Aging process of polyamidoamine dendrimers: Effect of pH and shaking in the fluorescence emission and aggregation‐state

2021 ◽  
Vol 138 (29) ◽  
pp. 50700
Author(s):  
Daniela E. Igartúa ◽  
David E. Ybarra ◽  
Darío M. Cabezas ◽  
Silvia del V. Alonso ◽  
Fernando C. Alvira
Keyword(s):  
Aging Process ◽  
Fluorescence Emission ◽  
Aggregation State ◽  
Effect Of Ph ◽  
Polyamidoamine Dendrimers

scholarly journals Aging Process of Polyamidoamine Dendrimers: Effect of pH and Shaking in the Fluorescence Emission and Aggregation-State

2020 ◽  
Author(s):  
Igartua Daniela ◽  
David Ybarra ◽  
Dario Cabezas ◽  
Silvia del Valle Alonso ◽  
Fernando Alvira
Keyword(s):  
Aging Process ◽  
Aqueous Suspension ◽  
Chemical Change ◽  
Fluorescence Emission ◽  
Pamam Dendrimers ◽  
Aggregation State ◽  
Polyamidoamine Dendrimers ◽  
Ph Conditions ◽  
In Vivo Administration

In the last years, it has been discovered and intensely studied the non-traditional intrinsic fluorescence of PAMAM dendrimers. Nevertheless, their aging process in aqueous suspension is scarcely studied, being unknown the causes of the observed changes in their fluorescence properties. Hence, this work aims to characterize the PAMAM dendrimers of generation 4.0 (DG4.0) and 4.5 (DG4.5) through the aging process at three different pH conditions, stored with or without shaking. We studied, up to 16 days, the UV-Vis absorption, the fluorescence emission, and the size of dendrimers/aggregates. In a different way than the already published work, we demonstrated that there is no chemical change in dendrimers through the aging process, even though changes in fluorescence emission were observed. Besides, we have put in evidence that changes in the agglomeration patterns of dendrimers would not be related to change in the fluorescence emission thought aging. Moreover, we demonstrated that DG4.5 formed large aggregates in water that need to be disrupted by shaking previous to an in vivo administration. <br>

scholarly journals Aging Process of Polyamidoamine Dendrimers: Effect of pH and Shaking in the Fluorescence Emission and Aggregation-State

2020 ◽  
Author(s):  
Igartua Daniela ◽  
David Ybarra ◽  
Dario Cabezas ◽  
Silvia del Valle Alonso ◽  
Fernando Alvira
Keyword(s):  
Aging Process ◽  
Aqueous Suspension ◽  
Chemical Change ◽  
Fluorescence Emission ◽  
Pamam Dendrimers ◽  
Aggregation State ◽  
Polyamidoamine Dendrimers ◽  
Ph Conditions ◽  
In Vivo Administration

In the last years, it has been discovered and intensely studied the non-traditional intrinsic fluorescence of PAMAM dendrimers. Nevertheless, their aging process in aqueous suspension is scarcely studied, being unknown the causes of the observed changes in their fluorescence properties. Hence, this work aims to characterize the PAMAM dendrimers of generation 4.0 (DG4.0) and 4.5 (DG4.5) through the aging process at three different pH conditions, stored with or without shaking. We studied, up to 16 days, the UV-Vis absorption, the fluorescence emission, and the size of dendrimers/aggregates. In a different way than the already published work, we demonstrated that there is no chemical change in dendrimers through the aging process, even though changes in fluorescence emission were observed. Besides, we have put in evidence that changes in the agglomeration patterns of dendrimers would not be related to change in the fluorescence emission thought aging. Moreover, we demonstrated that DG4.5 formed large aggregates in water that need to be disrupted by shaking previous to an in vivo administration. <br>

pH sensitive smart gels of cetylpyridinium chloride in binary solvent mixtures: phase behaviour, structure and composition

RSC Advances ◽  
2015 ◽  
Vol 5 (62) ◽  
pp. 50306-50311 ◽  
Author(s):  
Illa Ramakanth ◽  
Jaromír Pištora
Keyword(s):  
Cetylpyridinium Chloride ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Phase Behaviour ◽  
Binary Solvent ◽  
Solvent Mixtures ◽  
Gel Formation ◽  
Fluorescence Emission Spectra ◽  
Effect Of Ph ◽  
Binary Solvent Mixtures

Figure showing the effect of pH on CPC gel formation at 25 °C and fluorescence emission spectra of CPC solutions at pH ∼ 11.8.

