Revolutionizing Therapy: Nanomaterials in Liposomes Redefine the Future of Medicinal Drugs

Abstract

Liposomes are microscopic lipid-based vesicles that have emerged as a promising vehicle for transporting therapeutic agents with precision and efficiency. From enhanced drug bioavailability to targeted delivery, combining nanomaterials and liposomes offers a transformative approach to therapeutic interventions. Encapsulating nanomaterials with drugs in liposomes holds immense significance as it enhances precision, efficiency, and targeted delivery, revolutionizing therapeutic interventions in medicine. This chapter delves into the unique properties of nanomaterials encapsulated within liposomes, examining their potential to revolutionize medicine. In addition, it highlights key advancements, challenges, and prospects in this dynamic and rapidly evolving field, providing readers with a comprehensive understanding of the revolutionary impact on the future of medicinal drugs.

1. Introduction

The efficient delivery of medications is a constant challenge in the healthcare field, and liposomes (LPs) emerge as a promising solution to overcome many of the limitations associated with conventional drug administration. These bilayered lipid vesicles have stood out due to their remarkable advantages in terms of bioavailability, controlled drug release, and specific targeting. The ability to encapsulate both hydrophilic and lipophilic drugs confers unique versatility to liposomes, expanding the spectrum of therapeutic substances that can be effectively administered [1, 2, 3].

The lipid structure of liposomes also provides a valuable protective layer, beneficial for drugs sensitive to enzymatic degradation or other external agents [4]. Controlled release and the ability to target drug delivery to specific tissues contribute to reducing side effects and achieving more efficient administration. The capacity to combine different therapies within a single liposomal system offers a multifaceted approach to treating various medical conditions [5, 6, 7]. Combining other therapies within a single liposomal system provides a multifaceted and highly versatile approach to treating various medical conditions. This strategy enables the coordinated delivery of multiple drugs, gene therapies, or contrast agents, allowing for a more comprehensive and effective approach to managing complex diseases. This therapeutic synergy can significantly improve clinical outcomes, providing new opportunities for personalized treatments tailored to patients’ needs.

Liposomes also have demonstrated usefulness in imaging diagnostic applications, acting as contrast agents that enhance the visualization of specific body areas. Their low toxicity and ability to improve the stability of unstable drugs further extend their clinical potential, offering a safe and effective approach to enhance diagnostic accuracy and therapeutic monitoring in various medical conditions [8, 9, 10].

Collectively, these characteristics make liposomes a remarkable tool in drug delivery, promoting significant advancements in therapeutic efficacy and the minimization of adverse effects (Figure 1). Thus, liposomes can contribute to the ongoing progress of modern medicine. This chapter aims to demonstrate the importance and advancement of liposome utilization in biomedicine. We compiled works published in the last five years from three databases (Web of Science, PubMed, and Virtual Health Library) to achieve this. We described their main contributions and perspectives for scientific advancement. Our search was conducted using the following descriptors: “Liposome,” “Pharmaceutical Preparations,” and “Nanoparticles.” Accordingly, we illustrate the progress and advantages of incorporating nanomaterials, drugs, and natural products used in treating various diseases into liposomes and the various functionalizations of liposomes (Figure 1).

Figure 1.

Schematic representation of different types of liposomes for drug delivery and other bioactives. In the image, we observe various classifications of liposomes, highlighted by the presence of polyethylene glycol (PEG), electrostatic charges, antibodies, enzymes, peptides, carbohydrates, imaging agents, and other specific ligands. Due to their numerous functionalities, their advantages, safety, and toxicity are highlighted in the figure, emphasizing their promising use in nanomedicine.

2. Incorporation of nanomaterials into liposomes

Utilizing inorganic nanoparticles in liposomes represents an innovative strategy for developing drug delivery systems. This approach aims to enhance liposomes’ physical, chemical, and therapeutic properties, endowing them with specific characteristics crucial for advanced clinical applications. Such formulations can also be employed for loading liposomes with luminescent nanomaterials, such as rare earth elements, quantum dots (QDs), or silica, thereby creating bioimages for theranostics.

