Polydopamine Coating Enhances Mucopenetration and Cell Uptake of Nanoparticles

Inhalable lipid-based nanocarriers covered by polydopamine for effective mucus penetration and pulmonary retention

To overcome the critical challenge in drug inhalation for pulmonary diseases, we innovatively proposed that polydopamine (PDA) as a surface modification material had great potential to improve the mucus permeation and pulmonary retention of inhalable lipid-based nanocarriers. We prepared PDA coated lipid nanoemulsions/solid lipid nanoparticles/liposomes and systematically evaluated their interactions with mucin and pulmonary retention after inhalation. PDA-coated lipid-based nanocarriers exhibited weaker interactions with mucins, higher mucus permeability and cellular uptake by the respiratory epithelium cells compared to PEGylated lipid-based nanocarriers. However, the pulmonary retention advantage of PDA coating was shown in lipid nanoemulsions (< 50 nm) and solid lipid nanoparticles (< 100 nm). Liposomes (∼ 150 nm) with PEGylation possessed higher pulmonary retention than that coated by PDA. It was suggested that PEGylated liposomes were liable to be phagocytosed by alveolar macrophages due to binding with specific antibodies. Overall, this work suggests that PDA as a surface modification material of inhalable lipid-based nanocarriers holds promise for effective mucus penetration and pulmonary retention.

Deamidation modifies gliadin digestion affecting peptide behaviors in self-assembly, mucus permeation, and intestinal epithelial cell viability

Gliadin induces direct intestinal epithelial damage due to the interaction between the intestinal epithelium and gliadin peptides with particular self-assembly properties after digestion. This study explored if and how deamidation affected intestinal epithelial damage. The results demonstrated the alteration of self-assembly that when the degree of deamidation (DD) was less than 20 %, the decrease of peptide length and increase of polarity were the main reasons for the reduction of particle size and spherical nanoparticles. As DD was 26 %, the increase of negative charges was responsible for size increase and shape alteration to linear strands due to the electrostatic attraction. These alterations of self-assembly behaviors facilitated mucus permeation. Deamidated gliadin peptides inhibited the Caco-2 cell damage due to the weakened interaction with the cell membrane. The work demonstrated how deamidation modified the gliadin peptides after digestion in minimizing intestinal epithelial damage, ensuring the safety of deamidation as a modification method.

Preparation and characterization of tamarind seed polysaccharide-pullulan sublingual films loaded with muco-inert nanoparticles for mucosal co-delivery of BSA and resveratrol

Drug delivery via the sublingual mucosal route presents considerable challenges due to the presence of a complex mucus barrier. To improve the mucus permeability of resveratrol and bovine serum albumin (BSA) and achieve their co-delivery, muco-inert resveratrol-BSA nanoparticles (Res-BSA) were prepared. The mucus penetration of Res-BSA was 3.6 times higher than that of resveratrol and BSA. Res-BSA was incorporated into sublingual films based on mucoadhesive tamarind seed polysaccharide and pullulan (TSP-Pul) to prolong its residence time in the sublingual area. The introduction of Res-BSA enhanced the surface roughness and hydrophilicity of TSP-Pul and preserved the favorable mechanical strength and flexibility of TSP-Pul. The 5 % addition of Res-BSA dramatically increased the initial swelling capacity (435 % at 2 min) of TSP-Pul (284 % at 2 min), and all films completely disintegrated within 60 min. During disintegration, the holes in the internal network of the films became progressively larger and more heterogeneous. The main initial release form of the films containing Res-BSA was determined to be nanoparticles. Compared to TSP-Pul, the addition of 1 % Res-BSA accelerated the release of resveratrol and BSA within the first 2 h. Overall, TSP-Pul containing Res-BSA may be an attractive platform for sublingual co-delivery of resveratrol and BSA.

Engineered Probiotics with Low Oxygen Targeting Porphyromonas gingivalis and Gingival Fibroblasts for the Treatment of Periodontitis

The overuse of antibiotics has increased the prevalence of drug-resistant bacteria in periodontitis. "Sentinel" gingival fibroblasts, stimulated by pathogenic bacteria, continue to release signaling factors that affect stem cell repair and recruit immune cells, resulting in persistent inflammation in periodontal tissues, eventually leading to the loosening and loss of teeth. Periodontal pathogenic bacteria cause surface hypoxia, and gingival fibroblasts in the inflammatory microenvironment express HIF-1α, promoting hypoxic areas in periodontal pockets. No drug delivery system is available for the hypoxic region of periodontal pockets. We synthesized BI NPs via berberine (BBR) and indocyanine green (ICG) and formed BIP NPs by wrapping BI NPs with polydopamine (PDA), and the BIP NPs were delivered to the hypoxic region of the periodontal pocket by hitchhiking with the anaerobic probiotic Bifidobacterium bifidum (Bif). The BIP NPs released berberin (BBR) under near-infrared (NIR) irradiation, which inhibited the sulfur metabolism of Porphyromonas gingivalis via mild photothermal action and BBR-targeted serine acetyltransferase, resulting in a decrease in resistance to oxidative stress, thus exerting a nonantibiotic bacteriostatic effect. This mild photothermal effect facilitated the uptake of BIP NPs bygingival fibroblasts. Moreover, BBR targeted nuclear factor-erythroid 2-related factor 2 (NRF2) to reduce ferroptosis, and the gingival fibroblast supernatant modulated macrophage polarization through the NF-κB pathway. In the periodontitis rat model, Bif@BIP+NIR treatment carried the drug to deep periodontal pockets, decreasing local gingival ferroptosis and alleviating periodontitis symptoms. To summarize, engineered probiotics target low-oxygen periodontal pockets for drug delivery, P. gingivalis for nonantibiotic bacterial inhibition, and gingival fibroblasts to mitigate ferroptosis, thus alleviating periodontitis to reduce periodontitis.

Orally disintegrating films based on pullulan and HPMC with carbopol-coated mucoadhesive nanoparticles for dual-pattern drug release

Dual-pattern drug release systems are a new type of drug delivery system designed to achieve both immediate and sustained drug release. This study developed a dual-pattern system by combining orally disintegrating films (ODFs) with mucoadhesive nanoparticles (NPs). The NPs were made from silk fibroin (SF) coated with carbopol polymer (CP) and loaded with midazolam (MID) (MID-CP/SFNPs). MID was chosen for its rapid onset, high lipophilicity, and excellent bioavailability, making it ideal for buccal administration. The MID-CP/SFNPs had an average diameter of 260.3 nm, a negative zeta potential of -22 mV, and an 80.6 % encapsulation efficiency. When tested against rabbit buccal mucosa, the CP/SFNPs demonstrated excellent mucoadhesive properties. Using a casting process, the MID-CP/SFNPs were combined with polysaccharide films made from pullulan and hydroxypropyl methylcellulose (PUL/HPMC) containing MID. The final product, MID-CP/SFNPs@MID-ODFs, had a uniform thickness of 68.8 μm, a consistent drug content of 87.5 %, significant flexibility (219 times), and a suitable disintegration time of 16 s. This formulation showed a rapid initial drug release of 45.6 % within the first 30 min, followed by a sustained release, resulting in a total of 91 % of the drug being released over 20 h. Histological evaluations confirmed no adverse effects on the microscopic structure of the buccal mucosa. This innovative system, combining ODFs with mucoadhesive NPs, showed promising results, making it a viable candidate for biomedical applications.

Stabilization of chitosan-based nanomedicines in cancer therapy: a review

Chitosan (CS), a versatile and alkaline polysaccharide, has gained significant attention in nanomedicine due to its biocompatibility and biodegradability. In recent years, its applications in cancer therapy, particularly for the delivery of chemotherapeutic drugs, diagnostic agents, and genes, have advanced considerably. However, many CS-based nanomedicines suffer from poor stability in biological fluids, especially under physiological conditions. The neutral pH and the presence of electrolytes in physiological environments reduce the charge density of CS, which can account for this application limitation of CS-based nanomedicines. To improve the stability and prevent dissociation or aggregation of these nanomedicines before reaching the target sites, this review summarizes common stabilization strategies including hydrophilic or hydrophobic modification of CS, as well as incorporation with metal ions (e.g. Fe3+ or Zn2+), complexation with anionic cross-linkers (e.g. TPP) or anionic polymers. Additionally, the review highlights the application of stabilized CS-based nanocarriers in drug delivery, with a particular focus on cancer therapy. The challenges and future perspectives for accelerating the clinical translation of these nanomedicines are also discussed.

