Advances in Inhaled Nanoparticle Drug Delivery for Pulmonary Disease Management

Liposomes are spherical, self‐assembled vesicles enclosed by a single lipid bilayer, primarily composed of amphiphilic phospholipids and cholesterol [98, 99]. The unique spatial arrangement structure of liposomes allows them to encapsulate hydrophilic and hydrophobic drugs in the inner aqueous core or lipid bilayer, thereby enhancing drug solubility, stability, and sustained release. Resembling the composition of mammalian cell membranes, liposomes have good biocompatibility and biodegradation. The additional flexibility of surface modification makes liposome a valuable and versatile drug carrier.

Doxil, doxorubicin hydrochloride liposome injection, is the first FDA‐approved nano‐drug for AIDS‐related Kaposi's sarcoma and ovarian cancer treatment, which is composed of HSPC, cholesterol, and DSPE‐PEG₂₀₀₀ [100, 101]. Arikayce is the first FDA‐approved inhaled liposome drug that is administered once daily by nebulization using the Lamira nebulizer system. Amikacin liposome comprises DPPC and cholesterol with a size of 200–300 nm [102]. The successful launch of Arikayce paves the way for further exploration of inhaled liposomes and other nanoparticles in clinical applications.

As an endogenous phospholipid and a main component of surfactant, DPPC has a high surfactant‐penetrating, lung‐targeting capability and excellent biocompatibility [103]. PEG‐lipids, like DSPE‐PEG₂₀₀₀, are frequently used to enhance the mucus penetration of nanoparticles [76, 104]. Pachypodol and bergapten, two natural compounds with anti‐inflammatory properties, have limited clinical application due to poor solubility. Sun et al. and Liao et al. developed inhalable pachypodol and bergapten liposomes, respectively, using DPPC, cholesterol, and DSPE‐PEG₂₀₀₀ [7, 8]. After nebulization, both liposomes target the inflamed lung and ameliorate ALI in mice via promoting anti‐inflammatory M2 macrophage polarization.

Nintedanib and pirfenidone are two FDA‐approved drugs for the treatment of idiopathic pulmonary fibrosis (IPF) through the inhibition of fibroblast activation and ECM production. While both drugs only delay IPF progression, they do not reverse the disease or significantly improve patient survival [105], suggesting multiple mechanisms are involved and targeting them with combination therapies may have the potential to improve the anti‐fibrotic effects. Yang et al. developed inhalable liposomes (soy lecithin, cholesterol, DSPE‐PEG₂₀₀₀‐NH₂) co‐loaded with nintedanib and ABT‐263, featuring dual mucus‐ and ECM‐penetrating capabilities achieved via surface modification with tris‐(2‐carboxyethyl)‐phosphine and L‐arginine [74]. Following nebulization, the liposomes uniformly distribute in all lung lobes, released ABT‐263 selectively eliminates senescent epithelial cells, and suppresses the secretion of profibrotic factors that activate myofibroblasts, thereby synergistically improving the therapeutic efficacy of nintedanib in treating IPF. Han et al. developed inhalable liposomes (PC, cholesterol, DSPE‐PEG₂₀₀₀) co‐loaded with verteporfin and pirfenidone. Following intratracheal atomization, verteporfin reduces the fluidization of airway epithelium to alveoli and the formation of honeycomb cysts, while pirfenidone reduces fibroblast overactivation, jointly reversing IPF and restoring lung function [75]. Zhang et al. developed inhalable S‐allylmercapto‐N‐acetylcysteine (ASSNAC) and nintedanib co‐loaded liposomes (phospholipid, cholesterol, DSPE‐PEG₂₀₀₀) [76]. ASSNAC, with an anti‐inflammatory property, inhibits nintedanib‐induced inflammation. After nebulization, the co‐loaded liposomes at a 30‐time lower dose of nintedanib show superior anti‐fibrotic efficacy in rats compared to the oral nintedanib product. Chen et al. developed inhalable myofibroblast targeting liposomes (DOTAP, cholesterol) co‐loading nintedanib and IL‐11 siRNA [10]. After intratracheal inhalation, the liposomes superiorly deposit in the lung and selectively target myofibroblasts. Released nintedanib and IL‐11 siRNA synergistically inhibit fibroblast activation and ECM deposition, promote epithelium repair, and remodel the immune microenvironment, notably improving pulmonary fibrosis.

