Advances in functional lipid nanoparticles: from drug delivery platforms to clinical applications

Since Doxil's first clinical approval in 1995, lipid nanoparticles have garnered great interest and shown exceptional therapeutic efficacy. It is clear from the licensure of two RNA treatments and the mRNA-COVID-19 vaccination that lipid nanoparticles have immense potential for delivering nucleic acids. The review begins with a list of lipid nanoparticle types, such as liposomes and solid lipid nanoparticles. Then it moves on to the earliest lipid nanoparticle forms, outlining how lipid is used in a variety of industries and how it is used as a versatile nanocarrier platform. Lipid nanoparticles must then be functionally modified. Various approaches have been proposed for the synthesis of lipid nanoparticles, such as High-Pressure Homogenization (HPH), microemulsion methods, solvent-based emulsification techniques, solvent injection, phase reversal, and membrane contractors. High-pressure homogenization is the most commonly used method. All of the methods listed above follow four basic steps, as depicted in the flowchart below. Out of these four steps, the process of dispersing lipids in an aqueous medium to produce liposomes is the most unpredictable step. A short outline of the characterization of lipid nanoparticles follows discussions of applications for the trapping and transporting of various small molecules. It highlights the use of rapamycin-coated lipid nanoparticles in glioblastoma and how lipid nanoparticles function as a conjugator in the delivery of anticancer-targeting nucleic acids. High biocompatibility, ease of production, scalability, non-toxicity, and tailored distribution are just a meager of the enticing allowances of using lipid nanoparticles as drug delivery vehicles. Due to the present constraints in drug delivery, more research is required to utterly realize the potential of lipid nanoparticles for possible clinical and therapeutic purposes.

Novel GRPR-Targeting Peptide for Pancreatic Cancer Molecular Imaging in Orthotopic and Liver Metastasis Mouse Models

Despite advancements in pancreatic cancer treatment, it remains one of the most lethal malignancies with extremely poor diagnosis and prognosis. Herein, we demonstrated the efficiency of a novel peptide GB-6 labeled with a near-infrared (NIR) fluorescent dye 3H-indolium, 2-[2-[2-[(2-carboxyethyl)thio]-3-[2-[1,3-dihydro-3,3-dimethyl-5-sulfo-1-(3-sulfopropyl)-2H-indol-2-ylidene]ethylidene]-1-cyclohexen-1-yl]ethenyl]-3,3-dimethyl-5-sulfo-1-(3-sulfopropyl)-, inner salt (MPA) and radionuclide technetium-99m (99mTc) as targeting probes using the gastrin-releasing peptide receptor (GRPR) that is overexpressed in pancreatic cancer as the target. A short linear peptide with excellent in vivo stability was identified, and its radiotracer [99mTc]Tc-HYNIC-PEG4-GB-6 and the NIR probe MPA-PEG4-GB-6 exhibited selective and specific uptake by tumors in an SW1990 pancreatic cancer xenograft mouse model. The favorable biodistribution of the tracer [99mTc]Tc-HYNIC-PEG4-GB-6 in vivo afforded tumor-specific accumulation with high tumor-to-muscle and -bone contrasts and renal body clearance at 1 h after injection. The biodistribution analysis revealed that the tumor-to-pancreas and -intestine fluorescence signal ratios were 5.2 ± 0.3 and 6.3 ± 1.5, respectively, in the SW1990 subcutaneous xenograft model. Furthermore, the high signal accumulation in the orthotopic pancreatic and liver metastasis tumor models with tumor-to-pancreas and -liver fluorescence signal ratios of 7.66 ± 0.48 and 3.94 ± 0.47, respectively, enabled clear tumor visualization for intraoperative navigation. The rapid tumor targeting, precise tumor boundary delineation, chemical versatility, and high potency of the novel GB-6 peptide established it as a high-contrast imaging probe for the clinical detection of GRPR, with compelling additional potential in molecular-targeted therapy.

