Effect of Cross-Link Homogeneity on the High-Strain Behavior of Elastic Polymer Networks.

Cross-link heterogeneity and topological defects have been shown to affect the moduli of polymer networks in the low-strain regime. Probing their role in the high-strain regime, however, has been difficult because of premature network fracture. Here, we address this problem by using a double-network approach to investigate the high-strain behavior of both randomly and regularly cross-linked networks with the same backbone chemistry. Randomly cross-linked poly(n-butyl acrylate) networks with target molecular weights between cross-links of 5-30 kg/mol were synthesized via free-radical polymerization, while regularly cross-linked poly(n-butyl acrylate) networks with molecular weights between cross-links of 7-38 kg/mol were synthesized via cross-linking of tetrafunctional star polymers. Both types of networks were then swollen in a monomer/cross-linker mixture, polymerized to form double networks, and characterized via uniaxial tensile testing. The onset of strain stiffening was found to occur later in regular networks than in random networks with the same modulus but was well-predicted by the target molecular weight between cross-links of each sample. These results indicate that the low- and high-strain behavior of polymer networks result from different molecular-scale features of the material and suggest that controlling network architecture offers new opportunities to both further fundamental understanding of architecture-property relationships and design materials with independently controlled moduli and strain stiffening responses.

Implementation of a Urologic Surgery Skills Fair for Medical Students.

OBJECTIVES: To increase the proportion of applicants to urology residencies, we created a surgical skills fair to introduced urology early in undergraduate medical education. DESIGN: Funded by the Department of Urology, the fair was designed to have student rotations through 12 hands-on practice stations supervised by faculty and an advanced care practitioner or resident physicians. At conclusion, medical students completed a voluntary survey about their experience. SETTING: Surgical skills fairs were organized at Yale School of Medicine (New Haven, CT) in 2022 and 2023. PARTICIPANTS: The fair was designed to encourage interaction between medical students, urology residents, and urology faculty by highlighting common urologic procedures and skills. RESULTS: The fair was well received by medical students at all levels of training. Over 2 years, 155 medical students attended, including 67 (43%) first-year and 60 (39%) second-year medical students. Eighty-two medical students completed the survey. An average of 19 attendings, advanced care practitioners and residents attended each event. Of the survey respondents, 42.7% reported prior interest in a surgical specialty but had not considered urology. Students reported increased interest in urology and greater confidence in urologic skills after the event (p < 0.001). CONCLUSIONS: We demonstrate that creating a surgical fair in urology is feasible and enhances early exposure and interest in urology. For students who do not pursue urology, the fair provides knowledge of urological pathologies and valuable skills for all physicians.

Correction to "Effect of Polymer Composition and Morphology on Mechanochemical Activation in Nanostructured Triblock Copolymers".

[This corrects the article DOI: 10.1021/acs.macromol.2c02475.].

Evaluating Treatment Patterns and the Role of Neoadjuvant Chemotherapy in Plasmacytoid Urothelial Carcinoma: Insights from a Combined National and Institutional Series.

BACKGROUND: Plasmacytoid urothelial carcinoma (PUC) is a rare histologic subtype of urothelial carcinoma of the bladder (BC). Our objective was to characterize treatment patterns and outcomes of PUC in the NCDB and our recent institutional experience. METHODS: The NCDB was queried for localized PUC cases between 2004 and 2020. Patients with PUC from a single institution (Yale School of Medicine) were also incorporated from 2021 onwards to not double-count patients. The primary outcomes were overall survival and treatment trends. RESULTS: A total of 146 patients were included, 123 from NCDB and 23 from Yale. The median overall survival (mOS) was 28 [IQR 7.5, 50.3] months, 23 [IQR 8.4, 46.3] months for the NCDB patients, and 36 [IQR 4.3, 68.1] for the Yale patients. The mOS for patients receiving neoadjuvant chemotherapy (NAC) was 60.0 [28.0, 91.9] vs. 14.8 months [0, 34.3] for patients without NAC, p = 0.038, though the benefit was not preserved in a Cox proportional hazard analysis incorporating the clinical stage, receipt of NAC, and age. The peritoneum was the most common site of metastasis (78.3%), followed by the liver and bones. CONCLUSION: Our findings underscore the formidable challenge posed by PUC, emphasizing its limited response to current therapies. Despite higher pT0 rates with NAC, the OS benefit remains inconclusive, highlighting the need for more effective treatments.

