Synthesis and characterization of bioactive conjugated near-infrared fluorescent proteinoid-poly(L-lactic acid) hollow nanoparticles for optical detection of colon cancer

Abstract

Colon cancer is one of the major causes of death in the Western world. Early detection significantly improves long-term survival for patients with colon cancer. Near-infrared (NIR) fluorescent nanoparticles are promising candidates for use as contrast agents for tumor detection. Using NIR offers several advantages for bioimaging compared with fluorescence in the visible spectrum: lower autofluorescence of biological tissues and lower absorbance and, consequently, deeper penetration into biomatrices. The present study describes the preparation of new NIR fluorescent proteinoid-poly(L-lactic acid) (PLLA) nanoparticles. For this purpose, a P(EF-PLLA) random copolymer was prepared by thermal copolymerization of L-glutamic acid (E) with L-phenylalanine (F) and PLLA. Under suitable conditions, this proteinoid-PLLA copolymer can self-assemble to nanosized hollow particles of relatively narrow size distribution. This self-assembly process was used for encapsulation of the NIR dye indocyanine green. The encapsulation process increases significantly the photostability of the dye. These NIR fluorescent nanoparticles were found to be stable and nontoxic. Leakage of the NIR dye from these nanoparticles into phosphate-buffered saline containing 4% human serum albumin was not detected. Tumor-targeting ligands such as peanut agglutinin and anticarcinoembryonic antigen antibodies were covalently conjugated to the surface of the NIR fluorescent P(EF-PLLA) nanoparticles, thereby increasing the fluorescent signal of tumors with upregulated corresponding receptors. Specific colon tumor detection by the NIR fluorescent P(EF-PLLA) nanoparticles was demonstrated in a chicken embryo model. In future work, we plan to extend this study to a mouse model, as well as to encapsulate a cancer drug such as doxorubicin within these nanoparticles for therapeutic applications.

Engineering of New UV-Blocking Hollow Proteinoid Nanoparticles of Narrow Size Distribution Containing All-trans Retinoic Acid for Biomedical Applications

“…Until recently, most of the reported proteinoids in the literature were synthesized from at least seven amino acids and possessed relatively low molecular weights with higher PDIs (above 1.5), as common for step-growth polymerization mechanism [28]. The high molecular weights shown in the present study indicate that the polymerization procedure used here may provide relatively long polymer chains which resemble long proteins [29]. Long polymers usually possess improved mechanical properties than short ones, due to the increased number of physical interactions between the polymer chains [23].…”

“…This self-assembly process may be utilized to encapsulate different suitable molecules within the core of the particles, achieving a biocompatible drug carrier [27]. In recent studies, our group used this procedure to encapsulate anti-cancer drugs and near infrared fluorescent dyes within nano-sized particles for cancer therapy and detection [24,28,29].…”

“…5/RA NPs have sufficient cell penetration after 4 h of incubation. These results can be explained by the fact that the proteinoid NPs are similar to proteins, hence the cells may utilize them as nutrients [29]. Since, the at-RA is protected by the proteinoid particles, higher concentration of at-RA can penetrate the cells in comparison to free at-RA, since free at-RA can be converted to a less potent form, from the time it is applied until the time it reaches the cell DNA.…”

Nanotechnology in Colorectal Cancer for Precision Diagnosis and Therapy

“…Recently, one of the near-infra-red fluorescent proteinoidpoly(L-lactic acid)(PLLA) NPs preparation was described where a P(EF-PLLA) random copolymer was prepared using thermal copolymerization of L-phenylalanine(F), L-glutamicacid(E), and PLLA (Kolitz-Domb et al, 2014). The study revealed that under optimal conditions, the proteinoid-PLLA copolymer can self-assemble into hollow nano-sized particles that can be used to encapsulate the indocyanine green and NIR dye.…”

Potential applications and human biosafety of nanomaterials used in nanomedicine

“…NIR fluorescent NPs are also considered promising candidates for use as contrast agents for tumor detection (Ren et al, 2015). Kolitz-Domb et al (2014) demonstrated that bioactive conjugated NIR fluorescent proteinoid-poly (L-lactic acid) hollow NPs can be used for optical detection of colon cancer in a chicken embryo model. Will et al.…”