Development of a novel cyclic RGD peptide for multiple targeting approaches of liposomes to tumor region

Brain-Derived Neurotrophic Factor-Loaded Low-Temperature-Sensitive liposomes as a drug delivery system for repairing podocyte damage

Podocytes, cells of the glomerular filtration barrier, play a crucial role in kidney diseases and are gaining attention as potential targets for new therapies. Brain-Derived Neurotrophic Factor (BDNF) has shown promising results in repairing podocyte damage, but its efficacy via parenteral administration is limited by a short half-life. Low temperature sensitive liposomes (LTSL) are a promising tool for targeted BDNF delivery, preserving its activity after encapsulation. This study aimed to improve LTSL design for efficient BDNF encapsulation and targeted release to podocytes, while maintaining stability and biological activity, and exploiting the conjugation of targeting peptides. While cyclic RGD (cRGD) was used for targeting endothelial cells in vitro, a homing peptide (HITSLLS) was conjugated for more specific uptake by glomerular endothelial cells in vivo. BDNF-loaded LTSL successfully repaired cytoskeleton damage in podocytes and reduced albumin permeability in a glomerular co-culture model. cRGD conjugation enhanced endothelial cell targeting and uptake, highlighting an improved therapeutic effect when BDNF release was induced by thermoresponsive liposomal degradation. In vivo, targeted LTSL showed evidence of accumulation in the kidneys, and their BDNF delivery decreased proteinuria and ameliorated kidney histology. These findings highlight the potential of BDNF-LTSL formulations in restoring podocyte function and treating glomerular diseases.

Lipid-based nanosystems: the next generation of cancer immune therapy

Immunotherapy has become an important part of the oncotherapy arsenal. Its applicability in various cancer types is impressive, as well as its use of endogenous mechanisms to achieve desired ends. However, off-target or on-target-off-tumor toxicity, limited activity, lack of control in combination treatments and, especially for solid tumors, low local accumulation, have collectively limited clinical use thereof. These limitations are partially alleviated by delivery systems. Lipid-based nanoparticles (NPs) have emerged as revolutionary carriers due to favorable physicochemical characteristics, with specific applications and strengths particularly useful in immunotherapeutic agent delivery. The aim of this review is to highlight the challenges faced by immunotherapy and how lipid-based NPs have been, and may be further utilized to address such challenges. We discuss recent fundamental and clinical applications of NPs in a range of areas and provide a detailed discussion of the main obstacles in immune checkpoint inhibition therapies, adoptive cellular therapies, and cytokine therapies. We highlight how lipid-based nanosystems could address these through either delivery, direct modulation of the immune system, or targeting of the immunosuppressive tumor microenvironment. We explore advanced and emerging liposomal and lipid nanoparticle (LNP) systems for nucleic acid delivery, intrinsic and extrinsic stimulus-responsive formulations, and biomimetic lipid-based nanosystems in immunotherapy. Finally, we discuss the key challenges relating to the clinical use of lipid-based NP immunotherapies, suggesting future research directions for the near term to realize the potential of these innovative lipid-based nanosystems, as they become the crucial steppingstone towards the necessary enhancement of the efficacy of immunotherapy.

Engineering aspects of lipid-based delivery systems: In vivo gene delivery, safety criteria, and translation strategies

Defects in the genome cause genetic diseases and can be treated with gene therapy. Due to the limitations encountered in gene delivery, lipid-based supramolecular colloidal materials have emerged as promising gene carrier systems. In their non-functionalized form, lipid nanoparticles often demonstrate lower transgene expression efficiency, leading to suboptimal therapeutic outcomes, specifically through reduced percentages of cells expressing the transgene. Due to chemically active substituents, the engineering of delivery systems for genetic drugs with specific chemical ligands steps forward as an innovative strategy to tackle the drawbacks and enhance their therapeutic efficacy. Despite intense investigations into functionalization strategies, the clinical outcome of such therapies still needs to be improved. Here, we highlight and comprehensively review engineering aspects for functionalizing lipid-based delivery systems and their therapeutic efficacy for developing novel genetic cargoes to provide a full snapshot of the translation from the bench to the clinics. We outline existing challenges in the delivery and internalization processes and narrate recent advances in the functionalization of lipid-based delivery systems for nucleic acids to enhance their therapeutic efficacy and safety. Moreover, we address clinical trials using these vectors to expand their clinical use and principal safety concerns.

An all-in-one tetrazine reagent for cysteine-selective labeling and bioorthogonal activable prodrug construction

The prodrug design strategy offers a potent solution for improving therapeutic index and expanding drug targets. However, current prodrug activation designs are mainly responsive to endogenous stimuli, resulting in unintended drug release and systemic toxicity. In this study, we introduce 3-vinyl-6-oxymethyl-tetrazine (voTz) as an all-in-one reagent for modular preparation of tetrazine-caged prodrugs and chemoselective labeling peptides to produce bioorthogonal activable peptide-prodrug conjugates. These stable prodrugs can selectively bind to target cells, facilitating cellular uptake. Subsequent bioorthogonal cleavage reactions trigger prodrug activation, significantly boosting potency against tumor cells while maintaining exceptional off-target safety for normal cells. In vivo studies demonstrate the therapeutic efficacy and safety of this prodrug design approach. Given the broad applicability of functional groups and labeling versatility with voTz, we foresee that this strategy will offer a versatile solution to enhance the therapeutic range of cytotoxic agents and facilitate the development of bioorthogonal activatable biopharmaceuticals and biomaterials.

The interaction between particles and vascular endothelium in blood flow

Particle-based drug delivery systems have shown promising application potential to treat human diseases; however, an incomplete understanding of their interactions with vascular endothelium in blood flow prevents their inclusion into mainstream clinical applications. The flow performance of nano/micro-sized particles in the blood are disturbed by many external/internal factors, including blood constituents, particle properties, and endothelium bioactivities, affecting the fate of particles in vivo and therapeutic effects for diseases. This review highlights how the blood constituents, hemodynamic environment and particle properties influence the interactions and particle activities in vivo. Moreover, we briefly summarized the structure and functions of endothelium and simulated devices for studying particle performance under blood flow conditions. Finally, based on particle-endothelium interactions, we propose future opportunities for novel therapeutic strategies and provide solutions to challenges in particle delivery systems for accelerating their clinical translation. This review helps provoke an increasing in-depth understanding of particle-endothelium interactions and inspires more strategies that may benefit the development of particle medicine.