Osteitis pubis following holmium laser enucleation of the prostate.

Osteitis pubis is a rare, inflammatory condition involving the pubic symphysis. While osteitis pubis has been reported following many urological procedures, including those addressing bladder outlet obstruction such as transurethral resection of the prostate, it has never been reported after holmium laser enucleation of the prostate (HoLEP). Here, we detail the clinical course of a patient found to have osteitis pubis following HoLEP. This patient presented several weeks after surgery with non-specific, persistent symptoms of groin pain and difficulty ambulating, alerting our clinicians to consider osteitis pubis which was confirmed on MRI of the pelvis. While the majority of osteitis pubis cases are managed with locally invasive techniques, our patient's symptoms were successfully managed conservatively with Foley catheter placement, oral antibiotics and close follow-up. At 9 months postoperative, the patient has reported complete resolution of symptoms and continues to be followed closely.

Effect of Polymer Composition and Morphology on Mechanochemical Activation in Nanostructured Triblock Copolymers.

The effect of composition and morphology on mechanochemical activation in nanostructured block copolymers was investigated in a series of poly(methyl methacrylate)-block-poly(n-butyl acrylate)-block-poly(methyl methacrylate) (PMMA-b-PnBA-b-PMMA) triblock copolymers containing a force-responsive spiropyran unit in the center of the rubbery PnBA midblock. Triblock copolymers with identical PnBA midblocks and varying lengths of PMMA end-blocks were synthesized from a spiropyran-containing macroinitiatior via atom transfer radical polymerization, yielding polymers with volume fractions of PMMA ranging from 0.21 to 0.50. Characterization by transmission electron microscopy revealed that the polymers self-assembled into spherical and cylindrical nanostructures. Simultaneous tensile tests and optical measurements revealed that mechanochemical activation is strongly correlated to the chemical composition and morphologies of the triblock copolymers. As the glassy (PMMA) block content is increased, the overall activation increases, and the onset of activation occurs at lower strain but higher stress, which agrees with predictions from our previous computational work. These results suggest that the self-assembly of nanostructured morphologies can play an important role in controlling mechanochemical activation in polymeric materials and provide insights into how polymer composition and morphology impact molecular-scale force distributions.

A Combined Conduit-Bioactive Hydrogel Approach for Regeneration of Transected Sciatic Nerves.

Transected peripheral nerve injury (PNI) affects the quality of life of patients, which leads to socioeconomic burden. Despite the existence of autografts and commercially available nerve guidance conduits (NGCs), the complexity of peripheral nerve regeneration requires further research in bioengineered NGCs to improve surgical outcomes. In this work, we introduce multidomain peptide (MDP) hydrogels, as intraluminal fillers, into electrospun poly(ε-caprolactone) (PCL) conduits to bridge 10 mm rat sciatic nerve defects. The efficacy of treatment groups was evaluated by electromyography and gait analysis to determine their electrical and motor recovery. We then studied the samples' histomorphometry with immunofluorescence staining and automatic axon counting/measurement software. Comparison with negative control group shows that PCL conduits filled with an anionic MDP may improve functional recovery 16 weeks postoperation, displaying higher amplitude of compound muscle action potential, greater gastrocnemius muscle weight retention, and earlier occurrence of flexion contracture. In contrast, PCL conduits filled with a cationic MDP showed the least degree of myelination and poor functional recovery. This phenomenon may be attributed to MDPs' difference in degradation time. Electrospun PCL conduits filled with an anionic MDP may become an attractive tissue engineering strategy for treating transected PNI when supplemented with other bioactive modifications.

Engineering Brightness Matched Indium Phosphide Quantum Dots.

