Short- and long-term effect of colorectal cancer targeting peptides conjugated to gold nanoparticles in rats' liver and colon after single exposure

Abstract

Peptides play important roles in the diagnosis, prognostic predictors, and treatment of various kinds of cancer. Peptides (p.C, p.L and p.14), derived from the phage display peptide libraries, specifically binds to colorectal cancer (CRC) cells in vitro. To allow tumor specificity and selectivity for in vivo diagnosis of CRC, biotinylated p.C, p.L and p.14 were conjugated to AuNPs (14 nm) via the biotin-streptavidin interaction. Male Wistar rats were intravenously injected with a single dose (100 µg/kg body weight) of AuNPs (citrate-AuNPs, PEG-AuNPs, p.C-PEG-, p.L-PEG- and p.14-PEG-AuNPs). Animals were monitored for behavioral changes, and sacrificed either 14 days or 84 days post-injection. Biochemical changes, oxidative stress, and histology of the liver and colon were assessed. No significant changes were noted in the rats injected with all the AuNPs, except p.L-PEG-AuNPs that caused significant toxicity (p < 0.05) 14 days post-exposure when compared to control group, as evidenced by increased relative liver weight, increased malondialdehyde levels and histological changes in the liver. These changes, however, returned to normalcy 84 days post-injection. It can be concluded, based on these findings, that p.L induced a transient toxicity in rats after a single intravenous injection, and can therefore be considered non-toxic long-term after a single exposure.

Keywords: Colorectal cancer; Diagnosis; Gold nanoparticles; Peptides; Polyethylene glycol.

Fig. 1

Steps involved in the synthesis of the peptide-PEG-AuNPs

Fig. 2

UV–Vis spectra of AuNPs showing the surface plasmon resonance shifts

Fig. 3

Transmission electron micrograph of a Cit-AuNPs (scale bar 10 nm), b PEG-AuNPs (Scale bar 10 nm), c p.C-PEG-AuNPs (Scale bar 10 nm), d p.L-PEG-AuNPs (Scale bar 10 nm), p.14-PEG-AuNPs (Scale bar 20 nm)

Fig. 4

Fourier transmission infrared spectroscopy of the AuNPs

Fig. 5

Body weights (g) of rats during 84 days post-injection of AuNPs

Fig. 6

Relative organ weights of rats a 14 days and b 84 days post-injection of AuNPs (per 100 g body weight). Cit citrate, PBS phosphate-buffered saline, AuNPs gold nanoparticles. Values are expressed as Mean ± SD, n = 6. ^ap < 0.05 when compared to the PBS control group; ^bp < 0.05 when compared to Cit-AuNP group

Fig. 7

Effect of a single intravenous injection of AuNPs on serum marker enzymes after a 14 days and b 84 days. Cit citrate, PBS phosphate-buffered saline, AuNPs gold nanoparticles, (/10) actual values divided by 10. Values are expressed as Mean ± SD, n = 6. ^ap < 0.05, when compared to PBS control group; ^bp < 0.05, when compared to p.C-PEG-AuNPs group

Fig. 8

Effect of AuNPs on the levels of albumin and total protein after a 14 days and b 84 days. Cit citrate, PBS phosphate-buffered saline, AuNPs gold nanoparticles. Values are expressed as Mean ± SD, n = 6. ^ap < 0.05 when compared to Cit-AuNP group; ^bp < 0.05 when compared to PEG-AuNPs group; ^cp < 0.05 when compared to p.L-AuNPs group

Fig. 9

Histology of the liver a 14 days, and b 84 days after treatment with AuNPs (Haematoxylin and Eosin, × 400 original magnification, Scale bar = 50 µm). Key: 1 = PBS control; 2 = Citrate-AuNPs; 3 = PEG-AuNPs; 4 = p.C-PEG-AuNPs; 5 = p.L-PEG-AuNPs; 6 = p.14-PEG-AuNPs. CV central vein, thick arrow bile ducts, arrow head sinusoidal spaces, thick arrow  chromatin material, BD bile ducts, PV portal vein

Fig. 10

Histology of the colon a 14 days, and b 84 days post-injection of AuNPs. (Haematoxylin and Eosin, × 400 original magnification, Scale Bar = 50 µm). Key: 1 = PBS control; 2 = Citrate-AuNPs; 3 = PEG-AuNPs; 4 = p.C-PEG-AuNPs; 5 = p.L-PEG-AuNPs; 6 = p.14-PEG-AuNPs. Thick/thin arrow epithelium, C crypts