Cell internalization kinetics and surface charge accessibility of surface-modified PAMAM dendrimers.

Surface-modified PAMAM dendrimers have important applications in drug delivery, yet a gap remains about the role that surface functionalization plays on their cell internalization capacity. We examined the cell internalization kinetics of PAMAM dendrimers that were surface-modified with acetyl, folate and poly(ethylene glycol), as model functional groups differing in size, charge, and chemical functionality. Dendrimers with 25% functionalization were internalized by HEK cells, but with slower rates and lower maximum uptakes than the native dendrimer between 1-6 h of incubation. Dendrimers with 50% functionalization exhibited negligible internalization capacities at all incubation times. Molecular dynamics simulations revealed that the solvent accessibility of the cationic surface charges is a key factor affecting cell internalization, unlike the total charge, functionality or size of surface-modified PAMAM dendrimers. These findings provide valuable insights to assist the design of PAMAM-based systems for drug delivery applications.

Rational Discovery of Microtubule-Stabilizing Peptides.

Microtubule (MT) stabilization is an attractive pharmacological strategy to hamper the progress of neurodegenerative diseases. In this regard, seeking peptides with MT-stabilizing properties has awoken great interest. This work reports the rational discovery of two structurally related MT-stabilizing octapeptides using a combination of protein-peptide docking, conventional molecular dynamics, Gaussian accelerated molecular dynamics (GaMD), and tubulin polymerization assays. FASTA sequences for ∼1000 peptides were crafted from single and double mutants of davunetide (NAP) and docked against the Taxol (TX) site on an octameric MT model representing a portion of the MT wall. Docked peptides were rescored after MM minimization and binding free energy refinement through single-point MM/GBSA calculations. The 60 best-ranked peptides were subjected to 50 ns MD simulations on peptide-MT complexes at the terminal TX site in the octameric Tau-MT model resulting in 11 complexes with occupancies greater than 99% and peptide-protein binding free energies less than -40 kcal/mol. Selected peptides were then examined through 300 ns GaMD simulations in complexes containing two identical ligands at the terminal and intermediate TX sites in the Tau-MT model to account for the differential association of MT-binding peptides to different regions of the MT structure. Six candidates showed a favorable MT-binding potential based on the analysis of interaction frequencies and relative mobilities of the complex components, suggesting a pivotal role of Arg278, Gln281, and Arg369 residues for peptides recognition. Four candidates were predicted to preserve an adequate balance of longitudinal and lateral interactions between tubulin dimers in peptide-MT complexes such that MT-stabilizing effects could be expected. MT polymerization experiments confirmed that four peptides (HAPVSIHQ, NYPVSIHQ, NWPVSIWQ, HAPVSIIQ) exhibit MT-stabilizing activity in vitro with NWPVSIWQ (P43) and HAPVSIIQ (P52) being the most active. Tryptophan quenching assays verified that P43 and P52 bind to nonpolymeric tubulin, whereas viability experiments on HEK cells confirmed their safety to pursue future pharmacological studies. The results herein presented are valuable to making progress in the rational design of MT-stabilizing peptides.

Cytotoxicity and in vivo plasma kinetic behavior of surface-functionalized PAMAM dendrimers.

Understanding the molecular features responsible for the plasma kinetics of surface-modified polyamido amine (PAMAM) dendrimers is critical to explore novel biomedical applications for these nanomaterials. In this report, polyethylene glycol (PEG) and folic acid (FA) were employed to obtain partially-substituted PAMAM dendrimers as model biocompatible nanomaterials with different size, charge and surface functionality. Cytotoxicity assays on HEK cells at 1-500 µM concentration confirmed that PEG and FA incorporation increased the cell viability of PAMAM-based nanomaterials. Measurements of plasma kinetics in vivo revealed that PEG-PAMAM has an extended circulation time in mice blood (71.7 min) over native PAMAM (53.3 min) and FA-PAMAM (41.8 min). Molecular dynamics simulations revealed a direct relationship between circulation time and dendrimer size, thus providing valuable evidence to increase understanding about the modulation of functional properties of PAMAM-based systems through surface modification, and to guide future efforts on the rational design of novel biomedical nanomaterials.

Partially PEGylated PAMAM dendrimers as solubility enhancers of Silybin.

PEGylated PAMAM-G4 dendrimers with substitution percentages of 50% and intermediate size PEG chains (0.55 and 2.0 kDa) were synthesized and evaluated as solubility enhancers and potential supramolecular carriers for the poorly soluble drug Silybin (SIL). Aqueous solubility profiles revealed that the PEGylated system with 2.0 kDa chains induced a five-fold solubility increase for SIL and the largest drug-loading capacity within the systems under study with an average complex stoichiometry of 71:1 according to the Higuchi-Connors formulation for multiple binding sites. The supramolecular interaction between SIL and PEGylated PAMAM-G4 dendrimers was confirmed by 2D-NOESY experiments, which evidenced the simultaneous complexation of the drug in both PAMAM-G4 branches and outermost PEG chains. In vitro release studies showed that 2.0 kDa PEG chains induced a more extended release time compared with 0.5 kDa PEG chains. This result was attributed to the enhancement of PEG assistance to SIL complexation in systems with longer PEG chains, which are able to self-penetrate into dendrimer cavities and cooperate in the stabilization of SIL complexes, thus delaying the release of SIL from the supramolecular host. These results are valuable for the future design and development of novel PAMAM-based systems for SIL complexation and delivery.

