodified proteins, PICUP, was extended to core–shell silica-polypeptide composite particles to produce poly­(colloid)­s. Silica particles coated with poly­(l-tyrosine), PTYR-SiO₂, served as the monomer units. The PICUP reaction accomplished the formation of dityrosil linkages between the tyrosine units by illumination of photo-oxidizing ruthenium­(II) bipyridyl catalyst under physiological conditions. The PICUP method was compared with an enzymatic route intermediated by horseradish peroxidase as catalyst. The PTYR-SiO₂ particles feature high PTYR content in the shell, which facilitated the formation of heavily cross-linked but unstructured aggregates. After magnetic alignment of superparamagnetic PTYR-SiO₂-cobalt composite particles, only the PICUP approach enabled the preparation of isolated chain-like poly­(colloid)­s. The cross-linking products were confirmed by FTIR. The native secondary structure of poly­(l-tyrosine) is preserved in these poly­(colloid)­s. Because the PICUP reaction does not require the modification of the polypeptide structure, the cross-linked PTYR will retain its characteristic functions as a poly­(amino acid). The PICUP method opens the door to a variety of PTYR-based poly­(colloid) architectures

Modulation of Methoxyfenozide Release from Lignin Nanoparticles Made of Lignin Grafted with PCL by ROP and Acylation Grafting Methods

An efficient and sustainable agriculture calls for the development of novel agrochemical delivery systems able to release agrochemicals in a controlled manner. This study investigated the controlled release of the insecticide methoxyfenozide (MFZ) from lignin (LN) nanoparticles (LNPs). LN-grafted poly(ε-caprolactone) (LN-g-PCL) polymers were synthesized using two grafting methods, ring-opening polymerization (ROP)(LN-g-PCLp) and acylation reaction (LN-g-PCLa), creating polymers capable of self-assembling into nanoparticles of different properties, without surfactants. The LN-g-PCLp polymers exhibited a degree of polymerization (DP) from 22 to 101, demonstrating enhanced thermal stability after LN incorporation. LNPs loaded with MFZ exhibited a spherical core–shell structure with a hydrophilic LN outer layer and hydrophobic PCL core, with sizes affected by grafting methods and DP. LNPs controlled MFZ release, displaying variation in release profiles depending on the grafting methodology used, LN-g-PCLp DP, and temperature variations (23 to 30 °C). LNPs formulated with LN-g-PCLa showed a cumulative release of MFZ of 36.78 ± 1.23% over 196 h. Comparatively, increasing the DP of the LN-g-PCLp polymers, a reduction of the LNPs release rate from 92.39 ± 1.46% to 70.59 ± 2.40% was achieved within the same time frame. These findings contribute to identifying ways to modulate the controlled release of agrochemicals by incorporating them in renewable-based LNPs

Synthesis and Rapid Characterization of Amine-Functionalized Silica

Amine-functionalized colloidal silica finds use in a variety of applications and fundamental investigations. To explore convenient methods of synthesis and characterization of research-grade materials in relatively large quantities, nearly monodisperse colloidal silica particles were prepared by base-catalyzed hydrolysis of reagent-grade tetraethyl orthosilicate (TEOS) without the traditional time- and energy-consuming distillation step. Radius was varied reliably from 30 to 125 nm by changing the water/TEOS ratio. Asymmetric flow field flow fractionation (AF4) methods with online light scattering detection proved effective in assessing the uniformity of the various preparations. Even highly uniform commercial standards were resolved by AF4. The surface of the colloidal silica was decorated with amino groups using (3-aminopropyl) trimethoxysilane and spacer methyl groups from methyl-trimethoxysilane. The surface density of amino groups was quantified spectrophotometrically after reaction with ninhydrin; the nature of this analysis avoids interference from sample turbidity. As an alternative to the ninhydrin test, an empirical relationship between surface density of amino groups and zeta potential at low pH was found. The size of the colloidal silica was predictably decreased by etching with HF; this method will be effective for some preparations, despite a modest reduction in size uniformity

Asymmetric Flow Field-Flow Fractionation with Multiangle Light Scattering Detection for Characterization of Cellulose Nanocrystals

Cellulose nanocrystals (CNCs) were analyzed by asymmetric flow field-flow fractionation (AF4) coupled with multiangle light scattering (MALS) detection. Small fractions were collected from the output of the AF4 apparatus for investigation by transmission electron microscopy (TEM). The influence of CNC injection amount, the number of passes through a high-pressure homogenizer, and different CNC sources on the elution behavior and particle size distribution was investigated. The AF4-MALS results on crystal length were compared with those from TEM. Peak distortion and variation in elution profiles with the increase in sample load were observed. Good resolution was obtained when the injection mass varied from 20 to 40 μg, corresponding to injections of 4–8 μL at a starting concentration of ∼5 μg/μL; concentrations during the separation process and at the detector were significantly lower. As the number of homogenization treatments increased, the peak shape became narrower and more symmetrical. This indicates a narrowed crystal length distribution, but regardless of source or homogenization treatment, no CNC preparation was as uniform as tobacco mosaic virus, a well-known rigid rod model structure, whose length was found by AF4-MALS to be in agreement with literature values. CNCs derived from cotton contained longer crystals than those derived from microcrystalline cellulose, as shown by both AF4-MALS and TEM techniques. An advantage of AF4-MALS compared to TEM is the ability to sample large numbers of rodlike particles, which is challenging and time-consuming for TEM image analysis, especially without the presorting afforded by AF4. The good TMV results suggest a high degree of accuracy will pertain to the CNC size distribution measurements