Mechanism exploration of intestinal mucus penetration of nano-Se: regulated by polysaccharides with different functional groups and molecular weights

Selenium deficiency associated with a high risk of many diseases remains a global challenge. Owing to the narrow margin between "nutrition-toxicity" doses of selenium, it is imperative to achieve accurate selenium supplement. Nano‑selenium (SeNPs) is a novel form of selenium supplement with low toxicity, but it could be trapped and removed by intestinal mucus, thus limiting its oral delivery. The mucus penetration of SeNPs is highly associated with interactions between SeNPs and mucin (the structural component of mucus). In this study, we selected four polysaccharides with different functional groups and molecular weights, i.e. chitosan oligosaccharide (COS), chitosan (CS), chitosan quaternary ammonium salt (HACC), and carboxymethyl cellulose (CMC) as templates to modify SeNPs. Then we systematically explored the non-covalent interactions between polysaccharides stabilized nano-Se (PS-SeNPs) and mucin, determined and examined mucus penetration behavior and mechanism of different PS-SeNPs by coarse-grained molecular dynamics simulations, both in vitro and in vivo. It could be observed that penetration of PS-SeNPs depends on their distinct surface properties and mucus pH conditions. COS-SeNPs with short oligosaccharide chains accumulated and bridged with mucin, hindering its mucus penetration at pH 7.4. While HACC-SeNPs with NH3+ and N+ exhibited high binding affinity with mucin, inducing its mucus penetration. The negatively charged CMC-SeNPs diffused freely in mucus due to their electrostatic-repelled interaction and hydrophobic interaction with mucin. This study establishes a theoretical foundation for precise application of SeNPs in oral administration and offers valuable insights into the precise utilization of polysaccharides as tailored carriers of nanoparticles in mucus-covered tissues.

Multifunctional Hydrogel with Photothermal ROS Scavenging and Antibacterial Activity Accelerates Diabetic Wound Healing

Poor diabetic wound healing poses a critical threat to human health. Excessive oxidative stress and increased susceptibility to bacterial infection are key issues that impede diabetic wound healing. Cerium oxide nanoparticles (CeO2 NPs) have attracted increasing attention because of their unique antioxidant and antimicrobial properties. Here, this work designs a near-infrared (NIR) light-responsive gelatin methacryloyl (GelMA)/CeO2/polydopamine (PDA) hydrogel with antibacterial and antioxidant effects. The hydrogel exhibits a stable, efficient, and controllable photothermal conversion capacity under NIR stimulation. The hydrogel can be used to construct a local microenvironment conducive to chronic diabetic wound healing. Significant antibacterial effects of the NIR-responsive GelMA/CeO2/PDA hydrogel on both Escherichia coli (E.coli) and methicillin-resistant Staphylococcus aureus (MRSA) are demonstrated by counting colony-forming units (CFUs) and in bacterial live/dead staining experiments. The strong antioxidant activity of hydrogels is demonstrated by measuring the level of reactive oxygen species (ROS). The effect of the NIR-responsive GelMA/CeO2/PDA hydrogel in terms of promoting diabetic wound healing is validated in full-thickness cutaneous wounds of diabetic rat models. Additionally, this work describes the mechanism by which the NIR-responsive GelMA/CeO2/PDA hydrogel promotes diabetic wound healing; the hydrogel inhibits the interleukin (IL)-17 signaling pathway. This NIR-responsive, multifunctional hydrogel dressing provides a targeted approach to diabetic wound healing.

Tuning mucoadhesion and mucopenetration in self-assembled poly(lactic acid)-block-poly(oligoethylene glycol methacrylate) block copolymer nanoparticles by controlling side-chain lengths

The capacity to tune the degree of mucoadhesion and mucopenetration of nanoparticles is essential to improving drug bioavailability, transport, and efficacy at mucosal interfaces. Herein, self-assembled nanoparticles (NPs) fabricated from amphiphilic block copolymers of poly(lactic acid) (PLA) and poly(oligo(ethylene glycol) methacrylate) (POEGMA) with various side chain lengths (PLA-POEGMAn) are reported to facilitate tunable mucosal interactions. PLA-POEGMAn nanoparticles with long PEG side chain lengths (n = 20, or 40) demonstrated mucoadhesive properties based on rheological synergism, calorimetric tracking of mucin-nanoparticle interactions, and the formation of larger NP-mucin hybrid structures; in contrast, NPs fabricated from block copolymers with shorter PEG side chains (n = 2/8-9 or n = 8,9) showed poor mucoadhesion but penetrated through the mucin layer with significantly higher permeation rates (>80%). All NP formulations showed good cytocompatibility (viability > 70%) with human corneal epithelial cells in vitro and no detectable acute in vivo ocular irritation in Sprague-Dawley rats. Coupled with the capacity of the synthetic route to easily incorporate different brush lengths and/or different functional groups into the hydrophilic block, we anticipate this approach may offer a solution in applications in which balancing mucoadhesion and mucopenetration is critical for enabling effective drug delivery.

An injectable composite hydrogel containing polydopamine-coated curcumin nanoparticles and indoximod for the enhanced combinational chemo-photothermal-immunotherapy of breast tumors

The complexity and compensatory evolution of tumors weaken the effectiveness of single antitumor therapies. Therefore, multimodal combination therapies hold great promise in defeating tumors. Herein, we constructed a multi-level regulatory co-delivery system based on chemotherapy, phototherapy, and immunotherapy. Briefly, curcumin (Cur) was prepared as nanoparticles and coated with polydopamine (PDA) to form PCur-NPs, which along with an immune checkpoint inhibitor (indoximod, IND) were then loaded into a thermosensitive Pluronic F127 (F127) hydrogel to form a multifunctional nanocomposite hydrogel (PCur/IND@Gel). The in situ-formed hydrogel exhibited excellent photothermal conversion efficiency and sustained drug release behavior both in vitro and in vivo. In addition, PCur-NPs showed enhanced cellular uptake and cytotoxicity under NIR laser irradiation and induced potent immunogenic cell death (ICD). After intratumoral injection of PCur/IND@Gel, significant apoptosis in 4T1 tumors was induced, dendritic cells in lymph nodes were highly activated, potent CD8+ and CD4+ antitumor immune responses were elicited and regulative T cells in tumors were significantly reduced, which notably inhibited the tumor growth and prolonged the survive time of 4T1 tumor-bearing mice. Therefore, this injectable nanocomposite hydrogel is a promising drug co-delivery platform for chemo-photothermal-immunotherapy of breast tumors.

Understanding of Polydopamine Formulation for Oral Therapeutic Delivery in Ulcerative Colitis Treatment

Oral therapeutic delivery remains challenged by gastrointestinal tract (GI) barriers, which hinders the successful transition of therapeutic candidates into clinical treatments. Polydopamine (PDA), with its versatile ability to overcome GI barriers, offers a promising drug formulation technology to address the challenge. Nevertheless, many critical questions remain unanswered regarding the practicality of PDA‐based formulations. Building on the previous research, which tackled multiple physicochemical aspects, the current study aims to address another three outstanding issues, including the quantification of residual dopamine (DA) in PDA‐based formulations, the examination of these formulations stimulatory effects on colon tissue, and the potential anti‐inflammatory properties. To facilitate this investigation, a curcumin‐containing nanomedicine (CP@CCS) is prepared as a representative PDA‐based formulation. The results reveal a marked decrease of residual DA within the formulation. In the treatment of ulcerative colitis (UC), the formulation do not provoke the substantial contractions in colon tissue typically induced by DA. Furthermore, in vivo evaluation verified the supplementary anti‐UC benefits of PDA. These outcomes add evidence for the practicality of PDA‐based formulations in terms of safety and therapeutic efficacy. Finally, a conceptual framework is proposed for understanding the role of PDA in oral therapeutic delivery, thereby providing insightful directions for subsequent research.

