Design and potential application of PEGylated gold nanoparticles with size-dependent permeation through brain microvasculature.

Gold nanoparticles (AuNPs) have gained prominence in several targeting applications involving systemic cancers. Their enhanced permeation and retention within permissive tumor microvasculature provides a selective advantage for targeting. Malignant brain tumors also exhibit transport-permissive microvasculature secondary to blood-brain barrier disruption. Hence AuNPs may have potential relevance for brain tumor targeting. However, there are currently no studies that systematically examine brain microvasculature permeation of polyethylene glycol (PEG)-functionalized AuNPs. Such studies could pave the way for rationale AuNP design for passive targeting of malignant tumors. In this report we designed and characterized AuNPs with varying core particle sizes (4-24 nm) and PEG chain lengths [molecular weight 1000-10,000]. Using an in-vitro model designed to mimic the transport-permissive brain microvasculature, we demonstrate size-dependent permeation properties with respect to core particle size and PEG chain length. In general short PEG chain length (molecular weight 1000-2000) in combination with smallest core size led to optimum permeation in our model system. FROM THE CLINICAL EDITOR: In this report the authors designed and characterized PEGylated gold NPs with varying core particle sizes and PEG chain lengths and demonstrate that short PEG chain length in combination with smallest core size led to optimum permeation of a blood-brain barrier model system. These findings may pave the way to optimized therapy of malignant brain tumors.

Suppression of interleukin-10 release from human periodontal ligament cells by interleukin-1beta in vitro.

Periodontitis is characterized by an inflammatory process induced by periodontopathogenic bacteria in the subgingival plaque. Periodontal inflammation can be enhanced by both an increase of inflammatory stimulators, e.g. interleukin (IL)-6, and a decrease of inflammatory inhibitors, e.g. IL-10. The amount of IL-1beta is known to be increased in gingival tissues and in the gingival crevicular fluid from inflamed sites compared to healthy sites. This in vitro study sought to clarity whether IL-1beta (1 ng/ml) has a regulatory effect on the release of these two cytokines from human periodontal ligament (PDL) cells. PDL cells derived from healthy premolars were grown in the presence and absence (control) of IL-1beta. The concentration of IL-6 and IL-10 in the supernatants was assessed by enzyme-linked immunosorbent assay after 48 h of culture. PDL cells incubated with IL-1beta released significantly (p < 0.05) higher amounts of IL-6 and significantly (p < 0.01) smaller amounts of IL-10 compared to control. These results give further support to the observation that IL-1beta can increase the IL-6 secretion from PDL cells. Moreover, they provide original evidence that PDL cells secrete IL-10, which can be suppressed by IL-1beta. It is concluded that PDL cells can function as accessory immunoinflammatory cells amplifying the inflammatory process in periodontitis and, thereby, contributing to periodontal breakdown.

Crossover of exhaustion between dentists and dental nurses.

The aim of this study was to investigate the conditions under which job-related exhaustion may transmit (cross over) from dentists to dental nurses and vice versa. We conducted a cross-sectional survey study among 470 Finnish dentist-dental nurse dyads and used moderated structural equation modelling analyses. We found no support for the direct crossover of exhaustion from one work partner to the other. Instead, we found that exhaustion transferred from dentists to dental nurses only when collaboration was frequent and dental nurses perceived the collaboration as friendly or consisting of mutual feedback. In contrast, dentists were not affected by dental nurses' exhaustion. These results indicate that exhaustion can be contagious in work dyads and may be fuelled by positive and frequent interpersonal relationships when the partner who is higher in the hierarchy has high (versus low) levels of exhaustion. Thus, interpersonal and hierarchical relationships among work partners may play an important role in the crossover process. Limitations and implications are mentioned.

How dentists cope with their job demands and stay engaged: the moderating role of job resources.

This study focuses on job demands, job resources, and work engagement among 1,919 Finnish dentists employed in the public sector. Based on the Job Demands - Resources model, it was first predicted that the inverse relationship between job demands (e.g. workload, physical environment) and work engagement would be weaker when dentists had many resources (e.g. variability in the required professional skills, peer contacts). Second, using the Conservation of Resources theory it was hypothesized that job resources are most beneficial in maintaining work engagement under conditions of high job demands. The data were based on a postal questionnaire with a response rate of 71%. The dentists were split into two random groups in order to cross-validate the results. A set of hierarchical regression analyses resulted in 17 out of 40 significant interactions (40%). Four out of 20 possible interaction effects could be cross-validated showing, for example, that variability in professional skills mitigated the negative effect of qualitative workload on work engagement and, in addition, boosted work engagement when the qualitative workload was high. The main conclusion is that job resources are useful in coping with the high demands in dentistry and help dentists to stay engaged.

Lysolecithin analogs as adjuvants in delayed-type hypersensitivity in mice. I. Characterization of the adjuvant effect.

The adjuvant activity of 5 different lysolecithin analogs (LLA) has been studied in delayed-type hypersensitivity (DTH) using fowl gamma globulin, bovine serum albumin and the terpolymer L-glutamic acid 60-L-alanine30-L-tyrosine10(GAT), as antigens. Increased DTH responses, by factors of 1.8--2.0 in CBA and BALB/c mice, showed that LLA are immunopotentiators if given intraperitoneally (i.p.) or subcutaneously (s.c.) together with the antigen. The concentration range, within which LLA are active, is limited to 10--20 micrograms/mouse s.c. and 100--300 micrograms/mouse i.p. Adjuvanticity was tested as a function of the LLA structure. The most pronounced immunopotentiation was obtained with racemic 1-octadecyl-2-methylglycero-3-phosphorylcholine (ET18-O-CH3). The LLA became less active with decreasing numbers of C atoms in the alkyl chain.