Original title: HIV infection and unawareness among men who have sex with men in Puerto Rico: data from The National HIV behavioral surveillance system 2011-2014.

BACKGROUND: Unawareness of HIV infection is a public health challenge that needs to be addressed, particularly in the case of men who have sex with men (MSM), since recent data are reporting increasing rates of HIV in this population in Puerto Rico. OBJECTIVES: We examined differences in the prevalence of HIV infection and unawareness among MSM in 2011 and 2014 using data from the National HIV Behavioral Surveillance System, 2011 and 2014. METHODS: Bivariate analyses was used to compare demographical and behavioral characteristics in both cycles (2011 and 2014). Prevalence ratio (PR) was assessed with Poisson regression models to determine changes in HIV prevalence and unawareness across cycles, using the 2011 NHBS-MSM cycle as reference group. RESULTS: A stable rate in HIV prevalence was observed in 2011 and 2014. There was a higher prevalence in 2014 than in 2011 in multiple behavioral characteristics such as age at sexual initiation, the number of sexual partners in the 12 months prior to being interviewed, HIV testing in the year prior to being interview, and the disclosure of sexual orientation to a healthcare provider. A significant decrease in HIV unawareness was reported (76.67%, 2011; 46.51%, 2014). Age-adjusted regression models showed a marginal reduction of 55% in HIV unawareness for men who disclosed their sexual orientation to their healthcare providers. CONCLUSION: Behavioral surveillance systems in groups such as MSM in on the island will aid to monitor prospectively the effectiveness of HIV testing outreach and engagement, as well as capacity capacity-building strategies targeted towards health care providers, aimed to increase HIV testing and awareness among this group.

Mechanism of PAMAM Dendrimers Internalization in Hippocampal Neurons.

Polyamidoamine (PAMAM) dendrimers are hyperbranched macromolecules which have been described as one of the most promising drug nanocarrier systems. A key process to understand is their cellular internalization mechanism because of its direct influence on their intracellular distribution, association with organelles, entry kinetics, and cargo release. Despite that internalization mechanisms of dendrimers have been studied in different cell types, in the case of neurons they are not completely described. Considering the relevance of central nervous system (CNS) diseases and neuropharmacology, the aim of this report is to describe the molecular internalization mechanism of different PAMAM-based dendrimer systems in hippocampal neurons. Four dendrimers based on fourth generation PAMAM with different surface properties were studied: unmodified G4, with a positively charged surface; PP50, with a substitution of the 50% of amino surface groups with polyethylene glycol neutral groups; PAc, with a substitution of the 30% of amino surface groups with acrylate anionic groups; and PFO, decorated with folic acid groups in a 25% of total terminal groups. Confocal images show that both G4 and PFO are able to enter the neurons, but not PP50 and PAc. Colocalization study with specific endocytosis markers and specific endocytosis inhibitor assay demonstrate that clathrin-mediated endocytosis would be the main internalization mechanism for G4, whereas clathrin- and caveolae-mediated endocytosis would be implicated in PFO internalization. These results show the existence of different internalization mechanisms for PAMAM dendrimers in neurons and the possibility to control their internalization properties with specific chemical modifications.

Demographic and High-Risk Behaviors associated with HPV and HPV Vaccine Awareness among Persons Aged 15-74 Years in Puerto Rico.

OBJECTIVE: Studies of human papillomavirus (HPV) awareness in Puerto Rico (PR) are limited and are of interest given low HPV vaccine uptake in this population. This cross-sectional study aimed to determine factors associated to HPV and HPV vaccine awareness among persons aged 15-74 years living in Puerto Rico. METHODS: We analysed data from a sub-sample of 1,476 men and women who participated in a 2008 population-based island-wide household survey and who completed an HPV module. Multivariate logistic regression models were used to examine factors associated with HPV and HPV vaccine awareness. RESULTS: Overall, 37.2% of participants had heard about HPV and 33.4% had heard of the vaccine. Multivariate logistic regression showed that women were more likely to have heard of HPV (OR adjusted: 4.54; 95% CI=3.45, 5.98) or of the HPV vaccine (OR adjusted: 6.15; 95% CI=4.50, 8.40) as compared to men. HPV awareness was also lower among older adults, persons with lower income and with lower educational attainment, those without children and smokers (p < 0.05). CONCLUSION: In 2008, two years after the introduction of the first HPV vaccine in PR and the US, public awareness about HPV infection and the HPV vaccine was lower in Hispanics in PR as compared to other populations. Identified high-risk populations should be targeted in preventive care strategies. Future efforts should increase HPV knowledge and vaccine use in this population in order to maximize the impact of vaccination programs.