In Vivo Staging the Progression of Colitis and Associated Cancer by Concurrent Microimaging of Key Biomarkers

Currently colorectal cancer (CRC) staging (colitis, adenoma, and carcinoma) mainly relies on ex vivo pathologic analysis requiring an invasive surgical process with limited sample collection and increased metastatic risk. Thus, in vivo noninvasive pathological diagnosis is extremely demanded. By verifying the samples of clinical patients and CRC mouse models, it was found that vascular endothelial growth factor receptor 2 (VEGFR2) was barely expressed in the colitis stage and only appeared in adenoma and carcinoma stages with obvious elevation, while prostaglandin E receptor 4 (PTGER4) could be observed from colitis to adenoma and carcinoma stages with a gradient increase of expression. VEGFR2 and PTGER4 were further chosen as key biomarkers for molecular pathological diagnosis in vivo and corresponding molecular probes were constructed. The feasibility of in vivo noninvasive CRC staging by concurrent microimaging of dual biomarkers using confocal laser endoscopy (CLE) was verified in CRC mouse models and further confirmed by ex vivo pathological analysis. In vivo CLE imaging exhibited the correlation of severe colonic crypt structural alteration with a higher biomarker expression in adenoma and carcinoma stages. This strategy shows promise in benefiting patients undergoing CRC progression with in-time, noninvasive, and precise pathological staging, thus providing valuable guidance for selecting therapeutic strategies.

Targeting the Gastrin-Releasing Peptide Receptor (GRP-R) in Cancer Therapy: Development of Bombesin-Based Peptide-Drug Conjugates

Targeted tumour therapy has proved to be an efficient alternative to overcome the limitations of conventional chemotherapy. Among several receptors upregulated in cancer cells, the gastrin-releasing peptide receptor (GRP-R) has recently emerged as a promising target for cancer imaging, diagnosing and treatment due to its overexpression on cancerous tissues such as breast, prostate, pancreatic and small-cell lung cancer. Herein, we report on the in vitro and in vivo selective delivery of the cytotoxic drug daunorubicin to prostate and breast cancer, by targeting GRP-R. Exploiting many bombesin analogues as homing peptides, including a newly developed peptide, we produced eleven daunorubicin-containing peptide-drug conjugates (PDCs), acting as drug delivery systems to safely reach the tumour environment. Two of our bioconjugates revealed remarkable anti-proliferative activity, an efficient uptake by all three tested human breast and prostate cancer cell lines, high stability in plasma and a prompt release of the drug-containing metabolite by lysosomal enzymes. Moreover, they revealed a safe profile and a consistent reduction of the tumour volume in vivo. In conclusion, we highlight the importance of GRP-R binding PDCs in targeted cancer therapy, with the possibility of further tailoring and optimisation.

In vivo near-infrared fluorescence and SPECT-CT imaging of colorectal Cancer using the bradykinin B2R-specific ligand icatibant

Cancer molecular imaging using specific probes designed to identify target proteins in cancer is a powerful tool to guide therapeutic selection, patient management, and follow-up. We demonstrated that icatibant may be used as a targeting probe for the significantly upregulated bradykinin B2R in colorectal cancer (CRC). Icatibant-based probes with high affinity towards bradykinin B2R were identified. The near-infrared (NIR) fluorescent dye conjugate MPA-PEG₃-k-Icatibant and radioconjugate [^99mTc]Tc-HYNIC-PEG₄-Icatibant exhibited favourable selective and specific uptake in tumours when the subcutaneous and orthotopic colorectal tumour-bearing mouse models were imaged using NIR fluorescence imaging and Single-Photon Emission Computed Tomography-Computed Tomography (SPECT-CT), respectively. The tracer of [^99mTc]Tc-HYNIC-PEG₄-Icatibant accumulated in tumours according to biodistribution studies and peaked at 4 h with an uptake value of 3.41 ± 0.27%ID/g in HT29 tumour-bearing nude mice following intravenous injection (i.v.). The tumour-to-colorectal signal ratios were 5.03 ± 0.37, 15.45 ± 0.32, 13.58 ± 1.19 and 11.33 ± 1.73 1, 2, 4 and 6 h after tail-veil injection, respectively. Overall, in the wake of rapid and precise tumour delineation and penetration characteristics, icatibant-based probes represent promising high-contrast molecular imaging probes for the detection of bradykinin B2R.

Design, synthesis and biological evaluation of novel 1, 3, 4-oxadiazole PD176252 analogues as potential GRPR inhibitors

Background:

GRPR is over-expressed in cancer cells and is a potential drug target for the treatment of cancer. PD176252, as the most representative non-peptide inhibitor of GRPR, can inhibit the growth of cancer cells, but its low selectivity to cancer cells and normal cells limits its further application.

