TPGS and CS-Surface-Modified DPPC Liposomes Coloaded with Docetaxel and 5-Fluorouracil: A Potential Avenue for Enhanced Colorectal Cancer Therapy

Abstract

Colorectal cancer (CRC) continues to be a foremost human health concern globally, with chemotherapy being the cornerstone of the therapy. However, conventional chemotherapy is often hampered by nonspecific targeting, limited efficiency, drug resistance, and undesirable adverse effects. 5-Fluorouracil (5-FU), the primary agent for CRC treatment, has a short duration of action and causes systemic toxicity. Docetaxel (DTX), another chemotherapeutic agent, has shown potential in CRC therapy, but its use is also hindered by poor targeting and resistance. Therefore, advanced drug delivery carriers can enhance their therapeutic efficacy. This combination offers a synergistic effect by targeting multiple pathways concurrently. This study aimed to design and assess dipalmitoylphosphatidylcholine (DPPC) liposomes (LPs) coloaded with DTX and 5-FU, surface-modified with d-α-tocopheryl poly(ethylene glycol) succinate (TPGS-LPs) and chitosan (CS-LPs), as a dual-drug delivery for CRC therapy. Various LPs based on TPGS and CS, containing 5-FU and DTX, were successfully prepared and characterized by dynamic light scattering (DLS), and their entrapment efficiencies (EE%) were determined. The optimized formulations, DTX-TPGS-LPs, 5-FU-TPGS-LPs, and DTX/5-FU-TPGS-LPs, were subjected to in vitro release, cytotoxicity, and apoptosis studies using HT-116 cell lines. The LPs were successfully produced, with sizes ranging from 117.3 ± 2.7 to 205.6 ± 2.3 nm, and achieved EE% over 70% for DTX and 20% for 5-FU. The selected formulations, including DTX-TPGS-LPs, 5-FU-TPGS-LPs, and DTX/5-FU-TPGS-LPs, exhibited spherical morphology and controlled release profiles. Among these, the DTX/5-FU-TPGS-LPs formulation exhibited enhanced cytotoxicity and effectively induced apoptosis in HT-116 cells. These results highlight the potential of DTX/5-FU-TPGS-LPs as an effective dual-drug delivery system for CRC treatment; however, further optimization is required to balance its efficacy and toxicity for clinical application.

Introduction

Cancer remains the leading cause of mortality worldwide, with colorectal cancer (CRC) being a major contributor to global cancer-related deaths. (1,2) Traditional chemotherapy, although widely employed, faces several challenges, including systemic toxicity, insufficient drug delivery to tumor sites, and the development of drug resistance. (3) Despite its success in some cases, its efficacy is hindered by a lack of selectivity, which necessitates high doses and increases the risk of side effects. (4) Therefore, there is an urgent need for an alternative strategy that improves therapeutic efficiency while minimizing side effects. (5) One promising approach is combination therapy, in which multiple anticancer drugs are employed to target different pathways involved in cancer cell growth. (6) This plan is more effective than single-drug therapies, as it reduces the risk of drug resistance and improves overall therapeutic outcomes. (7) Such combined therapies have been successfully applied in clinical practice, particularly in the treatment of CRC. (8)

CRC is a slowly progressing malignancy that originates as a polyp or abnormal growth in the lining of the colon or rectum. (2) Among chemotherapeutic agents, 5-fluorouracil (5-FU) has demonstrated strong potential in CRC treatment. (9) 5-FU is a pyrimidine analog that inhibits thymidylate synthase, disrupting DNA synthesis and inducing apoptosis. (10) However, the clinical response to 5-FU is often suboptimal, with its efficacy hindered by low response rates. (9) In addition, a significant obstacle in cancer therapy is the development of multidrug resistance (MDR). (9) Therefore, high doses are necessary, which increase the risk of side effects such as gastrointestinal and cardiotoxicity. (12) The combination of 5-FU with other anticancer agents has excellent potential to overcome these limitations and MDR, thereby improving its effectiveness. (11) Combining 5-FU with docetaxel (DTX) could enhance the antitumor efficacy and prevent the development of MDR. (13,14) DTX is a taxane chemotherapeutic agent that inhibits microtubules, leading to mitotic arrest and apoptosis. (13) DTX has demonstrated efficacy against various human malignancies, including breast, cervical, small and non-small cell lung, prostate, colorectal, and stomach cancers. (15) Therefore, DTX is a promising candidate for further therapeutic combinations. DTX has significant limitations, including poor water solubility, nonspecific distribution, and dose-limiting toxicity. (16)