Lung cancer is a prevalent and deadly disease that can metastasize to other organs, while other cancers can also spread to the lungs [106, 107]. Fu et al. developed inhalable osimertinib and DNA plasmid encoding IGF2BP3 siRNA co‐loaded liposomes (lecithins, cholesterol), which are coated with a stem cell membrane enriched with surfactant SP‐B [77]. Following nebulization, the liposomes are largely retained in the lungs with the help of SP‐B, where they target tumor cells and release their therapeutic payload. Osimertinib inhibits oncogenic EGFR signaling in tumors, while DNA plasmid‐derived siRNA downregulates IGF2BP3 expression and induces the production of rabies virus glycoprotein‐engineered exosomes carrying IGF2BP3 siRNA. These exosomes further target brain tumors, resulting in effective suppression of both primary lung cancer and metastatic brain tumors. Wang et al. developed inhalable erdafitinib‐loaded liposomes (soybean phospholipid, cholesterol, DSPE‐PEG‐Maleimide) with surface modification of CXCL12‐binding W4 peptide [78]. After nebulization, the liposomes capture and accumulate in the CXCL12 highly expressed pulmonary pre‐metastatic niche (PMN), resulting in the release of erdafitinib to mitigate fibrosis, PMN formation, and lung metastasis in a mouse model of breast cancer. Notably, triple therapy combined with liposomal inhalation, CXCR4 antagonist spray hydrogel in the resection cavity of breast tumor, and Doxil chemotherapy significantly prolongs postoperative mouse survival.

Liposomes are also employed for pulmonary mRNA delivery. Hexokinase 2 (HK2) is a critical enzyme involved in glucose metabolism [108]. Huang et al. developed inhalable liposomes (DOPS, cholesterol, DSPE‐PEG₂₀₀₀) loading a complex core of calcium phosphate‐mRNA based CRISPR/Cas9 system targeting HK2. After nebulization, the liposomes induce HK2 knockout in alveolar macrophages and extensively inhibit lung inflammation and ALI in mice [79]. To address the nebulization instability and incompatibility with the pulmonary microenvironment (e.g., pulmonary surfactant and low serum) of mRNA‐LNPs, Jang et al. developed inhalable ionizable mRNA‐loaded liposomes (Dlin‐MC3‐DMA, cholesterol, DSPC) [109]. After nebulization, the liposomes widely distribute in the deep lung and target epithelial cells, which have therapeutic potential for various pulmonary diseases.

LNPs have emerged as a key nonviral carrier for RNA delivery. LNPs are formed by the self‐assembly of four‐component lipids including ionizable lipid, helper phospholipid, cholesterol, and PEG‐lipid [110]. DLin‐MC3‐DMA, ALC‐0315, and SM‐102 LNPs are clinically exploited as carriers to deliver siRNA and mRNA (Table 1) [111]. mRNA‐based therapeutics that encode proteins, vaccine antigens, and gene editors hold tremendous promise for treating a wide range of diseases [112]. Comirnaty and Spikevax have shown efficacy and safety as mRNA‐LNPs vaccines with intramuscular injection [113], paving the avenue for the application of inhaled mRNA‐LNPs in lung disease treatment. From 2023, several inhaled mRNA‐LNPs drugs, including ARCT‐032, VX‐522, RCT1100, and RCT2100 have started clinical trials for treating cystic fibrosis or primary ciliary dyskinesia [114].

