2 research outputs found
Colloidal Stability of Citrate and Mercaptoacetic Acid Capped Gold Nanoparticles upon Lyophilization: Effect of Capping Ligand Attachment and Type of Cryoprotectants
For
various applications of gold nanotechnology, long-term nanoparticle
stability in solution is a major challenge. Lyophilization (freeze–drying)
is a widely used process to convert labile protein and various colloidal
systems into powder for improved long-term stability. However, the
lyophilization process itself may induce various stresses resulting
in nanoparticle aggregation. Despite a plethora of studies evaluating
lyophilization of proteins, liposomes, and polymeric nanoparticles,
little is known about the stability of gold nanoparticles (GNPs) upon
lyophilization. Herein, the effects of lyophilization and freeze–thaw
cycles on the stability of two types of GNPs: Citrate-capped GNPs
(stabilized via weakly physisorbed citrate ions, Cit-GNPs) and mercaptoacetic
acid-capped GNPs (stabilized via strongly chemisorbed mercaptoacetic
acid, MAA-GNPs) are investigated. Both types of GNPs have similar
core size and effective surface charge as evident from transmission
electron microscopy and zeta potential measurements, respectively.
Plasmon absorption of GNPs and its dependence on nanoparticle aggregation
was employed to follow stability of GNPs in combination with dynamic
light scattering analysis. Plasmon peak broadening index (PPBI) is
proposed herein for the first time to quantify GNPs aggregation using
nonlinear Gaussian fitting of GNPs UV–vis spectra. Our results
indicate that Cit-GNPs aggregate irreversibly upon freeze–thaw
cycles and lyophilization. In contrast, MAA-GNPs exhibits remarkable
stability under the same conditions. Cit-GNPs exhibit no significant
aggregation in the presence of cryoprotectants (molecules that are
typically used to protect labile ingredients during lyophilization)
upon freeze–thaw cycles and lyophilization. The effectiveness
of the cyroprotectants evaluated was on the order of trehalose or
sucrose > sorbitol > mannitol. The ability of cryoprotectants
to prevent
GNPs aggregation was dependent on their chemical structure and their
ability to interact with the GNPs as assessed with zeta potential
analysis
Colloidal Stability of Citrate and Mercaptoacetic Acid Capped Gold Nanoparticles upon Lyophilization: Effect of Capping Ligand Attachment and Type of Cryoprotectants
For
various applications of gold nanotechnology, long-term nanoparticle
stability in solution is a major challenge. Lyophilization (freeze–drying)
is a widely used process to convert labile protein and various colloidal
systems into powder for improved long-term stability. However, the
lyophilization process itself may induce various stresses resulting
in nanoparticle aggregation. Despite a plethora of studies evaluating
lyophilization of proteins, liposomes, and polymeric nanoparticles,
little is known about the stability of gold nanoparticles (GNPs) upon
lyophilization. Herein, the effects of lyophilization and freeze–thaw
cycles on the stability of two types of GNPs: Citrate-capped GNPs
(stabilized via weakly physisorbed citrate ions, Cit-GNPs) and mercaptoacetic
acid-capped GNPs (stabilized via strongly chemisorbed mercaptoacetic
acid, MAA-GNPs) are investigated. Both types of GNPs have similar
core size and effective surface charge as evident from transmission
electron microscopy and zeta potential measurements, respectively.
Plasmon absorption of GNPs and its dependence on nanoparticle aggregation
was employed to follow stability of GNPs in combination with dynamic
light scattering analysis. Plasmon peak broadening index (PPBI) is
proposed herein for the first time to quantify GNPs aggregation using
nonlinear Gaussian fitting of GNPs UV–vis spectra. Our results
indicate that Cit-GNPs aggregate irreversibly upon freeze–thaw
cycles and lyophilization. In contrast, MAA-GNPs exhibits remarkable
stability under the same conditions. Cit-GNPs exhibit no significant
aggregation in the presence of cryoprotectants (molecules that are
typically used to protect labile ingredients during lyophilization)
upon freeze–thaw cycles and lyophilization. The effectiveness
of the cyroprotectants evaluated was on the order of trehalose or
sucrose > sorbitol > mannitol. The ability of cryoprotectants
to prevent
GNPs aggregation was dependent on their chemical structure and their
ability to interact with the GNPs as assessed with zeta potential
analysis