Osteoarthritis/Inflammation <i>In Vitro</i> Detection Using a Hyaluronate-Coated Au Nano-Contrast Probe

Osteoarthritis (OA) is a common and painful chronic joint disease that affects large joints, such as the knees, spine, hips, and shoulders. It is the most prevalent chronic joint disease in the world, with half of the world’s population aged 65 or older suffering from some form. OA relates to the decomposition of hyaluronic acid (HA) in the joints, which is part of synovial fluid, and a high molecular weight physical hydrogel that lubricates the joint surfaces and reduces friction between articular cartilages with movement. Current OA diagnosis involves imaging with MRI, X-rays, and X-ray computed tomography (CT). Taking advantage of an FDA-approved treatment for OA, which includes HA injections in the knee of OA patients to reduce cartilage or bone friction, we have developed a HA-based nano-contrast agent that can detect OA and inflammation through reactive oxygen species (ROS) produced in inflamed joints, as well as hyaluronidase (HAse), as analytes of in vitro diagnosis. The presence of ROS and HAse leads to lysis of the HA coating of the nanoparticle (NP) scaffold and induces metal core aggregation (nanometer-sized), which significantly augments the CT signal. Material synthesis and detailed characterization are provided herein, along with NP stability, cell compatibility studies and in vitro studies with ROS and HAse. The NP metal clustering can be captured by several techniques, including UV–vis, TEM, and CT. The material could be administered intra-articularly into the knee of OA animals or patients in the future and be retained, similar to the FDA-approved HA, providing non-invasive OA, inflammation, or joint injury detection (e.g., elderly people, veterans, soldiers, and sports athletes) through X-rays or CT

Osteoarthritis/Inflammation <i>In Vitro</i> Detection Using a Hyaluronate-Coated Au Nano-Contrast Probe

Osteoarthritis (OA) is a common and painful chronic joint disease that affects large joints, such as the knees, spine, hips, and shoulders. It is the most prevalent chronic joint disease in the world, with half of the world’s population aged 65 or older suffering from some form. OA relates to the decomposition of hyaluronic acid (HA) in the joints, which is part of synovial fluid, and a high molecular weight physical hydrogel that lubricates the joint surfaces and reduces friction between articular cartilages with movement. Current OA diagnosis involves imaging with MRI, X-rays, and X-ray computed tomography (CT). Taking advantage of an FDA-approved treatment for OA, which includes HA injections in the knee of OA patients to reduce cartilage or bone friction, we have developed a HA-based nano-contrast agent that can detect OA and inflammation through reactive oxygen species (ROS) produced in inflamed joints, as well as hyaluronidase (HAse), as analytes of in vitro diagnosis. The presence of ROS and HAse leads to lysis of the HA coating of the nanoparticle (NP) scaffold and induces metal core aggregation (nanometer-sized), which significantly augments the CT signal. Material synthesis and detailed characterization are provided herein, along with NP stability, cell compatibility studies and in vitro studies with ROS and HAse. The NP metal clustering can be captured by several techniques, including UV–vis, TEM, and CT. The material could be administered intra-articularly into the knee of OA animals or patients in the future and be retained, similar to the FDA-approved HA, providing non-invasive OA, inflammation, or joint injury detection (e.g., elderly people, veterans, soldiers, and sports athletes) through X-rays or CT

Osteoarthritis/Inflammation <i>In Vitro</i> Detection Using a Hyaluronate-Coated Au Nano-Contrast Probe