Experimental Findings about the Fluorescence Emission of Generation 4.0 and 4.5 Polyamidoamine Dendrimers

2020 ◽  
Vol 5 (44) ◽  
pp. 14062-14068
Author(s):  
David E. Ybarra ◽  
Daniela E. Igartúa ◽  
Silvia V. Alonso ◽  
Fernando C. Alvira
Keyword(s):  
Fluorescence Emission ◽  
Polyamidoamine Dendrimers ◽  
Experimental Findings

scholarly journals Changes in aggregation states of light-harvesting complexes as a mechanism for modulating energy transfer in desert crust cyanobacteria

2017 ◽  
Vol 114 (35) ◽  
pp. 9481-9486 ◽  
Author(s):  
Leeat Bar Eyal ◽  
Reza Ranjbar Choubeh ◽  
Eyal Cohen ◽  
Ido Eisenberg ◽  
Carmen Tamburu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Light Harvesting ◽  
Excitation Energy Transfer ◽  
Fluorescence Emission ◽  
Light Energy ◽  
Thermal Dissipation ◽  
Transmission Electron Microscopy Data ◽  
Maximum Efficiency ◽  
Light Harvesting Complexes ◽  
Aggregation State

In this paper we propose an energy dissipation mechanism that is completely reliant on changes in the aggregation state of the phycobilisome light-harvesting antenna components. All photosynthetic organisms regulate the efficiency of excitation energy transfer (EET) to fit light energy supply to biochemical demands. Not many do this to the extent required of desert crust cyanobacteria. Following predawn dew deposition, they harvest light energy with maximum efficiency until desiccating in the early morning hours. In the desiccated state, absorbed energy is completely quenched. Time and spectrally resolved fluorescence emission measurements of the desiccated desert crustLeptolyngbya ohadiistrain identified (i) reduced EET between phycobilisome components, (ii) shorter fluorescence lifetimes, and (iii) red shift in the emission spectra, compared with the hydrated state. These changes coincide with a loss of the ordered phycobilisome structure, evident from small-angle neutron and X-ray scattering and cryo-transmission electron microscopy data. Based on these observations we propose a model where in the hydrated state the organized rod structure of the phycobilisome supports directional EET to reaction centers with minimal losses due to thermal dissipation. In the desiccated state this structure is lost, giving way to more random aggregates. The resulting EET path will exhibit increased coupling to the environment and enhanced quenching.

Estrogens and the aging process. The detection, prevention, and retardation of osteoporosis

JAMA ◽  
1966 ◽  
Vol 196 (3) ◽  
pp. 219-224 ◽  
Author(s):  
M. E. Davis
Keyword(s):  
Aging Process

Images of Aging in the Psychotherapeutic Context

GeroPsych ◽  
2015 ◽  
Vol 28 (2) ◽  
pp. 47-55 ◽  
Author(s):  
Eva-Marie Kessler ◽  
Catherine E. Bowen
Keyword(s):  
Old Age ◽  
Diagnostic Tests ◽  
Aging Process ◽  
Developmental Psychology ◽  
Mental Representations ◽  
Later Life ◽  
Future Research ◽  
Psychotherapeutic Process ◽  
Images Of Aging ◽  
Client Communication

Both psychotherapists and their clients have mental representations of old age and the aging process. In this conceptual review, we draw on available research from gerontology, social and developmental psychology, and communication science to consider how these “images of aging” may affect the psychotherapeutic process with older clients. On the basis of selected empirical findings we hypothesize that such images may affect the pathways to psychotherapy in later life, therapist-client communication, client performance on diagnostic tests as well as how therapists select and apply a therapeutic method. We posit that interventions to help both older clients and therapists to reflect on their own images of aging may increase the likelihood of successful treatment. We conclude by making suggestions for future research.

Analysis of Self-Concept in Older Adults in Different Contexts

2004 ◽  
Vol 20 (4) ◽  
pp. 262-274 ◽  
Author(s):  
Manuel de Gracia Blanco ◽  
Josep Garre Olmo ◽  
María Marcó Arbonès ◽  
Pilar Monreal Bosch
Keyword(s):  
Older Adults ◽  
Nursing Home ◽  
Depressive Symptoms ◽  
External Validity ◽  
Aging Process ◽  
Well Being ◽  
Self Esteem ◽  
Self Concept ◽  
Self Perceptions ◽  
Discriminatory Capacity

Summary: Self-concept is a construct consisting of a group of specific self-perceptions that are hierarchically organized. Age-associated changes of self-concept are related to the individual's perception of the changes occurring throughout the aging process. The authors examined external validity and internal consistency of an instrument that has been developed to assess self-concept in older adults and examined self-concept's characteristics in two different contexts. Results confirm the multidimensionality of the scale and show a satisfactory external validity, indicating good discriminatory capacity. Findings support the hypothesis that older people who live in a nursing home have a poor self-esteem, self-concept, and psychological well-being and have a greater presence of depressive symptoms than people who live in their own home.

Bilingualism and the Aging Process of Cognitive Flexibility

2013 ◽  
Author(s):  
Li Qu ◽  
Joel Jia Wei Low ◽  
Chengcheng Jiang ◽  
Qiao Dai ◽  
Ting Zhang ◽  
...  
Keyword(s):  
Cognitive Flexibility ◽  
Aging Process
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