Mussel-like polydopamine-assisted aggregation-induced emission nanodot for enhanced broad-spectrum antimicrobial activity: In vitro and in vivo validation

Emerging luminogens with aggregation-induced emission properties, namely AIEgens, demonstrated excellent anti-bacteria activity potential. However, their application still limited by the low antibacterial activity caused by the poor binding with bacteria. Polydopamine (PDA), an important biological macromolecule, possesses superior adhesion ability toward various material surface, including bacteria. In this study, the novel mussel-like PDA-assisted AIE Nanodot was proposed, achieving with robust bacterial binding ability and enhanced broad-spectrum antibacterial activity. Binding ability inherited from the PDA enables the constructed PDA-assisted AIE Nanodot to adhere efficiently to the bacterial membrane surface. Meanwhile, the AIE properties endowed them with monitoring capability, allowing for tracking their interaction with bacteria through facile fluorescence imaging in real time. More importantly, excellent killing of both Gram-positive and Gram-negative bacteria were successfully achieved in vitro antibacterial tests with excellent biocompatibility. Furthermore, in the treatment of Methicillin-resistant S. aureus (MRSA)-infected mouse-wound model, the mice exhibited accelerated wound healing with low bacterial load. This novel integrated strategy introduced a simple but effectively design to enhance the binding and antibacterial ability of AIEgens and would diversify the existing pool of antibacterial agents.

Effect of Polymer and Cell Membrane Coatings on Theranostic Applications of Nanoparticles: A Review

The recent decade has witnessed a remarkable surge in the field of nanoparticles, from their synthesis, characterization, and functionalization to diverse applications. At the nanoscale, these particles exhibit distinct physicochemical properties compared to their bulk counterparts, enabling a multitude of applications spanning energy, catalysis, environmental remediation, biomedicine, and beyond. This review focuses on specific nanoparticle categories, including magnetic, gold, silver, and quantum dots (QDs), as well as hybrid variants, specifically tailored for biomedical applications. A comprehensive review and comparison of prevalent chemical, physical, and biological synthesis methods are presented. To enhance biocompatibility and colloidal stability, and facilitate surface modification and cargo/agent loading, nanoparticle surfaces are coated with different synthetic polymers and very recently, cell membrane coatings. The utilization of polymer- or cell membrane-coated nanoparticles opens a wide variety of biomedical applications such as magnetic resonance imaging (MRI), hyperthermia, photothermia, sample enrichment, bioassays, drug delivery, etc. With this review, the goal is to provide a comprehensive toolbox of insights into polymer or cell membrane-coated nanoparticles and their biomedical applications, while also addressing the challenges involved in translating such nanoparticles from laboratory benchtops to in vitro and in vivo applications. Furthermore, perspectives on future trends and developments in this rapidly evolving domain are provided.

Inhalable mucin-permeable nanomicelles deliver antibiotics for effective treatment of chronic pneumonia

Pseudomonas aeruginosa (P. aeruginosa) pneumonia can have serious physiological consequences, particularly when P. aeruginosa biofilms are formed. Although inhaled therapy is preferred, inhaled drugs tend to get trapped by pulmonary mucus, which hinders efficient antibiotic permeability through mucus and biofilms. In this study, we prepare poly[2-(pentamethyleneimino)ethyl methacrylate]-block-poly[2-(N-oxide-pentamethyleneimino)ethyl methacrylate] (PPEMA-b-PPOEMA) micelles loaded with azithromycin (AZM) using reversible addition-fragmentation chain transfer (RAFT) polymerization to achieve effective treatment of P. aeruginosa pneumonia. The zwitterionic structure on the surface of the micelle facilitates the successful traversal of the mucus and optimal concentration within the biofilm. Furthermore, the protonation of piperidine in the polymer enables the micelles to exhibit a positive charge in the acidic environment of a bacterial infection, enhancing AZM's interaction with the bacterium. Both in vivo and in vitro experiments demonstrate that this transmucosal zwitterionic polymer, in combination with a charge reversal strategy, effectively promotes the enrichment of micelles at the site of bacterial infection, thereby increasing the number of antibiotics reaching the bacterial interior and demonstrating remarkable antibacterial synergy. Overall, this work offers a promising approach for trans-airway drug delivery in the treatment of pneumonia.

Lymphoid organ-targeted nanomaterials for immunomodulation of cancer, inflammation, and beyond

Nanomaterials exhibit significant potential for stimulating immune responses, offering both local and systemic modulation across a variety of diseases. The lymphoid organs, such as the spleen and lymph nodes, are home to various immune cells, including monocytes and dendritic cells, which contribute to both the progression and prevention/treatment of diseases. Consequently, many nanomaterial formulations are being rationally designed to target these organs and engage with specific cell types, thereby inducing therapeutic and protective effects. In this review, we explore crucial cellular interactions and processes involved in immune regulation and highlight innovative nano-based immunomodulatory approaches. We outline essential considerations in nanomaterial design with an emphasis on their impact on biological interactions, targeting capabilities, and treatment efficacy. Through selected examples, we illustrate the strategic targeting of therapeutically active nanomaterials to lymphoid organs and the subsequent immunomodulation for infection resistance, inflammation suppression, self-antigen tolerance, and cancer immunotherapy. Additionally, we address current challenges, discuss emerging topics, and share our outlook on future developments in the field.

Polydopamine-Modified Liposomes: Preparation and Recent Applications in the Biomedical Field

Polydopamine (PDA) is a bioinspired polymer that has unique and desirable properties for emerging applications in the biomedical field, such as extraordinary adhesiveness, extreme ease of functionalization, great biocompatibility, large drug loading capacity, good mucopenetrability, strong photothermal capacity, and pH-responsive behavior. Liposomes are consolidated and attractive biomimetic nanocarriers widely used in the field of drug delivery for their biocompatibility and biodegradability, as well as for their ability to encapsulate hydrophobic, hydrophilic, and amphiphilic compounds, even simultaneously. In addition, liposomes can be decorated with appropriate functionalities for targeted delivery purposes. Thus, combining the interesting properties of PDA with those of liposomes allows us to obtain multifunctional nanocarriers with enhanced stability, biocompatibility, and functionality. In this review, a focus on the most recent developments of liposomes modified with PDA, either in the form of polymer layers trapping multiple vesicles or in the form of PDA-coated nanovesicles, is proposed. These innovative PDA coatings extend the application range of liposomes into the field of biomedical applications, thereby allowing for easier functionalization with targeting ligands, which endows them with active release capabilities and photothermal activity and generally improves their interaction with biological fluids. Therefore, hybrid liposome/PDA systems are proposed for surface-mediated drug delivery and for the development of nanocarriers intended for systemic and oral drug delivery, as well as for multifunctional nanocarriers for cancer therapy. The main synthetic strategies for the preparation of PDA-modified liposomes are also illustrated. Finally, future prospects for PDA-coated liposomes are discussed, including the suggestion of potential new applications, deeper evaluation of side effects, and better personalization of medical treatments.

Combination of PEGylation and Cationization on Phospholipid-Coated Cyclosporine Nanosuspensions for Enhanced Ocular Drug Delivery

Strong precorneal clearance mechanisms including reflex blink, constant tear drainage, and rapid mucus turnover constitute great challenges for eye drops for effective drug delivery to the ocular epithelium. In this study, cyclosporine A (CsA) for the treatment of dry eye disease (DED) was selected as the model drug. Two strategies, PEGylation for mucus penetration and cationization for potent cellular uptake, were combined to construct a novel CsA nanosuspension (NS@lipid-PEG/CKC) by coating nanoscale drug particles with a mixture of lipids, DSPE-PEG2000, and a cationic surfactant, cetalkonium chloride (CKC). NS@lipid-PEG/CKC with the mean size ∼173 nm and positive zeta potential ∼+40 mV showed promoted mucus penetration, good cytocompatibility, more cellular uptake, and prolonged precorneal retention without obvious ocular irritation. More importantly, NS@lipid-PEG/CKC recovered tear production and goblet cell density more efficiently than the commercial cationic nanoemulsion on a dry eye disease rat model. All results indicated that a combination of PEGylation and cationization might provide a promising strategy to coordinate mucus penetration and cellular uptake for enhanced drug delivery to the ocular epithelium for nanomedicine-based eye drops.

