Preparation and characterization of folate-poly(ethylene glycol)-grafted-trimethylchitosan for intracellular transport of protein through folate receptor-mediated endocytosis

Super-resolution imaging of folate receptor alpha on cell membranes using peptide-based probes

Folate receptor alpha (FRα) is a vital membrane protein which have great association with cancers and involved in various biological processes including folate transport and cell signaling. However, the distribution and organization pattern of FRα on cell membranes remains unclear. Previous studies relied on antibodies to recognize the proteins. However, multivalent crosslinking and large size of antibodies confuse the direct observation to some extent. Fortunately, the emergence of peptide, which are small-sized and monovalent, has supplied us an unprecedented choice. Here, we applied fluorophore-conjugated peptide probe to recognize the FRα and study the distribution pattern of FRα on cell membrane using dSTORM super-resolution imaging technique. FRα were found to organized as clusters on cell surface with different sizes. And they have a higher expression level and formed larger clusters on various cancer cells than normal cells, which hinted that its specific distribution could be utilized for cancer diagnosis. Furthermore, we revealed that the lipid raft and cortical actin as restrictive factors for the FRα clustering, suggesting a potential assembly mechanism insight into FRα clustering on cell membrane. Collectively, our work clarified the morphology distribution and clustered organization of FRα with peptide probes at the nanometer scale, which paves the way for further revealing the relationship between the spatial organization and functions of membranal proteins.

Supramolecular imaging of spermine in cancer cells

As an important biomarker, the overexpressed spermine has been widely investigated for cancer diagnosis and treatment. However, bioimaging of spermine in living cells is still a formidable challenge. Herein, we design a supramolecular imaging ensemble for spermine by the host-guest complexation of amphiphilic sulfonatocalix[5]arene (SC5A12C) assembly with lucigenin (LCG). Strong binding ability and complexation-induced fluorescence quenching properties enable SC5A12C to quench the fluorescence of LCG dramatically and to recover it completely due to the competition of overexpressed spermine in cancer cells. SC5A12C also exhibits excellent biocompatibility and promotes cellular uptake due to its ability to form ultra-stable assembly. Co-assembling folate further promotes the cellular uptake of folate receptor overexpressed cancer cells, contributing to enhanced bioimaging.

Co-delivery of Metformin and Paclitaxel Via Folate-Modified pH-Sensitive Micelles for Enhanced Anti-tumor Efficacy

Single chemotherapeutic agent like paclitaxel (PTX) has shown some limitations in anti-tumor treatment, such as undesirable side effects, multidrug resistance, and high toxicity. In order to reduce the toxicity of PTX and increase the anti-tumor effect, folate-modified amphiphilic and biodegradable biomaterial was developed to co-deliver PTX and metformin (MET) for exerting the synergistic effect. PTX was physically entrapped in the hydrophobic inner core of the amphiphilic block copolymer by a solvent evaporation method, whereas MET was chemically conjugated to the hydrophilic terminals of copolymer via a pH-sensitive cis-aconityl linkage (Cis). The in vitro release behaviors of the drugs were analyzed by high-performance liquid chromatography (HPLC), and the synergistic effect of the drugs was evaluated by a Q value method. Results showed that drug-loaded micelles with an average size about 100 nm were successfully constructed. In acidic environments, the chemically conjugated MET was rapidly released after the breakage of sensitive bond between drug and copolymer. In vitro anti-tumor studies demonstrated that MET and PTX had a synergistic effect and co-delivery micelles induced higher cytotoxicity and apoptosis against 4T1 breast cancer cells than free drugs. Furthermore, folate-targeted co-delivery micelles increased the cellular uptake of drugs and were found to be effective for the treatment of solid tumor in vivo. These findings indicated that co-delivery of MET and PTX through the polymeric micelles is a promising strategy for cancer therapy.

