Development of the poly(l-histidine) grafted carbon nanotube as a possible smart drug delivery vehicle

Polyhistidine is among the cell-penetrating peptides that in an acidic environment can facilitate membrane transition. Keeping in mind that the pH of the tumor intercellular medium is ∼5.5, in this paper, we examined the functionalization of a convenient drug delivery vehicle with cell-penetrating poly(l-histidine) to provide a smart drug delivery system. Classical molecular dynamics and metadynamics simulations are used to investigate the interactions between doxorubicin, carbon nanotube, poly(l-histidine), and the cell membrane. Metadynamics simulation revealed that not only the global minimum of FES reduced in an acidic environment but also the difference between the free energy of Doxorubicin as being adsorbed on poly(l-histidine) compared to when being freely dissolved in the aqueous medium show a dramatic reduction. MD simulations showed that functionalization of carbon nanotube with poly(l-histidine) groups has no detriment effect in the adsorption of Doxorubicin. The L-J interaction between Doxorubicin and carrier at the equilibrium states reached around -600 kJ/mol, both for the pristine and functionalized carbon nanotube. The coulombic interactions for both complexes were negligible in the neutral environment. At the acidic environment, the L-J interactions retained the same values as the neutral, while the coulombic interactions showed positive values, which suggested its participation in the detachments. At the vicinity of the membrane, the complexes retain their integrity both in neutral and acidic environments. In the present work, we performed metadynamics simulation to investigate the effects of poly(l-histidine) on the adsorption capacity of the carbon nanotubes, and explore the adsorption/desorption processed of Doxorubicin on pristine and poly(l-histidine)-grafted carbon nanotube. The resulted complexes were then subjected to interact with the POPC membrane model in both acidic and neutral environments via molecular dynamic simulations. The results provided here will hopefully help in a better understanding of future drug delivery systems and be helpful in designing more efficient and smart drug delivery systems.

Designing a high-performance smart drug delivery system for the synergetic co-absorption of DOX and EGCG on ZIF-8

Due to the extreme pore volume and valuable surface area, zeolitic imidazole frameworks (ZIFs) are promising vehicles that enhance the delivery of therapeutic agents to tissues. Furthermore, these nanoporous materials have high stability in the pH and temperature of the surrounding healthy cells (37 °C and pH = 7) and an exotic potential to deform in carcinogenic environment (T > 37 °C and pH ∼ 5.5), which make them perfect smart drug delivery vehicle candidates. In this work, a series of molecular dynamics (MD) and metadynamics simulations have been performed to gain molecular insight into the mechanisms involved in the process of co-loading of doxorubicin (DOX) and EpiGalloCatechin-3 Gallate (EGCG) on ZIF-8, which form a smart drug delivery system (SDDS). The obtained results revealed that DOX was adsorbed on the carrier mostly through electrostatic interactions (E_coul = ∼−1200 kJ mol⁻¹, E_tot = −1700 kJ mol⁻¹), and EGCG was stacked on ZIF-8 mainly via van der Waals interactions (E_L-J = ∼−600 kJ mol⁻¹, E_tot = ∼−1200 kJ mol⁻¹). It is worth mentioning that the drug–drug L-J interactions (E_L-J = ∼500 kJ mol⁻¹) were also important in the co-loading process. The insertion of DOX and EGCG as additive agents to the initial ZIF-8/EGCG and ZIF-8/DOX systems led to the enhancement of the drug–carrier pair interactions to about ∼−2300 kJ mol⁻¹ and ∼−2000 kJ mol⁻¹, respectively. This finding implied that the drug–drug interactions had a complementary role in the development of SDDS via ZIF-8. From the metadynamics simulation, it was found that the geometry of the drugs is a determining factor in an efficient co-loading SDDS.

Adsorption free energy of a molecule depends on where and how the molecule meets ZIF-8 surface.

P2440Increased mortality with high versus normal ejection fraction in elderly women

Methods

NEDA contains echo data (>530,000, years 1997–2017) from laboratories (N=14) across Australia, linked to the National Death Index (NDI). 331,344 individuals aged >18 years (n=172,251 [52%] men, age=60.8±18.0 years and 152,095 [48%] women, 60.9±19.2 years) had a mean follow up of 5.4 person-years and 63,142 fatal events. LVEF using Method Of Discs (MOD) could be calculated in 116,544 individuals. We compared mortality in those with normal LVEF (52–72% for males and 54–74% for females) compared with high LVEF (>72% and >74% for males and females, respectively).

Results

Mortality was 11% higher in females with high LVEF vs females with normal LVEF. On multivariable logistic regression, high ejection fraction remained an independent predictor of mortality after correction for age, gender and body mass index. High LVEF was positively associated with female gender, age and diastolic dysfunction. Of 96,033 individuals in the study population, there were 46,876 males (48.8%), mean age 61.19±17.09 years, not significantly different from their female counterparts. 44,282 males had normal LVEF (52–72%) as opposed to 2,594 with high LVEF (>72%). In females, 46,186 had normal LVEF (54–74%) and 2,971 had high LVEF.InCox proportional hazard models, the hazard ratio (HR) for mortality in males with normal EF was 1.105 for age (95% CI 1.102 to 1.07) and 1.074 (95% CI 0.988 to 1.167) for high LVEF (p<0.001 for all outputs). In females, the corresponding adjusted HR was 1.107 for age (95% CI 1.105 to 1.110) and 1.140 for high LVEF (95% CI 1.057 to 1.230).

Conclusion

High LVEF, particularly in older women, is associated with increased mortality compared with an LVEF within the reference range. Further study is required to evaluate possible mechanisms for worse outcomes in patients with high LVEF.