Is DFT Accurate Enough to Calculate Regioselectivity? The Case of 1,3-Dipolar Cycloaddition of Azide to Alkynes and Alkenes.

The importance of regioselectivity in 1,3-dipolar cycloadditions (DCs) makes it surprising that no benchmarking study on this problem has appeared. We investigated whether DFT calculations are an accurate tool to predict the regioselectivity of uncatalyzed thermal azide 1,3-DCs. We considered the reaction between HN3 and 12 dipolarophiles, comprising ethynes HC≡C-R and ethenes H2 C=CH-R (R=F, OH, NH2 , Me, CN, CHO), which cover a broad range of electron demand and conjugation ability. We established benchmark data by the W3X protocol [complete-basis-set-extrapolated CCSD(T)-F12 energy with T-(T) and (Q) corrections and MP2-calculated core/valence and relativistic effects] and showed that core/valence effects and high-order excitations are important for accurate regioselectivity. Regioselectivities calculated using an extensive set of density functional approximations (DFAs) were compared with benchmark data. Range-separated and meta-GGA hybrids gave the best results. Good treatment of self-interaction and electron exchange are the key features for accurate regioselectivity. Dispersion correction slightly improves agreement with W3X results. The best DFAs provide the isomeric TS energy difference with an expected error ≈0.7 mh and errors ≈2 mh can occur. The isomer yield provided by the best DFA has an expected error of ±5 %, though errors up to 20 % are not rare. At present, an accuracy of 1-2 % is unfeasible but it seems that we are not far from achieving this goal.

Substituent-Guided Cluster Nuclearity for Tetranuclear Iron(III) Compounds with Flat {Fe4(µ3-O)2} Butterfly Core.

The tetranuclear iron(III) compounds [Fe4(µ3-O)2(µ-LZ)4] (1-3) were obtained by reaction of FeCl3 with the shortened salen-type N2O2 tetradentate Schiff bases N,N'-bis(salicylidene)-o-Z-phenylmethanediamine H2LZ (Z = NO2, Cl and OMe, respectively), where the one-carbon bridge between the two iminic nitrogen donor atoms guide preferentially to the formation of oligonuclear species, and the ortho position of the substituent Z on the central phenyl ring selectively drives towards Fe4 bis-oxido clusters. All compounds show a flat almost-symmetric butterfly-like conformation of the {Fe4(µ3-O)2} core, surrounded by the four Schiff base ligands, as depicted by both the X-ray molecular structures of 1 and 2 and the optimized geometries of all derivatives as obtained by UM06/6-311G(d) DFT calculations. The strength of the antiferromagnetic exchange coupling constants between the iron(III) ions varies among the three derivatives, despite their magnetic cores remain structurally almost unvaried, as well as the coordination of the metal ions, with a distorted octahedral environment for the two-body iron ions, Feb, and a pentacoordination with trigonal bipyramidal geometry for the two-wing iron ions, Few. The different magnetic behavior within the series of examined compounds may be ascribed to the influence of the electronic features of Z on the electron density distribution (EDD) of the central {Fe4(µ3-O)2} core, substantiated by a Quantum Theory of Atoms In Molecules (QTAIM) topological analysis of the EDD, as obtained by UM06 calculations 1-3.

Personalised Profiling of Innate Immune Memory Induced by Nano-Imaging Particles in Human Monocytes.

Engineered nanoparticles used for medical purposes must meet stringent safety criteria, which include immunosafety, i.e., the inability to activate possibly detrimental immune/inflammatory effects. Even medical nanomaterials devoid of direct immunotoxic or inflammatory effects may have an impact on human health if able to modify innate memory, which is the ability to "prime" future immune responses towards a different, possibly more detrimental reactivity. Although innate memory is usually protective, anomalous innate memory responses may be at the basis of immune pathologies. In this study, we have examined the ability of two nanomaterials commonly used for diagnostic imaging purposes, gold and iron oxide nanoparticles, to induce or modulate innate memory, using an in vitro model based on human primary monocytes. Monocytes were exposed in culture to nanoparticles alone or together with the bacterial agent LPS (priming phase/primary response), then rested for six days (extinction phase), and eventually challenged with LPS (memory/secondary response). The memory response to the LPS challenge was measured as changes in the production of inflammatory (TNFα, IL-6) and anti-inflammatory cytokines (IL-10, IL-1Ra), as compared to unprimed monocytes. The results show that both types of nanoparticles can have an effect in the induction of memory, with changes observed in the cytokine production. By comparing nanomaterials of different shapes (spherical vs. rod-shaped gold particles) and different size (17 vs. 22 nm diameter spherical iron oxide particles), it was evident that innate memory could be differentially induced and modulated depending on size, shape and chemical composition. However, the main finding was that the innate memory effect of the particles was strongly donor-dependent, with monocytes from each donor showing a distinct memory profile upon priming with the same particles, thereby making impossible to draw general conclusions on the particle effects. Thus, in order to predict the effect of imaging nanoparticles on the innate memory of patients, a personalised profiling would be required, able to take in consideration the peculiarities of the individual innate immune reactivity.