Comparing patient-reported outcomes and lifestyle factors before and after the COVID-19 pandemic among Black and Hispanic breast cancer survivors in New Jersey.

PURPOSE: The impact of the COVID-19 pandemic restrictions in the US since March 2020 on cancer survivorship among Black and Hispanic breast cancer (BC) survivors remains largely unknown. We aimed to evaluate associations of the pandemic with participant characteristics, patient-reported outcomes (PROs), and lifestyle factors among Black and Hispanic BC survivors in the Women's Circle of Health Follow-Up Study and the New Jersey BC Survivors Study. METHODS: We included 447 Black (npre = 364 and npost = 83) and 182 Hispanic (npre = 102 and npost = 80) BC survivors who completed a home interview approximately 24 months post-diagnosis between 2017 and 2023. The onset of the pandemic was defined as March 2020. The association of the pandemic with binary outcomes was estimated using robust Poisson regression models. RESULTS: Hispanic and Black BC survivors recruited after the onset of the pandemic reported higher socioeconomic status and fewer comorbidities. Black women in the post-pandemic group reported a higher prevalence of clinically significant sleep disturbance (prevalence ratio (PR) 1.43, 95% CI 1.23, 1.68), lower sleep efficiency, and lower functional well-being, compared to the pre-pandemic group. Hispanic women were less likely to report low health-related quality of life (vs. high; PR 0.62, 95% CI 0.45, 0.85) after the onset of the pandemic. CONCLUSIONS: Ongoing research is crucial to untangle the impact of the pandemic on racial and ethnic minorities participating in cancer survivorship research, as well as PROs and lifestyle factors. IMPLICATIONS FOR CANCER SURVIVORS: This study highlights the importance of considering the impact of the pandemic in all aspects of research, including the interpretation of findings.

Neighborhood Archetypes and Cardiovascular Health in Black Breast Cancer Survivors.

Background: Maintaining cardiovascular health (CVH) is critical for breast cancer (BC) survivors, particularly given the potential cardiotoxic effects of cancer treatments. Poor CVH among Black BC survivors may be influenced by various area-level social determinants of health, yet the impact of neighborhood archetypes in CVH among this population remains understudied. Objectives: This study aimed to characterize the neighborhood archetypes where Black BC survivors resided at diagnosis and evaluate their associations with CVH. Methods: We assessed CVH 24 months post-diagnosis in 713 participants diagnosed between 2012 and 2017 in the Women's Circle of Health Follow-Up Study, a population-based study of Black BC survivors in New Jersey. Neighborhood archetypes, identified via latent class analysis based on 16 social and built environment features, were categorized into tertiles. Associations between neighborhood archetypes and CVH scores were estimated using polytomous logistic regression. Results: CVH scores were assessed categorically (low, moderate, and optimal) and as continuous variables. On average, Black BC survivors achieved only half of the recommended score for optimal CVH. Among the 4 identified archetypes, women in the Mostly Culturally Black and Hispanic/Mixed Land Use archetype showed the lowest CVH scores. Compared to this archetype, Black BC survivors in the Culturally Diverse/Mixed Land Use archetype were nearly 3 times as likely to have optimal CVH (relative risk ratio: 2.92; 95% CI: 1.58-5.40), with a stronger association observed in younger or premenopausal women. No significant CVH differences were noted for the other 2 archetypes with fewer built environment features. Conclusions: Neighborhood archetypes, integrating social and built environment factors, may represent crucial targets for promoting CVH among BC survivors.

Breast and Colorectal Cancer Screening Utilization after Hurricane María and the COVID-19 Pandemic in Puerto Rico.

Puerto Rico (PR) has faced environmental and public health challenges that could have significantly affected cancer screening access. Using administrative claims data from PR's Medicaid population, this study assessed trends in colorectal and breast cancer screening from 2016 to 2021, the impact of disasters in screening, and the absolute deficit in screening due to the pandemic. The monthly rates of claims were analyzed using Poisson regression. Significant reductions in breast and colorectal cancer screening utilization were observed. The colorectal cancer screening rate in 2017 was 77% lower a month after Hurricanes Irma and María [RRadj: 0.23; 95% CI: 0.20, 0.25] compared to the same time period in 2016. Breast cancer screening dropped 50% in November 2017 compared to November 2016 [RRadj: 0.50; 95% CI: 0.47, 0.54]. Prospectively, a recovery in utilization has been observed only for breast cancer screening. The results revealed that cancer screening utilization substantially declined after environmental disasters and the pandemic. These findings have potentially severe long-term implications for cancer health disparities and mortality in PR.