Functionalisation of extracellular vesicles with cyclic-RGDyC potentially for glioblastoma targeted intracellular drug delivery

With the intrinsic ability to cross the blood-brain barrier, small extracellular vesicles (sEVs) hold promise as endogenous brain-targeted drug delivery nano-platforms for glioblastoma (GBM) treatment. To increase GBM targetability, this study aimed to functionalise sEVs with cyclic arginine-glycine-aspartic acid-tyrosine-cysteine (cRGDyC), a ligand for integrin (α_vβ₃) that is overexpressed in GBM cells. Firstly, the intrinsic cellular uptake of sEVs derived from GBM U87 and pancreatic cancer MIA PaCa-2 cells was investigated on the donor cells. To obtain functionalised sEVs (cRGDyC-sEVs), DSPE-mPEG₂₀₀₀-maleimide was incubated with the selected (U87) sEVs, and cRGDyC was subsequently conjugated to the maleimide groups via a thiol-maleimide coupling reaction. The GBM cell targetability and intracellular trafficking of cRGDyC-sEVs were evaluated on U87 cells by fluorescence and confocal microscopy, using unmodified sEVs as a reference. The cytotoxicity of doxorubicin-loaded vesicles (Dox@sEVs, Dox@cRGDyC-sEVs) was compared with a standard liposome formulation (Dox@Liposomes) and free Dox. Both U87 and MIA PaCa-2 cell-derived sEVs displayed tropism with the former being >4.9-fold more efficient to be internalised into U87. Therefore, the U87-derived sEVs were chosen for GBM-targeting. Approximately 4000 DSPE-mPEG₂₀₀₀-maleimide were inserted onto each sEV with cRGDyC conjugated to the maleimide group. The cell targetability of cRGDyC-sEVs to U87 cells improved 2.4-fold than natural sEVs. Despite their proneness to be colocalised with endosomes/lysosomes, both Dox@sEVs and Dox@cRGDyC-sEVs showed superior cytotoxicity to U87 GBM cells compared to Dox@Liposomes, particularly Dox@cRGDyC-sEVs. Overall, U87-derived sEVs were successufully conjugated with cRGDyC via a PEG linker, and cRGDyC-sEVs were demonstrated to be a potnetial integrin-targeting drug delivery vehicle for GBM treatment. Graphic abstract.

Combinatorial Polydopamine-Liposome Nanoformulation as an Effective Anti-Breast Cancer Therapy

Introduction

Drug delivery systems (DDSs) based on liposomes are potential tools to minimize the side effects and substantially enhance the therapeutic efficacy of chemotherapy. However, it is challenging to achieve biosafe, accurate, and efficient cancer therapy of liposomes with single function or single mechanism. To solve this problem, we designed a multifunctional and multimechanism nanoplatform based on polydopamine (PDA)-coated liposomes for accurate and efficient combinatorial cancer therapy of chemotherapy and laser-induced PDT/PTT.

Methods

ICG and DOX were co-incorporated in polyethylene glycol modified liposomes, which were further coated with PDA by a facile two-step method to construct PDA-liposome nanoparticles (PDA@Lipo/DOX/ICG). The safety of nanocarriers was investigated on normal HEK-293 cells, and the cellular uptake, intracellular ROS production capacity, and combinatorial treatment effect of the nanoparticles were assessed on human breast cancer cells MDA-MB-231. In vivo biodistribution, thermal imaging, biosafety assessment, and combination therapy effects were estimated based on MDA-MB-231 subcutaneous tumor model.

Results

Compared with DOX·HCl and Lipo/DOX/ICG, PDA@Lipo/DOX/ICG showed higher toxicity on MDA-MB-231 cells. After endocytosis by target cells, PDA@Lipo/DOX/ICG produced a large amount of ROS for PDT by 808 nm laser irradiation, and the cell inhibition rate of combination therapy reached up to 80.4%. After the tail vein injection (DOX equivalent of 2.5 mg/kg) in mice bearing MDA-MB-231 tumors, PDA@Lipo/DOX/ICG significantly accumulated at the tumor site at 24 h post injection. After 808 nm laser irradiation (1.0 W/cm², 2 min) at this timepoint, PDA@Lipo/DOX/ICG efficiently suppressed the proliferation of MDA-MB-231 cell and even thoroughly ablated tumors. Negligible cardiotoxicity and no treatment-induced side effects were observed.

Conclusion

PDA@Lipo/DOX/ICG is a multifunctional nanoplatform based on PDA-coated liposomes for accurate and efficient combinatorial cancer therapy of chemotherapy and laser-induced PDT/PTT.

A Multilayered Mesoporous Gold Nanoarchitecture for Ultraeffective Near-Infrared Light-Controlled Chemo/Photothermal Therapy for Cancer Guided by SERS Imaging

Surface-enhanced Raman scattering (SERS) imaging has emerged as a promising tool for guided cancer diagnosis and synergistic therapies, such as combined chemotherapy and photothermal therapy (chemo-PTT). Yet, existing therapeutic agents often suffer from low SERS sensitivity, insufficient photothermal conversion, or/and limited drug loading capacity. Herein, a multifunctional theragnostic nanoplatform consisting of mesoporous silica-coated gold nanostar with a cyclic Arg-Gly-Asp (RGD)-coated gold nanocluster shell (named RGD-pAS@AuNC) is reported that exhibits multiple "hot spots" for pronouncedly enhanced SERS signals and improved near-infrared (NIR)-induced photothermal conversion efficiency (85.5%), with a large capacity for high doxorubicin (DOX) loading efficiency (34.1%, named RGD/DOX-pAS@AuNC) and effective NIR-triggered DOX release. This nanoplatform shows excellent performance in xenograft tumor model of HeLa cell targeting, negligible cytotoxicity, and good stability both in vitro and in vivo. By SERS imaging, the optimal temporal distribution of injected RGD/DOX-pAS@AuNCs at the tumor site is identified for NIR-triggered local chemo-PTT toward the tumor, achieving ultraeffective therapy in tumor cells and tumor-bearing mouse model with 5 min of NIR irradiation (0.5 W cm^-2 ). This work offers a promising approach to employing SERS imaging for effective noninvasive tumor treatment by on-site triggered chemo-PTT.

Study of FA12 peptide-modified PEGylated liposomal doxorubicin (PLD) as an effective ligand to target Muc1 in mice bearing C26 colon carcinoma: in silico, in vitro, and in vivo study

OBJECTIVES

This study tried to achieve active targeting of Muc1 in cancer; the surface of PEGylated liposomal doxorubicin (PLD/Doxil®) was decorated with FA12 peptide.

METHODS

According to docking results, FA12 was selected for this study, among four different peptides. MD simulation was also conducted as an additional confirmation of the binding interaction between FA12 and Muc1. Liposomal formulations were prepared; ¹HNMR and HPLC techniques were used to verify peptide conjugation to DSPE-PEG2000-COOH. Afterward, DSPE-PEG2000-FA12 was post-inserted into the PLD at 50, 100, 200, and 400 peptides per liposome. The size, zeta potential, release profile, cytotoxicity (IC₅₀), and cell uptake (using fluorescence microscopy and flow cytometry) were evaluated. In vivo biodistribution and antitumor activities were studied on mice bearing C-26 colon carcinoma.

RESULTS

Cell uptake and cytotoxicity results revealed that PLD-100 (targeted PLD with 100 FA12 per liposome) could significantly enhance cellular binding. Furthermore, PLD-100 demonstrated higher antitumor efficacy, indicating more remarkable survival compared to PLD and other targeted PLDs. PLD-100 exhibited higher doxorubicin tumor accumulation compared to PLD.