The formulation of inhaled mRNA‐LNPs is primarily based on the benchmark formulations of marketed LNPs. Maintaining stability during nebulization remains a significant challenge. The high shear forces of nebulization can potentially disrupt LNPs' integrity and cause LNPs disintegration, aggregation, and mRNA leakage, leading to unsatisfactory delivery and transfection efficiency. For example, only 17% SM102 LNPs remain intact after nebulization [12]. Inhaled LNPs formulations are optimized to improve their stability and effectiveness during aerosolization by adjusting lipids' ratios, using novel ionizable lipids (e.g., IR‐117‐17, IR‐19‐Py), and zwitterionic polymer‐functionalized lipid as a replacement of PEG‐lipid [80, 115, 116]. Liu et al. developed inhalable charged‐assisted stabilization (CAS) of LNPs by integrating peptide‐conjugated DOPE into SM102 LNPs [12]. CAS‐LNPs exhibit exceptional stability during nebulization and efficiently deliver mRNA into the lungs of mice, dogs, and pigswhile primarily targeting dendritic cells (DCs). Following nebulization, CAS‐LNPs elicit robust systemic and mucosal immune responses, demonstrating therapeutic efficacy as both a COVID‐19 vaccine and a cancer vaccine.

In addition to FDA‐approved ionizable lipids, other novel ionizable lipids with superior performance are developed for pulmonary mRNA delivery. As IL‐11 is a potential target for treating IPF, Bai et al. optimized inhalable AA3‐Dlin LNPs to load mRNA encoding IL‐11 single chain fragment variable (scFv) [80]. Following nebulization, the LNPs effectively deliver IL‐11 scFv mRNA into the lungs and produce antibody to neutralize IL‐11, significantly ameliorating lung fibrosis through suppression of fibroblast activation and ECM deposition. Cytochrome b5 reductase 3 (CYB5R3) and bone morphogenetic protein 4 (BMP4), two essential genes for alveolar epithelial repair, are downregulated in AT2 cells during IPF. Wang et al. developed inhalable mucus‐penetrating GAE14 LNPs encapsulating dual mRNAs of CYB5R3 and BMP4 [81]. After nebulization, expressed CYB5R3 reduces mitochondrial damage and attenuates AT2 cell senescence, while BMP4 alleviates impaired AT2‐mediated epithelial remodeling and suppresses fibroblast activation. Together, these effects contribute to the dual mitigation of lung fibrosis and improved survival in mice. Thymic stromal lymphopoietin (TSLP) released from injured airway epithelial cells contributes to steroid resistance in severe asthma [117]. Tezepelumab, a clinical human monoclonal antibody binding to TSLP, is used to treat severe asthma via subcutaneous injection [118]. Huang et al. developed inhalable AA3‐Dlin LNPs co‐loading TSLP mRNA and budesonide [82]. After nebulization, the LNPs distribute in the whole lung and primarily target immune and epithelial cells. Produced TSLP antibody blocks the upstream immune cascade and restores steroid resistance, while budesonide suppresses the transcription of downstream inflammatory genes, jointly alleviating asthma symptoms in severe asthma mice and steroid‐resistant asthmatic mice, compared to inhaled budesonide product or injected tezepelumab. CD44 and glucose transporters are highly expressed in cancer cells and macrophages [119, 120, 121, 122]. Tang et al. developed polymer‐lipid hybrid mRNA‐LNPs, composed of cationic lipid G0‐C14, polymer hyaluronic acid targeting CD44, and DSPE‐PEG‐Mannose targeting glucose transporters [61]. After inhalation, the LNPs exhibit excellent dual‐targeting ability and effectively deliver mRNA into cancer cells in a murine model of orthotopic lung cancer, as well as proinflammatory macrophages in a murine model of pneumonia.