Theranostic materials with dual diagnostic and therapeutic properties facilitate the localization and/or tracking of liposomes within the organism or in cultured cells while enhancing contrast in imaging modalities such as magnetic resonance imaging (MRI) and X-ray imaging, among others [11, 12, 13]. To study the physiology of metabolic diseases such as diabetes and obesity [14], the liposomes with lanthanide nanoparticles (NPs@Lips) enable imaging acquisition through the near-infrared I window (NIR-I, 700–900 nm). Following in vitro and in vivo testing, the authors successfully visualized the inter-scapular brown adipose tissue (BAT) and distinguished it from the white adipose tissue (WAT) in NIR-I bioimages using the NPs@Lips with low toxicity. Similarly, in a parallel study, when Ytterbium (Yb³⁺) was incorporated into the liposome formulation with doxorubicin, the element was sensitized, generating emission in the near-infrared (NIR) region, thereby enabling the monitoring of drug release [15]. Thus, using rare earth NPs and a lanthanide can add potential for multifunctional applications in nanomedicine.

Various types of inorganic nanoparticles have been incorporated into lipid vesicles, each playing a unique role for specific purposes [5, 16, 17]. Some examples are shown in Table 1. The incorporation of nanoparticles (NPs) into liposomes (LipoNPs) such as metallic gold (Au), zinc oxide (ZnO), and silver (Ag) NPs aims to improve the stability of liposomes and provide controlled drug release. Additionally, adding carbon nanotubes and modified polymers strengthens the mechanical properties and extends the half-life of liposomes. Meanwhile, the presence of magnetic nanoparticles offers the ability to target and control the delivery of these vesicles through external magnetic fields. At the same time, modified polymeric dendrimers alter the surface of liposomes to enhance drug transport capabilities [7, 17, 18].

Nanoparticles (NPs)	Liposomes type	Applications	Nanostructures’ size	Author
Iron oxide	soy phospholipids and cholesterol	Treatment for anemia	125 ± 5.8 nm	[23]
Cooper	soy lecithin	Breast cancer treatment	≥ 100 nm	[30]
Gold	Conventional liposomes	in vitro: cancer cell lines of osteosarcoma (U2OS)	131.1 ± 20.1 nm	[49]
Ytterbium	Conventional liposomes	in vivo: mouse	~50 nm	[15]
CdSe/CdSe	Conventional liposomes	diagnosis bioimage	2–5 nm	[34]
Lanthanide	Conventional liposomes	in vitro: human liver; cells in vivo: mouse	71.4 ± 1.5 nm	[14]
Platinum	Biotin-modified liposomes	Clinical diagnosis and treatment of diseases	100 nm	[35]
Iron oxide coated with citric acid	Thermosensitive liposomes	in vitro: breast cancer cells	8.11 ± 1.12 nm	[24]
Iron oxide coated with citric acid	Cationic liposomes	in vitro: U87 human primary glioblastoma cells	< 20 nm	[25]
Gold NPs	Cationic liposomes	in vitro: human colorectal cancer cell in vivo: mouse	100 nm - 140 nm	[31]

Table 1.

Incorporations and applications of the nanoparticles into liposomes in biomedicine.

CdSe/CdSe = CdSe/CdS_xSe_1-x magic-sized quantum dots (MSQDs).

These strategies offer remarkable benefits, such as improved stability, controlled drug release, increased loading capacity, directional guidance, optical properties for imaging diagnostics, and the potential for therapy combination. The combination of different nanoparticle-mediated therapies may lead to a synergistic therapeutic outcome, enhancing various types of cancer treatments [17, 18], infectious diseases, fungal infections, antibacterial therapies [19], and medical imaging [20]. The careful selection of inorganic nanoparticles to be incorporated into liposomes depends on the intended clinical application, highlighting the versatility of this innovative approach in the field of drug delivery.

Anemia is a public health issue prevalent worldwide and affects individuals of all ages, with women, pregnant women, children, and the elderly being particularly vulnerable. This condition can have serious health consequences, including fatigue, weakness, difficulty concentrating, impaired cognitive development in children, pregnancy complications, and untreated cases that may lead to death [21, 22]. The primary treatment for anemia involves the intake of iron pills, which may cause discomfort for the patient. Considering this, Fathy et al. [23] encapsulated magnetic iron oxide nanoparticles (MNPs) within liposomes, creating liposomes loaded with MNPs (LMNPs) to investigate their efficacy in treating iron-deficiency anemia. LMNPs were engineered to enhance the stability and surface properties of MNPs, allowing them to evade the reticuloendothelial system (RES) and avoid opsonization. A study on female rats revealed that oral administration of LMNPs for 13 days was more effective in treating anemia. They successfully restored hematological parameters from anemic to normal levels. This outcome holds promise for advancing the efficiency of anemia treatment. Furthermore, MNPs encapsulated in thermosensitive liposomes (TSLs) could present a promising therapeutic strategy for enhanced treatment of breast cancer [24, 25].