The size-dependent optoelectronic properties of semiconductor nanocrystals quantum dots (QDs) are hugely beneficial for color tunability but induce an inherent relative PL brightness mismatch in QDs emitting different colors, as larger emitters absorb more incident photons than smaller particles. Here, we examine the effect of core composition, shell composition, and shell thickness on optical properties including high energy absorption, quantum yield (QY), and the relative brightness of InP/ZnS and InP/ZnSe core/shell and InP/ZnSe/ZnS core/shell/shell QDs at different excitation wavelengths. Our analysis reveals that the presence of an intermediate ZnSe shell changes the wavelength of enhanced absorption onset and leads to highly excitation wavelength dependent QYs. Switching from commercial CdSe/ZnS to InP/ZnS reduces the brightness-mismatch between green and red emitters from 33- to 5-fold. Incorporating a 4-monolayer thick optically absorbing ZnSe shell into the QD heterostructure and heating the QDs in a solution of zinc oleate and trioctylphosphine produces InP/ZnSe/ZnS QDs that are ~10-fold brighter than their InP/ZnS counterparts. In contrast to CdSe/CdS/ZnS core/shell/shell QDs, which only photoluminesce at red wavelengths with thicker CdS shells due to their Quasi-Type II bandstructure, Type I InP/ZnSe/ZnS QDs are uniquely suited to creating a rainbow of visible-emitting, brightness matched emitters. By tailoring the thickness of the intermediate ZnSe shell, heavy metal-free, brightness-matched green and red emitters are produced. This study highlights the ability to overcome the inherent brightness mismatch seen in QDs through concerted materials design of heterostructured core/shell InP-based QDs.

Temperature-Dependent Partitioning of C152 in Binary Phosphatidylcholine Membranes and Mixed Phosphatidylcholine/Phosphatidylethanolamine Membranes.

Time-resolved fluorescence and differential scanning calorimetry were used to determine the partitioning of coumarin 152 (C152) into large unilamellar vesicles composed of binary mixtures of two phosphatidylcholines (12:0/12:0 DLPC and 14:0/14:0 DMPC) and vesicles composed of binary mixtures of a phosphatidylcholine and a phosphatidylethanolamine (14:0/14:0 DMPC and 14:0/14:0 DMPE). Differential scanning calorimetry showed that both DLPC/DMPC and DMPC/DMPE are miscible in lipid vesicles. Time-resolved fluorescence indicated that C152 partitioning into DLPC/DMPC mixtures showed nearly ideal behavior that was described with weighted contributions from C152 partitioning into pure DLPC and pure DMPC vesicles. In contrast, C152 partitioning into DMPC/DMPE mixtures was distinctly nonideal. For DMPC/DMPE lipid vesicles having DMPC mole fractions between 10 and 80%, C152 partitioning into the bilayer was measurably enhanced near the melting temperature, relative to expectations based simply on weighted contributions from C152 partitioning into vesicles comprised of pure lipids. The origin of this behavior remains uncertain. For vesicles comprised of pure DMPE, C152 shows almost no partitioning into the membrane, with ≥80% of the solute remaining in the buffer solution at temperatures between 10 and 50 °C.

Temperature Dependent Solvation and Partitioning of Coumarin 152 in Phospholipid Membranes.

Time resolved fluorescence emission was used to quantify coumarin 152 (C152) partitioning into a model lipid vesicle membrane. For these studies, the lipid vesicles were composed of the symmetric, saturated phosphocholine, 1,2-dimyristoyl-sn-glycero-3-phosphocholine (14:0 DMPC). C152 fluorescence lifetimes were measured as a function of sample temperature, and changes in the relative contributions of these lifetimes (corrected for quantum yield) to the overall emission decay data were attributed to changes in the distribution of C152 solutes between the aqueous buffer, the polar vesicle headgroup region, and the hydrophobic interior of the vesicle bilayer. When the bilayer was in its more rigid, gel state, C152 remained predominantly in the aqueous buffer. Upon melting to its liquid crystalline state, each bilayer showed evidence of accommodating more C152 into a polar region associated with the lipid headgroups. At no temperature did C152 show strong affinity for the bilayer's hydrophobic interior. Above 50 °C, this behavior reversed itself with C152 moving back out of the vesicle membrane and into the buffer. All observed changes in partitioning behavior were reversible. The interesting temperature dependence of C152 partitioning suggests that C152 solvation within the lipid headgroup region represents a sensitive balance between enthalpic and entropic contributions with C152 accommodation by the bilayer being exothermic but entropically unfavorable.