In addition, biodegradable ionizable lipids are designed to build LNPs with lower toxicity and more efficacy. Li et al. synthesized a new biodegradable ionizable lipid RCB‐4‐8 to develop inhalable LNPs, which efficiently delivered mRNA or CRISPR‐Cas9 mRNA for genome editing into the mice airway epithelium [123]. Huang et al. developed inhalable LNPs using degradable ionizable glycerolipid TG4C to load mRNA encoding hepatocyte growth factor (HGF) [83]. The LNPs show high stability, uniform distribution in the lungs, and primarily target epithelial cells. After intratracheal administration, HGF mRNA‐LNPs significantly attenuate lung inflammation and alveoli wall thinning, and ameliorate pulmonary emphysema in mice. To address the immunogenicity and suboptimal pulmonary mRNA delivery of LNPs, Zhao et al. constructed a biodegradable, cationic phosphoramide‐derived lipid PL32 and developed non‐inflammatory PL32 LNPs by incorporating ursolic acid, which enhanced mRNA expression and relieved inflammation via activating vacuolar‐type ATPase (V‐ATPase) and consequently promoting endosome acidification [84]. The LNPs mainly target epithelial and immune cells in the lungs and enhance lung protein expression by 40 folds without causing inflammation compared to ALC‐0315 LNPs. After nebulization, LNPs loading mRNA encoding the nuclear receptor subfamily 1 group D member 1 (NR1D1), a circadian regulatory gene, markedly improve efficiency in treating bronchopulmonary dysplasia (BPD) in rats and pulmonary fibrosis in mice.

Intranasal delivery is also utilized for treating respiratory system diseases. Maniyamgama et al. designed liquid lipid nanoparticles (iLLNs) with a liquid lipid core for intranasal mRNA delivery, using lipid components of ALC‐0315, DOTMA, ‐sitosterol, DOPE, triolein, and DSPE‐PEG [85]. The near‐electroneutral, muco‐inert surface, and high deformability of iLLNs render them a good muco‐penetrating ability to cross the nasal epithelium. mRNA‐iLLNs predominantly induce protein expression in the noses and lungs. Intranasal immunization of mRNA‐iLLNs encoding spike protein of SARS‐CoV‐2 notably elicits mucosal immunity at the upper airway, showing prophylactic potential for COVID‐19 infection and transmission. In addition to mRNA, LNPs are also used to deliver circular RNA (circRNA). Li et al. developed intranasal circRNA vaccine using SM102 LNPs [86]. After intranasal administration, circRNA‐LNPs initiate protein expression in the lungs, and induce antigen‐specific T cells immune responses via targeting alveolar macrophages and DCs, leading to robust anti‐tumor efficacy against lung cancer. Moreover, the intranasal circRNA vaccine has combined effects with CAR‐T cell therapy.

Polymeric nanoparticles are gaining increasing attention for pulmonary drug delivery, as their polymeric structure can be conjugated with specific groups to enable efficient delivery of therapeutic agents [124, 125]. Commonly used polymers include both natural (e.g., starch, chitosan, alginate) and synthetic types (e.g., PLGA, poly(lactic‐co‐glycolic acid); PEG; PEI, polyethylenimine). PLGA has been approved by the FDA for clinical application with excellent biocompatibility, biodegradation, and sustained‐release properties [126].

Starch is a natural neutral polysaccharide with high biocompatibility. Ren et al. developed inhalable tobramycin (TOB)‐loaded oxidized soluble starch nanoparticles modified with mPEG‐NH₂ [39]. Following nebulization, the nanoparticles effectively penetrate the mucus and release TOB in the acidic environment of the bacteria‐infected site, and ameliorate bacterial pneumonia and inflammation. ROS generation during radiation induces the formation of neutrophil extracellular traps (NETs), compromising the anti‐tumor effects of radiation [127]. Sun et al. developed inhalable DNase I‐loaded PLGA nanoparticles coated with gold (Au) nanoparticles [87]. After nebulization, Au nanoparticles enhance radiation sensitization, while DNase I eliminates NETs formation. Together, the dual‐action effectively inhibits lung metastasis in mice. Both as anti‐inflammatory agents, FTY720 exhibits frequent adverse effects, while nobiletin has poor solubility [128, 129]. Zhang et al. developed inhaled FTY720 and nobiletin co‐loaded PLGA nanoparticles [88]. After nebulization, the nanoparticles distribute in lung alveoli and notably target macrophages and neutrophils, suppress cytokine release, immune cell infiltration, and NF‐κB expression in the lungs, enhancing lung recovery in ALI mice. As IL‐11 is a pivotal cytokine involved in IPF, Dong et al. developed inhalable IL‐11‐siRNA nanoparticles using PEI modified with 4‐guanidinobenzoic acid [89]. Following nebulization, the nanoparticles are accumulated in lung fibrotic lesions and primarily target epithelial, endothelial, and immune cells, ultimately attenuating IPF progression and improving lung functions.