Colloidal polymer-coated Zn-doped iron oxide nanoparticles with high relaxivity and specific absorption rate for efficient magnetic resonance imaging and magnetic hyperthermia.

Colloidally stable nanoparticles-based magnetic agents endowed with very high relaxivity and specific absorption rate are extremely desirable for efficient magnetic resonance imaging and magnetic hyperthermia, respectively. Here, we report a water dispersible magnetic agent consisting of zinc-doped superparamagnetic iron oxide nanoparticles (i.e., Zn-SPIONs) of 15 nm size with high saturation magnetization coated with an amphiphilic polymer for effective magnetic resonance imaging and magnetic hyperthermia of glioblastoma cells. These biocompatible polymer-coated Zn-SPIONs had 24 nm hydrodynamic diameter and exhibited high colloidal stability in various aqueous media, very high transverse relaxivity of 471 mM-1 s-1, and specific absorption rate up to 743.8 W g-1, which perform better than most iron oxide nanoparticles reported in the literature, including commercially available agents. Therefore, using these polymer-coated Zn-SPIONs even at low concentrations, T2-weighted magnetic resonance imaging and moderate magnetic hyperthermia of glioblastoma cells under clinically relevant magnetic field were successfully implemented. In addition, the results of this in vitro study suggest the superior potential of Zn-SPIONs as a theranostic nanosystem for brain cancer treatment, simultaneously acting as a contrast agent for magnetic resonance imaging and a heat mediator for localized magnetic hyperthermia.

pH-sensitive polymersomes: controlling swelling via copolymer structure and chemical composition.

pH-sensitive vesicles used as drug delivery systems (DDSs) are generally composed of protonable copolymers. The disaggregation of these nanoparticles (NPs) during drug release implies the dispersion of positively charged cytotoxic polyelectrolytes in the human body. To alleviate such issue, we synthesised A(BC)n amphiphilic block copolymers with linear (n = 1) and branched (n = 2) architectures to obtain pH-sensitive vesicles capable of releasing drugs in acidic conditions via controlled swelling instead of disaggregation. We obtained this feature by fine-tuning the relative amount of pH-sensitive and hydrophobic monomers. We studied pH-driven swelling by measuring NPs size in neutral and acidic conditions, the latter typical of tumours or inflamed tissues (pH∼6) and lysosomes (pH∼4.5). Dynamic light scattering (DLS) and zeta potential data provided useful indications about the influence of architecture and chemical composition on NPs swelling, stability and polycation release. Results demonstrated that vesicles made of linear copolymers with ∼22-28% in mol of protonable monomers in the 'BC' block swelled more than other species following a pH change from pH 7.4 to pH 4.5. We finally evaluated the cytotoxicity of vesicles composed of linear species, and paclitaxel (PTX) release from the latter in both cancer and normal cells.

Zwitterion-Coated Iron Oxide Nanoparticles: Surface Chemistry and Intracellular Uptake by Hepatocarcinoma (HepG2) Cells.