Numerous studies highlight cancer as one of the leading causes of mortality worldwide. However, treating this disease poses notable limitations, especially in systemic chemotherapy, where low drug concentration in the tumor, coupled with rapid elimination from circulation, results in significant toxic effects outside the tumor region [26]. Liposome and NP complexes are also being tested and utilized to diagnose and treat different cancer types and effectively transport anticancer drugs. These liposome complexes have the property of maximizing therapeutic efficacy and minimizing side effects of pure metallic complexes that exhibit efficiency in treating the disease, such as Ag, Au, copper (Cu), and nickel (Ni) NPs [27, 28, 29]. For instance, Cu NPs, when encapsulated in liposomes synthesized from soy lecithin, showed promising and effective results in breast cancer treatment and were less toxic to normal cells. The Cu NPs in liposomes demonstrated improved safety profiles in MCF-7 cells compared to their free form [30].

Gold nanoparticles (GNPs) and carboplatin encapsulated in liposomes (LipoGold) were tested against human colorectal carcinoma cells (HCT-116). The LipoGold was produced using the scaled-up microfluidic fishbone method and administered simultaneously. This study [31] demonstrates that drug and gold nanoparticles (AuNPs) encapsulation enhances the efficiency in reducing cancer cell proliferation. LipoGold significantly delays tumor growth compared to other formulations, even at lower doses. Additionally, it was possible to suggest that the LipoGold formulation enables a more realistic in vivo treatment with significantly lower amounts of GNPs, which may allow for greater clinical viability.

Carbon nanotubes (CNTs) are hollow graphitic nanomaterials with diameters ranging from 2 to 20 nm and extremely high aspect ratios. This nanomaterial can also be utilized as a novel drug delivery mechanism. They can be loaded with drugs and covalently attached to CNTs to form CLC (Carbon Nanotube Liposome Complex). This approach combines the efficient cellular uptake of CNTs with liposome’s well-known high drug-loading capacity. This combination can significantly reduce the toxicity associated with free CNTs and offer the potential for more effective and targeted combination therapies [32], such as cancer treatment [33].

Innovative drug delivery systems utilizing liposomes and nanocrystals also stand out in their potential applications in theranostics (therapy and diagnosis) [34]. Liposomes containing CdSe/CdS magic-sized quantum dots (MSQDs) have the potential to serve as stable fluorescent reporters and, consequently, can be explored as an innovative luminescent tool for drug delivery. The co-encapsulation of MSQDs within liposomes enables precise monitoring of their spatial distribution through luminescent emission while facilitating targeted delivery of drugs to desired sites [34].

The application of liposomes in single-particle collision electrochemical biosensors (SPCE) for detecting H9N2 avian influenza virus (H9N2 AIV) is promising. This biosensor is constructed by integrating liposome release strategy with immunomagnetic separation. Liposomes, modified with biotin and loaded with platinum nanoparticles (Pt NPs), act as signal probes for virus detection. Upon contact with H9N2 AIV, controlled release of Pt NPs from liposomes occurs, resulting in a detectable increase in electrochemical signal. This strategy enables enhanced electrochemical sensitivity for precise and rapid detection of H9N2 AIV in clinical samples. Liposomes’ controllable release amplification strategy offers significant versatility for applications in other biosensors and detection systems. This combination of nanotechnologies holds great potential in contributing to developing new technologies for rapid and accurate diagnosis of viral diseases [35].

The encapsulation of nanoparticles (NPs) within liposomes offers an innovative and promising approach to developing advanced drug delivery systems. Combining different types of NPs within liposomes, yields benefits in enhancing stability, controlling drug release, increasing loading capacity, providing directional targeting, and reducing toxicity. Furthermore, liposome-nanoparticle complexes have shown efficacy in cancer treatment while mitigating the side effects associated with conventional therapies. However, studies still have significant gaps regarding incorporating NPs into liposomes. One such gap is the long-term stability of liposomes, which may impact their therapeutic efficacy. Additionally, further investigations are required on the toxicity of formulations to normal cells, immune responses in various cell types and in vivo, and better standardization of synthesis methods. Given the promise of these formulations, LipoNPs could be further investigated and explored for application in the treatment of other diseases, such as neglected diseases, and provide more efficient and targeted drug delivery with reduced side effects for various clinical applications.