New polymeric materials are being developed and applied in pulmonary drug delivery. Indole acetic acid (IAA), a microbial metabolite with anti‐inflammatory properties, has poor solubility limiting its application. Wang et al. developed IAA‐loaded generation 4 polyamidoamine nanoparticles [90]. After nebulization, the nanoparticles mainly retain in the lungs, target, and promote macrophage polarization toward the anti‐inflammatory M2 phenotype, reducing inflammation and improving lung function in COPD mice. T‐box transcription factor 2 (Tbx2), a crucial transcription factor in lung development and growth, is down‐regulated in silicosis. Yong et al. synthesized polyplexes 20% b‐3C‐2P12, a “four‐in‐one” LNPs‐like highly branched polys (β‐amino ester) by integrating the four components of LNPs to deliver mRNA encoding Tbx2 [91]. After nebulization, Tbx2 mRNA‐loaded nanoparticles effectively restore lung function in silicosis mice. Glutathione S‐transferase (GST)‐induced conjugation of GSH with cisplatin contributes to cisplatin resistance in cancer [130]. Tang et al. developed inhalable PEOz‐b‐PLA‐GSNO nanoparticles modified with targeting molecule dibenzyl cyclooctyne (DBCO) to deliver a platinum prodrug composed of ethacrynic acid (EA, a GST inhibitor) and cisplatin [92]. With targeting and entering into bioorthogonal molecule azide‐prelabeled tumor cells, the nanoparticles release EA under the acidic and high GSH environment to inhibit GST activity, while released nitric oxide (NO) from donor GSNO triggered by GSH improves cisplatin uptake, both processes pronouncedly deplete GSH due to simultaneous GSH consumption, collectively reversing cisplatin resistance and inhibiting the growth of cisplatin‐resistant orthotopic non‐small cell lung cancer after nebulization.

Polymeric nanoparticles can integrate with other types of nanoparticles to create hybrid nanocarriers. Inspired by the virus structure, Li et al. developed inhalable anionic polymer hyaluronic acid‐bisphosphonate‐based nanogel within LNPs to deliver an immunostimulatory agent poly(I:C) [93]. After intratracheal inhalation, the nanoparticles predominantly distribute in lung tumors and target DCs and macrophages, robustly activating antitumor immunity and suppressing lung metastases. Furthermore, poly(I:C) and PD‐L1 siRNA co‐loaded nanoparticles exhibit a synergistic therapeutic effect. Neonatal Fc receptor (FcRn) is overexpressed in lung epithelium and macrophages. Yu et al. developed inhalable dexamethasone‐loaded PLGA‐lipid nanoparticles with surface modification of FcRn peptide, which facilitates transepithelial transport of nanoparticles and subsequent entry into inflammatory cells [58]. After intranasal administration, the nanoparticles uniformly distribute and retain in the lungs, reduce inflammation and airway epithelium thickness, effectively reversing asthma in mice. The Wang group developed cell membrane‐coated PLGA nanoparticles loading drugs, followed by conjugation with natural algae to create a series of biohybrid microrobots [32, 94, 95]. Integrating the active motility of algae, cell‐mimicking properties of cell membranes (e.g., neutrophil, red blood cell, platelet), and sustained‐release capability of PLGA nanoparticles, the dynamic microrobots uniformly distribute into deep lungs, prolong lung retention, and evade clearance by alveolar macrophages. After intratracheal administration or nebulization, ciprofloxacin‐, doxorubicin‐, and vancomycin‐loaded microrobots effectively inhibit acute Pseudomonas aeruginosa pneumonia, lung metastasis, and acute methicillin‐resistant Staphylococcus aureus pneumonia, respectively.