Objective:

The aim of this study was to design and synthesize novel GRPR inhibitor with stronger anti-cancer activity and higher affinity with GRPR than the lead compound PD176252.

Methods:

A series of 1, 3, 4-oxadiazole derivatives as PD176252 analogues (4a-4j, 6a-6q) were synthesized and investigated their cytotoxic activity on four cancer lines with high expression of GRPR (gastric (HGC-27), colon (HCT-116), prostate (PC-3), and lung (A549)) and one human cell line (gastric mucosal epithelial (GES-1)) by MTT assay. Flow cytometry analysis and Western Blot were used to determine whether the compound induced programmed apoptosis of cancer cells. Competitive binding experiment was used to verify the affinity between GRPR and the optimal compound.

Results:

Compound 6m exhibited significant growth inhibition on all tested cancer cell lines, especially gastric cancer cells (HGC-27 cellular IC50 0.37±0.04μM). Also, the selectivity of 6m to HGC-27 was much higher than that of PD176252. Flow cytometric analysis and Western Blot proved that 6m significantly promoted the apoptosis of HGC-27 cells. Moreover, competitive binding experiment confirmed the close binding of 6m with GRPR, which indicated 6m with a higher affinity than lead compound PD176252.

Conclusion:

Our results suggested that 6m, as a novel GRPR inhibitor, had a higher affinity with GRPR and potential anti-cancer effect than PD176252, which can be used as a template for further optimization.

Near-infrared (NIR) fluorescence-emitting small organic molecules for cancer imaging and therapy

We discuss recent advances made in the development of NIR fluorescence-emitting small organic molecules for tumor imaging and therapy.

An innovative fluorescent probe targeting IGF1R for breast cancer diagnosis

Breast cancer is the most dangerous, among all malignant tumors that threaten women's lives and health. Surgical resection can effectively prolong the survival time of patients with early breast cancer. Insulin-like growth factor type 1 receptor (IGF1R) is a member of the large family of receptor tyrosine kinases, and it's significantly overexpressed in breast cancer cells, which make them ideal biomarkers for the diagnosis and surgery navigation of breast cancer. Herein, we developed a series of IGF1R-targeted probes (YQ-L) for fluorescent imaging in breast cancer based on the strategy of drug repositioning. YQ-L exhibited specific IGF1R binding both in vitro and in vivo, especially probe 5d exhibited higher tumor uptake with a high tumor/normal ratio in the MCF-7 tumor bearing mouse. The maximum T/N ratio of probe 5d was 4.9, which was about 3 times that of indocyanine green (ICG). Meanwhile, probe 5d displayed more favorable in vivo pharmacokinetic properties than that of ICG with less hepatic and intestinal uptake. Convenient preparation, excellent IGF1R specificity in breast cancer, rapid clearance from normal organs and good biosafety profiles of probe 5d warrant further investigations for clinical translation in detection and surgery navigation of breast cancer.

SPECT Imaging of Hepatocellular Carcinoma Detection by the GPC3 Receptor

The glypican-3 (GPC3) receptor is a membrane protein that is highly expressed in tumor tissues but rarely expressed in the normal liver and can be used as a target for early diagnosis of hepatocellular carcinoma (HCC). Herein, we developed a GPC3-targeted ^99mTc-labeled probe for SPECT imaging in HCC. ^99mTc-HPG was rapidly radiosynthesized within 20 min with an excellent radiochemical purity (>98%), possessing good stability. Results from in vitro cell binding assays indicated that the binding specificity of ^99mTc-HPG to GPC3-positive HepG2 cells was acceptable. For SPECT/CT imaging, the HepG2 tumors were clearly visualized with the highest tumor/muscle ratio (11.55 ± 0.54) at 1 h post-injection, and the tumor uptake of ^99mTc-HPG reduced from 2.99 ± 0.15 to 1.17 ± 0.09% ID/g in the blocking study. Convenient preparation, excellent GPC3 specificity in HCC, rapid clearance from normal organs, and good biosafety profiles of ^99mTc-HPG warrant further investigations for clinical translation.