3. Nanoparticle-liposome hybrid systems: revolutionizing pharmaceuticals in nanomedicine

In recent years, biomedical research has been intensively dedicated to developing innovative strategies for efficient drug delivery. Biotechnology aims to enhance therapeutic efficacy, reduce potential adverse effects such as side effects and toxicity, and address issues such as low solubility. A prominent approach in this scenario is incorporating drugs, natural products, or their bioactive substances into liposomes. This versatile technique has been applied to various drugs, ranging from chemotherapeutic agents, nanoparticles, and nanoparticles adsorbed onto natural products such as plant extracts and essential oils to pharmaceuticals and vaccines, standing out as a promising platform in clinical applications [36, 37, 38, 39].

Liposomes enable the encapsulation of both water-soluble and lipid-soluble compounds. For hydrophilic substances like many conventional chemotherapeutic agents, liposomes provide an aqueous environment within their interior, facilitating solubilization and stability of these substances during administration. For lipophilic drugs, the lipid bilayer of liposomes provides a hydrophobic compartment, allowing for the incorporation and bioavailability of these substances.

Moxifloxacin hydrochloride (MOX) encapsulated in liposomes tested against Staphylococcus epidermidis demonstrated greater efficacy in inhibiting bacterial growth and reducing the formation of bacterial biofilms. In terms of public health, effective control of biofilm growth by S. epidermidis and other bacteria associated with medical devices is crucial for reducing rates of hospital-acquired infections and improving the safety of medical procedures [40]. Incorporating antibiotics into liposomes, such as Tylosin, is also a promising strategy for effectively treating antibiotic-resistant bacterial pathogens [41].

Simvastatin (STAT) is clinically prescribed orally to reduce serum cholesterol and can be used as an anti-inflammatory. However, STAT has low bioavailability in the bloodstream and needs to be administered at high doses, which can cause undesired effects. Nevertheless, when STAT was encapsulated in liposomes, the drug could be delivered directly to the atherosclerotic plaque for anti-atherosclerotic benefit. The formulation’s administration reduced inflammation and increased cholesterol efflux in 2D and 3D cell models. Additionally, it reduced the secretion of pro-inflammatory cytokines and the expression of cell adhesion molecules, suggesting a potential anti-inflammatory and lipid-reducing effect [42].

In oncology, the ability of liposomes to selectively accumulate in tumors, leveraging the phenomenon known as the “enhanced permeability and retention” (EPR) effect, has allowed for a more targeted delivery of antitumor agents, thereby reducing side effects in healthy tissues [43, 44]. An example is the incorporation of tuftsin co-encapsulated with doxorubicin and curcumin in liposomes for cancer treatment. Tuftsin is a tetrapeptide that enhances the anti-tumorigenic potential of drugs encapsulated in liposomes. The innovative formulation inhibited Ehrlich ascites carcinoma tumor growth in rats and human cervical cancer cell lines (HeLa). Adding curcumin can act as a chemosensitizer to reverse doxorubicin resistance against solid tumors [45].

Liposomes can also overcome barriers to using plant extracts for disease treatment [38]. Loading liposomes with natural products (e.g., plant extracts, essential oils, propolis, bioactive compounds, and natural antibiotics) surpasses existing limitations. It can also make versatile formulations for treating cancer and other diseases [37, 46, 47]. For example, Melchior et al. [48] synthesized and characterized liposomes loaded with quercetin. The authors observed that encapsulation of the natural product was more efficient in reducing the viability of colon cancer cells (HCT-116 p53+/+ cells) compared to free quercetin. Similarly, in the study by Melchior et al. [48], the synthesis and characterization of liposomes loaded with quercetin demonstrated promising results. The researchers noted that encapsulation of this natural compound resulted in a more efficient reduction of HCT-116 p53+/+ cell viability than free quercetin. These findings underscore the potential of liposomes as delivery vehicles to enhance the therapeutic efficacy of bioactive compounds, offering new perspectives for treating cancer and other pathologies.