Oral In-Situ Nanoplatform with Balanced Hydrophobic-Hydrophilic Property for Transport Across Gastrointestinal Mucosa

Transport of oral nanocarriers across the GI epithelium necessitates transport across hydrophilic mucus layer and the hydrophobic epithelium. Based on hydrophobic-hydrophilic balance, Curcumin-Lipomer (lipid-polymer hybrid nanoparticles) comprising hydrophobic stearic acid and hydrophilic Gantrez™ AN 119 (Gantrez) were developed, by a radical in-situ approach, to successfully traverse both barriers. A monophasic preconcentrate (Cur-Pre) comprising Cur (Curcumin), stearic acid, Gantrez and stabilizers, prepared by simple solution, was added to an aqueous phase to instantaneously generate Curcumin-Lipomer (Cur-Lipo) of nanosize and high entrapment efficiency (EE). Cur-Lipo size and EE was optimized by Box-Behnken Design. Cur-Lipomers of varying hydrophobic-hydrophilic property obtained by varying the stearic acid: Gantrez ratio exhibited size in the range 200-400 nm, EE > 95% and spherical morphology as seen in the TEM. A decrease in contact angle and in mucus interaction, evident with increase in Gantrez concentration, indicated an inverse corelation with hydrophilicity, while a linear corelation was observed for mucopenetration and hydrophilicity. Cur-SLN (solid lipid nanoparticles) which served as the hydrophobic reference revealed contact angle > 90°, maximum interaction with mucus and minimal mucopenetration. The ex-vivo permeation study through chicken ileum, revealed maximum permeation with Cur-Lipo1 and comparable and significantly lower permeation of Cur-Lipo1-D and Cur-SLN proposing the importance of balancing the hydrophobic-hydrophilic property of the nanoparticles. A 1.78-fold enhancement in flux of hydrophobic Cur-SLN, with no significant change in permeation of the hydrophilic Cur-Lipomers (p > 0.05) following stripping off the mucosal layer was observed. This reiterated the significance of hydrophobic-hydrophilic balance as a promising strategy to design nanoformulations with superior permeation across the GI barrier.

Lysine-Polydopamine Nanocrystals Loaded with the Codrug Abemaciclib-Flurbiprofen for Oral Treatment of Cancer

Nonsteroidal anti-inflammatory drugs (NSAIDs) combined with chemotherapeutic agents for the treatment of colorectal cancer (CRC) are a promising therapeutic strategy. NSAIDs can effectively boost the antitumor efficacy of chemotherapeutic agents by inhibiting the synthesis of COX-2. However, hazardous side effects and barriers to oral drug absorption are the main challenges for combination therapy with chemotherapeutics and NSAIDs. To address these issues, a safe and effective lysine-polydopamine@abemaciclib-flurbiprofen (Flu) codrug nanocrystal (Lys-PDA@AF NCs) was designed. Abemaciclib (Abe), a novel and effective inhibitor of the CDK4/6 enzyme, and Flu were joined to prepare Abemaciclib-Flu codrug (AF) by amide bonds, and then the AF was made into nanocrystals. Lysine-modified polydopamine was selected as a shell to encapsulate nanocrystals to enhance intestinal adhesion and penetration and lengthen the duration time of drugs in vivo. Nuclear magnetic resonance, Fourier transform infrared, Massspectrometry, X-ray photoelectron spectroscopy, Transmission electron microscopy, and drug loading were used to evaluate the physicochemical characteristics of the nanocrystals. In our study, Abe and Flu were released to exert their synergistic effect when the amide bond of AF was broken and the amide bond was sensitive to cathepsin B which is overexpressed in most tumor tissues, thus increasing the selectivity of the drug to the tumor. The results showed that Lys-PDA@AF NCs had higher cytotoxicity for CRC cell with an IC50 of 4.86 μg/mL. Additionally, pharmacokinetics showed that Abe and Flu had similar absorption rates in the Lys-PDA@AF NCs group, improving the safety of combination therapy. Meanwhile, in vivo experiments showed that Lys-PDA@AF NCs had excellent antitumor effects and safety. Overall, it was anticipated that the created Lys-PDA@AF NCs would be a potential method for treating cancer.

Attenuation of inflammatory bowel disease by oral administration of mucoadhesive polydopamine-coated yeast β-glucan via ROS scavenging and gut microbiota regulation

Treatment for inflammatory bowel disease (IBD) is challenging since current anti-inflammatory and immunosuppressive therapies do not address the underlying causes of the illness, which include increased levels of reactive oxygen species (ROS) and dysbiosis of the gut commensal microbiota. Additionally, these treatments often have systemic off-target effects and adverse side effects. In this study, we have developed a prebiotic yeast β-glucan nanocomplex coated with bio-adhesive polydopamine (YBNs@PDA) to effectively prolong their retention time in the gastrointestinal (GI) tract. The oral administration of YBNs@PDA restored the epithelium barriers, reduced ROS levels, and minimized systemic drug exposure while improved therapeutic efficacy in an acute colitis mouse model. Furthermore, 16S ribosomal RNA genes sequencing demonstrated a higher richness and diversity in gut microflora composition following the treatments. In particular, YBNs@PDA markedly augmented the abundance of Lachnospiraceae NK4A136 and Bifidobacterium, both of which are probiotics with crucial roles in relieving colitis via retaining gut homeostasis. Cumulatively, these results demonstrate that the potential of YBNs@PDA as a novel drug-free, ROS-scavenging and gut microbiota regulation nanoplatform for the treatment of GI disorders.

Light-responsive polymeric nanoparticles for retinal drug delivery: design cues, challenges and future perspectives

A multitude of sight-threatening retinal diseases, affecting hundreds of millions around the globe, lack effective pharmacological treatments due to ocular barriers and common drug delivery limitations. Polymeric nanoparticles (PNPs) are versatile drug carriers with sustained drug release profiles and tunable physicochemical properties which have been explored for ocular drug delivery to both anterior and posterior ocular tissues. PNPs can incorporate a wide range of drugs and overcome the challenges of conventional retinal drug delivery. Moreover, PNPs can be engineered to respond to specific stimuli such as ultraviolet, visible, or near-infrared light, and allow precise spatiotemporal control of the drug release, enabling tailored treatment regimens and reducing the number of required administrations. The objective of this study is to emphasize the therapeutic potential of light-triggered drug-loaded polymeric nanoparticles to treat retinal diseases through an exploration of ocular pathologies, challenges in drug delivery, current production methodologies and recent applications. Despite challenges, light-responsive PNPs hold the promise of substantially enhancing the treatment landscape for ocular diseases, aiming for an improved quality of life for patients.

Polydopamine-based plasmonic nanocomposites: rational designs and applications

Taking advantage of its adhesive nature and chemical reactivity, polydopamine (PDA) has recently been integrated with plasmonic nanoparticles to yield unprecedented hybrid nanostructures. With advanced architectures and optical properties, PDA-based plasmonic nanocomposites have showcased their potential in a wide spectrum of plasmon-driven applications, ranging from catalysis and chemical sensing, to drug delivery and photothermal therapy. The rational design of PDA-based plasmonic nanocomposites entails different material features of PDA and necessitates a thorough understanding of the sophisticated PDA chemistry; yet, there is still a lack of a systematic review on their fabrication strategies, plasmonic properties, and applications. In this Highlight review, five representative types of PDA-based plasmonic nanocomposites will be featured. Specifically, their design principles, synthetic strategies, and optical behaviors will be elucidated with an emphasis on the irreplaceable roles of PDA in the synthetic mechanisms. Together, their essential functions in diverse applications will be outlined. Lastly, existing challenges and outlooks on the rational design and assembly of next-generation PDA-based plasmonic nanocomposites will be presented. This Highlight review aims to provide synthetic insights and hints to inspire and aid researchers to innovate PDA-based plasmonic nanocomposites.