CONCLUSIONS

FA12 peptide is a promising targeting ligand for PLD to treat cancers with a high level of Muc1 expression and merits further investigations.

Temperature-sensitive polymers to promote heat-triggered drug release from liposomes: Towards bypassing EPR

Heat-triggered drug release from temperature-sensitive nanocarriers upon the application of mild hyperthermia is a promising approach to achieve site-specific delivery of drugs. The combination of mild hyperthermia (41-42 °C) and temperature-sensitive liposomes (TSL) that undergo lipid phase-transition and drug release has been studied extensively and has shown promising therapeutic outcome in a variety of animal tumor models as well as initial indications of success in humans. Sensitization of liposomes to mild hyperthermia by means of exploiting the thermal behavior of temperature-sensitive polymers (TSP) provides novel opportunities. Recently, TSP-modified liposomes (TSPL) have shown potential for enhancing tumor-directed drug delivery, either by triggered drug release or by triggered cell interactions in response to heat. In this review, we describe different classes of TSPL, and analyze and discuss the mechanisms and kinetics of content release from TSPL in response to local heating. In addition, the impact of lipid composition, polymer and copolymer characteristics, serum components and PEGylation on the mechanism of content release and TSPL performance is addressed. This is done from the perspective of rationally designing TSPL, with the overall goal of conceiving efficient strategies to increase the efficacy of TSPL plus hyperthermia to improve the outcome of targeted anticancer therapy.

Overview of Nanoparticle-Based Approaches for the Combination of Photodynamic Therapy (PDT) and Chemotherapy at the Preclinical Stage

Simple Summary

The present review represents the outstanding and promising recent literature reports (2017–2022) on nanoparticle-based formulations developed for anticancer therapy with photodynamic therapy (PDT), photosensitizers, and chemotherapeutics. Besides brief descriptions of chemotherapeutics’ classification and of PDT mechanisms and limitations, several examples of nanosystems endowed with different responsiveness (e.g., acidic pH and reactive oxygen species) and peculiarity (e.g., tumor oxygenation capacity, active tumor targeting, and biomimetic features) are described, and for each drug combination, in vitro and in vivo results on preclinical cancer models are reported.

Abstract

The widespread diffusion of photodynamic therapy (PDT) as a clinical treatment for solid tumors is mainly limited by the patient’s adverse reaction (skin photosensivity), insufficient light penetration in deeply seated neoplastic lesions, unfavorable photosensitizers (PSs) biodistribution, and photokilling efficiency due to PS aggregation in biological environments. Despite this, recent preclinical studies reported on successful combinatorial regimes of PSs with chemotherapeutics obtained through the drugs encapsulation in multifunctional nanometric delivery systems. The aim of the present review deals with the punctual description of several nanosystems designed not only with the objective of co-transporting a PS and a chemodrug for combination therapy, but also with the goal of improving the therapeutic efficacy by facing the main critical issues of both therapies (side effects, scarce tumor oxygenation and light penetration, premature drug clearance, unspecific biodistribution, etc.). Therefore, particular attention is paid to the description of bio-responsive drugs and nanoparticles (NPs), targeted nanosystems, biomimetic approaches, and upconverting NPs, including analyzing the therapeutic efficacy of the proposed photo-chemotherapeutic regimens in in vitro and in vivo cancer models.

Profiling target engagement and cellular uptake of cRGD-decorated clinical-stage core-crosslinked polymeric micelles

Polymeric micelles are increasingly explored for tumor-targeted drug delivery. CriPec® technology enables the generation of core-crosslinked polymeric micelles (CCPMs) based on thermosensitive (mPEG-b-pHPMAmLac_n) block copolymers, with high drug loading capacity, tailorable size, and controlled drug release kinetics. In this study, we decorated clinical-stage CCPM with the α_vβ₃ integrin-targeted cyclic arginine-glycine-aspartic acid (cRGD) peptide, which is one of the most well-known active targeting ligands evaluated preclinically and clinically. Using a panel of cell lines with different expression levels of the α_vβ₃ integrin receptor and exploring both static and dynamic incubation conditions, we studied the benefit of decorating CCPM with different densities of cRGD. We show that incubation time and temperature, as well as the expression levels of α_vβ₃ integrin by target cells, positively influence cRGD-CCPM uptake, as demonstated by immunofluorescence staining and fluorescence microscopy. We demonstrate that even very low decoration densities (i.e., 1 mol % cRGD) result in increased engagement and uptake by target cells as compared to peptide-free control CCPM, and that high cRGD decoration densities do not result in a proportional increase in internalization. In this context, it should be kept in mind that a more extensive presence of targeting ligands on the surface of nanomedicines may affect their pharmacokinetic and biodistribution profile. Thus, we suggest a relatively low cRGD decoration density as most suitable for in vivo application.

Understanding the Phagocytosis of Particles: the Key for Rational Design of Vaccines and Therapeutics

A robust comprehension of phagocytosis is crucial for understanding its importance in innate immunity. A detailed description of the molecular mechanisms that lead to the uptake and clearance of endogenous and exogenous particles has helped elucidate the role of phagocytosis in health and infectious or autoimmune diseases. Furthermore, knowledge about this cellular process is important for the rational design and development of particulate systems for the administration of vaccines or therapeutics. Depending on these specific applications and the required biological responses, particles must be designed to encourage or avoid their phagocytosis and prolong their circulation time. Functionalization with specific polymers or ligands and changes in the size, shape, or surface of particles have important effects on their recognition and internalization by professional and nonprofessional phagocytes and have a major influence on their fate and safety. Here, we review the phagocytosis of particles intended to be used as carrier or delivery systems for vaccines or therapeutics, the cells involved in this process depending on the route of administration, and the strategies employed to obtain the most desirable particles for each application through the manipulation of their physicochemical characteristics. We also offer a view of the challenges and potential opportunities in the field and give some recommendations that we expect will enable the development of improved approaches for the rational design of these systems.

Performance of nanoparticles for biomedical applications: The in vitro/in vivo discrepancy

Nanomedicine has a great potential to revolutionize the therapeutic landscape. However, up-to-date results obtained from in vitro experiments predict the in vivo performance of nanoparticles weakly or not at all. There is a need for in vitro experiments that better resemble the in vivo reality. As a result, animal experiments can be reduced, and potent in vivo candidates will not be missed. It is important to gain a deeper knowledge about nanoparticle characteristics in physiological environment. In this context, the protein corona plays a crucial role. Its formation process including driving forces, kinetics, and influencing factors has to be explored in more detail. There exist different methods for the investigation of the protein corona and its impact on physico-chemical and biological properties of nanoparticles, which are compiled and critically reflected in this review article. The obtained information about the protein corona can be exploited to optimize nanoparticles for in vivo application. Still the translation from in vitro to in vivo remains challenging. Functional in vitro screening under physiological conditions such as in full serum, in 3D multicellular spheroids/organoids, or under flow conditions is recommended. Innovative in vivo screening using barcoded nanoparticles can simultaneously test more than hundred samples regarding biodistribution and functional delivery within a single mouse.