Protein and peptide utilize amino acids as fundamental building blocks. Protein‐based nanoparticles can be prepared using emulsion, self‐assembly, and desolvation methods, while peptide‐based nanoparticles are spontaneously self‐assembled peptide nanostructures driven by the forces of intermolecular interactions [131, 132, 133]. Both nanoparticles possess excellent properties of stability, biocompatibility, biodegradation, and low immunogenicity. In 2005 and 2021, the FDA approved Abraxane, paclitaxel albumin protein‐bound nanoparticles (~130 nm) for intravenous use to treat breast cancer, and Fyarro, sirolimus albumin protein‐bound nanoparticles for intravenous use to treat perivascular epithelioid cell tumor (PEComa), respectively. Non‐bioactive peptide nanoparticles can act as drug carriers, while certain bioactive peptide nanoparticles can also be utilized as therapeutics or for enhanced targeting and cell penetration.

Polymyxin B (PMB) is recognized as the last‐line antibiotic against multidrug‐resistant Gram‐negative bacteria; however, it has severe neurotoxicity and nephrotoxicity when administered by intravenous injection. Li et al. developed inhaled pH‐responsive PMB‐loaded albumin nanoparticles conjugated with an acid‐responsive molecule (PEBA) and Amine‐PEG‐Thiol [38]. The thiol groups with a mucolytic effect, mucus‐inert PEG modification, and negative charge of nanoparticles enable them to achieve good mucus penetration. After aerosol inhalation, the nanoparticles distribute in the alveoli and release PMB in the acidic microenvironment of the bacterial infection area, decreasing lung bacterial load and inflammation in pneumonia mice infected with carbapenem‐resistant Klebsiella pneumonia. Zhang et al. constructed inhalable ribosomal protein‐based and RGD peptide‐modified nanoparticles co‐loading MMP13 mRNA and keratinocyte growth factor (KGF) [14]. The nanoparticles release KGF to decrease intrapulmonary ECM in fibrotic lesions, while MMP13 mRNA is delivered in integrin‐enriched myofibroblasts and injured AT2 cells to re‐epithelialize the disrupted alveolar epithelium, synergistically improving lung function and reversing pulmonary fibrosis in mice. Notably, the inhaled nanoparticles show combined effects with oral pirfenidone and provide a potential strategy for IPF treatment. Jeong et al. developed inhalable thiolated mussel adhesive protein‐based nanoparticles loading curcumin [47]. Following nebulization, the nanoparticles retain in the lungs and target tumor cells through thiol‐mediated internalization, then release curcumin triggered by high levels of GSH in tumors, resulting in significantly suppressing lung metastasis in mice.