Synthesis and characterization of cystamine conjugated chitosan-SS-mPEG based 5-Fluorouracil loaded polymeric nanoparticles for redox responsive drug release

The principle objective of this study was to develop and characterize redox responsive polymeric nanoparticles (PNPs) as a stimuli responsive drug delivery system. The chitosan-cystamine-methoxy poly(ethylene glycol) (CH-SS-mPEG) copolymer was synthesized by conjugation of cystamine appended chitosan with carboxylic acid-terminated mPEG and characterized by FTIR, ¹H NMR, XRD analysis and colorimetric assay. This copolymer could be formulated as 5-Fluorouracil (5-FU) loaded PNPs and the characteristics of PNPs were evaluated. Moreover, folic acid functionalized PNPs were prepared for folate receptor targeted drug delivery. Drug release studies indicated that the redox sensitive PNPs were stable in physiological condition while quickly releasing 5-FU in the trigger of redox potential due to the cleavage of the disulfide linkages. In contrast, less quantity of drug was released from the reduction insensitive chitosan-g-methoxy poly(ethylene glycol) (CH-g-mPEG) based PNPs under both reduction sensitive and non-reductive conditions. From the cytotoxicity studies, it was evident that 5-FU loaded PNPs had higher toxicity against MCF7 cells when compared to 5-FU free PNPs. Subsequently, cellular uptake studies showed significantly increased internalization of folic acid attached PNPs. In conclusion, the developed PNPs appeared to be of great promise in redox responsive drug release for targeted drug delivery.

Super-paramagnetic loaded nanoparticles based on biological macromolecules for in vivo targeted MR imaging

Target-specific MRI contrast agent based on super-paramagnetic iron oxide-chitosan-folic acid (SPIONP-CS-FA) nanoparticles was fabricated by using an ionotropic gelation method, which involved the loading of SPIONPs at various concentrations into CS-FA nanoparticles by electrostatic interaction. The SPIONP-CS-FA nanoparticles were characterized by ATR-FTIR, XRD, TEM, and VSM techniques. This study revealed that the advantages of this system would be green fabrication, low cytotoxicity at iron concentrations ranging from 0.52 mg/L to 4.16 mg/L, and high water stability (pH 6) at 4°C over long periods. Average particle size and positive zeta-potential of the SPIONP-CS-FA nanoparticles was found to be 130 nm with narrow size distribution and 42 mV, respectively. In comparison to SPIONP-0.5-CS nanoparticles, SPIONP-0.5-CS-FA nanoparticles showed higher and specific cellular uptake levels into human cervical adenocarcinoma cells due to the presence of folate receptors, while in vivo results (Wistar rat) indicated that only liver tissue showed significant decreases in MR image intensity on T2 weighted images and T2* weighted images after post-injection, in comparison with other organs. Our results demonstrated that SPIONP-CS-FA nanoparticles can be applied as an either tumor or organ specific MRI contrast agents.

Folic acid conjugated magnetic iron oxide nanoparticles for nondestructive separation and detection of ovarian cancer cells from whole blood

An effective method for separation and detection of ovarian cancer cells from whole blood using folic acid conjugated magnetic nanoparticles.

"Click and go": simple and fast folic acid conjugation

Folic acid targeting by functionalization of the terminal γ-carboxylic acid is one of the most important strategies to selectively deliver chemotherapeutics and dyes to cancer cells which overexpress folate receptors. However, conjugation of folic acid is limited by its unique solubility and by selectivity issues imposing the need for expensive preparative reverse-phase chromatographic purification to isolate γ-folate conjugates. Herein is provided a novel synthetic tool for the synthesis of new folic acid conjugates with excellent γ-purity based on strain-promoted alkyne-azide cycloadditions with a γ-folate-cyclooctyne conjugate 3. To demonstrate the potential of this methodology several new folate conjugates were synthesized with high γ-purity and without using any type of chromatographic purification by reacting conjugate 3 with several fluorescent probes, polymers and siliceous materials bearing azide. In addition, the cycloaddition reaction between conjugate 3 and an azido-derived fluorescent dye was successfully performed in cellular media leading to an increase of fluorescence in the cells which overexpress folate receptors (NCI-H460).