Increased Targeting Area in Tumors by Dual-Ligand Modification of Liposomes with RGD and TAT Peptides

Modification with polyethylene glycol (PEGylation) and the use of rigid phospholipids drastically improve the pharmacokinetics of chemotherapeutics and result in more manageable or reduced side-effects. A major drawback is retarded cellular delivery of content, which, along with tumor heterogeneity, are the two main obstacles against tumor targeting. To enhance cellular delivery and reach a bigger area of a tumor, we designed liposomes decorated with two ligands: one for targeting tumor vasculature via a cyclic-pentapeptide containing arginine-glycine-aspartic acid (RGD), which impacts tumor independent of passive accumulation inside tumors, and one for extravascular targeting of tumor cells via a cell-penetrating peptide derived from human immunodeficiency virus type 1 transactivator of transcription (TAT). Liposomes with different ligand combinations were prepared and compared with respect to performance in targeting. Intravital imaging illustrates the heterogeneous behavior of RGD-liposomes in both intravascular and extravascular distribution, whereas TAT-liposomes exhibit a predictable extravascular localization but no intravascular targeting. Dual-ligand modification results in enhanced vascular targeting and a predictable extravascular behavior that improves the therapeutic efficacy of doxorubicin-loaded liposomes but also an augmented clearance rate of liposomes. However, the dual-modified liposome could be a great candidate for targeted delivery of non-toxic payloads or contrast agents for therapeutic or diagnostic purposes. Here we show that the combination of vascular-specific and tumor cell-specific ligands in a liposomal system is beneficial in bypassing the heterogeneous expression of tumor-specific markers.

Near-Infrared Light-Triggered Lysosome-Targetable Carbon Dots for Photothermal Therapy of Cancer

Photothermal therapy (PTT) has inherent advantages in the treatment of hypoxic tumors due to its optically controlled selectivity on tumor ablation and oxygen-independent nature. The subcellular organelle-targeting capability and photothermal conversion efficiency (PCE) at near-infrared (NIR) wavelength are the key parameters in the assessment of the photothermal agent (PTA). Here, we report that carbon dots (CDs) prepared by the hydrothermal treatment of coronene derivatives show a high PCE of 54.7% at 808 nm, which can be attributed to the narrow band gap and the presence of amounts of continuous energy bands on CDs. Moreover, the vibrations in the layered graphite structures of the CDs also increase the rate of nonradiative transition and thus enhance the PCE. Furthermore, the CDs also possess excellent photostability, biocompatibility, and cell penetration capability and could mainly accumulate in the lysosomes. These experiment results have proved that the CDs are suitable as an efficient NIR light-triggered PTA for efficient PTT against cancer.

An Overview of Methods and Tools for Transfection of Eukaryotic Cells in vitro

Transfection is a powerful analytical tool enabling studies of gene products and functions in eukaryotic cells. Successful delivery of genetic material into cells depends on DNA quantity and quality, incubation time and ratio of transfection reagent to DNA, the origin, type and the passage of transfected cells, and the presence or absence of serum in the cell culture. So far a number of transfection methods that use viruses, non-viral particles or physical factors as the nucleic acids carriers have been developed. Among non-viral carriers, the cationic polymers are proposed as the most attractive ones due to the possibility of their chemical structure modification, low toxicity and immunogenicity. In this review the delivery systems as well as physical, biological and chemical methods used for eukaryotic cells transfection are described and discussed.

Redox-sensitive irinotecan liposomes with active ultra-high loading and enhanced intracellular drug release

In this report, a novel irinotecan (IR) encapsulated redox-responsive liposome was developed. The redox-responsive liposomes were prepared based on disulfide phosphatidylcholine (SS-PC), DSPC, DSPE-PEG2000 and cholesterol by ethanol injection method. IR was actively loaded by triethylammonium sucrose octasulfate (TEA8-SOS) gradient method to generate IR/SS-PC liposomes (IR/SS-LP). The particle size of IR/SS-PC was characterized by using dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was found that IR/SS-LP with 30 % content of SS-PC (IR/SS30-LP) had an average size of 125.5 ± 5.8 nm with a negative zeta potential of -19.5 ± 0.1. The encapsulation efficiency (EE) was further determined to be 98.1 ± 0.8 % and drug loading (DL) was 31.8 ± 0.1 %. The redox-responsiveness of IR/SS-LP was investigated by observing the change of particle size and morphology as well as the release behavior of IR triggered by glutathione (GSH). The data indicated GSH breaks the disulfide bonds in SS-PC and leads to the controlled release of IR. At 1 mM GSH, 60.2 % irinotecan was released from IR/SS30-LP within 24 h. Finally, the effects of IR/SS-LP in cell and animal experiments were evaluated in detail. The results showed that IR/SS30-LP had superior pharmacokinetic and antitumor efficacy compared to free irinotecan and traditional irinotecan liposome (ONIVYDE®-like). Taken together, IR/SS30-LP displayed redox-responsive release of IR, ultra-high loading and enhanced anti-tumor activity, which has great potential for clinical application as a new generation of IR liposomal formulation.

Theranostic potential of biodegradable polymeric nanoparticles with paclitaxel and curcumin against breast carcinoma

In this study, integrin-mediated targeting and near-infrared fluorescence (NIRF) traceable polyethylene glycol-b-poly(lactic-co-glycolic acid) (PEG-PLGA)-based polymeric nanoparticles (NPs) were prepared to investigate the effects of paclitaxel (PTX) and curcumin (CUR) combination therapy on breast cancer. Cyclic (arginine-glycine-aspartic acid-phenylalanine-lysine) (cRGDfK) was selected as a ligand for breast cancer and conjugated to the end of NPs (cRGDfK-NPs). For fluorescence imaging, sulfo-cyanine 5.5 (Cy5.5) was incorporated into NPs (Cy5.5-NPs). A series of hybrid NPs consisting of NPs, cRGDfK-NPs, and Cy5.5-NPs with drugs encapsulated inside the core (Cy5.5-cRGDfK-NPs/PTX + CUR) were prepared by self-assembly. The efficacy of PTX and CUR combination and the ability of the integrin-mediated targeting of NPs were systemically investigated using a 4T1 mouse breast cancer cell line and a nude mouse xenograft model. We suggested that Cy5.5-cRGDfK-NPs/PTX + CUR has superior theranostic potential against breast carcinoma.

