Scattering scanning near-field optical microscopy (s-SNOM) is a powerful technique for mid-infrared spectroscopy at nanometer length scales. By investigating objects in aqueous environments through ultrathin membranes, s-SNOM has recently been extended toward label-free nanoscopy of the dynamics of living cells and nanoparticles, assessing both the optical and the mechanical interactions between the tip, the membrane and the liquid suspension underneath. Here, the study reports that the tapping AFM tip induces a reversible nanometric deformation of the membrane manifested as either an indentation or protrusion. This mechanism depends on the driving force of the tapping cantilever, which is exploited to minimize topographical deformations of the membrane to improve optical measurements. Furthermore, it is shown that the tapping phase delay between driving signal and tip oscillation is a highly sensitive observable to study the mechanics of adhering objects, exhibiting highest contrast at low tapping amplitudes where the membrane remains nearly flat. Mechanical responses are correlated with simultaneously recorded spectroscopy data to reveal the thickness of nanometric water layers between membrane and adhering objects. Besides a general applicability of depth profiling, the technique holds great promise for studying mechano-active biopolymers and living cells, biomaterials that exhibit complex behaviors when under a mechanical load.

The human head can sometimes experience impact loads that result in skull fractures or other injuries, leading to the need for a craniectomy. Cranioplasty is a procedure that involves replacing the removed portion with either autologous bone or alloplastic material. While titanium has traditionally been the preferred material for cranial implants due to its excellent properties and biocompatibility, its limitations have prompted the search for alternative materials. This research aimed to explore alternative materials to titanium for cranial implants in order to address the limitations of titanium implants and improve the performance of the cranioplasty process. A 3D model of a defective skull was reconstructed with a cranial implant, and the implant was simulated using various stiff and soft materials (such as alumina, zirconia, hydroxyapatite, zirconia-reinforced PMMA, and PMMA) as alternatives to titanium under 2000N impact forces. Alumina and zirconia implants were found to reduce stresses and strains on the skull and brain compared to titanium implants. However, PMMA implants showed potential for causing skull damage under current loading conditions. Additionally, PMMA and hydroxyapatite implants were prone to fracture. Despite these findings, none of the implants exceeded the limits for tensile and compressive stresses and strains on the brain. Zirconia-reinforced PMMA implants were also shown to reduce stresses and strains on the skull and brain compared to PMMA implants. Alumina and zirconia show promise as alternatives to titanium for the production of cranial implants. The use of alternative implant materials to titanium has the potential to enhance the success of cranial reconstruction by overcoming the limitations associated with titanium implants.

Introduction Provisional prosthetic restorations play a crucial role in dentistry by protecting dentinal tubules, offering thermal insulation, and ensuring a precise fit during dental treatments. Computer-aided design and computer-aided manufacturing (CAD/CAM) have improved polymethyl methacrylate (PMMA), enhancing its mechanical properties such as hardness and resistance compared to traditional methods. However, bacterial accumulation remains a challenge due to inherent surface roughness. This study aims to assess and compare Streptococcus mutans adhesion on milled PMMA and conventional self-cure acrylic resin, providing insights into their microbial interaction dynamics. Materials and methods This study was a prospective trial approved by the Institutional Human Ethical Committee (SRB-IHEC) (registration number: IHEC/SDC/PROSTHO-2104/24/045) and registered in the Clinical Trial Registry, India (registration number: CTRI/2024/05/068196). The study involved 20 patients requiring single crowns in the right and left molar regions. Two groups were established: Group I (the milled PMMA group) and Group II (the conventional PMMA group). Criteria for participant selection and exclusion were set. A total of 120 swab samples from the buccal mucosa and tooth surfaces were collected before tooth preparation (the baseline) at one week and three weeks. Culture for S. mutans was done, and colony-forming units were counted. Data analysis was carried out using IBM SPSS Statistics for Windows, Version 26 (Released 2019; IBM Corp., Armonk, New York, United States). An independent sample t-test was employed to compare the two materials for crowns. To analyze changes over time within each group, a repeated-measures analysis of variance (ANOVA) was conducted. When the ANOVA test indicated significance, Tukey\'s post-hoc test was utilized for pairwise mean comparison. The level of significance was set at P < 0.05. Results The mean colony-forming units (CFU) counts for the milled PMMA group were 4.46 ± 0.167 CFU at baseline, 4.163 ± 0.058 CFU at one week, and 3.87 ± 0.19 CFU at three weeks. The mean CFU counts for the conventional PMMA group were 4.41 ± 0.13 CFU at baseline, 4.29 ± 0.114 CFU at one week, and 4.16 ± 0.108 CFU at three weeks. At baseline (before cementation), there was no difference between milled PMMA and conventional PMMA (P = 0.578). After one week, a significant difference between milled PMMA and conventional PMMA was observed (P < 0.005). After three weeks, a significant difference between milled PMMA and conventional PMMA persisted (P < 0.005).  Conclusion There was a significant reduction in microbial adhesion in both the milled and conventional PMMA groups. However, milled PMMA demonstrated a greater decrease in microbial adhesion as compared to conventional PMMA.

