On the size-dependent internalization of sub-hundred polymeric nanoparticles

Nanocarriers for targeted drug delivery in the vascular system: focus on endothelium

Endothelial cells (ECs) are pivotal in maintaining vascular health, regulating hemodynamics, and modulating inflammatory responses. Nanocarriers hold transformative potential for precise drug delivery within the vascular system, particularly targeting ECs for therapeutic purposes. However, the complex interactions between vascular ECs and nanocarriers present significant challenges for the development and clinical translation of nanotherapeutics. This review assesses recent advancements and key strategies in employing nanocarriers for drug delivery to vascular ECs. It suggested that through precise physicochemical design and surface modifications, nanocarriers can enhance targeting specificity and improve drug internalization efficiency in ECs. Additionally, we elaborated on the applications of nanocarriers specifically designed for targeting ECs in the treatment of cardiovascular diseases, cancer metastasis, and inflammatory disorders. Despite these advancements, safety concerns, the complexity of in vivo processes, and the challenge of achieving subcellular drug delivery remain significant obstacles to the effective targeting of ECs with nanocarriers. A comprehensive understanding of endothelial cell biology and its interaction with nanocarriers is crucial for realizing the full potential of targeted drug delivery systems.

Endocytosis: the match point of nanoparticle-based cancer therapy

Nanomedicine has inspired a ground-breaking strategy for cancer therapy. By intelligently assembling diverse moieties to form nanoparticles, numerous functionalities such as controlled release, synergistic efficiency, and in situ killing can be achieved. The emerging nanoparticles have been designed with elevated targeting efficiency as targeting cancer cells is the primary requirement for nanoparticles. However, effective targeting does not guarantee therapeutic effects as endocytosis is a prerequisite for nanoparticles to exert effects. The recent decade has witnessed the rapid development of endocytosis-oriented nanoparticles, and this review subtly analyzes, categorizes, and exemplifies these nanoparticles according to their biological internalization patterns, and the correlation between the endocytosis mechanism and the property of nanoparticles is bridged. Based on the interdisciplinary vision, the present challenges and future perspectives of nanoparticle design for successful endocytosis are discussed, highlighting the potential strategies for the future development of endocytosis-oriented nanoparticles, thus facilitating the endocytosis-oriented strategy from bench to bedside. The undeniable fact is that endocytosis-oriented nanoparticles will definitely bring new blood to the next generation of advanced cancer therapies.

How big nanoparticles carry small ones into cells: Actions captured by transmission electron microscopy

The mechanism of cellular uptake of nanoparticles (NPs) is critical for both bio-application and risk evaluation of NPs, but is still not fully understood due to many influencing factors, among which particle size is a major one. Recent studies show that there is an unusual interplay among differently-sized NPs when they simultaneously interact with cells, e.g., 100 nm silica NPs (SNP100) can promote the cellular uptake of 50 nm silica NPs (SNP50). However, the underlying mechanism is still unclear. Herein, we manage to capture individual endocytosis events in HeLa and A549 cells after co-exposure to SNP50 and SNP100 for 2 hours, using transmission electron microscopy (TEM). TEM images clearly show that there is a size threshold for SNPs to trigger clathrin-mediated endocytosis: One single SNP100 can efficiently trigger it, while it needs about 6 SNP50 to do so. Remarkably, TEM also captures how SNP100 triggers the endocytosis and carries nearby SNP50 into cells, and statistical data show that the average number of SNP50 carried by one SNP100 could be up to about 6. In addition, the mechanism was further verified by using mixed 60 nm SNPs (SNP60) and SNP100. This mechanism has an immediate implication for the design of drug-deliver nanocarriers, and as a proof-of-concept, more catalase functionalized SNP50 (CAT@SNP50) was delivered into HeLa cells by adding some SNP100, resulting in a more severe cell damage compared to CAT@SNP50 alone under same conditions. The findings have general impact on the nanotoxicity study of NP products that commonly have certain distributions in size, and provide new insights on designing efficient drug delivery systems by deliberately control the combinations of NPs of different sizes.

Intestinal lymphatic transport of Smilax china L. pectic polysaccharide via Peyer's patches and its uptake and transport mechanisms in mononuclear phagocytes

Recently, the intestinal lymphatic transport based on Peyer's patches (PPs) is emerging as a promising absorption pathway for natural polysaccharides. Herein, the aim of this study is to investigate the PP-based oral absorption of a pectic polysaccharide from Smilax china L. (SCLP), as well as its uptake and transport mechanisms in related immune cells. Taking advantages of the traceability of fluorescently labeled SCLP, we confirmed that SCLP could be absorbed into PPs and captured by their mononuclear phagocytes (dendritic cells and macrophages) following oral administration. Subsequently, the systematic in vitro study suggested that the endocytic mechanisms of SCLP by model mononuclear phagocytes (BMDCs and RAW264.7 cells) mainly involved caveolae-mediated endocytosis, macropinocytosis and phagocytosis. More importantly, SCLP directly binds and interacts with toll-like receptor 2 (TLR2) and galectin 3 (Gal-3) receptor, and was taken up by mononuclear phagocytes in receptor-mediated manner. After internalization, SCLP was intracellularly transported primarily through endolysosomal pathway and ultimately localized in lysosomes. In summary, this work reveals novel information and perspectives about the in vivo fate of SCLP, which will contribute to further research and utilization of SCLP and other pectic polysaccharides.