The effect of RGD-targeted and non-targeted liposomal Galbanic acid on the therapeutic efficacy of pegylated liposomal doxorubicin: From liposomal preparation to in-vivo studies

The anti-cancer therapeutic application of Galbanic acid (Gba) as a strong antiangiogenic sesquiterpene coumarin has been limited due to its low water solubility. This issue necessitates developing new liposomal formulations for the efficient delivery of Gba in vivo. In this study, various liposomal formulations were prepared by a thin-film hydration method, and Gba was incorporated into the liposomal bilayers, which consequently increased its release profile compared to formulations in our previous study prepared by remote loading methods. The most stable formulation with desired properties was selected and decorated with RGD peptide (cyclo [Arg-Gly-Asp-D-Tyr-Cys]) to target tumor vasculature actively. The fluorescently-labeled model liposomes showed that the targeting could improve the receptor-mediated endocytosis of the liposomes higher than those prepared in our previous study in vitro in human umbilical vein endothelial cells (HUVECs), which was confirmed by chicken chorioallantoic membrane angiogenesis (CAM) model in vivo. Although not significant, it also could increase the accumulation of liposomes in colon tumors. In BALB/c mice bearing colon cancer, not only non-targeted Gba liposomes but also even RGD-targeted ones combinatorial therapy with pegylated liposomal doxorubicin could improve the anti-tumor efficacy as compared to their monotherapy. These outcomes have strong consequences for cancer therapy.

Tumor acidic microenvironment-induced drug release of RGD peptide nanoparticles for cellular uptake and cancer therapy

Spatial accuracy is crucial in drug delivery, especially to increase the efficacy and reduce the side effects of antitumor drugs. In this study, we developed a simple and broadly applicable strategy in which a target peptide ligand was introduced to construct a pH-responsive drug-loading system to achieve targeted delivery and drug release in lesions. In addition to reaching the tumor tissue through passive targeting modalities such as the enhanced permeability and retention (EPR) effect, active targeting nanoparticles used RGD motifs coupled to nanocarriers to specifically bind certain integrins, such as ανβ3, which is expressed on the surface of tumor cells, to achieve active tumor cell targeting. Self-assembling peptides have significant advantages in their structural design. The amphiphilic peptide LKR could form a spherical and self-assembled nanoparticle, which encapsulated the fat-soluble antitumor drug doxorubicin (Dox) in neutral medium. The Dox-encapsulating peptide nanoparticles swelled and burst, rapidly releasing Dox in an acidic microenvironment. Flow cytometry and fluorescence detection showed that the self-assembled LKR nanoparticles enhanced the drug accumulation in tumor cells compared with normal mammalian cells. The Dox-encapsulating peptide nanoparticles exhibited desirable antitumor effects in vivo. In summary, the acidic microenvironment of tumors was used to induce drug release from a targeted peptide drug-loading system to enhance cellular uptake and therapeutic effects in situ, providing a promising therapeutic approach for the treatment of major diseases such as hepatoma.

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.

Nano-delivery vehicle based on chlorin E6, photodynamic therapy, doxorubicin chemotherapy provides targeted treatment of HER-2 negative, ανβ3-positive breast cancer

The prognosis for patients with HER-2 negative breast cancer is currently poor, largely due to the lack of efficacious targeted therapeutics. Photodynamic nanomaterial technologies have rapidly developed in recent years, but their anti-tumor effects are often limited by poor targeting, low transformation efficiency, toxicity, and other factors. Thus, we prepared a new type of nanoparticles (Ce6/Dox@NPs-cRGD, CDNR) with cyclo(Arg-Gly-Asp-d-Phe-Cys) (c(RGDfC)) that target the ανβ3 receptor. We loaded those nanoparticles (NPs) with a combination of the doxorubicin (Dox) and photosensitizer chlorin E6 (Ce6) to test synergy between chemotherapy and photodynamic therapy (PDT) for the treatment of ανβ3 receptor positive and HER-2 negative breast cancer. Through analysis of the Fourier transform infrared and UV-vis spectra of these NPs, we found that Ce6 and Dox were successfully loaded into the CDNR. According to dynamic light scattering (DLS) analyses, CDNR particles had a diameter of 112.6 nm (polydispersity index 0.11), which was also confirmed via TEM characterization. The zeta potential was about -21.5 mV. Stability studies showed that CDNR particle size was stable in ddH₂O, PBS, and DMEM + 5 % FBS for 16 days. The drug loading content of Dox and Ce6 were 5.3 and 6.8 %, respectively. Release studies of CDNR showed that the slow release of Dox was accelerated with increasing GSH concentration, and there was no burst release effect. From studying the absorbance of 9,10-dimethylanthrancene (ABDA), we found that CDNR produces high levels of ROS after excitation with a 670 nm laser, and ROS production increased with increasing radiation time. CDNR was significantly taken up by MCF-7 cells at 6 h because of cRGD targeting. In a CCK8 test, the relative growth rate (RGR) of CDNR +670 nm laser for MCF-7 cells was less than 75 % at 20 μg/mL after 24 h treatment and 15 μg/mL after 48 h treatment. We found that CDNR's effects on RGR were concentration dependent. Live-cell staining with a DCFH-DA kit and flow cytometry assay further supported that a CDNR +670 nm laser provided the maximum chemotherapy-PDT toxicity and production of intracellular ROS, and that cell death was mainly caused by necrosis and apoptosis. In vivo experiments showed that using the cRGD-targeting strategy, CDNR had a stronger affinity and increased half-life relative to Ce6/Dox@NPs in mice with MCF-7 xenograft tumors. Further, the C_max of CDNR in the transplanted tumor occurred 8 h post-injection (HPI) and there was still detectable signal at 24 HPI. In addition, MCF-7 bearing mice that were treated with CDNR +670 nm PDT at 8 HPI had a significantly decreased tumor volume (P < 0.05) and prolonged survival time compared to other groups. Thus, CDNR plus 670 nm PDT was associated with favorable anti-tumor activity with no appreciable impact on body weight or the major organs in mice, as determined by immunohistochemistry/immunofluorescence and hematoxylin-eosin staining. In conclusion, CDNR with 670 nm laser irradiation represents a promising new potential treatment paradigm for the management of breast cancers that are ανβ3-receptor positive and HER-2 negative.

Application of advances in endocytosis and membrane trafficking to drug delivery

Multidisciplinary research efforts in the field of drug delivery have led to the development of a variety of drug delivery systems (DDS) designed for site-specific delivery of diagnostic and therapeutic agents. Since efficient uptake of drug carriers into target cells is central to effective drug delivery, a comprehensive understanding of the biological pathways for cellular internalization of DDS can facilitate the development of DDS capable of precise tissue targeting and enhanced therapeutic outcomes. Diverse methods have been applied to study the internalization mechanisms responsible for endocytotic uptake of extracellular materials, which are also the principal pathways exploited by many DDS. Chemical inhibitors remain the most commonly used method to explore endocytotic internalization mechanisms, although genetic methods are increasingly accessible and may constitute more specific approaches. This review highlights the molecular basis of internalization pathways most relevant to internalization of DDS, and the principal methods used to study each route. This review also showcases examples of DDS that are internalized by each route, and reviews the general effects of biophysical properties of DDS on the internalization efficiency. Finally, options for intracellular trafficking and targeting of internalized DDS are briefly reviewed, representing an additional opportunity for multi-level targeting to achieve further specificity and therapeutic efficacy.