Interferon sensitive and insensitive MHC variants of a murine thymoma differentially resistant to methotrexate-containing antibody-directed liposomes and immunotoxin.

We evaluated the ability of methotrexate-containing liposomes or a ricin alpha-chain immunotoxin, both associated with monoclonal antibodies specific for the major histocompatibility complex-encoded class I molecule H-2Kk, to kill cells of the murine k haplotype thymoma RDM4. Cells were incubated with liposomes or immunotoxin in the presence or absence of interferon-gamma, which is known to augment the expression of the target class I molecules. The great majority of cells were killed by either of these reagents. Two types of mutant cells were obtained: type 1 cells, selected by methotrexate-containing liposomes, failed to express sufficient target H-2k molecules to be killed by liposomes in the absence of interferon-gamma. In the presence of interferon-gamma, these cells increased expression of all H-2 class I molecules and could be killed by targeted liposomes. Type 2 cells were immunoselected from cloned type 1 cells by liposomes in the presence of interferon. These cells failed to respond to interferon with expression of the H-2Kk molecule, but continued to augment H-2Dk expression in response to interferon. A third variant (type 3) selected from the wild type population by an H-2Kk specific immunotoxin in the absence of interferon phenotypically resembled type 1 cells. Type 1 but not type 2 cells respond to interferon by augmented synthesis of H-2Kk specific mRNA. The results suggest that for interferon-sensitive cell surface molecules of tumor cells, use of interferon improves the efficacy of targeted chemotherapy, but does not prevent development of mutants lacking the target molecule.

Phosphatidyl glycerolphosphate serves as glycerolphosphate donor in polymer synthesis.

Phosphatidyl glycerolphosphate was found to serve as the glycerolphosphate donor for polymer synthesis. When CDP-diglyceride and radiolabeled glycerolphosphate were incubated with the membrane enzyme prepared from Streptococcus sanguis, active syntheses of radiolabeled lipids and polymers were observed. The synthesis of polymer was not inhibited by low concentration of unlabeled phosphatidylglycerol. When [3H, 32P]glycerolphosphate was used, the polymer synthesized contained both 3H and 32P. The lipids formed were characterized as phosphatidylglycerol and phosphatidyl glycerolphosphate. The polymers formed from the latter were characterized as lipoteichoic acid like compounds by sodium dodecylsulfate-polyacrylamide gel electrophoresis.

Synthesis of poly(ethylene glycol)-based saquinavir prodrug conjugates and assessment of release and anti-HIV-1 bioactivity using a novel protease inhibition assay.

Various poly(ethylene glycol)(PEG)-based prodrug conjugates of the HIV-1 protease inhibitor (PI) saquinavir (SQV) were prepared using several types of chemical groups potentially capable of modifying its pharmacokinetic properties. These prodrug conjugates included SQV-cysteine-PEG3400, SQV-cysteine-PEG3400-biotin, SQV-cysteine(R.I.CK-Tat9) [a cationic retro-inverso-cysteine-lysine-Tat nonapeptide]-PEG3400, and SQV-cysteine(R.I.CK(stearate)-Tat9)-PEG3400. SQV was linked to cysteine to form a releasable SQV-cysteine ester bond in all of the conjugates. The amino group of the cysteine moiety provided an attachment site for a slower-degrading amide bond with N-hydroxysuccinimide-activated forms of PEG- and PEG-biotin. Disulfide bonds were used to attach the cationic peptides, R.I.CK-Tat9 and R.I.CK(stearate)-Tat9 to the cysteine moiety in order to provide cell-specific release. An assay was established and validated for measuring the activity of SQV and other protease inhibitors in biological samples. In this assay, cleavage of an internally quenched fluorescent substrate, Arg-Glu(EDANS)-Ser-Gln-Asn-Tyr-Pro-Ile-Val-Gly-Lys(DABCYL)-Arg by HIV-1 protease was inhibited by SQV in a dose-dependent manner at concentrations of 0.05-0.5 microM. All prodrug conjugates were shown to be inactive in this assay until the ester bond was cleaved and active SQV was released. The prodrug reconversion half-lives in 0.1 N HCl, phosphate-buffered saline (PBS) at pH 7.4 and in spiked plasma at 37 degrees C were 9, 14, and 0.9 h, respectively. The anti-HIV-1 activity (ED(50)) of the PEG-based SQV prodrug conjugates was evaluated in MT-2 cells using an MTT assay. The activity of conjugated SQV was reduced (ED(50) = 900 nM) for the PEG only conjugate, but restored with the addition of biotin (ED(50) = 125 nM), R.I.CK-Tat9 (ED(50) = 15 nM), and R.I.CK(stearate)-Tat9 (ED(50) = 62 nM) as compared to maximum achievable anti-HIV-1 activity (unconjugated SQV, control, ED(50) = 15 nM), suggesting enhanced cellular uptake of conjugates. Cytotoxicity (LD(50)) was assessed for all prodrug conjugates using non-HIV-1 infected cells and was found to be in the micromolar range. The difference between the LD(50) and ED(50) suggests a favorable therapeutic index for the prodrug conjugates. In conclusion, these promising initial results demonstrate that the reconversion of the conjugate prodrugs was complete and that active SQV was released. Since the major delivery advantages of PEG prodrug conjugates can only be observed in vivo, issues of reconversion and elimination half-lives in plasma will have to be further studied in an in vivo model. The current results also demonstrate that the protease inhibition assay is a simple yet effective bioanalytical tool that can be used to assess the release and anti-HIV-1 activity of HIV-1 PIs from their prodrug forms.