Compared to proteins, peptides exhibit a simpler structure, less immunogenicity, and superior design flexibility in the modification of peptide sequences and conjugation with various molecules to tailor their properties and functions [134, 135]. Peng et al. developed inhalable self‐assembling peptide‐based nanoparticles conjugated with cerium‐based tannic acid nanozyme [46]. The peptide self‐assembles and aggregates into β‐sheets under high ROS levels in inflamed areas, driving the nanozyme to form an active fibrous structure displaying enzyme‐like antioxidant properties. Following nasal inhalation, the nanozyme primarily targets the macrophages and epithelial cells, and effectively alleviates lung inflammation, lung damage, and viral load through neutralization in a murine model of viral pneumonia. Chen et al. constructed inhalable self‐assembly peptide‐based nanoparticles conjugated with a membrane‐permeable motif [96]. Following intratracheal injection, the nanoparticles accumulate in injured lungs and specifically target macrophages, resulting in inhibiting proinflammatory responses, expediting lung regeneration through promoting M2 macrophage polarization, and eradicating bacteria through membrane disruption, collectively extending the survival rate in bacteria‐induced ALI mice. To solve the low efficiency and cytotoxicity during the intracellular delivery of nucleic acids and proteins, Eweje et al. constructed a recombinant elastin‐like polypeptide fused to an endosomal escape peptide, and developed self‐assembling nanoparticles [9]. The nanoparticles superiorly deliver siRNA, mRNA, plasmid DNA, proteins, and CRISPR gene editors to multiple cell lines and primary cells in vitro. Furthermore, intranasal instillation of the nanoparticles loading Cre recombinase protein effectively delivers protein to lung epithelial cells and induces gene editing in mice, while the benchmark SM‐102 LNPs show minimal effects. Pentameric cholera toxin B subunit (CTB) is a potent mucosal adjuvant. Ye et al. constructed self‐adjuvanting self‐assembled nanoparticles by fusion of a trimer‐forming peptide to CTB, displaying the SARS‐CoV‐2 receptor‐binding domain (RBD) antigen [97]. The nanoparticles are incorporated into porous PLGA microcapsules to form a dry powder with a suitable aerodynamic size. After inhalation, the microcapsules predominantly deposit in the alveoli, and released nanoparticles mainly target the antigen‐presenting cells (APCs) and induce robust systemic and mucosal immune responses, effectively protecting against SARS‐CoV‐2 in mice, hamsters, and nonhuman primates. Furthermore, inhaled vaccine co‐displaying wild‐type RBD and Omicron variant RBD significantly prevents Omicron transmission in hamsters.

Mesoporous silica nanoparticles (MSNs) are inorganic nanoparticles characterized by a porous structure that enables the encapsulation of therapeutic agents. The structural features of MSNs, such as high surface area, adjustable size and volume, and ease of surface modification, make them promising drug carriers. These properties support high drug loading, controlled release, targeted delivery, as well as good biocompatibility and biodegradability [136, 137].

Bacterial infections are a significant factor contributing to poor survival outcomes in patients with lung cancer [138]. Ma et al. developed inhalable MSNs co‐loading doxorubicin (DOX) and antimicrobial peptide (AMP) [48]. Following nebulization, MSNs biodegradation is caused by high GSH in the tumor microenvironment, followed by the release of DOX and AMP to kill tumor cells and commensal bacteria simultaneously, achieving an improved therapeutic effect against lung cancer in tumor/bacterial commensal mice. Tumor‐associated macrophages (TAMs) provide a high level of iron required for cancer stem cells (CSCs) growth, while excessive iron may induce CSCs ferroptosis [139, 140]. Feng et al. developed nebulized iron‐doped MSNs [11]. After nebulization, MSNs are taken up by TAMs through endocytosis and degraded in the lysosome. This process releases elevated levels of iron and reduces the antioxidative glucose‐6‐phosphate within lung tumor microlesions, collaboratively enhancing CSCs ferroptosis and suppressing tumor progression in an early orthotopic lung cancer model. We should note that in this study iron‐based nanoparticles regulate TAMs and indirectly trigger CSCs ferroptosis. It is worthwhile to explore new strategies that directly target and induce CSCs ferroptosis in future research. The hypersecretion of mucus and formation of bacterial biofilm prevent effective antimicrobials delivery for COPD treatment [141]. Zhu et al. developed inhalable ceftazidime (CAZ)‐loaded MSNs gated with polypeptides [40]. These nanoparticles effectively penetrate mucus and biofilm, and polypeptides are activated under the acidic environment in biofilm to disrupt bacterial membranes, scavenge bacterial DNA, and unmask MSNs pores to release CAZ. The combined antibacterial, antioxidative, and anti‐inflammatory effects of inhaled nanoparticles synergistically facilitate the resolution of inflammation and improve lung function in patients with COPD.

Nevertheless, occupational exposure to crystalline silica dust in industrial settings may lead to silicosis, characterized by lung inflammation and fibrosis [142]. The inhalation of MSNs raises the potential safety concerns regarding their possible role in inducing pulmonary fibrosis. MSNs, a form of amorphous silica, possess a distinct biosafety profile compared to crystalline silica. Recent studies have shown that synthetic amorphous silica does not induce lung fibrosis in rats [143, 144, 145].