Tumor Targeting by αvβ3-Integrin-Specific Lipid Nanoparticles Occurs via Phagocyte Hitchhiking

Although the first nanomedicine was clinically approved more than two decades ago, nanoparticles' (NP) in vivo behavior is complex and the immune system's role in their application remains elusive. At present, only passive-targeting nanoformulations have been clinically approved, while more complicated active-targeting strategies typically fail to advance from the early clinical phase stage. This absence of clinical translation is, among others, due to the very limited understanding for in vivo targeting mechanisms. Dynamic in vivo phenomena such as NPs' real-time targeting kinetics and phagocytes' contribution to active NP targeting remain largely unexplored. To better understand in vivo targeting, monitoring NP accumulation and distribution at complementary levels of spatial and temporal resolution is imperative. Here, we integrate in vivo positron emission tomography/computed tomography imaging with intravital microscopy and flow cytometric analyses to study α_vβ₃-integrin-targeted cyclic arginine-glycine-aspartate decorated liposomes and oil-in-water nanoemulsions in tumor mouse models. We observed that ligand-mediated accumulation in cancerous lesions is multifaceted and identified "NP hitchhiking" with phagocytes to contribute considerably to this intricate process. We anticipate that this understanding can facilitate rational improvement of nanomedicine applications and that immune cell-NP interactions can be harnessed to develop clinically viable nanomedicine-based immunotherapies.

Lipid-Based Drug Delivery Nanoplatforms for Colorectal Cancer Therapy

Colorectal cancer (CRC) is a prevalent disease worldwide, and patients at late stages of CRC often suffer from a high mortality rate after surgery. Adjuvant chemotherapeutics (ACs) have been extensively developed to improve the survival rate of such patients, but conventionally formulated ACs inevitably distribute toxic chemotherapeutic drugs to healthy organs and thus often trigger severe side effects. CRC cells may also develop drug resistance following repeat dosing of conventional ACs, limiting their effectiveness. Given these limitations, researchers have sought to use targeted drug delivery systems (DDSs), specifically the nanotechnology-based DDSs, to deliver the ACs. As lipid-based nanoplatforms have shown the potential to improve the efficacy and safety of various cytotoxic drugs (such as paclitaxel and vincristine) in the clinical treatment of gastric cancer and leukemia, the preclinical progress of lipid-based nanoplatforms has attracted increasing interest. The lipid-based nanoplatforms might be the most promising DDSs to succeed in entering a clinical trial for CRC treatment. This review will briefly examine the history of preclinical research on lipid-based nanoplatforms, summarize the current progress, and discuss the challenges and prospects of using such approaches in the treatment of CRC.

Endothelial Cell Targeting by cRGD-Functionalized Polymeric Nanoparticles under Static and Flow Conditions

Since α_vβ₃ integrin is a key component of angiogenesis in health and disease, Arg-Gly-Asp (RGD) peptide-functionalized nanocarriers have been investigated as vehicles for targeted delivery of drugs to the α_vβ₃ integrin-overexpressing neovasculature of tumors. In this work, PEGylated nanoparticles (NPs) based on poly(lactic-co-glycolic acid) (PLGA) functionalized with cyclic-RGD (cRGD), were evaluated as nanocarriers for the targeting of angiogenic endothelium. For this purpose, NPs (~300 nm) functionalized with cRGD with different surface densities were prepared by maleimide-thiol chemistry and their interactions with human umbilical vein endothelial cells (HUVECs) were evaluated under different conditions using flow cytometry and microscopy. The cell association of cRGD-NPs under static conditions was time-, concentration- and cRGD density-dependent. The interactions between HUVECs and cRGD-NPs dispersed in cell culture medium under flow conditions were also time- and cRGD density-dependent. When washed red blood cells (RBCs) were added to the medium, a 3 to 8-fold increase in NPs association to HUVECs was observed. Moreover, experiments conducted under flow in the presence of RBC at physiologic hematocrit and shear rate, are a step forward in the prediction of in vivo cell–particle association. This approach has the potential to assist development and high-throughput screening of new endothelium-targeted nanocarriers.

Molecular insights and novel approaches for targeting tumor metastasis

In recent years, due to the effective drug delivery and preciseness of tumor sites or microenvironment, the targeted drug delivery approaches have gained ample attention for tumor metastasis therapy. The conventional treatment approaches for metastasis therapy have reported with immense adverse effects because they exhibited maximum probability of killing the carcinogenic cells along with healthy cells. The tumor vasculature, comprising of vasculogenic impressions and angiogenesis, greatly depends upon the growth and metastasis in the tumors. Therefore, various nanocarriers-based delivery approaches for targeting to tumor vasculature have been attempted as efficient and potential approaches for the treatment of tumor metastasis and the associated lesions. Furthermore, the targeted drug delivery approaches have found to be most apt way to overcome from all the limitations and adverse effects associated with the conventional therapies. In this review, various approaches for efficient targeting of pharmacologically active chemotherapeutics against tumor metastasis with the cohesive objectives of prognosis, tracking and therapy are summarized.

Nanocrystallized Oleanolic Acid Better Inhibits Proliferation, Migration and Invasion in Intracranial Glioma via Caspase-3 Pathway

Glioma associates with high malignancy and poor prognosis for traditional treatment. Oleanolic acid (OA) has been confirmed to have an inhibitory effect on different kinds of tumors, while accompanying with low efficiency because of its large molecular mass and low solubility. Nanoliposome is an appropriate drug delivery system that can compensate for the limitations of traditional insoluble drugs, involving improvement of their solubility, stability and lipophilicity. In the present study, we comprised of OA covered with nanoliposomes, named OA^nano, to observe antitumor effects on U87 glioma cells. The results showed that OA^nano raised the solubility and oil-water partition coefficient. OA^nano suppressed proliferation of U87 glioma cells, and also had an anticancer effect on U87 glioma cells, which was found to be higher than that of OA. Moreover, treatment with OA^nano induced apoptosis and degraded migration ability by caspase-3 pathway. In conclusion, our results demonstrated that OA covered with nanoliposomes led to enhanced anticancer effects by suppressing proliferation, migration and invasion abilities. The findings may provide a reliable reference for development of new anti-cancer drugs.

Recent progress in biomedical applications of RGD-based ligand: From precise cancer theranostics to biomaterial engineering: A systematic review

Arginine-glycine-aspartic acid (RGD) peptide family is known as the most prominent ligand for extracellular domain of integrin receptors. Specific expression of these receptors in various tissue of human body and tight association of their expression profile with various pathophysiological conditions made these receptors a suitable targeting candidate for several disease diagnosis and treatment as well as regeneration of various organs. For these reasons, various forms of RGD-based integrins ligands have been greatly used in biomedical studies. Here, we summarized the last decade application progress of RGD for cancer theranostics, control of inflammation, thrombosis inhibition and critically discussed the effect of RGD peptides structure and sequence on the efficacy of gene/drug delivery systems in preclinical studies. Furthermore, we will show recent advances in application of RGD functionalized biomaterials for various tissue regenerations including cornea repair, artificial neovascularization and bone tissue regeneration. Finally, we analyzed clinically translatability of RGD peptides, considering examples of integrin ligands in clinical trials. In conclusion, prospects on using RGD peptide for precise drug delivery and biomaterial engineering are well discussed.