As previously mentioned, the conjugation of nanomaterials with liposomes has been employed to enhance the stability of formulations, which aids in the specific targeting of drugs. This enhancement significantly contributes to preserving the therapeutic efficacy of encapsulated medications. Leveraging this versatility, creating formulations combining nanoparticles, natural products, and liposomes is important for nanotechnology. This formulation improves the delivery of natural products, provides more protection and stability for extracts, and can enhance synergistic effects. Thus, creating formulations combining nanoparticles, natural products, and liposomes plays a significant role in nanotechnology. These formulations improve the delivery of natural products and offer greater protection and stability for the extracts, enhancing synergistic effects and opening new perspectives for developing more effective and safer therapies.

Additionally, they can potentiate therapeutic benefits, reduce the likelihood of drug resistance, increase bioavailability, and mitigate toxicity and associated side effects of treatment [36]. However, more studies still need to utilize this type of formulation. Our group has been developing formulations containing different natural products, such as curcumin and quercetin, adsorbed onto inorganic nanoparticles. These formulations have shown low toxicity and promising results in treating neurodegenerative diseases in in vivo experiments (unpublished data).

Therefore, co-encapsulating liposomes will significantly expand the spectrum of therapeutic agents that can be effectively delivered and broaden the possibilities for therapies in nanomedicine. Combining nanomaterials with liposomes represents an innovative approach to drug delivery, opening doors to significant advancements in therapeutic efficacy and minimizing undesired side effects. This technological convergence may redefine paradigms in medicine and offer adaptable and efficient solutions for a diverse range of applications in nanobiomedicine (Figure 2).

Figure 2.

Nanoparticle-liposome hybrid systems encapsulated with active plant or pharmaceutical principles for treating different human pathologies. References citations [40, 41, 42, 45, 48, 63].

4. Functionalization of liposomes

The functionalization of liposomes, both internally and externally, has emerged as an innovative and versatile strategy in drug delivery, providing significant advancements in optimizing therapeutic efficacy. This biotechnological phenomenon refers to the controlled and personalized modification of the surface or interior of liposomes to confer specific properties that go beyond the natural characteristics of these lipid vesicles. Both internal and external functionalizations of liposomes have their distinct methodologies, advantages, and disadvantages, delineating a fascinating research field with profound implications for various clinical applications.

Internal functionalization of liposomes involves incorporating bioactive molecules or nanomaterials within these vesicles’ lipid core or lipid bilayer. Frequently used methods include co-lipophilization, where hydrophobic compounds are encapsulated along with lipids during liposome formation. This process is particularly effective for protecting sensitive drugs and improving stability, allowing for controlled and targeted release. However, challenges associated with encapsulation efficiency and potential adverse interactions between internal components require careful consideration during internal functionalization.

External functionalization, on the other hand, focuses on modifying the surface of liposomes, allowing for the conjugation of specific ligands, polymers, or nanoparticles to the outer layer. Methodologies include these entities’ covalent or non-covalent attachment to the liposomal surface, providing precise customization of surface properties. This approach is valuable for selectively targeting liposomes to specific tissues or cells, enhancing the selectivity of drug delivery and diagnostics. For example, the formulation of intra-liposomal GNPs functionalized with SPE-PEG (2000)-maleimide-peptide demonstrated efficiency in penetrating mitochondria and inducing biological autoluminescence, directly impacting the functioning of these organelles [49]. Nanocarriers like this play a fundamental role in biological research, significantly contributing to understanding biochemical and physiological processes. Moreover, they have vast potential applications, including use in biosensor devices and detection. In nanomedicine, their versatility is evident, being employed for imaging live cells, real-time monitoring of biological processes, and early disease detection. This wide range of applications underscores the importance of nanocarriers in scientific research and the advancement of medicine.

In terms of applications, the functionalization of liposomes has gained prominence in domains such as oncologic therapy, where targeted delivery can maximize the effectiveness of antitumor agents. Additionally, in regenerative medicine and gene therapy, the functionalization of liposomes has shown promising implications for the efficient delivery of nucleic acids and growth factors. The highlighted applications of liposome functionalization extend to areas like oncologic therapy, where targeted delivery can enhance the efficacy of antitumor agents. Moreover, in regenerative medicine and gene therapy, liposome functionalization has demonstrated promising implications for the efficient delivery of nucleic acids and growth factors, paving the way for more effective and personalized treatments.