Nanoparticles (NPs) have received much attention in recent years for their diverse potential biomedical applications. However, the synthesis of NPs with desired biodistribution and pharmacokinetics is still a major challenge, with NP size and surface chemistry being the main factors determining the behavior of NPs in vivo. Here we report on the surface chemistry and in vitro cellular uptake of magnetic iron oxide NPs coated with zwitterionic dopamine sulfonate (ZDS). ZDS-coated NPs were compared to similar iron oxide NPs coated with PEG-like 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEA) to investigate how surface chemistry affects their in vitro behavior. ZDS-coated NPs had a very dense coating, guaranteeing high colloidal stability in several aqueous media and negligible interaction with proteins. Treatment of HepG2 cells with increasing doses (2.5-100 µg Fe/mL) of ZDS-coated iron oxide NPs had no effect on cell viability and resulted in a low, dose-dependent NP uptake, inferior than most reported data for the internalization of iron oxide NPs by HepG2 cells. MEEA-coated NPs were scarcely stable and formed micrometer-sized aggregates in aqueous media. They decreased cell viability for dose ≥50 µg Fe/mL, and were more efficiently internalized than ZDS-coated NPs. In conclusion, our data indicate that the ZDS layer prevented both aggregation and sedimentation of iron oxide NPs and formed a biocompatible coating that did not display any biocorona effect. The very low cellular uptake of ZDS-coated iron NPs can be useful to achieve highly selective targeting upon specific functionalization.

A smart platform for hyperthermia application in cancer treatment: cobalt-doped ferrite nanoparticles mineralized in human ferritin cages.

Magnetic nanoparticles, MNPs, mineralized within a human ferritin protein cage, HFt, can represent an appealing platform to realize smart therapeutic agents for cancer treatment by drug delivery and magnetic fluid hyperthermia, MFH. However, the constraint imposed by the inner diameter of the protein shell (ca. 8 nm) prevents its use as heat mediator in MFH when the MNPs comprise pure iron oxide. In this contribution, we demonstrate how this limitation can be overcome through the controlled doping of the core with small amount of Co(II). Highly monodisperse doped iron oxide NPs with average size of 7 nm are mineralized inside a genetically modified variant of HFt, carrying several copies of α-melanocyte-stimulating hormone peptide, which has already been demonstrated to have excellent targeting properties toward melanoma cells. HFt is also conjugated to poly(ethylene glycol) molecules to increase its in vivo stability. The investigation of hyperthermic properties of HFt-NPs shows that a Co doping of 5% is enough to strongly enhance the magnetic anisotropy and thus the hyperthermic efficiency with respect to the undoped sample. In vitro tests performed on B16 melanoma cell line demonstrate a strong reduction of the cell viability after treatment with Co doped HFt-NPs and exposure to the alternating magnetic field. Clear indications of an advanced stage of apoptotic process is also observed from immunocytochemistry analysis. The obtained data suggest this system represents a promising candidate for the development of a protein-based theranostic nanoplatform.

Colloidal stability of iron oxide nanocrystals coated with a PEG-based tetra-catechol surfactant.

Long-term colloidal stability of magnetic iron oxide nanoparticles (NPs) is an important goal that has not yet been fully achieved. To make an advance in our understanding of the colloidal stability of iron oxide NPs in aqueous media, we prepared NPs comprising a monodisperse (13 nm) iron oxide core coated with a PEG-based (PEG: polyethyleneglycol) surfactant. This consists of a methoxy-terminated PEG chain (MW = 5000 Da) bearing four catechol groups via a diethylenetriamine linker. The surfactant was grafted onto the nanocrystals by ligand exchange monitored by infrared spectroscopy. The colloidal stability of these nanoparticles was probed by monitoring the time evolution of the Z-average intensity-weighted radius R(h) and volume-weighted size distribution P(v) obtained from analysis of dynamic light scattering data. The nanoparticles showed no sign of aggregation for four months in deionized water at room temperature and also when subjected to thermal cycling between 25 and 75 °C. In 0.01 M PBS (phosphate buffered saline), aggregation (if any) is slow and partial; after 66 h, about 50% of NPs have not aggregated. Aggregation is more effective in 0.15 M NH(4)AcO buffer, where isolated particles are not observed after 66 h, and especially in acidic NH(4)AcO/AcOH buffer, where aggregation is complete within 1 h and precipitation is observed. The differing stability of the NPs in the above aqueous media is closely related to their ζ potential.

Alternative low-energy mechanisms for isotopic exchange in gas-phase D2O-H+(H2O)n reactions.