Peptide functionalized liposomes for receptor targeted cancer therapy

Most clinically approved cancer therapies are potent and toxic small molecules that are limited by severe off-target toxicities and poor tumor-specific localization. Over the past few decades, attempts have been made to load chemotherapies into liposomes, which act to deliver the therapeutic agent directly to the tumor. Although liposomal encapsulation has been shown to decrease toxicity in human patients, reliance on passive targeting via the enhanced permeability and retention (EPR) effect has left some of these issues unresolved. Recently, investigations into modifying the surface of liposomes via covalent and/or electrostatic functionalization have offered mechanisms for tumor homing and subsequently controlled chemotherapeutic delivery. A wide variety of biomolecules can be utilized to functionalize liposomes such as proteins, carbohydrates, and nucleic acids, which enable multiple directions for cancer cell localization. Importantly, when nanoparticles are modified with such molecules, care must be taken as not to inactivate or denature the ligand. Peptides, which are small proteins with <30 amino acids, have demonstrated the exceptional ability to act as ligands for transmembrane protein receptors overexpressed in many tumor phenotypes. Exploring this strategy offers a method in tumor targeting for cancers such as glioblastoma multiforme, pancreatic, lung, and breast based on the manifold of receptors overexpressed on various tumor cell populations. In this review, we offer a comprehensive summary of peptide-functionalized liposomes for receptor-targeted cancer therapy.

A novel peptide targeting c-Met for hepatocellular carcinoma diagnosis

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with limited diagnosis. Mesenchymal epithelial transition factor (c-Met) has become a hot target for cancer diagnosis and therapy, which is overexpressed in HCC. In this study, we labeled a novel c-Met targeting peptide YQ-M3 with a near-infrared fluorescent dye MPA and a radionuclide technetium-99m for HCC detection. YQ-M3-MPA showed high affinity for c-Met positive HepG2 tumor in vitro and higher tumor uptake and higher T/N ratio than GE137-MPA (a positive tracer for c-Met) in HepG2 tumor-bearing mice in vivo by fluorescence imaging. In addition, 99mTc-HYNIC-YQ-M3 also showed significant tumor uptake in vivo through SPECT imaging. These results indicated that c-Met positive tumors were successfully detected via fluorescence and SPECT imaging using YQ-M3-MPA and 99mTc-HYNIC-YQ-M3, respectively, and further suggested that YQ-M3-MPA and 99mTc-HYNIC-YQ-M3 have some possibly potential clinical applications for HCC diagnosis.

Resection and survival data from a clinical trial of glioblastoma multiforme-specific IRDye800-BBN fluorescence-guided surgery

Supra-maximum surgical tumor resection without neurological damage is highly valuable for treatment and prognosis of patients with glioblastoma multiforme (GBM). We developed a GBM-specific fluorescence probe using IRDye800CW (peak absorption/emission, 778/795 nm) and bombesin (BBN), which (IRDye800-BBN) targets the gastrin-releasing peptide receptor, and evaluated the image-guided resection efficiency, sensitivity, specificity, and survivability. Twenty-nine patients with newly diagnosed GBM were enrolled. Sixteen hours preoperatively, IRDye800-BBN (1 mg in 20 ml sterile water) was intravenously administered. A customized fluorescence surgical navigation system was used intraoperatively. Postoperatively, enhanced magnetic resonance images were used to assess the residual tumor volume, calculate the resection extent, and confirm whether complete resection was achieved. Tumor tissues and nonfluorescent brain tissue in adjacent noneloquent boundary areas were harvested and assessed for diagnostic accuracy. Complete resection was achieved in 82.76% of patients. The median extent of resection was 100% (range, 90.6-100%). Eighty-nine samples were harvested, including 70 fluorescence-positive and 19 fluorescence-negative samples. The sensitivity and specificity of IRDye800-BBN were 94.44% (95% CI, 85.65-98.21%) and 88.24% (95% CI, 62.25-97.94%), respectively. Twenty-five patients were followed up (median, 13.5 [3.1-36.0] months), and 14 had died. The mean preoperative and immediate and 6-month postoperative Karnofsky performance scores were 77.9 ± 11.8, 71.3 ± 19.2, and 82.6 ± 14.7, respectively. The median overall and progression-free survival were 23.1 and 14.1 months, respectively. In conclusion, GBM-specific fluorescent IRDye800-BBN can help neurosurgeons identify the tumor boundary with sensitivity and specificity, and may improve survival outcomes.