The functionalization of liposomes can also be utilized to achieve targeted drug delivery while circumventing the individual’s immune system. Due to their biocompatibility, phagocytes readily capture liposomes, rapidly removing them from the bloodstream. Stealth liposomes, which feature a coating of inert and biocompatible polymers, have been developed to overcome this scenario. Poly(ethylene glycol) (PEG) is the most widely employed polymer for this purpose, thereby preventing the drug or biomolecule transported by the liposome from triggering an immune response in the body. This strategy aims to prolong the circulation time of liposomes and improve the efficacy of therapeutic loading, minimizing detection and removal by the phagocytic system [50].

Fusogenic liposomes can be considered an ideal tool for adoptive cell therapy (ACT). This liposome can fuse with biological membranes, thereby increasing contact of the medication and delivery into cells. Zheng et al. [51] developed a fusogenic liposome termed anti-phagocytosis-blocking repolarization-resistant membrane-fusogenic liposome (ARMFUL). This liposome features a core-shell structure, with a CSF1 receptor inhibitor (BLZ945) and anti-CD47 (aCD47) conjugated to the fusogenic lipid surface. ARMFUL was fused with the cell membrane of M1 macrophages, ensuring effective phagocytosis of tumor cells under CD47 antiphagocytic blockade. Additionally, ARMFUL/M1 effectively inhibited the growth of the mouse melanoma cell line (B16F10) and activated T cell-mediated immunity to suppress distant tumors, preventing tumor metastasis.

Therefore, ARMFUL proved to be a versatile tool for the synchronized engineering of adoptive cells, offering a platform for multimodal customization of cellular functions and behaviors. This promotes improvements in ACT against tumors, indicating significant potential for advanced therapeutic applications.

In biomimetic nanotechnology using RNAi, hybrid nanovesicles are developed. This type of nanovesicle was tested by ref. [52] in the treatment against non-small cell lung carcinoma (NSCLC), which accounts for approximately 85% of lung neoplasms [53]. The authors constructed the nanovesicles with cancer cell membranes (Cm) and charge-reversal liposome membranes (Lipm), using switchable matrix metallopeptidase 9 (MMP-9) peptides to coat polypeptides modified with lipoic acid (LC). These polypeptides are co-loaded with phosphoglycerate mutase 1 (PGAM1) siRNA and docetaxel (DTX). The coating in the intermediate layer was negatively charged (poly-L-lysine grafted with citraconic anhydride, PC), enabling pH-triggered charge conversion functionalization. Research results demonstrated that the integrated hybrid nanovesicle exhibits prolonged circulation half-life, effective lung cancer targeting, biocompatibility, high tumor accumulation, penetration into MMP-9 activated tumor cells, pH and redox-triggered DTX, and siRNA release.

Developed to co-deliver siPGAM1 and DTX, the nanovesicle showed a synergistic effect on tumor inhibition in vitro and in vivo, regulating glycolysis without notable toxicity and prolonging the lifespan of xenografted mice. The innovative proposal can also be adapted for different types of cancer through artificially functionalized lipid membranes with specific natural cell membranes, thus ensuring the release of drugs sensitive to the tumor microenvironment.

Doxorubicin is a broad-spectrum chemotherapeutic agent used alone or in combination to treat various solid tumors. However, it is a molecule that can cause cellular toxicity both acutely and chronically. This anthracycline can induce excessive formation of reactive oxygen species (ROS), senescence, morphological changes in healthy cells, and even lead to apoptosis [54]. The primary direct effect of doxorubicin is cardiotoxicity, and in response to this limitation, targeted liposomes have emerged, aiming to optimize the delivery of doxorubicin [55]. In response to this limitation, targeted liposomes have been synthesized, aiming to optimize the delivery of this therapeutic agent. This targeted approach aims to minimize unwanted side effects in healthy tissues while maximizing the effectiveness of cancer treatment. These liposomes act as smart delivery vehicles, selectively directing doxorubicin to cancer cells. In this way, they reduce systemic toxicity and improve the safety and efficacy of the treatment.