Mesoporous Silicon Nanoparticles with Liver-Targeting and pH-Response-Release Function Are Used for Targeted Drug Delivery in Liver Cancer Treatment

This article aims to develop an aspirin-loaded double-modified nano-delivery system for the treatment of hepatocellular carcinoma. In this paper, mesoporous silica nanoparticles (MSN) were prepared by the "one-pot two-phase layering method", and polydopamine (PDA) was formed by the self-polymerization of dopamine as a pH-sensitive coating. Gal-modified PDA-modified nanoparticles (Gal-PDA-MSN) were synthesized by linking galactosamine (Gal) with actively targeted galactosamine (Gal) to PDA-coated MSN by a Michael addition reaction. The size, particle size distribution, surface morphology, BET surface area, mesoporous size, and pore volume of the prepared nanoparticles were characterized, and their drug load and drug release behavior in vitro were investigated. Gal-PDA-MSN is pH sensitive and targeted. MSN@Asp is different from the release curves of PDA-MSN@Asp and Gal-PDA-MSN@Asp, the drug release of PDA-MSN@Asp and Gal-PDA-MSN@Asp accelerates with increasing acidity. In vitro experiments showed that the toxicity and inhibitory effects of the three nanodrugs on human liver cancer HepG2 cells were higher than those of free Asp. This drug delivery system facilitates controlled release and targeted therapy.

Virus-Inspired Glucose and Polydopamine (GPDA)-Coating as an Effective Strategy for the Construction of Brain Delivery Platforms

The ability of drugs to cross the blood-brain barrier (BBB) is crucial for treating central nervous system (CNS) disorders. Inspired by natural viruses, here we report a glucose and polydopamine (GPDA) coating method for the construction of delivery platforms for efficient BBB crossing. Such platforms are composed of nanoparticles (NPs) as the inner core and surface functionalized with glucose-poly(ethylene glycol) (Glu-PEG) and polydopamine (PDA) coating. Glu-PEG provides selective targeting of the NPs to brain capillary endothelial cells (BCECs), while PDA enhances the transcytosis of the NPs. This strategy is applicable to gold NPs (AuNPs), silica, and polymeric NPs, which achieves as high as 1.87% of the injected dose/g of brain in healthy brain tissues. In addition, the GPDA coating manages to deliver NPs into the tumor tissue in the orthotopic glioblastoma model. Our study may provide a universal strategy for the construction of delivery platforms for efficient BBB crossing and brain drug delivery.

Immune cell receptor-specific nanoparticles as a potent adjuvant for nasal split influenza vaccine delivery

Mucosal delivery systems have gained much attention as effective way for antigen delivery that induces both systemic and mucosal immunity. However, mucosal vaccination faces the challenges of mucus barrier and effective antigen uptake and presentation. In particular, split, subunit and recombinant protein vaccines that do not have an intact pathogen structure lack the efficiency to stimulate mucosal immunity. In this study, poly (lactic acid-co-glycolic acid-polyethylene glycol) (PLGA-PEG) block copolymers were modified by mannose to form a PLGA-PEG-Man conjugate (mannose modified PLGA-PEG), which were characterized. The novel nanoparticles (NPs) prepared with this material had a particle size of about 150 nm and a zeta potential of -15 mV, and possessed ideal mucus permeability, immune cell targeting, stability and low toxicity. Finally, PLGA-PEG-Man nanoparticles (PLGA-PEG-Man NPs) were successfully applied for intranasal delivery of split influenza vaccine in rat for the first time, which triggered strong systemic and mucosal immune responses. These studies suggest that PLGA-PEG-Man NPs could function as competitive potential nano-adjuvants to address the challenge of inefficient mucosal delivery of non-allopathogenic antigens.

Impact of polyethylene glycol and polydopamine coatings on the performance of camptothecin-loaded liposomes for localised treatment of colorectal cancer

Orally delivered therapeutics offer great promise for localized treatment of colorectal cancer. However, various natural barriers along the gastrointestinal tract need to be tackled to allow effective drug delivery to tumoral sites.

Photoacoustic Imaging Endometriosis Lesions with Nanoparticulate Polydopamine as a Contrast Agent

Endometriosis (EM) is a prevalent and debilitating gynecological disorder primarily affecting women of reproductive age. The diagnosis of EM is historically hampered by delays, owing to the absence of reliable diagnostic and monitoring techniques. Herein, it is reported that photoacoustic imaging can be a noninvasive modality for deep-seated EM by employing a hyaluronic-acid-modified polydopamine (PDA@HA) nanoparticle as the contrast agent. The PDA@HA nanoparticles exhibit inherent absorption and photothermal effects when exposed to near-infrared light, proficiently converting thermal energy into sound waves. Leveraging the targeting properties of HA, distinct photoacoustic signals emanating from the periphery of orthotopic EM lesions are observed. These findings are corroborated through anatomical observations and in vivo experiments involving mice with green fluorescent protein-labeled EM lesions. Moreover, the changes in photoacoustic intensity over a 24 h period reflect the dynamic evolution of PDA@HA nanoparticle biodistribution. Through the utilization of a photoacoustic ultrasound modality, in vivo assessments of EM lesion volumes are conducted. This innovative approach not only facilitates real-time monitoring of the therapeutic kinetics of candidate drugs but also obviates the need for the sacrifice of experimental mice. As such, this study presents a promising avenue for enhancing the diagnosis and drug-screening processes of EM.

Nanocarriers transport across the gastrointestinal barriers: The contribution to oral bioavailability via blood circulation and lymphatic pathway

Oral administration is the preferred route of drug delivery in clinical practice due to its noninvasiveness, safety, convenience, and high patient compliance. The gastrointestinal tract (GIT) plays a crucial role in facilitating the targeted delivery of oral drugs. However, the GIT presents multiple barriers that impede drug absorption, including the gastric barrier in the stomach and the mucus and epithelial barriers in the intestine. In recent decades, nanotechnology has emerged as a promising approach for overcoming these challenges by utilizing nanocarrier-based drug delivery systems such as liposomes, micelles, polymeric nanoparticles, solid lipid nanoparticles, and inorganic nanoparticles. Encapsulating drugs within nanocarriers not only protects them from degradation but also enhances their transport and absorption across the GIT, ultimately improving oral bioavailability. The aim of this review is to elucidate the mechanisms underlying nanocarrier-mediated transportation across the GIT into systemic circulation via both the blood circulation and lymphatic pathway.

In Vitro/In Vivo Preparation and Evaluation of cRGDyK Peptide-Modified Polydopamine-Bridged Paclitaxel-Loaded Nanoparticles

Cancer remains a disease with one of the highest mortality rates worldwide. The poor water solubility and tissue selectivity of commonly used chemotherapeutic agents contribute to their poor efficacy and serious adverse effects. This study proposes an alternative to the traditional physicochemically combined modifications used to develop targeted drug delivery systems, involving a simpler surface modification strategy. cRGDyK peptide (RGD)-modified PLGA nanoparticles (NPs) loaded with paclitaxel were constructed by coating the NP surfaces with polydopamine (PD). The average particle size of the produced NPs was 137.6 ± 2.9 nm, with an encapsulation rate of over 80%. In vitro release tests showed that the NPs had pH-responsive drug release properties. Cellular uptake experiments showed that the uptake of modified NPs by tumor cells was significantly better than that of unmodified NPs. A tumor cytotoxicity assay demonstrated that the modified NPs had a lower IC50 and greater cytotoxicity than those of unmodified NPs and commercially available paclitaxel formulations. An in vitro cytotoxicity study indicated good biosafety. A tumor model in female BALB/c rats was established using murine-derived breast cancer 4T1 cells. RGD-modified NPs had the highest tumor-weight suppression rate, which was higher than that of the commercially available formulation. PTX-PD-RGD-NPs can overcome the limitations of antitumor drugs, reduce drug toxicity, and increase efficacy, showing promising potential in cancer therapy.