Targeting Tumor Endothelial Cells with Nanoparticles

Because angiogenesis is a major contributor to cancer progression and metastasis, it is an attractive target for cancer therapy. Although a diverse number of small compounds for anti-angiogenic therapy have been developed, severe adverse effects commonly occur, since small compounds can affect not only tumor endothelial cells (TECs), but also normal endothelial cells. This low selectivity for TECs has motivated researchers to develop alternate types of drug delivery systems (DDSs). In this review, we summarize the current state of knowledge concerning the delivery of nano DDSs to TECs. Their payloads range from small compounds to nucleic acids. Perspectives regarding new therapeutic targets are also mentioned.

Liposomal formulation of Galbanic acid improved therapeutic efficacy of pegylated liposomal Doxorubicin in mouse colon carcinoma

Galbanic acid (Gba), a sesquiterpene coumarin, with strong antiangiogenic activity could serve as an excellent anti-cancer agent. However, Gba is a poor water-solube which hampered its clinical application. In this study, a pegylated liposomal Gba (PLGba) with HSPC/Cholesterol/mPEG2000-DSPE (56.2, 38.3, 5.3% molar ratio) was developed by the thin film hydration plus extrusion and calcium acetate gradient remote loading method, to address the issue of poor Gba solubility. Moreover, an integrin-targeting ligand (RGD peptide, cyclo[Arg-Gly-Asp-D-Tyr-Cys]) was post-inserted into liposomes in order to increase Gba cell delivery. Using fluorescently-labeled model liposomes, it was found that the targeting could improve the integrin-mediated cellular uptake of the liposomes in vitro in human umbilical vein endothelial cells (HUVECs), and in vivo as evidenced by chicken chorioallantoic membrane angiogenesis (CAM) model. It also could enrich the liposome accumulation in C26 tumor. Interestingly, co-treatment with PLGba and pegylated liposomal doxorubicin (PLD, also known as Doxil®) had a synergistic and antagonistic antiproliferative effect on the C26 tumor cell line and the normal HUVEC, respectively. In C26 tumor bearing BALB/c mice, the PLGba and PLD combinatorial therapy improved the antitumor efficacy of the treatment as compared to those of single agents. This results have clear implications for cancer therapy.

RNA-Guided Adenosine Deaminases: Advances and Challenges for Therapeutic RNA Editing

Targeted transcriptome engineering, in contrast to genome engineering, offers a complementary and potentially tunable and reversible strategy for cellular engineering. In this regard, adenosine to inosine (A-to-I) RNA base editing was recently engineered to make programmable base conversions on target RNAs. Similar to the DNA base editing technology, A-to-I RNA editing may offer an attractive alternative in a therapeutic setting, especially for the correction of point mutations. This Perspective introduces five currently characterized RNA editing systems and serves as a reader's guide for implementing an appropriate RNA editing strategy for applications in research or therapeutics.

Targeted co-delivery of protein and drug to a tumor in vivo by sophisticated RGD-modified lipid-calcium carbonate nanoparticles

Synchronized bio-distribution of combination therapies has several merits such as synergistic effects and reduced side-effects. Co-delivery of a protein and small molecule drug using a single nanocarrier is challenging because they possess totally different characteristics. Herein, we report the development of sophisticated nanoparticles composed of lipids, calcium carbonate and RGD peptide ligands for the co-delivery of a protein and small molecule drug combination via a simple preparation method. A 'one-step' ethanol injection method was employed to prepare the highly organized nanoparticles. The nanoparticles exhibited a spherical shape with ca. 130 nm diameter, and clearly had an integrated lipid layer covering the periphery. As a ligand, an RGD-modified lipid was post-inserted into the nanoparticles, which was important to overcome the 'PEG dilemma'. The pH-sensitivity of the targeted nanoparticles contributed to the efficient intracellular co-delivery of a protein and drug combination in Colon26 tumor cells, and noticeably improved their accumulation in the tumor region of xenograft mice. Synchronized bio-distribution of the protein and drug was achieved, which was the foundation for the synergistic effects of the combination. The targeting capability of the nanoparticles along with their pH-sensitive drug release and the synchronized bio-distribution of their cargos led to the significant antitumor activity of the SOD and paclitaxel combination in mice. This study provides novel information for the design and preparation of functionalized nanoparticles for the delivery of a protein/drug combination in vivo.

Histidine-Rich Cell-Penetrating Peptide for Cancer Drug Delivery and Its Uptake Mechanism

In this work, we report a drug delivery system based on the pH-responsive self-assembly and -disassembly behaviors of peptides. Here, a systematically designed histidine-rich lipidated peptide (NP1) is presented to encapsulate and deliver an anticancer drug ellipticine (EPT) into two model cells: non-small-cell lung carcinoma and Chinese hamster ovary cells. The mechanism of pH-responsive peptide self-assembly and -disassembly involved in the drug encapsulation and release process are extensively investigated. We found that NP1 could self-assemble as a spherical nanocomplex (diameter = 34.43 nm) in a neutral pH environment with EPT encapsulated and positively charged arginine amino acids aligned outward and EPT is released in an acidic environment due to the pH-triggered disassembly. Furthermore, the EPT-encapsulating peptide could achieve a mass loading ability of 18% (mass of loaded-EPT/mass of NP1) with optimization. More importantly, it is revealed that the positively charged arginine on the periphery of the NP1 peptides could greatly facilitate their direct translocation through the negatively charged plasma membrane via electrostatic interaction, instead of via endocytosis, which provides a more efficient uptake pathway.

Regulation of in vivo behavior of TAT-modified liposome by associated protein corona and avidity to tumor cells

Introduction

PEGylated liposomes are widely used and studied as carriers for chemotherapeutics. While pharmacokinetics of the encapsulated drug is drastically altered resulting in favorable circulation time, improved tumor accumulation, and better manageable or reduced side effects, therapeutic efficacy has been disappointing. Major drawbacks are a failure to reach the tumor cell, limited penetration depth, and impaired uptake by tumor cells.

Materials and methods

Here, we study the implication of HIV-1 transactivator of transcription (TAT)-derived peptides inserted on PEGylated liposomal doxorubicin (PLD) and followed in vitro and in vivo fate. PLDs were installed with 25–400 TAT peptides per liposome without an effect on PLD stability.

Results

While TAT peptides facilitate active endocytosis of the carriers, we observed that these peptides did not promote endosomal escape or enhanced intracellular availability of doxorubicin. Interestingly, incorporation of TAT peptides did not change pharmacokinetics or biodistribution, which we found to result from a dysopsonization of the TAT-modified liposomes by serum proteins. A protein corona (PC) on TAT peptide-modified PLDs shields the active moieties and effectively reduces clearance of the TAT peptide containing nanoparticles. However, intratumoral activity was influenced by the number of TAT peptides present. The best antitumor efficacy was observed with a TAT peptide density of 100, while lower amounts showed results comparable to unmodified PLDs. At 200 TAT peptides, the preparation appeared to be least effective, which likely results from augmented interaction with tumor cells directly upon extravasation.