In the context of breast cancer, PEGylated liposomes functionalized with the incorporation of doxorubicin can contribute to the control of tumor growth. In this regard, ref. [56] functionalized liposomes with peptides targeting SREKA (Ser-Arg-Glu-Lys-Ala), whose identification is crucial for the effectiveness of cancer treatment, thus providing selective delivery of doxorubicin as a therapeutic agent. It was observed that inhibition in primary tumor growth and metastasis incidence was observed; moreover, it increased the survival rate of tumor-bearing mice.

PEGylation functionalization can also stabilize and target liposomes to the tumor site, increasing therapeutic efficacy and reducing systemic toxicity. Gold nanoparticles (AuNPs) are already used in therapies and diagnostics against different types of cancer [57]. Functionalized liposomes with PEGylated AuNPs confer a hybrid and targeted therapeutic strategy, in addition to pH and temperature-sensitive nucleolipids with functionalization. Sensitivity to pH and temperature changes in the tumor microenvironment allows for controlled and selective release of doxorubicin. At the same time, PEGylated AuNPs provide stability and targeting to liposomes, facilitating their accumulation in the tumor. This integrated approach aims to maximize the effectiveness of cancer treatment while minimizing the side effects associated with conventional chemotherapy, thus significantly contributing to the advancement of antitumor therapy [58].

Liposomes are also used in treating neurodegenerative diseases such as Alzheimer’s and Parkinson’s, not only for their properties but also for their ability to cross the blood-brain barrier (BBB) [59, 60] easily. Therefore, given the inherent complexity of neurological disorders such as Alzheimer’s disease, which involve various mechanisms and affect multiple brain regions, the choice of liposomes offers a precise and targeted delivery approach [61].

Vitamin B12, although demonstrating anti-amyloidogenic properties in vitro, faces significant challenges, such as its high molecular weight and hydrophilicity, hindering its effective clinical application due to the difficulty of crossing the BBB. To overcome this limitation, liposomes were functionalized with transferrin (Tf), a protein that binds to transferrin receptors (TfRs) abundantly expressed in the endothelial cells of the BBB. This enabled receptor-mediated transcytosis, an effective strategy for crossing the BBB, increasing the efficiency and specificity of brain delivery against Alzheimer’s disease. The developed nanosystem exhibited the capability to delay Aβ fibril formation and disaggregate mature fibrils, demonstrating its significant potential for Alzheimer’s disease prevention and treatment [62].

Liposomes can selectively accumulate in inflamed sites, allowing them to deliver drugs specifically to inflamed tissues while sparing healthy ones. In this perspective, Ref. [63] investigated the potential use of dexamethasone (Dex), a corticosteroid with anti-inflammatory and immunosuppressive properties, in treating inflammatory lung diseases such as asthma, acute lung injury, and COVID-19. Despite its therapeutic benefits, prolonged systemic administration of Dex can result in adverse side effects. However, local pulmonary administration of corticosteroids, especially inhalation, is efficient and associated with better patient tolerance. The researchers developed three surface-modified liposomes containing Dex: Lip-PEG-Dex, Lip-PEGHA-Dex, and Lip-HA-Dex. These liposomes were designed to overcome the challenges of inhalation therapy, such as moderate deposition in the lower airways, toxicity to healthy lung tissues, and limited pulmonary retention time.

The inclusion of poly(ethylene glycol) (PEG) and/or hyaluronic acid (HA) in the nanoparticles aims to improve mucus penetration and target alveolar macrophages. In vitro assays conducted in RAW 264.7, macrophages indicated that liposomes containing HA showed more efficient targeting to activated macrophages. Furthermore, in vivo results in C57BL/6 J mice revealed more consistent efficacy of encapsulated Dex.

The nasal route has shown promise for insulin administration in treating diabetes. However, some barriers to drug absorption may compromise bioavailability. These barriers include thick nasal mucosa, rapid mucociliary clearance, and enzymatic degradation. Overcoming these barriers is essential to ensure the efficacy of nasal insulin administration and maximize its benefits in glycemic control for diabetic patients.

Liposomes loaded with insulin, when functionalized with cell-penetrating peptides (CPPs) such as TAT and Penetration (PNT), which act as promoters of drug penetration and absorption, promote lower release and permeation values through the nasal mucosa compared to liposomal systems without functionalization. This suggests that this behavior occurred due to electrostatic action. What happens is an interaction between insulin and CPPs and the consequent complexation between them, which reduces the incorporation of the drugs by the liposome and may inhibit the absorption-promoting activity of the peptide. However, liposomes loaded with insulin without functionalization with CPPs showed an increased permeability coefficient, suggesting that the developed system can optimize insulin absorption through the nasal route, which is an innovative aspect [64].