Osteoarthritis (OA) is a common and painful chronic joint disease that affects large joints, such as the knees, spine, hips, and shoulders. It is the most prevalent chronic joint disease in the world, with half of the world’s population aged 65 or older suffering from some form. OA relates to the decomposition of hyaluronic acid (HA) in the joints, which is part of synovial fluid, and a high molecular weight physical hydrogel that lubricates the joint surfaces and reduces friction between articular cartilages with movement. Current OA diagnosis involves imaging with MRI, X-rays, and X-ray computed tomography (CT). Taking advantage of an FDA-approved treatment for OA, which includes HA injections in the knee of OA patients to reduce cartilage or bone friction, we have developed a HA-based nano-contrast agent that can detect OA and inflammation through reactive oxygen species (ROS) produced in inflamed joints, as well as hyaluronidase (HAse), as analytes of in vitro diagnosis. The presence of ROS and HAse leads to lysis of the HA coating of the nanoparticle (NP) scaffold and induces metal core aggregation (nanometer-sized), which significantly augments the CT signal. Material synthesis and detailed characterization are provided herein, along with NP stability, cell compatibility studies and in vitro studies with ROS and HAse. The NP metal clustering can be captured by several techniques, including UV–vis, TEM, and CT. The material could be administered intra-articularly into the knee of OA animals or patients in the future and be retained, similar to the FDA-approved HA, providing non-invasive OA, inflammation, or joint injury detection (e.g., elderly people, veterans, soldiers, and sports athletes) through X-rays or CT

Thermoresponsive and Mechanical Properties of Poly(l‑proline) Gels

Gelation of the left helical N-substituted homopolypeptide poly­(l-proline) (PLP) in water was explored, employing rheological and small-angle scattering studies at different temperatures and concentrations in order to investigate the network structure and its mechanical properties. Stiff gels were obtained at 10 wt % or higher at 5 °C, the first time gelation has been observed for homopolypeptides. The secondary structure and helical rigidity of PLP has large structural similarities to gelatin but as gels the two materials show contrasting trends with temperature. With increasing temperature in D₂O, the network stiffens, with broad scattering features of similar correlation length for all concentrations and molar masses of PLP. A thermoresponsive transition was also achieved between 5 and 35 °C, with moduli at 35 °C higher than gelatin at 5 °C. The brittle gels could tolerate strains of 1% before yielding with a frequency-independent modulus over the observed range, similar to natural proline-rich proteins, suggesting the potential for thermoresponsive or biomaterial-based applications

Sub-Rouse Dynamics in Poly(isobutylene) as a Function of Molar Mass

We report on the molar mass dependence of the segmental, sub-Rouse, and terminal relaxation processes of poly­(isobutylene). For this purpose, seven samples were synthesized with molar masses in the range from 2.8 to 172 kg·mol–1 and investigated by temperature-modulated differential scanning calorimetry, dielectric spectroscopy, and rheology. Rheology provided access to the terminal times that were found to scale as τterm ∼ Μ3.2. On the other hand, the sub-Rouse dielectric process shows a very weak molar mass dependence (τsub – Rouse/τSM ∼ M0.1), that is, distinctly different from the Rouse and terminal dynamics. We infer that the sub-Rouse mode has a lengthscale intermediate to the statistical segment length (∼1.25 nm) and the length of an entanglement strand (∼2.3 nm)

Well-Defined Homopolypeptides, Copolypeptides, and Hybrids of Poly(l-proline)

l-Proline is the only, out of 20 essential, amino acid that contains a cyclized substituted α-amino group (is formally an imino acid), which restricts its conformational shape. The synthesis of well-defined homo- and copolymers of l-proline has been plagued either by the low purity of the monomer or the inability of most initiating species to polymerize the corresponding N-carboxy anhydride (NCA) because they require a hydrogen on the 3-N position of the five-member ring of the NCA, which is missing. Herein, highly pure l-proline NCA was synthesized by using the Boc-protected, rather than the free amino acid. The protection of the amine group as well as the efficient purification method utilized resulted in the synthesis of highly pure l-proline NCA. The high purity of the monomer and the use of an amino initiator, which does not require the presence of the 3-N hydrogen, led for the first time to well-defined poly(l-proline) (PLP) homopolymers, poly(ethylene oxide)-b-poly(l-proline), and poly(l-proline)-b-poly(ethylene oxide)-b-poly(l-proline) hybrids, along with poly(γ-benzyl-l-glutamate)-b-poly(l-proline) and poly(Boc-l-lysine)-b-poly(l-proline) copolypeptides. The combined characterization (NMR, FTIR, and MS) that results for the l-proline NCA revealed its high purity. In addition, all synthesized polymers exhibit high molecular and compositional homogeneity