Engineered microparticles of hyaluronic acid hydrogel for controlled pulmonary release of salbutamol sulphate

Most pulmonary drugs are immediate-release formulations with short duration of action. Controlled release systems provide the ability to deliver drugs at a controlled rate, which helps maintain drug concentrations within the therapeutic window for a longer period of time. This study aimed to produce microparticles (MPs) of hyaluronic acid hydrogel (HAGA) loaded with salbutamol sulphate (SS) for controlled release in the lung. The drug-loaded MPs were prepared via spray drying and underwent extensive characterization, which revealed that SS was successfully encapsulated in the HAGA matrix. The prepared MPs (denoted as HASS) ranged in size from 1.6 ± 0.4 μm to 1.7 ± 0.5 μm with a fine particle fraction (FPF) of 48-56% and showed improvement in aerodynamic properties compared to unloaded HAGA hydrogel MPs. In vitro drug release studies performed in a Transwell system confirmed the potential of the particles to release the drug in a sustained manner. The drug release was delayed for all formulations, with a t63 between 5 and 30 min, compared to <1min for pure SS. This study advances our understanding of the formulation of a highly soluble drug to achieve controlled release in the lung.

pH-Mediated Mucus Penetration of Zwitterionic Polydopamine-Modified Silica Nanoparticles

Zwitterionic polymers have emerged as promising trans-mucus nanocarriers due to their superior antifouling properties. However, for pH-sensitive zwitterionic polymers, the effect of the pH microenvironment on their trans-mucus fate remains unclear. In this work, we prepared a library of zwitterionic polydopamine-modified silica nanoparticles (SiNPs-PDA) with an isoelectric point of 5.6. Multiple-particle tracking showed that diffusion of SiNPs-PDA in mucus with a pH value of 5.6 was 3 times faster than that in mucus with pH value 3.0 or 7.0. Biophysical analysis found that the trans-mucus behavior of SiNPs-PDA was mediated by hydrophobic and electrostatic interactions and hydrogen bonding between mucin and the particles. Furthermore, the particle distribution in the stomach, intestine, and lung demonstrated the pH-mediated mucus penetration behavior of the SiNPs-PDA. This study reveals the pH-mediated mucus penetration behavior of zwitterionic nanomaterials, which provides rational design strategies for zwitterionic polymers as nanocarriers in various mucus microenvironments.

Functionalization of and through Melanin: Strategies and Bio-Applications

A unique feature of nanoparticles for bio-application is the ease of achieving multi-functionality through covalent and non-covalent functionalization. In this way, multiple therapeutic actions, including chemical, photothermal and photodynamic activity, can be combined with different bio-imaging modalities, such as magnetic resonance, photoacoustic, and fluorescence imaging, in a theragnostic approach. In this context, melanin-related nanomaterials possess unique features since they are intrinsically biocompatible and, due to their optical and electronic properties, are themselves very efficient photothermal agents, efficient antioxidants, and photoacoustic contrast agents. Moreover, these materials present a unique versatility of functionalization, which makes them ideal for the design of multifunctional platforms for nanomedicine integrating new functions such as drug delivery and controlled release, gene therapy, or contrast ability in magnetic resonance and fluorescence imaging. In this review, the most relevant and recent examples of melanin-based multi-functionalized nanosystems are discussed, highlighting the different methods of functionalization and, in particular, distinguishing pre-functionalization and post-functionalization. In the meantime, the properties of melanin coatings employable for the functionalization of a variety of material substrates are also briefly introduced, especially in order to explain the origin of the versatility of melanin functionalization. In the final part, the most relevant critical issues related to melanin functionalization that may arise during the design of multifunctional melanin-like nanoplatforms for nanomedicine and bio-application are listed and discussed.

Fabrication of a composite 3D-printed titanium alloy combined with controlled in situ drug release to prevent osteosarcoma recurrence

Osteosarcoma is a malignant bone tumor occurring in adolescents. Surgery combined with adjuvant or neoadjuvant chemotherapy is the standard treatment. However, systemic chemotherapy is associated with serious side effects and a high risk of postoperative tumor recurrence, leading to a high amputation rate and mortality in cancer patients. Implant materials that can simultaneously repair large bone defects and prevent osteosarcoma recurrence are in urgent need. Herein, an intelligent system comprising 3D-printed titanium scaffold (TS) and pH-responsive PEGylated paclitaxel prodrugs was fabricated for bone defect reconstruction and recurrence prevention following osteosarcoma surgery. The drug-loaded implants exhibited excellent stability and biocompatibility for supporting the activity of bone stem cells under normal body fluid conditions and the rapid release of drugs in response to faintly acidic environments. An in vitro study demonstrated that five human osteosarcoma cell lines could be efficiently eradicated by paclitaxel released in an acidic microenvironment. Using mice models, we demonstrated that the drug-loaded TS can enable a pH-responsive treatment of postoperative tumors and effectively prevent osteosarcoma recurrence. Therefore, local implantation of this composite scaffold may be a promising topical therapeutic method to prevent osteosarcoma recurrence.

In Situ Polymerization-Mediated Antigen Presentation

Activating antigen-presenting cells is essential to generate adaptive immunity, while the efficacy of conventional activation strategies remains unsatisfactory due to suboptimal antigen-specific priming. Here, in situ polymerization-mediated antigen presentation (IPAP) is described, in which antigen-loaded nanovaccines are spontaneously formed and efficiently anchored onto the surface of dendritic cells in vivo through co-deposition with dopamine. The resulting chemically bound nanovaccines can promote antigen presentation by elevating macropinocytosis-based cell uptake and reducing lysosome-related antigen degradation. IPAP is able to prolong the duration of antigen reservation in the injection site and enhance subsequent accumulation in the draining lymph nodes, thereby eliciting robust antigen-specific cellular and humoral immune responses. IPAP is also applicable for different antigens and capable of circumventing the disadvantages of complicated preparation and purification. By implementation with ovalbumin, IPAP induces a significant protective immunity against ovalbumin-overexpressing tumor cell challenge in a prophylactic murine model. The use of the SARS-CoV-2 Spike protein S1 subunit also remarkably increases the production of S1-specific immunoglobulin G in mice. IPAP offers a unique strategy for stimulating antigen-presenting cells to boost antigen-specific adaptive responses and proposes a facile yet versatile method for immunization against various diseases.

Palmitic acid- and cysteine-functionalized nanoparticles overcome mucus and epithelial barrier for oral delivery of drug

Nanoparticles (NPs) used for oral administration have greatly improved drug bioavailability and therapeutic efficacy. Nevertheless, NPs are limited by biological barriers, such as gastrointestinal degradation, mucus barrier, and epithelial barrier. To solve these problems, we developed the PA-N-2-HACC-Cys NPs loaded with anti-inflammatory hydrophobic drug curcumin (CUR) (CUR@PA-N-2-HACC-Cys NPs) by self-assembled amphiphilic polymer, composed of the N-2-Hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC), hydrophobic palmitic acid (PA), and cysteine (Cys). After oral administration, the CUR@PA-N-2-HACC-Cys NPs had good stability and sustained release under gastrointestinal conditions, followed by adhering to the intestine to achieve drug mucosal delivery. Additionally, the NPs could penetrate mucus and epithelial barriers to promote cellular uptake. The CUR@PA-N-2-HACC-Cys NPs could open tight junctions between cells for transepithelial transport while striking a balance between mucus interaction and diffusion through mucus. Notably, the CUR@PA-N-2-HACC-Cys NPs improved the oral bioavailability of CUR, which remarkably relieved colitis symptoms and promoted mucosal epithelial repair. Our findings proved that the CUR@PA-N-2-HACC-Cys NPs had excellent biocompatibility, could overcome mucus and epithelial barriers, and had significant application prospects for oral delivery of the hydrophobic drugs.

Nose to brain delivery of ibudilast micelles for treatment of multiple sclerosis in an experimental autoimmune encephalomyelitis animal model

Multiple sclerosis is a chronic inflammatory disease of the central nervous system ultimate to neurodegeneration and demyelination. Ibudilast is a phosphodiesterase inhibitor, effective on the function of glial cells and lymphocytes, and inhibits the release of TNF-α by inflammatory cells. Dysregulation of glia is one of the most important pathological causes of MS. Therefore, ibudilast as a glial attenuator can be a useful treatment. The objective of the present study was to investigate the effect of nasal spray of polydopamine coated micelles of surfactin, a biosurfactant, loaded with ibudilast on its brain targeted delivery and effectiveness in remylination and neuroprotection in animal model of MS. In animal studies the micelles were administrated intranasally in different doses of 10, 25 and 50 mg/kg/day in C57/BL6 mice immunized by experimental autoimmune encephalomyelitis (EAE) model. The results of Luxol fast blue staining indicated increment in myelin fiber percent more significantly (p<0.05) in the groups treated with the polydopamine coated micelles (PDAM) compared to nasal spray of free drug or oral administration. These formulations also increased expression of Mbp, Olig2 and Mog genes in the corpus callosum. These results suggest a positive outcome of polydopamine coated micelles loaded with ibudilast in active MS as an anti-inflammatory and neuroprotective agent.