Bortezomib (BAN) is a proteasome inhibitor approved for the treatment of multiple myeloma and lymphoma. Despite its efficacy in various tumor models, systemic administration can result in toxicity to healthy organs. The purpose of this study is to evaluate the elution profile of BAN from PMMA cement for the local treatment of orthopedic tumors. BAN solution (5 mg; 2 mg/mL) was mixed with Simplex cement (40 g, Stryker), followed by injection of cement into an antibiotic cement nail mold (13 mm) to coat a 10 mm titanium femoral nail (DePuy Synthes). Once the cement polymerized, the nail was cut into 2 cm segments for the BAN elution study. There is a sustained release of BAN for up to 28 days. The overall concentration of BAN released at each time point was between 74 and 263 ng/ml, which is compatible with the peak blood concentration of a single intravenous BAN injection. This study demonstrates the feasibility of using PMMA bone cement as a local BAN delivery tool, essential for future studies and treatment targeting multiple myeloma cells.

BACKGROUND: Polymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn\'t provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics.
OBJECTIVE: The purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers.
METHODS: PMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05).
RESULTS: The findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups.
CONCLUSIONS: The novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

Minimally invasive spine treatments have been sought after for elderly patients with comorbidities suffering from advanced degenerative disc disease. Percutaneous cement discoplasty (PCD) is one such technique where cement is injected into a degenerated disc with a vacuum phenomenon to relieve patients from pain. Adjacent vertebral fractures (AVFs) are however an inherent risk, particularly for osteoporotic patients, due to the high stiffness of the used cements. While low-modulus cements have been developed for vertebroplasty through the addition of linoleic acid, there are no such variations with a high-viscosity base cement, which is likely needed for the discoplasty application. Therefore, a low-modulus polymethyl methacrylate was developed by the addition of 12%vol. linoleic acid to a high-viscosity bone cement (hv-LA-PMMA). Initial experimental validation of the cement was performed by mechanical testing under compression over a period of 24 weeks, after storage in 37 °C phosphate buffer saline (PBS) solution. Furthermore, cement extracts were used to evaluate residual monomer release and the cytotoxicity of hv-LA-PMMA using fibroblastic cells. Relative to the base commercial cement, a significant reduction of Young\'s modulus and compressive strength of 36% and 42% was observed, respectively. Compression-tension fatigue tests at 5 MPa gave an average fatigue limit of 31,078 cycles. This was higher than another low-modulus cement and comparable to the fatigue properties of the disc annulus tissue. Monomer release tests showed that hv-LA-PMMA had a significantly higher release between 24 h and 7 days compared to the original bone cement, similarly to other low-modulus cements. Also, the control cement showed cytocompatibility at all time points of extract collection for 20-fold dilution, while hv-LA-PMMA only showed the same for extract collections at day 7. However, the 20-fold dilution was needed for both the control and the hv-LA-PMMA extracts to demonstrate more than 70% fibroblast viability at day 7. In conclusion, the mechanical testing showed promise in the use of linoleic acid in combination with a high-viscosity PMMA cement to achieve properties adequate to the application. Further testing and in vivo studies are however required to fully evaluate the mechanical performance and biocompatibility of hv-LA-PMMA for possible future clinical application.

Over the past decade, new psychoactive substances (NPS) have emerged in the illegal drug market and have continued to attract attention from the international community. Among these, amphetamine-like NPS, classified as stimulants, constitute a significant proportion. However, the pharmacological characteristics and mechanisms underlying addiction to amphetamine-like NPS remain poorly understood. Given that circadian rhythms are linked to the brain stimulation effects of methamphetamine (METH) and amphetamine, we investigated the effects of METH, 1-(4-methoxyphenyl)-N-methylpropan-2-amine (PMMA), and 1-(benzofuran-5-yl)-N-ethylpropan-2-amine (5-EAPB) on intracranial self-stimulation (ICSS) in wild-type (WT) or Period circadian regulator 2 knockout mice. Amphetamine-like drugs increase intracellular Ca2+ levels to provoke dopamine release, so we examined the impact of Per2 knockdown on intracellular Ca2+ levels in PC12 cells to elucidate a potential mechanism underlying NPS-induced ICSS enhancement. Our ICSS results showed that METH and PMMA significantly increased brain stimulation in Per2 knockout mice compared to WT mice. Similarly, METH and PMMA induced higher Ca2+ fluorescence intensity in Per2 knockdown PC12 cells than in control cells. In contrast, 5-EAPB did not produce significant changes in either ICSS or Ca2+ signaling. These findings suggest that Per2 plays a crucial role in the brain stimulation effects of amphetamine-like drugs through the regulation of intracellular Ca2+.