Molecular-dynamics (MD) trajectories and high-level ab initio methods have been used to study the low-energy mechanism for D(2)O-H(+)(H(2)O)(n) reactions. At low collisional energies, MD simulations show that the collisional complexes are long-lived and undergo fast monomolecular isomerization, converting between different isomers within 50-500 ps. Such processes, primarily involving water-molecule shifts along a water chain, require the surmounting of very-low-energy barriers and present sizable non- Rice-Ramsperger-Kassel-Marcus (RRKM) effects, which are interpreted as a lack of randomization of the internal kinetic energy. Interestingly, the rate of water shifts was found to increase upon increasing the size of the cluster. Based on these findings, we propose to incorporate the following steps into the mechanism for low-energy isotopic scrambling these D(2)O-H(+)(H(2)O)(n) reactions: a) formation of the collisional complex [H(+)(H(2)O)(n)D(2)O]* in a vibro-rotational excited state; b) incorporation of the heavy-water molecule in the cluster core as HD(2)O(+) by means of isomerization involving molecular shifts; c) displacement of solvation molecules from the first shell of HD(2)O(+) inducing de-deuteration (shift of a D(+) to a neighbor water molecule); d) reorganization of the clusters and/or expulsion of one of the isotopic variants of water (H(2)O, HDO or D(2)O) from the periphery of the complex.

Adhesive capsulitis of the shoulder in human immunodeficiency virus-positive patients during highly active antiretroviral therapy.

Many adverse events have been described in patients treated with highly active antiretroviral therapy (HAART). Recently, among these, adhesive capsulitis of the shoulder has been described in some patients using protease inhibitors. We report our experience with 6 human immunodeficiency virus-positive patients in whom adhesive capsulitis of the shoulder developed during HAART. All 6 patients were treated with the same antiretroviral drug combination (HAART) including nucleoside reverse transcriptase (stavudine and lamivudine) and protease inhibitors (indinavir). The clinical pattern of adhesive capsulitis during HAART is similar to the classical form of adhesive capsulitis. Examining our case studies, we postulate a correlation between HAART and adhesive capsulitis. Discontinuation or reduction of the dosage of protease inhibitors associated with conventional conservative treatment is effective in reducing the symptoms and resolving the disease.

An unusual cause of popliteal cyst.

We describe a surgical treatment for popliteal cyst in a 41-year-old woman affected by diffuse pigmented villonodular synovitis (PVNS) of the knee with extra-articular spreading. The treatment consists of an arthroscopic synoviectomy followed immediately by an open removal of the cyst. At 28-month follow-up, the patient is asymptomatic and no evidence of recurrence of PVNS has been seen. We believe that this double surgical approach may reduce the probability of recurrence of PVNS.

Result of arthroscopic treatment of pigmented villonodular synovitis of the knee.

PURPOSE: We report 10 years' experience in arthroscopic treatment of pigmented villonodular synovitis (PVNS) of the knee in a series of patients affected by the localized or diffuse form of the disease. The purpose of the study is to critically examine the results of arthroscopic synovectomy in the knee affected by PVNS, to determine the safety and effectiveness of the procedure. TYPE OF STUDY: Retrospective case analysis. METHODS: The study population consists of 19 patients, with an average follow-up of 60 months (minimum, 12; maximum, 128). All patients underwent knee arthroscopy. The 3 standard portals were used; posteromedial and posterolateral portals were added if required. Four patients were affected by localized PVNS and were subject to partial synovectomy with excision of the pathologic tissue. The remaining 15 patients presented a diffuse form of PVNS; 7 of them underwent extended arthroscopic synovectomy and 8 underwent partial synovectomy. The diagnosis was confirmed by synovial biopsy. RESULTS: In the group affected by the localized form of PVNS, the arthroscopic local excision resulted in a complete and persistent regression of the pathology. Among the patients affected by the diffuse form of PVNS, clinical results were better and the recurrence rate was lower in the group treated with extended synovectomy. No relevant complications were encountered. In particular, no cases of infection, stiffness, or neurovascular lesions were seen. CONCLUSIONS: Arthroscopic synovectomy is an appropriate treatment for knee PVNS. Extended synovectomy must be performed in all cases of diffuse PVNS.

Two cases of tibial nerve compression caused by uncommon popliteal cysts.

We report 2 cases of a popliteal mass of very unusual origin that induced compression neuropathy. The signs and symptoms could have been mistaken for those of a common Baker's cyst. Several recent studies have shown that the cause of Baker's cyst formation should be sought within the joint because of a communication between the gastrocnemio-semimembranosus bursa and the joint cavity. These 2 cysts had no communication with the articular joint, thus suggesting that the surgeon perform an open exploration of the popliteal fossa in the search for other cystic formations with origins and features different from Baker's cysts.