Airway mucus in pulmonary diseases: Muco-adhesive and muco-penetrating particles to overcome the airway mucus barriers

Airway mucus is a complex viscoelastic gel that provides a defensive physical barrier and shields the airway epithelium by trapping inhaled foreign pathogens and facilitating their removal via mucociliary clearance (MCC). In patients with respiratory diseases, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), non-CF bronchiectasis, and asthma, an increase in crosslinking and physical entanglement of mucin polymers as well as mucus dehydration often alters and typically reduces mucus mesh network pore size, which reduces neutrophil migration, decreases pathogen capture, sustains bacterial infection, and accelerates lung function decline. Conventional aerosol particles containing hydrophobic drugs are rapidly captured and removed by MCC. Therefore, it is critical to design aerosol delivery systems with the appropriate size and surface chemistry that can improve drug retention and absorption with the goal of increased efficacy. Biodegradable muco-adhesive particles (MAPs) and muco-penetrating particles (MPPs) have been engineered to achieve effective pulmonary delivery and extend drug residence time in the lungs. MAPs can be used to target mucus as they get trapped in airway mucus by steric obstruction and/or adhesion. MPPs avoid muco-adhesion and are designed to have a particle size smaller than the mucus network, enhancing lung retention of particles as well as transport to the respiratory epithelial layer and drug absorption. In this review, we aim to provide insight into the composition of airway mucus, rheological characteristics of airway mucus in healthy and diseased subjects, the most recent techniques to study the flow dynamics and particle diffusion in airway mucus (in particular, multiple particle tracking, MPT), and the advancements in engineering MPPs that have contributed to improved airway mucus penetration, lung distribution, and retention.

Surface design of nanocarriers: Key to more efficient oral drug delivery systems

As nanocarriers (NCs) can improve the solubility of drugs, prevent their degradation by gastrointestinal (GI) enzymes and promote their transport across the mucus gel layer and absorption membrane, the oral bioavailability of these drugs can be substantially enhanced. All these properties of NCs including self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), liposomes, polymeric nanoparticles, inorganic nanoparticles and polymeric micelles depend mainly on their surface chemistry. In particular, interaction with food, digestive enzymes, bile salts and electrolytes, diffusion behaviour across the mucus gel layer and fate on the absorption membrane are determined by their surface. Bioinert surfaces limiting interactions with gastrointestinal fluid and content as well as with mucus, adhesive surfaces providing an intimate contact with the GI mucosa and absorption enhancing surfaces can be designed. Furthermore, charge converting surfaces shifting their zeta potential from negative to positive directly at the absorption membrane and surfaces providing a targeted drug release are advantageous. In addition to these passive surfaces, even active surfaces cleaving mucus glycoproteins on their way through the mucus gel layer can be created. Within this review, we provide an overview on these different surfaces and discuss their impact on the performance of NCs in the GI tract.

Mucus Penetration of Surface-Engineered Nanoparticles in Various pH Microenvironments

The penetration behavior of nanoparticles in mucous depends on physicochemical properties of the nanoparticles and the mucus microenvironment, due to particle-mucin interactions and the presence of the mucin mesh space filtration effect. To date, it is still unclear how the surface properties of nanoparticles influence their mucus penetration behaviors in various physiological and pathophysiological conditions. In this study, we have prepared a comprehensive library of amine-, carboxyl-, and PEG-modified silica nanoparticles (SNPs) with controlled surface ligand densities. Using multiple particle tracking, we have studied the mechanism responsible for the mucus penetration behaviors of these SNPs. It was found that PEG- and amine-modified SNPs exhibited pH-independent immobilization under iso-density conditions, while carboxyl-modified SNPs exhibited enhanced movement only in weakly alkaline mucus. Biophysical characterizations demonstrated that amine- and carboxyl-modified SNPs were trapped in mucus due to electrostatic interactions and hydrogen bonding with mucin. In contrast, high-density PEGylated surface formed a brush conformation that shields particle-mucin interactions. We have further investigated the surface property-dependent mucus penetration behavior using a murine airway distribution model. This study provides insights for designing efficient transmucosal nanocarriers for prevention and treatment of pulmonary diseases.

Mucus-penetrating dendritic mesoporous silica nanoparticle loading drug nanocrystal clusters to enhance permeation and intestinal absorption

Multiple gastrointestinal barriers (mucus clearance and epithelium barrier) are the main challenges in the oral administration of nanocarriers. To achieve efficient mucus penetration and epithelial absorption, a novel strategy based on mesoporous silica nanoparticles with dendritic superstructure, hydrophilicity, and nearly neutral-charged modification was designed. The mPEG covalently grafted dendritic mesoporous silica nanoparticles (mPEG-DMSNs) had a particle size of about 200 nm and a loading capacity of up to 50% andrographolide (AG) as a nanocrystal cluster in the mesoporous structure. This dual strategy of combining with the surface topography structure and hydrophilic modification maintained a high mucus permeability and showed an increase in cell absorption. The mPEG-DMSN formulation also exhibited effective transepithelial transport and intestinal tract distribution. The pharmacokinetics study demonstrated that compared with other AG formulations, the andrographolide nanocrystals-loaded mPEG-DMSN (AG@mPEG-DMSN) exhibited much higher bioavailability. Also, AG@mPEG-DMSN could significantly improve the in vitro and in vivo anti-inflammatory efficacy of AG. In summary, mPEG-DMSN offers an interesting strategy to overcome the mucus clearance and epithelium barriers of the gastrointestinal tract.

An antioxidant and antibacterial polydopamine-modified thermo-sensitive hydrogel dressing for Staphylococcus aureus-infected wound healing

Bacteria-infected wound healing is a complex and chronic process that poses a great threat to human health. A thermo-sensitive hydrogel that undergoes a sol-gel transition at body temperature is an attractive wound dressing for healing acceleration and infection prevention. In this paper, we present a thermo-sensitive and reactive oxygen species (ROS)-scavenging hydrogel based on polydopamine modified poly(ε-caprolactone-co-glycolide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-glycolide) (PDA/P2) triblock copolymer. The PDA/P2 solution at a concentration of 30 wt% could form a gel at 34-38 °C. The ROS-scavenging ability of PDA/P2 was demonstrated by DPPH and ABTS assays and intracellular ROS downregulation in RAW264.7 cells. Furthermore, silver nanoparticles were encapsulated in the hydrogel (PDA/P2-4@Ag gel) to provide antibacterial activity against E. coli and S. aureus. An in vivo S. aureus-infected rat model demonstrated that the PDA/P2-4@Ag hydrogel dressing could promote wound healing via inhibiting bacterial growth, alleviating the inflammatory response, and inducing angiogenesis and collagen deposition. This study provides a new strategy to prepare temperature-sensitive hydrogel-based multifunctional wound dressings.

Applications of polydopaminic nanomaterials in mucosal drug delivery

Polydopamine (PDA) is a biopolymer with unique physicochemical properties, including free-radical scavenging, high photothermal conversion efficiency, biocompatibility, biodegradability, excellent fluorescent and theranostic capacity due to their abundant surface chemistry. Thus, PDA is used for a myriad of applications including drug delivery, biosensing, imaging and cancer therapy. Recent reports present a new functionality of PDA as a coating nanomaterial, with major implications in mucosal drug delivery applications, particularly muco-adhesion and muco-penetration. However, this application has received minimal traction in the literature. In this review, we present the physicochemical and functional properties of PDA and highlight its key biomedical applications, especially in cancer therapy. A detailed presentation of the role of PDA as a promising coating material for nanoparticulate carriers intended for mucosal delivery forms the core aspect of the review. Finally, a reflection on key considerations and challenges in the utilizing PDA for mucosal drug delivery, along with the possibilities of translation to clinical studies is expounded.