AT1R-Specific Ligand Angiotensin II as a Novel SPECT Agent for Hepatocellular Carcinoma Diagnosis

Hepatocellular carcinoma (HCC) is characterized by a high mortality and early diagnosis and treatment are critically needed. Ang II type 1 receptor (AT1R) has recently emerged as a potential molecular target for cancer diagnosis and intervention. Here, we labeled angiotensin II (Ang II), an AT1R ligand that is overexpressed in various solid cancers, with the near-infrared fluorescent dye, MPA, and radionuclide technetium-99m, and evaluated its capacity for HCC detection. These analyses were done in vitro using HepG2 (AT1R-positive) and BxPC3 (AT1R-negative) cell lines, and in vivo using a subcutaneous and orthotopic xenograft mouse model by fluorescence and SPECT imaging. Both Ang II-PEG₄-MPA- and [^99mTc]Tc-HYNIC-PEG₄-Ang II-bound AT1R exhibited a high affinity in vitro and [^99mTc]Tc-HYNIC-PEG₄-Ang II displayed an acceptable level of in vitro stability in rat plasma and whole blood. In vivo imaging revealed excellent specific tumor-targeting in HepG2 mouse xenografts models. In vitro and in vivo competition experiments revealed specific Ang II-PEG₄-MPA and [^99mTc]Tc-HYNIC-PEG₄-Ang II uptake by HepG2 cells and tumors. Altogether, AT1R-positive tumors were successfully detected via fluorescence and SPECT imaging using Ang II-PEG₄-MPA and [^99mTc]Tc-HYNIC-PEG₄-Ang II, respectively. Given their superior targeting capacity, Ang II-PEG₄-MPA and [^99mTc]Tc-HYNIC-PEG₄-Ang II are promising tools for HCC detection and warrant clinical translation.

GRPR-targeted SPECT imaging using a novel bombesin-based peptide for colorectal cancer detection

Colorectal cancer (CRC) is the third most common cancer worldwide, and the prognosis of CRC is better with an earlier diagnosis. The presence of the gastrin-releasing peptide receptor (GRPR) has been documented in very high numbers on colorectal cancer cells, which makes it an ideal biomarker for the diagnosis of CRC. Bombesin (BBN) peptide analogs have been extensively investigated for the imaging of human cancers with GRPR overexpression. Recently, we have reported a novel GRPR-targeted peptide named the GB-6 peptide. The GB-6 peptide based on BBN_7-14 was designed to improve in vivo metabolic stability and decrease intestinal uptake. Meanwhile, GB-6 greatly retained the original GRPR-binding affinity of BBN_7-14. In this study, the GB-6 peptide was labeled with radionuclide ^99mTc or fluorescent dye for colorectal cancer imaging. In vitro receptor binding was studied in Caco-2 cells, and the GRPR targeting capacity and kinetics in vivo were evaluated using Caco-2 tumor xenografted mice models. In addition, cells and mice were also subjected to the corresponding BBN_7-14 conjugations for comparison. The GB-6 peptide exhibited specific GRPR binding in vitro with a high affinity similar to that of BBN_7-14. Furthermore, we observed that GB-6 showed higher tumor uptake and displayed lower intestinal activity than corresponding unmodified probe BBN_7-14 in Caco-2 tumor-bearing mice. Overall, our studies demonstrated that GB-6 has the potential for early detection of CRC patients, and it may also serve as a valuable tool for non-invasive monitoring of colorectal tumor growth.

Anticancer peptide: Physicochemical property, functional aspect and trend in clinical application (Review)

Cancer is currently ineffectively treated using therapeutic drugs, and is also able to resist drug action, resulting in increased side effects following drug treatment. A novel therapeutic strategy against cancer cells is the use of anticancer peptides (ACPs). The physicochemical properties, amino acid composition and the addition of chemical groups on the ACP sequence influences their conformation, net charge and orientation of the secondary structure, leading to an effect on targeting specificity and ACP-cell interaction, as well as peptide penetrating capability, stability and efficacy. ACPs have been developed from both naturally occurring and modified peptides by substituting neutral or anionic amino acid residues with cationic amino acid residues, or by adding a chemical group. The modified peptides lead to an increase in the effectiveness of cancer therapy. Due to this effectiveness, ACPs have recently been improved to form drugs and vaccines, which have sequentially been evaluated in various phases of clinical trials. The development of the ACPs remains focused on generating newly modified ACPs for clinical application in order to decrease the incidence of new cancer cases and decrease the mortality rate. The present review could further facilitate the design of ACPs and increase efficacious ACP therapy in the near future.