Asymmetric Flow Field-Flow Fractionation with Multiangle Light Scattering Detection for Characterization of Cellulose Nanocrystals

Cellulose nanocrystals (CNCs) were analyzed by asymmetric flow field-flow fractionation (AF4) coupled with multiangle light scattering (MALS) detection. Small fractions were collected from the output of the AF4 apparatus for investigation by transmission electron microscopy (TEM). The influence of CNC injection amount, the number of passes through a high-pressure homogenizer, and different CNC sources on the elution behavior and particle size distribution was investigated. The AF4-MALS results on crystal length were compared with those from TEM. Peak distortion and variation in elution profiles with the increase in sample load were observed. Good resolution was obtained when the injection mass varied from 20 to 40 μg, corresponding to injections of 4–8 μL at a starting concentration of ∼5 μg/μL; concentrations during the separation process and at the detector were significantly lower. As the number of homogenization treatments increased, the peak shape became narrower and more symmetrical. This indicates a narrowed crystal length distribution, but regardless of source or homogenization treatment, no CNC preparation was as uniform as tobacco mosaic virus, a well-known rigid rod model structure, whose length was found by AF4-MALS to be in agreement with literature values. CNCs derived from cotton contained longer crystals than those derived from microcrystalline cellulose, as shown by both AF4-MALS and TEM techniques. An advantage of AF4-MALS compared to TEM is the ability to sample large numbers of rodlike particles, which is challenging and time-consuming for TEM image analysis, especially without the presorting afforded by AF4. The good TMV results suggest a high degree of accuracy will pertain to the CNC size distribution measurements

Sugar-Based Polyamides: Self-Organization in Strong Polar Organic Solvents

Periodic patterns resembling spirals were observed to form spontaneously upon unassisted cooling of d-glucaric acid- and d-galactaric acid–based polyamide solutions in <i>N</i>-methyl-<i>N</i>-morpholine oxide (NMMO) monohydrate. Similar observations were made in d-galactaric acid-based polyamide/ionic liquid (IL) solutions. The morphologies were investigated by optical, polarized light and confocal microscopy assays to reveal pattern details. Differential scanning calorimetry was used to monitor solution thermal behavior. Small- and wide-angle X-ray scattering data reflected the complex and heterogeneous nature of the self-organized patterns. Factors such as concentration and temperature were found to influence spiral dimensions and geometry. The distance between rings followed a first-order exponential decay as a function of polymer concentration. Fourier-Transform Infrared Microspectroscopy analysis of spirals pointed to H-bonding between the solvent and the pendant hydroxyl groups of the glucose units from the polymer backbone. Tests on self-organization into spirals of ketal-protected d-galactaric acid polyamides in NMMO monohydrate confirmed the importance of the monosaccharide’s pendant free hydroxyl groups on the formation of these patterns. Rheology performed on d-galactaric-based polyamides at high concentration in NMMO monohydrate solution revealed the optimum conditions necessary to process these materials as fibers by spinning. The self-organization of these sugar-based polyamides mimics certain biological materials

Determination of Particle Size Distributions, Molecular Weight Distributions, Swelling, Conformation, and Morphology of Dilute Suspensions of Cross-Linked Polymeric Nanoparticles via Size-Exclusion Chromatography/Differential Viscometry

Size-exclusion chromatography (SEC), coupled with differential viscometry detection (SEC/DV), is applied to the dilute suspension characterization of solvent-swollen cross-linked polymeric nanoparticles (PNPs). Cross-linked, unimolecular polymeric nanoparticles in the 5–50 nm weight-average diameter (<i>d</i>_w) range were prepared by batch and semibatch microemulsion polymerization techniques and isolated. SEC and SEC/DV characterization techniques yield, based on the principle of universal calibration, a wealth of information regarding the structural attributes of PNPs, including apparent and absolute molecular weight distributions, apparent and absolute molecular weight averages, peak and weight-average particle diameters, particle size distributions in both the solvent-swollen and solvent-free states, particle conformation (shape), and an estimate of the volumetric swell factor. These structural parameters are critical to understanding PNP performance, and all are obtained in a single rapid chromatographic experiment, when conducted under conditions where universal calibration applies. Particle sizes determined under such conditions are in excellent agreement with those obtained by dynamic light scattering, transmission electron microscopy, hydrodynamic chromatography, and SEC/static light scattering (SEC/SLS). In addition, Mark–Houwink exponents of approximately zero were found across the molecular weight and size distribution of many of these tightly cross-linked PNPs, which is consistent with a spherical particle conformation in these dilute suspensions. The SEC/DV methods are especially valuable to characterize the diameter, volume swell factor, and suspension conformation of small (4–5 nm <i>d</i>_w) PNPs