The advantages of liposome functionalization are extensive. Internally, the strategy allows for more effective and controlled drug loading, while external functionalization enables targeted and specific delivery, enhancing therapeutic efficacy. Both approaches contribute to reducing side effects and improving drug bioavailability. However, associated challenges include the complexity of the involved methodologies, careful and precise handling, and the need for rigorous control of experimental conditions to ensure consistent and reliable results. Additionally, issues related to the potential toxicity of the agents used need to be thoroughly assessed to ensure patient safety. These aspects underscore the importance of a multidisciplinary approach and careful preclinical evaluation for successfully developing these therapies. The functionalization of liposomes adds specific properties that go beyond their natural characteristics, allowing for targeted and effective drug delivery (Table 2). This reduces adverse effects such as side effects and toxicity and enhances therapeutic efficiency by increasing treatment precision. There are numerous possibilities for applying these particles, spanning areas such as oncology therapy, regenerative medicine, gene therapy, and the treatment of neurodegenerative diseases. Therefore, liposome functionalization, whether internal or external, represents a dynamic research field that offers opportunities for advances in personalized and precision drug delivery. Understanding these approaches’ methodologies, advantages, and disadvantages is essential for shaping the future of drug therapy and diagnostics.

Type of functionalization	Type of bioactive	Applications	Study model	Author
Core-shell anti-phagocytosis-blocking repolarization-resistant membrane-fusogenic liposome (ARMFUL)	BLZ945 (colony stimulating factor receptor inhibitor), aCD7; (anti-CD47)	Adoptive cell therapy (ACT) effective against solid tumors	in vitro: M1 macrophages, B16F10 cells in vivo: C57BL/6 and BALB/c mice	[51]
Hybrid nanovesicle integrated into cancer cell membrane-derived liposome fusing with charge-reversed liposomal membrane	Phosphoglycerate mutase 1 and docetaxel (DXT) siRNA	Treatment of non-Small Cell Lung Cancer (NSCLC)	in vitro: A549 cells in vivo: BALB/c mice carrying A549 cell tumor	[52]
PEGylated liposomes targeting Ser-Arg-Glu-Lys-Ala (SREKA) peptide	Doxorubicin	Treatment of highly metastatic breast cancer	in vitro: 4 T1-Luc and NIH-3 T3 cells in vivo: BALB/c mice	[56]
Transferrin-functionalized liposomes	Vitamin B12 (VB12)	Treatment of Alzheimer’s Disease	in vitro: cellulose dialysis membrane	[62]
Liposomes functionalized with cell-penetrating peptides (CPPs)	Insulin	Nasal administration	in situ: porcine nasal mucosa in vitro: Franz diffusion cell and synthetic cellulose acetate membrane	[64]
Liposomes containing nucleolipids sensitive to pH and temperature and functionalized with PEGylated AuNPs	Doxorubicin	Cancer therapy	in vitro: MDA-MB-231 and SK-OV-3 cells	[58]
Mito-liposome	Gold nanoparticles	Diagnostic method	in vitro: U2OS cells	[49]

Table 2.

Functionalization of liposomes.

5. Conclusion

In conclusion, the utilization of liposomes in drug delivery represents a pivotal advancement in pharmaceutical sciences, offering a versatile and efficient platform for various therapeutic applications. With their capability to encapsulate a wide range of drugs and provide controlled release, liposomes hold promise for optimizing therapy outcomes. Moreover, integrating nanomaterials with liposomes enhances formulation stability and facilitates precise drug targeting, further improving therapeutic efficacy. As research continues to explore the potential of liposomes, particularly in overcoming the challenges of drug bioavailability and stability, these nanostructures are poised to revolutionize drug delivery in the future. Integrating liposomes with nanomaterials stands at the forefront of innovation, offering tailored solutions to address complex therapeutic needs and ushering in a new era of precision medicine.

Acknowledgments

This work was supported by grants from CNPq, CAPES, FAPEAL, and RENORBIO.

Conflict of interest

The authors declare no conflict of interest.