Conclusion

We conclude that by optimizing TAT-modified PLDs, the occurring PC balances pharmacokinetics and tumor penetration through interference with avidity.

Nanoparticle Ligand-Decoration Procedures Affect in Vivo Interactions with Immune Cells

Ligand-decorated nanoparticles are extensively studied and applied for in vivo drug delivery and molecular imaging. Generally, two different ligand-decoration procedures are utilized; ligands are either conjugated with nanoparticle ingredients and incorporated during nanoparticle preparation, or they are attached to preformed nanoparticles by utilizing functionalized reactive surface groups (e.g., maleimide). Although the two procedures result in nanoparticles with very similar physicochemical properties, formulations obtained through the latter manufacturing process typically contain nonconjugated reactive surface groups. In the current study, we hypothesized that the different ligand-decoration procedures might affect the extent of interaction between nanoparticles and immune cells (especially phagocytes). In order to investigate our hypothesis, we decorated lipidic nanoparticles with a widely used cyclic Arg-Gly-Asp (cRGD) peptide using the two different procedures. As proven from in vivo experiments in mice, the presence of nonconjugated surface moieties results in increased recognition by the immune system. This is important knowledge considering the emerging focus on understanding and optimizing ways to target and track immune cells and the development of nanomedicine-based strategies in the field of immunotherapy.

Development of High-Functionality and -Quality Lipids with RGD Peptide Ligands: Application for PEGylated Liposomes and Analysis of Intratumoral Distribution in a Murine Colon Cancer Model

High-functionality and -quality (HFQ) lipids have a discrete molecular weight and good water dispersibility and can be produced by solid-phase peptide synthesis. Therefore, HFQ lipids are a promising material for the preparation of ligand-grafted PEGylated liposomes. Recently, we have reported serine-glycine repeated peptides ((SG) _n) as a spacer of HFQ lipids and to substitute a conventional PEG spacer. We demonstrated the advantage of using (SG) _n spacers for peptide ligand presentation on the liposomal surface in vitro; however, the use of (SG) _n spacers in ligand-grafted PEGylated liposomes in vivo has not been validated. The aim of this study was to validate the in vivo targeting ability of HFQ lipid-grafted PEGylated liposomes. We synthesized lipids containing GRGDS (RGD-(SG) _n-lipid) to target integrin α_vβ₃ and prepared RGD-(SG) _n/PEGylated liposomes. Subsequently, their cellular uptake characteristics in murine colon carcinoma (Colon-26) cells were evaluated. Two-color imaging of liposomes and tumor blood vessels following tissue clearing was performed to examine the spatial intratumoral distribution of liposomes. RGD-(SG)₅/PEGylated liposomes were selectively associated with the cells in vitro. In vivo analysis of intratumoral distribution following tissue clearing revealed the superior targeting ability of RGD-(SG)₅/PEGylated liposomes compared with that of conventional RGD-PEG₂₀₀₀/PEGylated liposomes for both tumor tissues and tumor blood vessels. We successfully synthesized RGD-HFQ lipids to prepare RGD-grafted PEGylated liposomes for the efficient targeting of integrin α_vβ₃-expressing cells. To the best of our knowledge, this is the first report of the intratumoral distribution of ligand-grafted PEGylated liposomes by two-color imaging following tissue clearing.

Surface modification of doxorubicin-loaded nanoparticles based on polydopamine with pH-sensitive property for tumor targeting therapy

One major challenge of current surface modification of nanoparticles is the demand for chemical reactive polymeric layers, such modification is always complicated, inefficient, and may lead the polymer lose the ability to encapsulate drug. To overcome this limitation, we adopted a pH-sensitive platform using polydopamine (PDA) as a way of functionalizing nanoparticles (NPs) surfaces. All this method needed to be just a brief incubation in weak alkaline solution of dopamine, which was simple and applicable to a variety of polymer carriers regardless of their chemical reactivity. We successfully conjugated the doxorubicin (DOX)-PDA-poly (lactic-co-glycolic acid) (PLGA) NPs with two typical surface modifiers: folate (FA) and a peptide (Arg-Gly-Asp, RGD). The DOX-PDA-FA-NPs and DOX-PDA-RGD-NPs (targeting nanoparticles) were characterized by particle size, zeta potential, and surface morphology. They were quite stable in various physiological solutions and exhibited pH-sensitive property in drug release. Compared to DOX-NPs, the targeting nanoparticles possessed an excellent targeting ability against HeLa cells. In addition, the in vivo study demonstrated that targeting nanoparticles achieved a tumor inhibition rate over 70%, meanwhile prominently decreased the side effects of DOX and improve drug distribution in tumors. Our studies indicated that the DOX-PLGA-NPs modified with PDA and various functional ligands are promising nanocarriers for targeting tumor therapy.

Non-viral delivery systems for CRISPR/Cas9-based genome editing: Challenges and opportunities

In recent years, CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) genome editing systems have become one of the most robust platforms in basic biomedical research and therapeutic applications. To date, efficient in vivo delivery of the CRISPR/Cas9 system to the targeted cells remains a challenge. Although viral vectors have been widely used in the delivery of the CRISPR/Cas9 system in vitro and in vivo, their fundamental shortcomings, such as the risk of carcinogenesis, limited insertion size, immune responses and difficulty in large-scale production, severely limit their further applications. Alternative non-viral delivery systems for CRISPR/Cas9 are urgently needed. With the rapid development of non-viral vectors, lipid- or polymer-based nanocarriers have shown great potential for CRISPR/Cas9 delivery. In this review, we analyze the pros and cons of delivering CRISPR/Cas9 systems in the form of plasmid, mRNA, or protein and then discuss the limitations and challenges of CRISPR/Cas9-based genome editing. Furthermore, current non-viral vectors that have been applied for CRISPR/Cas9 delivery in vitro and in vivo are outlined in details. Finally, critical obstacles for non-viral delivery of CRISPR/Cas9 system are highlighted and promising strategies to overcome these barriers are proposed.

Engineering liposomal nanoparticles for targeted gene therapy

Recent mechanistic studies have attempted to deepen our understanding of the process by which liposome-mediated delivery of genetic material occurs. Understanding the interactions between lipid nanoparticles and cells is still largely elusive. Liposome-mediated delivery of genetic material faces systemic obstacles alongside entry into the cell, endosomal escape, lysosomal degradation and nuclear uptake. Rational design approaches for targeted delivery have been developed to reduce off-target effects and enhance transfection. These strategies, which have included the modification of lipid nanoparticles with target-specific ligands to enhance intracellular uptake, have shown significant promise at the proof-of-concept stage. Control of physical and chemical specifications of liposome composition, which includes lipid-to-DNA charge, size, presence of ester bonds, chain length and nature of ligand complexation, is integral to the performance of targeted liposomes as genetic delivery agents. Clinical advances are expected to rely on such systems in the therapeutic application of liposome nanoparticle-based gene therapy. Here, we discuss the latest breakthroughs in the development of targeted liposome-based agents for the delivery of genetic material, paying particular attention to new ligand and cationic lipid design as well as recent in vivo advances.