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Gold nanostars (AuNSs) have achieved special relevance for potential biomedical applications, e.g., in theranostics. In relation to this, some authors have explored controlling the conditions that trigger structural and morphological changes in these structures. In this work, we studied conditions that can trigger morphological changes of AuNSs or maintain their stability, such as ligand exchange to nonthiolated and thiolated species. First, the synthesis stabilizing ligand of AuNS, 4-(2-hydroxyethyl)-1-piperazinapropanesulfonic acid (EPPS), was exchanged for nonthiolated species to trigger or prevent morphological changes. One of these species, triphenylphosphine-monosulfonate (TPPMS), generated a stable and unexplored nanostructure even at acidic pH, with interaction mediated mainly by aromatic groups and the phosphine moiety, in comparison to hexadecyltrimethylammonium bromide (CTAB) and citrate, which are ligands that trigger morphological changes of AuNS. Moreover, TPPMS-coated AuNSs can be exchanged by thiolated species, such as carboxylated poly-(ethylene glycol) (HS-PEG-COOH), offering more versatility through covalent strategies. In addition, properties related to the application of these stabilized AuNSs were explored, such as photothermia and biocompatibility. The photothermal transduction efficiency and cell viability of AuNSs coated with EPPS, TPPMS, and PEG-COOH were evaluated, showing a temperature increment of the colloidal solutions and optimal mitochondrial activity. We believe that this work contributes to understanding the phenomena and conditions that trigger changes in the morphology or stability of AuNSs and that AuNSs coated with TPPMS and PEG-COOH possess optimal properties for potential biomedical applications. [ABSTRACT FROM AUTHOR]

Dacarbazine (DB) is an antineoplastic drug extensively used in cancer therapy. However, present limitations on its performance are related to its low solubility, instability, and non-specificity. To overcome these drawbacks, DB was included in β-cyclodextrin (βCD), which increased its aqueous solubility and stability. This new βCD@DB complex has been associated with plasmonic gold nanoparticles (AuNPs), and polyethylene glycol (PEG) has been added in the process to increase the colloidal stability and biocompatibility. Different techniques revealed that DB allows for a dynamic inclusion into βCD, with an association constant of 80 M−1 and a degree of solubilization of 0.023, where βCD showed a loading capacity of 16%. The partial exposure of the NH2 group in the included DB allows its interaction with AuNPs, with a loading efficiency of 99%. The PEG-AuNPs-βCD@DB nanosystem exhibits an optical plasmonic absorption at 525 nm, a surface charge of −29 mV, and an average size of 12 nm. Finally, laser irradiation assays showed that DB can be released from this platform in a controlled manner over time, reaching a concentration of 56 μg/mL (43% of the initially loaded amount), which, added to the previous data, validates its potential for drug delivery applications. Therefore, the novel nanosystem based on βCD, AuNPs, and PEG is a promising candidate as a new nanocarrier for DB. [ABSTRACT FROM AUTHOR]

Drugs are widely used as therapeutic agents; however, they may present some limitations. To overcome some of the therapeutic disadvantages of drugs, the use of β-cyclodextrin-based nanosponges (βCDNS) constitutes a promising strategy. βCDNS are matrices that contain multiple hydrophobic cavities, increasing the loading capacity, association, and stability of the included drugs. On the other hand, gold nanoparticles (AuNPs) are also used as therapeutic and diagnostic agents due to their unique properties and high chemical reactivity. In this work, we developed a new nanomaterial based on βCDNS and two therapeutic agents, drugs and AuNPs. First, the drugs phenylethylamine (PhEA) and 2-amino-4-(4-chlorophenyl)-thiazole (AT) were loaded on βCDNS. Later, the βCDNS–drug supramolecular complexes were functionalized with AuNPs, forming the βCDNS–PhEA–AuNP and βCDNS–AT–AuNP systems. The success of the formation of βCDNS and the loading of PhEA, AT, and AuNPs was demonstrated using different characterization techniques. The loading capacities of PhEA and AT in βCDNS were 90% and 150%, respectively, which is eight times higher than that with native βCD. The functional groups SH and NH2 of the drugs remained exposed and allowed the stabilization of the AuNPs, 85% of which were immobilized. These unique systems can be versatile materials with an efficient loading capacity for potential applications in the transport of therapeutic agents. [ABSTRACT FROM AUTHOR]

Gold nanostars (AuNSs) exhibit modulated plasmon resonance and have a high SERS enhancement factor. However, their low colloidal stability limits their biomedical application as a nanomaterial. Cationic β-cyclodextrin-based polymer (CCD/P) has low cytotoxicity, can load and transport drugs more efficiently than the corresponding monomeric form, and has an appropriate cationic group to stabilize gold nanoparticles. In this work, we functionalized AuNSs with CCD/P to load phenylethylamine (PhEA) and piperine (PIP) and evaluated SERS-based applications of the products. PhEA and PIP were included in the polymer and used to functionalize AuNSs, forming a new AuNS-CCD/P-PhEA-PIP nanosystem. The system was characterized by UV–VIS, IR, and NMR spectroscopy, TGA, SPR, DLS, zeta potential analysis, FE-SEM, and TEM. Additionally, Raman optical activity, SERS analysis and complementary theoretical studies were used for characterization. Minor adjustments increased the colloidal stability of AuNSs. The loading capacity of the CCD/P with PhEA-PIP was 95 ± 7%. The physicochemical parameters of the AuNS-CCD/P-PhEA-PIP system, such as size and Z potential, are suitable for potential biomedical applications Raman and SERS studies were used to monitor PhEA and PIP loading and their preferential orientation upon interaction with the surface of AuNSs. This unique nanomaterial could be used for simultaneous drug loading and SERS-based detection. [ABSTRACT FROM AUTHOR]