OBJECTIVE: This study aimed to compare the clinical outcomes of polymethyl methacrylate (PMMA) and urethane dimethacrylate (UDMA) as materials for fixed provisional restorations, focusing on handling properties, chair time, and periodontal outcomes, due to their prevalent use in dental practice.
METHODS: A comparative clinical study was conducted with 150 patients at the Department of Fixed Prosthodontics, Damascus University, Damascus, Syria. Patients undergoing prosthetic treatments with crowns and bridges received two fixed provisional restorations using a direct approach. The first, made immediately after abutment preparation, used PMMA. The second, created post-clinical try-in of the final restoration, utilized UDMA. Both restorations were maintained for one week. We assessed chair time, handling properties via the Visual Analog Scale (VAS), and periodontal health using the Plaque Index and Gingival Index. The Kolmogorov-Smirnov test was used to assess data normality. Differences between the two groups in the outcome variables were analyzed using the Mann-Whitney U test. The level of significance was set at (P < 0.05).
RESULTS: The handling properties of chemically activated PMMA resin were superior to those of light-activated UDMA resin. However, UDMA resin outperformed in terms of chair time and periodontal outcomes. The mean chair time was 9.45 ± 1.01 minutes for PMMA and 4.40 ± 0.77 minutes for UDMA. Mild gingivitis or plaque accumulation was observed in 57.3% of PMMA restorations and 44.0% of UDMA restorations. Moderate gingivitis and plaque accumulation were noted in 42.7% of PMMA restorations, while 56.0% of UDMA restorations showed no plaque accumulation or gingival inflammation.
CONCLUSIONS: Chemically activated PMMA resin offers excellent handling properties, whereas light-activated UDMA resin provides advantages in chair time and periodontal health, making it a preferable choice for provisional restorations. Limitations and future research: The study was limited to short-term outcomes and did not assess the long-term durability of the restorations or their aesthetic impact on patient satisfaction. Further studies are recommended to evaluate the long-term performance of these materials, their cost-effectiveness, and their aesthetic outcomes to provide a more comprehensive understanding of their clinical utility.

A modular and 3D compartmentalized microfluidic system with electrospun porous membranes (PMs) for epithelialized organ-on-a-chip systems is presented. Our novel approach involves direct deposition of polymer nanofibers onto a patterned poly(methyl methacrylate) (PMMA) substrate using electrospinning, resulting in an integrated PM within the microfluidic chip. The in situ deposition of the PM eliminates the need for additional assembly processes. To demonstrate the high throughput membrane integration capability of our approach, we successfully deposited nanofibers onto various chip designs with complex microfluidic planar structures and expanded dimensions. We characterized and tested the fully PMMA chip by growing an epithelial monolayer using the Caco-2 cell line to study drug permeability. A comprehensive analysis of the bulk and surface properties of the membrane\'s fibers made of PMMA and polystyrene (PS) was conducted to determine the polymer with the best performance for cell culture and drug transport applications. The PMMA-based membrane, with a PMMA/PVP ratio of 5:1, allowed for the fabrication of a uniform membrane structure along the aligned nanofibers. By modulating the fiber diameter and total thickness of the membrane, we could adjust the membrane\'s porosity for specific cell culture applications. The PMMA-PVP nanofibers exhibited a low polydispersity index value, indicating monodispersed nanofibers and a more homogeneous and uniform fiber network. Both types of membranes demonstrated excellent mechanical integrity under medium perfusion flow rates. However, the PMMA-PVP composition offered a tailored porous structure with modulable porosity based on the fiber diameter and thickness. Our developed platform enables dynamic in vitro modeling of the epithelial barrier and has applications in drug transport and in vitro microphysiological systems.

Magneto-optical (MO) polymer nanocomposites have emerged as alternatives to conventional MO crystals, particularly in nanophotonics applications, thanks to their better processing flexibility and superior Verdet constants. However, a higher Verdet constant commonly comes with excessive optical loss due to increased absorption and scattering, resulting in a constant or reduced figure-of-merit (FOM) defined as the Verdet constant over optical loss. By doping magnetite (Fe3O4) nanoparticles with Tb3+ ions, we report a new strategy to enhance the Verdet constant without increasing the optical loss. The Fe3O4:Tb3+ nanocomposite is one of a kind that simultaneously achieves a state-of-the-art Verdet constant of 5.6 × 105 °/T·m and a state-of-the-art FOM of 31°/T in the near-infrared region.