RVG-peptide-linked trimethylated chitosan for delivery of siRNA to the brain

In this work, a peptide derived from the rabies virus glycoprotein (RVG) was linked to siRNA/trimethylated chitosan (TMC) complexes through bifunctional PEG for efficient brain-targeted delivery of siRNA. The physiochemical properties of the complexes, such as siRNA complexing ability, size and ζ potential, morphology, serum stability, and cytotoxicity, were investigated prior to studying the cellular uptake, in vitro gene silencing efficiency, and in vivo biodistribution. The RVG-peptide-linked siRNA/TMC-PEG complexes showed increased serum stability, negligible cytotoxicity, and higher cellular uptake than the unmodified siRNA/TMC-mPEG complexes in acetylcholine receptor positive Neuro2a cells. The potent knockdown of BACE1, a therapeutic target in Alzheimer's disease, demonstrated the gene silencing efficiency. In vivo imaging analysis showed significant accumulation of Cy5-siRNA in the isolated brain of mice injected with RVG-peptide-linked complexes. Therefore, the RVG-peptide-linked TMC-PEG developed in this study can be used as a potential carrier for delivery of siRNA to the brain.

Process optimization for the preparation of oligomycin-loaded folate-conjugated chitosan nanoparticles as a tumor-targeted drug delivery system using a two-level factorial design method

Oligomycin-A (Oli-A), an anticancer drug, was loaded to the folate (FA)-conjugated chitosan as a tumor-targeted drug delivery system for the purpose of overcoming the nonspecific targeting characteristics and the hydrophobicity of the compound. The two-level factorial design (2-LFD) was applied to modeling the preparation process, which was composed of five independent variables, namely FA-conjugated chitosan (FA-CS) concentration, Oli-A concentration, sodium tripolyphosphate (TPP) concentration, the mass ratio of FA-CS to TPP, and crosslinking time. The mean particle size (MPS) and the drug loading rate (DLR) of the resulting Oli-loaded FA-CS nanoparticles (FA-Oli-CSNPs) were used as response variables. The interactive effects of the five independent variables on the response variables were studied. The characteristics of the nanoparticles, such as amount of FA conjugation, drug entrapment rate (DER), DLR, surface morphology, and release kinetics properties in vitro were investigated. The FA-Oli-CSNPs with MPS of 182.6 nm, DER of 17.3%, DLR of 58.5%, and zeta potential (ZP) of 24.6 mV were obtained under optimum conditions. The amount of FA conjugation was 45.9 mg/g chitosan. The FA-Oli-CSNPs showed sustained-release characteristics for 576 hours in vitro. The results indicated that FA-Oli-CSNPs obtained as a targeted drug delivery system could be effective in the therapy of leukemia in the future.

Development of peptide and protein nanotherapeutics by nanoencapsulation and nanobioconjugation

The targeted delivery of therapeutic peptide by nanocarriers systems requires the knowledge of interactions of nanomaterials with the biological environment, peptide release, and stability of therapeutic peptides. Therapeutic application of nanoencapsulated peptides are increasing exponentially and >1000 peptides in nanoencapsulated form are in different clinical/trial phase. This review covers current scenario of therapeutic protein and peptides encapsulation on polymer to metallic nanocarriers including methods of protein encapsulation, peptide bioconjugation on nanoparticles, stability enhancement of encapsulated proteins and its biomedical applications.

Preparation, characterization, and in vitro targeted delivery of folate-decorated paclitaxel-loaded bovine serum albumin nanoparticles

Paclitaxel (Taxol^®) is an important anticancer drug in clinical use for treatment of a variety of cancers. Because of its low solubility, it is formulated in high concentration in Cremophor EL^® which induces hypersensitivity reactions. In this study, targeted delivery of paclitaxel-loaded nanoparticles was prepared by a desolvation procedure, crosslinked on the wall material of bovine serum albumin, and subsequently decorated by folic acid. The characteristics of the nanoparticles, such as amount of folate conjugation, surface morphology, drug entrapment efficiency, drug loading efficiency, and release kinetics were investigated in vitro. The targeting effect was investigated in vitro by cancer cell uptake of fluorescein isothiocyanate-labeled nanoparticles. The spherical nanoparticles obtained were negatively charged with a zeta potential of about −30 mV, and characterized around 210 nm with a narrow size distribution. Drug entrapment efficiency and drug loading efficiency were approximately 95.3% and 27.2%, respectively. The amount of folate conjugation was 9.22 μg/mg of bovine serum albumin. The folate-decorated nanoparticles targeted a human prostate cancer cell line effectively.