A highly efficient organic photocatalyst
(OPC) for photoinduced
electron/energy-transfer reversible addition–fragmentation
chain-transfer (PET-RAFT) polymerization was identified through a
systematic catalyst design and discovery. The devised OPC offers excellent
control over PET-RAFT polymerizations of methyl methacrylate at very
low catalyst loadings (5 ppm), that is, ca. 5–50 times lower
loadings than other OPCs reported so far. Moreover, excellent oxygen
tolerance was achieved using the discovered OPC combined with trithiocarbonate-based
chain-transfer agent (CTA) under low-energy light irradiation conditions.
In depth experimental and computational investigations revealed that
(1) strong visible-light absorption and efficient generation of long-lived
triplet states of the OPC due to its unique molecular structure and
(2) the oxidation stability and no rate retardation of trithiocarbonate-based
CTA are the key to the outstanding oxygen tolerance and ppm-level
catalyst loadings. Our approach is thus believed to address a variety
of challenging tasks related to polymer synthesis and living additive
manufacturing.
Since the pioneering discovery of a protein bound to poly(ethylene glycol), the utility of protein–polymer conjugates (PPCs) is rapidly expanding to currently emerging applications. Photoinduced energy/electron‐transfer reversible addition–fragmentation chain‐transfer (PET‐RAFT) polymerization is a very promising method to prepare structurally well‐defined PPCs, as it eliminates high‐cost and time‐consuming deoxygenation processes due to its oxygen tolerance. However, the oxygen‐tolerance behavior of PET‐RAFT polymerization is not well‐investigated in aqueous environments, and thereby the preparation of PPCs using PET‐RAFT polymerization needs a substantial amount of sacrificial reducing agents or inert‐gas purging processes. Herein a novel water‐soluble and biocompatible organic photocatalyst (PC) is reported, which enables visible‐light‐driven additive‐free “grafting‐from” polymerizations of a protein in ambient and aqueous environments. Interestingly, the developed PC shows unconventional “oxygen‐acceleration” behavior for a variety of acrylic and acrylamide monomers in aqueous conditions without any additives, which are apparently distinct from previously reported systems. With such a PC, “grafting‐from” polymerizations are successfully performed from protein in ambient buffer conditions under green light‐emitting diode (LED) irradiation, which result in various PPCs that have neutral, anionic, cationic, and zwitterionic polyacrylates, and polyacrylamides. It is believed that this PC will be widely employed for a variety of photocatalysis processes in aqueous environments, including the living cell system.
Background: Degenerative lumbar spondylolisthesis (DLS) is frequently associated with lumbar spinal stenosis (LSS) and conservative treatments such as epidural steroid injection do not have long-term benefits in LSS patients with DLS. This study evaluated the effectiveness of percutaneous epidural neuroplasty using a balloon catheter in patients with LSS and DLS. Methods: Patients' sex, age, body mass index, diabetes, hypertension, stenosis grading, pain duration, location, pain intensity, and medications were retrieved from electronic medical records. At 1, 3, and 6 months following the procedure, data on pain severity, medication usage, and physical functional status were analyzed. A generalized estimating equations model was used at the six-month follow-up. Patients were divided into those with DLS (the spondylolisthesis group) and those without DLS (the no spondylolisthesis group) to evaluate whether the effects of percutaneous epidural neuroplasty using a balloon catheter were different. Results: A total of 826 patients were included (spondylolisthesis: 433 patients, 52.4%; no spondylolisthesis: 393 patients, 47.6%). Age, body mass index, hypertension, pain location, and stenosis grading were statistically different between the two groups. The generalized estimating equations analyses with unadjusted and adjusted estimation revealed a significant improvement in the estimated mean numerical rating scale of pain intensities compared to that at baseline in both groups (P < 0.001). Any adverse events that occurred were minor and temporary. Conclusions: Percutaneous epidural neuroplasty using a balloon catheter may be an alternative treatment option for patients with chronic LSS, regardless of accompanying DLS, who have had failed conservative management.
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