Effect of the Conjugation Density of Triphenylphosphonium Cation on the Mitochondrial Targeting of Poly(amidoamine) Dendrimers

Abstract

Many clinically relevant diseases with known poor therapeutic outcomes, including cancer and neurodegenerative disorders, have been directly linked to mitochondrial dysfunction. The ability to efficiently target therapeutics to intracellular organelles such as mitochondria may represent new opportunities for the effective treatment of such ailments. The present study reports the synthesis, cellular uptake, cytotoxicity, and mitochondrial colocalization of conjugates of triphenylphosphonium cation (TPP) to amine-terminated, generation 4, poly(amidoamine) (PAMAM) dendrimer (G4NH2) nanocarriers. The mitochondrial-targeting moiety TPP was either directly conjugated to G4NH2 (G4NH2-TPP) or to the dendrimer through a flexible polyethylene glycol (PEG) linker (G4NH2-PEGTPP). Conjugation was done at various TPP densities to assess their biological activity and potential for mitochondrial-targeted drug delivery. Tests in an in vitro model of the human alveolar carcinoma (A549 cells) showed that even at a low TPP density (∼5 TPP) both the cellular internalization and mitochondrial targeting increase significantly, as determined by fluorescence activated cell sorting (FACS) and confocal microscopy (CM), respectively. At a density of ∼10 TPP per G4NH2, further increase in cellular internalization and mitochondrial targeting was achieved. However, at this higher density, the nanocarriers also showed pronounced cytotoxicity. It was observed that the toxicity of the conjugates is decreased upon the addition of a PEG linker between the dendrimer and TPP (G4NH2-PEGTPP), while the mitochondrial targeting ability of the nanocarriers is not affected as the PEG density increases. The proposed strategies indicate that TPP-conjugated G4NH2 dendrimers represent a potentially viable strategy for the targeting of therapeutic molecules to mitochondria, which may help improve therapeutic outcomes of diseases related to mitochondrial dysfunction.

Surface-modified particles loaded with CaMKII inhibitor protect cardiac cells against mitochondrial injury

“…This result is consistent with previously published data 16, 39, 46 . Bielski et al found that conjugating TPP onto poly(amidoamine) (PAMAM) dendrimer nanocarriers increased both cellular internalization and mitochondrial targeting in the human lung adenocarcinoma cell line, A549 16 . Guzman-Villaneuva et al (2015) reported that TPP-liposomes had higher cellular uptake than liposomes without surface-conjugated TPP 46 .…”

“…Since then, TPP has been a popular choice for mitochondria targeting strategies. Moreover, TPP has been reported to promote the rate and amount of cellular internalization of conjugated nanomaterials 16 . There are various TPP-conjugated drug molecules and bioactive compounds such as, vitamin E (MitoVit E) 17 , a ubiquinone derivative (MitoQ) 18 and doxorubicin 19 .…”

Triphenylphosphonium Decorated Liposomes and Dendritic Polymers: Prospective Second Generation Drug Delivery Systems for Targeting Mitochondria

“…This mitochondria-targeting dendrimer has the potential to be an effective drug delivery system by encapsulating bioactive molecules either in the dendrimeric core or by surface conjugation. In line with the previous publication and employing the same parent dendrimer, a very recent investigation 63 reported the synthesis of a number of TPP functionalized derivatives of the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 …”

Mitochondria-Targeted Triphenylphosphonium-Based Compounds: Syntheses, Mechanisms of Action, and Therapeutic and Diagnostic Applications

“…Bielski et al developed TPP + -conjugated to polyamidoamine (PAMAM) dendrimers, G4-NH 2 for nanocarrier purposes (Figure 4B). 156 It was shown that 10 TPP + groups conjugated to the dendrimer via a PEG linker yield a good mitochondrial accumulation, as verified by fluorescence colocalization with MitoTracker dye, and low toxicity.…”