Biomimetic nano‐delivery systems represent a novel biological approach to drug delivery, offering key advantages such as high biocompatibility, targeted delivery, and prolonged circulation or retention [146]. Recently, inhaled extracellular vesicles and cell membrane‐derived nanovesicles have been widely employed in the treatment of lung diseases.

For nanoparticle formulation in liquid solution or suspensions, favorable MMAD and FPF of aerosolized liquid droplets can be achieved by choosing appropriate inhalation devices (e.g., jet nebulizers, vibrating mesh nebulizers) [175]. For Arikayce, the MMAD of nebulized aerosol droplets is about 4.7 μm, and the FPF of the aerosol ranges from 50.3% to 53.5% [174]. The MMAD and FPF of ASSNAC and nintedanib co‐loaded liposomes are 1.85 μm and 81.1%, respectively [76]. The MMAD and FPF of thiolated mussel adhesive protein nanoparticles loading curcumin are 4.4 μm and 53%, respectively [47]. During nebulization of Arikayce, a portion of amikacin is released from liposomal encapsulation, resulting in the pulmonary delivery of both free and liposome‐associated amikacin. However, proteins and nucleic acids released from inhaled nanoparticles are susceptible to enzymatic degradation, compromising their transfection and delivery efficacy [12]. To enhance their stability during nebulization, formulation components such as buffering agents (e.g., sodium acetate, HEPEs), low salt buffers (e.g., 0.1 × PBS), and polymeric excipients (e.g., branched PEG20K, poloxamer 188) are incorporated [12, 80, 116]. Both mRNA COVID‐19 vaccines from Moderna and Pfizer/BioNTech use sucrose as a cryoprotectant for storage at frozen conditions [176]. Sucrose effectively enhances the post‐nebulization stability of mRNA‐LNPs at −20°C for 30 days, while LNPs without sucrose exhibit stability at 4°C for 7 days and instability at −20°C for 30 days [82]. Zhao et al. prepared lyophilized powder of mRNA‐LNPs with sucrose by freeze drying, which maintained protein expression in the lungs after reconstitution with water and stability at 4°C for over 90 days [84].

For dry powder‐based nanoparticle formulations, the MMAD and FPF of solid microparticles are predominantly influenced by the formulation composition and drying technology employed to encapsulate the nanoparticles. Dry powder inhalers have advantages of ease of use, portability, good drug stability, and accurate delivery dose [177].

Trehalose is commonly used as a matrix‐forming excipient in dry powder formulations for pulmonary delivery of nanoparticles. Inhalable dry powders of siRNA‐loaded lipid‐polymer hybrid nanoparticles with trehalose, and miR‐335‐loaded EVs with trehalose and leucine are prepared by spray drying and thin‐film freeze‐drying, respectively, both of which exhibit excellent aerosolization properties (MMAD: 2.96 μm, FPF: 65%; MMAD: 1.2 μm, FPF: 75.7%) while preserving the biological function of siRNA and miRNA [178, 179]. Dry powders of mRNA‐LNPs with trehalose and trileucine are prepared by spray drying, which show better stability and mRNA functionality stored at room temperature compared to liquid formulations stored at 4°C for 2 weeks [180]. Moreover, nanoparticles can be loaded in microparticulate drug delivery systems. Inhalable chitosan microparticles encapsulating CTS‐loaded liposomes and liposome‐exosome hybrid vesicles show good aerosolization performance (MMAD: 2.4 μm, FPF: 54%) and stability with storage under accelerated conditions for 3 months [59]. Inhalable clofazimine‐loaded MSNs exhibit excellent aerodynamic properties (MMAD: 1.65 μm, FPF: 50%) and stability for 12 months in refrigerated conditions [181]. Notably, the MSNs dissolve in lung fluid to release nanoparticles, thereby establishing a dual micro‐nano delivery platform.

The authors have nothing to report.