Hypoxia Alleviated and One Photo-Triggered Thermal/Dynamic Nanoplatform for Immunogenic Cell Death-Initiated Cancer Immunotherapy

Immunogenic cell death (ICD) induced by treatment modalities like chemotherapy, radiotherapy, and photothermal and photodynamic therapy has shown great potential to improve the low response rate of various solid tumors in cancer immunotherapy. However, extensive studies have revealed that the efficacy of cancer treatment is limited by the hypoxia and immunosuppression in the tumor microenvironment (TME). To address these challenges, a hypoxia alleviated and one phototriggered thermal/dynamic nanoplatform based on MnO₂@PDA/ICG-BSA (MPIB) is developed for oxygen (O₂) self-supply enhanced cancer phototherapy (PT). First, MnO₂ transfers intracellular overexpression H₂O₂ into O₂ in the acidic TME through its catalase-like activity to improve the hypoxia and also provide O₂ for the following photodynamic therapy. Then, under single NIR-808 nm light irradiation (called the "phototherapeutic window"), excellent photothermal and photodynamic performance of the MPIB is activated for combined PT. Finally, assisted with immune adjuvant cytosine-phospho-guanine, obvious ICD and systemic antitumor immunity was elicited in PT-treated mice and demonstrated significant growth inhibition on distant tumors. This MPIB-based nanoplatform highlights the promise to overcome the limitations of hypoxia and also challenges of immunosuppressive tumor microenvironments for improved cancer immunotherapy.

Applications of Nano/Micromotors for Treatment and Diagnosis in Biological Lumens

Natural biological lumens in the human body, such as blood vessels and the gastrointestinal tract, are important to the delivery of materials. Depending on the anatomic features of these biological lumens, the invention of nano/micromotors could automatically locomote targeted sites for disease treatment and diagnosis. These nano/micromotors are designed to utilize chemical, physical, or even hybrid power in self-propulsion or propulsion by external forces. In this review, the research progress of nano/micromotors is summarized with regard to treatment and diagnosis in different biological lumens. Challenges to the development of nano/micromotors more suitable for specific biological lumens are discussed, and the overlooked biological lumens are indicated for further studies.

Tumor immunotherapy boosted by R837 nanocrystals through combining chemotherapy and mild hyperthermia

Melanoma is a malignant skin cancer that is prone to metastasis in the early stage and has a poor prognosis. Immunomodulatory therapy for melanoma has been a hot research topic in recent years. However, low immune cell infiltration and loss of tumor immunogenicity may occur in tumors, resulting in low response rates to immunotherapy. Thus, immunomodulatory therapy is usually used in combination with chemotherapy and radiotherapy. Development of combined therapeutic strategies with low systemic toxicity, high immune responsiveness and long-term inhibition of metastasis and recurrence of melanoma is the goal of current research. In this study, the insoluble immune adjuvant imiquimod (R837) was prepared as nanocrystals and coated with polydopamine (PDA) to form R837@PDA, which was then loaded into chitosan hydrogel (CGP) to form the drug-loaded gel system, R837@PDA@CGP (RPC), to combine immunomodulation effects, induction of immunogenic cell death (ICD) effects and immune-enhancement effects. After treatment with RPC, ICD in melanoma was induced, and the infiltration rate of cytotoxic T cells (CTLs) in melanoma was also significantly enhanced, which turned the tumor itself into an in situ vaccine and boosted the cancer-immunity cycle at the tumor site. Therefore, melanoma growth, metastasis and recurrence were notably inhibited.

From Static to Dynamic: A Review on the Role of Mucus Heterogeneity in Particle and Microbial Transport

Mucus layers (McLs) are on the front line of the human defense system that protect us from foreign abiotic/biotic particles (e.g., airborne virus SARS-CoV-2) and lubricates our organs. Recently, the impact of McLs on human health (e.g., nutrient absorption and drug delivery) and diseases (e.g., infections and cancers) has been studied extensively, yet their mechanisms are still not fully understood due to their high variety among organs and individuals. We characterize these variances as the heterogeneity of McLs, which lies in the thickness, composition, and physiology, making the systematic research on the roles of McLs in human health and diseases very challenging. To advance mucosal organoids and develop effective drug delivery systems, a comprehensive understanding of McLs' heterogeneity and how it impacts mucus physiology is urgently needed. When the role of airway mucus in the penetration and transmission of coronavirus (CoV) is considered, this understanding may also enable a better explanation and prediction of the CoV's behavior. Hence, in this Review, we summarize the variances of McLs among organs, health conditions, and experimental settings as well as recent advances in experimental measurements, data analysis, and model development for simulations.

Polydopamine Biomaterials for Skin Regeneration

Designing biomaterials capable of biomimicking wound healing and skin regeneration has been receiving increasing attention recently. Some biopolymers behave similarly to the extracellular matrix (ECM), supporting biointerfacial adhesion and intrinsic cellular interactions. Polydopamine (PDA) is a natural bioadhesive and bioactive polymer that endows high chemical versatility, making it an exciting candidate for a wide range of biomedical applications. Moreover, biomaterials based on PDA and its derivatives have near-infrared (NIR) absorption, excellent biocompatibility, intrinsic antioxidative activity, antibacterial activity, and cell affinity. PDA can regulate cell behavior by controlling signal transduction pathways. It governs the focal adhesion behavior of cells at the biomaterials interface. These features make melanin-like PDA a fascinating biomaterial for wound healing and skin regeneration. This paper overviews PDA-based biomaterials' synthesis, properties, and interactions with biological entities. Furthermore, the utilization of PDA nano- and microstructures as a constituent of wound-dressing formulations is highlighted.

Pulmonary delivery nanomedicines towards circumventing physiological barriers: Strategies and characterization approaches

Pulmonary delivery of nanomedicines is very promising in lung local disease treatments whereas several physiological barriers limit its application via the interaction with inhaled nanomedicines, namely bio-nano interactions. These bio-nano interactions may affect the pulmonary fate of nanomedicines and impede the distribution of nanomedicines in its targeted region, and subsequently undermine the therapeutic efficacy. Pulmonary diseases are under worse scenarios as the altered physiological barriers generally induce stronger bio-nano interactions. To mitigate the bio-nano interactions and regulate the pulmonary fate of nanomedicines, a number of manipulating strategies were established based on size control, surface modification, charge tuning and co-delivery of mucolytic agents. Visualized and non-visualized characterizations can be employed to validate the robustness of the proposed strategies. This review provides a guiding overview of the physiological barriers affecting the in vivo fate of inhaled nanomedicines, the manipulating strategies, and the validation methods, which will assist with the rational design and application of pulmonary nanomedicine.

Extracellular polymeric substances mediate defect generation and phytotoxicity of single-layer MoS2

Two-dimensional transition metal dichalcogenide (TMDC) nanomaterials have attracted tremendous research interest in various fields, but the effects of eco-corona formation on the transformation mechanisms and ecological risk of TMDCs remain largely unknown. The effect of eco-corona formation on TMDC reactivity was explored using extracellular polymeric substances (EPS) as the eco-corona constituents and single-layer molybdenum disulfide (SLMoS₂) as the model TMDC. We found that EPS promoted lattice distortion and the formation of defects (sulfur vacancies and pores) on SLMoS₂ after it was aged (precoated) with EPS under simulated visible-light irradiation. In addition, the EPS-corona induced higher free radical (especially hyperoxide radical) photogeneration by SLMoS₂. Furthermore, compared to pristine SLMoS₂, SLMoS₂-EPS exhibited stronger developmental inhibition, oxidative stress, membrane damage, photosynthetic toxicity and metabolic perturbation effects on Chlorella vulgaris. However, the endocytosis pathway (especially macropinocytosis) of SLMoS₂ entry into C. vulgaris was inhibited by EPS. Metabolic and transcriptomic analyses revealed that the enhanced toxicity of SLMoS₂-EPS was associated with the downregulation of fatty acid metabolism and transcription related to photosynthesis, respectively. The present work provides mechanistic insights into the roles of the EPS-corona on the environmental transformation and phytotoxicity of TMDCs, which benefit environmental safety assessments and sustainable applications of engineered nanomaterials.