The combination of DTX and 5-FU, given their distinct mechanisms of action, holds great promise for improving treatment efficacy in CRC. Furthermore, an effective drug delivery system is required to overcome these problems and augment the performance of payload-loaded drugs. Liposomes (LPs) have the potential to increase the efficacy of various marketed drugs. However, to maximize their therapeutic potential, continuous optimization is required to achieve greater stability and drug efficacy. For effective delivery, 5-FU and DTX were formulated into LPs modified with d-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS) and chitosan (CS). Many studies have reported that the surface-modified LPs improve the therapeutic efficacy of anticancer drugs. It has been confirmed that TPGS can overcome MDR by inhibiting P-glycoprotein (P-gp) activity, a membrane efflux transporter responsible for drug resistance. (17)

For example, TPGS-coated LPs exhibited a significant enhancement in the cytotoxicity of DTX against MDR lung cancer cells (A549/DDP) compared with conventional and pegylated LPs. (18) The cellular uptake test showed the highest dye intensity in the cytoplasm with coumarin-6-loaded TPGS-coated liposomes compared with traditional and pegylated liposomes. (18) Similarly, Han et al. reported that TPGS-LPs have a positive impact on paclitaxel activity. The cellular uptake and cytotoxicity in MDR breast cancer cells. (19) The cellular uptake of paclitaxel-loaded TPGS-coated LPs was increased by 3 to 5-fold compared to paclitaxel-loaded LPs against MCF-7/ADR cells. (19) In addition, Song et al. also found that TPGS-LPs enhanced the bioavailability and therapeutic efficacy of Ziyuglycoside I in the treatment of myelosuppression. (20) Likewise, Kumari et al. showed that doxorubicin-loaded TPGS-LPs could serve as effective targeted nanocarriers for tumor treatment. (21)

Moreover, CS-LPs have also received attention for their positive charge and mucoadhesive properties, which promote cellular uptake of anticancer drugs. (3) Gil-Gonzalo et al. highlighted the efficacy of CS-LPs in improving the bioavailability of ciprofloxacin and etoposide. (22) These results highlight the potential of TPGS-LPs and CS-LPs to enhance the efficiency of loaded drugs. Similarly, Alomrani et al. confirmed the effectiveness of 5-FU-loaded CS-LPs against the human colon cancer cell line. (23) Moreover, Alshraim et al. demonstrated that DTX-loaded CS-coated LPs exhibited superior anticancer efficacy against HT29 CRC. (24) Moya-Garcia et al. further showed that etoposide-loaded CS-LPs significantly increased cytotoxicity in U373 glioblastoma cells. (25) These studies demonstrate the potential of TPGS-LPs and CS-LPs as effective drug carriers.

These findings provide a strong rationale for the continued exploration of surface-modified LPs to optimize anticancer treatment strategies. This study presents a triple-strategy approach: codelivery of 5-FU and DTX, a robust LPs platform for drug loading, and surface modification with TPGS and CS, which has not been reported previously. The surface modification of LPs represents a significant advancement in drug delivery, enhancing cellular uptake and tumor localization. This multifunctional platform produces a targeted, efficient, and synergistic approach to maximize therapeutic efficacy against CRC cells.

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Materials

Docetaxel (DTX) was purchased from Hangzhou Hyper Chemical Co., Ltd. (Zhejiang, China). 1,2-dipalmitoylsn-glycero-3-phosphocholine (DPPC) was supplied by Lipoid GmbH (Ludwigshafen, Germany). 5-Fluorouracil (5-FU), low molecular weight chitosan (50–190 kDa, viscosity20–300 cP), cholesterol (Chol), d-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS), and MTT (3-(4,5-dimethyl-thiazol-2-yl)- 2,5-diphenyltetrazolium bromide) were purchased from Sigma-Aldrich Chemical Co., Ltd. (St. Louis, MO). Tween 80 and glacial acetic acid were obtained from BDH Organic (Poole, Dorset, U.K.). Methanol and acetonitrile (HPLC grade) were provided by Fisher Scientific Co. (Loughborough, U.K.). HCT-116 cells were sourced from the American Type Culture Collection (ATCC, Manassas, VA). All other chemicals used were of analytical grade.

TPGS and CS-Surface-Modified DPPC Liposomes Coloaded with Docetaxel and 5-Fluorouracil: A Potential Avenue for Enhanced Colorectal Cancer Therapy, Abdullah H. Alomrani, Mohamed M. Badran, Turki Bin Duhaim, Saad Alobid, and Wajhul Qamar, ACS Omega Article ASAP, DOI: 10.1021/acsomega.5c10664

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