Complexation-Driven Mutarotation in Poly(l‑proline) Block Copolypeptides

Novel poly­(l-lysine)-<i>block</i>-poly­(l-proline) (PLL-<i>b</i>-PLP)-based materials with all PLP helical conformers, i.e., PLP II and the rare PLP I are here reported. Electrostatic supramolecular complexation of the adjacent cationic PLL with anionic molecules bearing DNA analogue H-bonding functionalities, such as deoxyguanosine monophosphate (dGMP), preserves the extended PLP II helix, and the complexed molecule is locked and held in position by orthogonal shape-persistent hydrogen-bonded dGMP ribbons and their extended π-stacking. The branched anionic surfactant dodecylbenzenesulfonic acid (DBSA) on the other hand, introduces periodicity frustration and interlayer plasticization, leading to a reversed mutarotation to the more compact PLP I helix by complexation, without external stimuli, and is here reported for the first time. We foresee that our findings can be used as a platform for novel molecularly adaptive functional materials, and could possibly give insight in many proline-related transmembrane biological functions

Effects of Nanometer Confinement on the Self-Assembly and Dynamics of Poly(γ-benzyl‑l‑glutamate) and Its Copolymer with Poly(isobutylene)

Poly­(γ-benzyl-l-glutamate) (PBLG) and its copolymer with poly­(isobutylene) (PIB) are studied in the bulk and under nanometer confinement in pores with emphasis on the self-assembly and dynamics, respectively, with X-ray diffraction, 13C NMR, dielectric spectroscopy, and differential scanning calorimetry. PBLG segments located within the α-helical and amorphous regions have distinct dielectric fingerprints. We have analyzed the dielectric signal from the segmental and α-helical segments to show that the α-helices are short and, furthermore, interrupted by amorphous segments. The effect of confinement is twofold: first, to speed up the segmental process and, second, to destabilize, in part, the secondary structure. The block copolymer architecture combined with confinement further destabilizes the α-helical secondary structure by introducing phase mixing. The results on the synthetic polypeptide demonstrate that both the chain configurations and the associated dynamic processes are affected when the PBLG chains are entering narrow pores. These results could pave the way for a better understanding of the behavior of more complex proteins in confined space

Extended Self-Assembled Long Periodicity and Zig-Zag Domains from Helix–Helix Diblock Copolymer Poly(γ-benzyl‑l‑glutamate)-<i>block</i>-poly(<i>O</i>‑benzyl‑l‑hydroxyproline)

We describe the synthesis and self-assembly of particularly high periodicity of diblock copolymers composed of poly­(benzyl-l-hydroxyproline) (PBLHyP) and poly­(γ-benzyl-l-glutamate) (PBLG), that is, two polypeptide blocks with dissimilar helical structures. The robust helicity of the PBLHyP block is driven by steric constraints of the repeat units, while PBLG forms α-helices driven by hydrogen bonding, allowing defects and deformations. Herein, high-molecular-weight diblock copolypeptides of PBLG-b-PBLHyP with three different volume fractions of the PBLHyP-blocks are discussed. For shorter PBLHyP blocks, hexagonal packing of PBLHyP helices is observed, while by increasing the length of the PBLHyP block, keeping at a similar PBLG block length, the packing is distorted. Zig-zag lamellar structures were obtained due to the mismatch in the packing periodicities of the PBLG and PBLHyP helices. The frustration that takes place at the interface leads the PBLHyP to tilt to match the PBLG periodicity. The zig-zag morphology is reported for the first time for high-molecular-weight helix–helix (rod–rod) copolypeptides, and the self-assembled periodicity is uncommonly large