Unlocking the Mitochondria for Nanomedicine-based Treatments: Overcoming Biological Barriers, Improving Designs, and Selecting Verification Techniques

Enhanced targeting approaches will support the treatment of diseases associated with dysfunctional mitochondria, which play critical roles in energy generation and cell survival. Obstacles to mitochondria-specific targeting include the presence of distinct biological barriers and the need to pass through (or avoid) various cell internalization mechanisms. A range of studies have reported the design of mitochondrially-targeted nanomedicines that navigate the complex routes required to influence mitochondrial function; nonetheless, a significant journey lies ahead before mitochondrially-targeted nanomedicines become suitable for clinical use. Moving swiftly forward will require safety studies, in vivo assays confirming effectiveness, and methodologies to validate mitochondria-targeted nanomedicines' subcellular location/activity. From a nanomedicine standpoint, we describe the biological routes involved (from administration to arrival within the mitochondria), the features influencing rational design, and the techniques used to identify/validate successful targeting. Overall, rationally-designed mitochondria-targeted-based nanomedicines hold great promise for precise subcellular therapeutic delivery.

Nanoparticles Internalization through HIP-55-Dependent Clathrin Endocytosis Pathway

Nanoparticles are promising tools for biomedicine. Many nanoparticles are internalized to function. Clathrin-mediated endocytosis is one of the most important mechanisms for nanoparticle internalization. However, the regulatory mechanism of clathrin-mediated nanoparticle endocytosis is still unclear. Here, we report that the adapter protein HIP-55 regulates clathrin-mediated nanoparticle endocytosis. CdSe/ZnS quantum dots (QDs), a typical nanoparticle, enter cells through the HIP-55-dependent clathrin endocytosis pathway. Both pharmacological inhibitor and genetic intervention demonstrate that QDs enter cells through clathrin-mediated endocytosis. HIP-55 can interact with clathrin and promote clathrin-mediated QDs endocytosis. Furthermore, HIP-55 ΔADF which is defective in F-actin binding fails to promote QDs endocytosis, indicating HIP-55 promotes clathrin-mediated QDs endocytosis depending on interaction with F-actin. In vivo, HIP-55 knockout also inhibits endocytosis of QDs. These findings reveal that HIP-55 acts as an intrinsic regulator for clathrin-mediated nanoparticle endocytosis, providing new insight into the nanoparticle internalization and a new strategy for nanodrug enrichment in target cells.

Intracellular Trafficking of Size-Tuned Nanoparticles for Drug Delivery

Polymeric nanoparticles (NPs) are widely used as drug delivery systems in nanomedicine. Despite their widespread application, a comprehensive understanding of their intracellular trafficking remains elusive. In the present study, we focused on exploring the impact of a 20 nm difference in size on NP performance, including drug delivery capabilities and intracellular trafficking. For that, poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PLGA-PEG) NPs with sizes of 50 and 70 nm were precisely tailored. To assess their prowess in encapsulating and releasing therapeutic agents, we have employed doxorubicin (Dox), a well-established anticancer drug widely utilized in clinical settings, as a model drug. Then, the beneficial effect of the developed nanoformulations was evaluated in breast cancer cells. Finally, we performed a semiquantitative analysis of both NPs' uptake and intracellular localization by immunostaining lysosomes, early endosomes, and recycling endosomes. The results show that the smaller NPs (50 nm) were able to reduce the metabolic activity of cancer cells more efficiently than NPs of 70 nm, in a time and concentration-dependent manner. These findings are corroborated by intracellular trafficking studies that reveal an earlier and higher uptake of NPs, with 50 nm compared to the 70 nm ones, by the breast cancer cells. Consequently, this study demonstrates that NP size, even in small increments, has an important impact on their therapeutic effect.

Orally-administered nanomedicine systems targeting colon inflammation for the treatment of inflammatory bowel disease: latest advances

Inflammatory bowel disease (IBD) is a chronic and idiopathic condition that results in inflammation of the gastrointestinal tract, leading to conditions such as ulcerative colitis and Crohn's disease. Commonly used treatments for IBD include anti-inflammatory drugs, immunosuppressants, and antibiotics. Fecal microbiota transplantation is also being explored as a potential treatment method; however, these drugs may lead to systemic side effects. Oral administration is preferred for IBD treatment, but accurately locating the inflamed area in the colon is challenging due to multiple physiological barriers. Nanoparticle drug delivery systems possess unique physicochemical properties that enable precise delivery to the target site for IBD treatment, exploiting the increased permeability and retention effect of inflamed intestines. The first part of this review comprehensively introduces the pathophysiological environment of IBD, covering the gastrointestinal pH, various enzymes in the pathway, transport time, intestinal mucus, intestinal epithelium, intestinal immune cells, and intestinal microbiota. The second part focuses on the latest advances in the mechanism and strategies of targeted delivery using oral nanoparticle drug delivery systems for colitis-related fields. Finally, we present challenges and potential directions for future IBD treatment with the assistance of nanotechnology.

Microfluidic Devices: A Tool for Nanoparticle Synthesis and Performance Evaluation

The use of nanoparticles (NPs) in nanomedicine holds great promise for the treatment of diseases for which conventional therapies present serious limitations. Additionally, NPs can drastically improve early diagnosis and follow-up of many disorders. However, to harness their full capabilities, they must be precisely designed, produced, and tested in relevant models. Microfluidic systems can simulate dynamic fluid flows, gradients, specific microenvironments, and multiorgan complexes, providing an efficient and cost-effective approach for both NPs synthesis and screening. Microfluidic technologies allow for the synthesis of NPs under controlled conditions, enhancing batch-to-batch reproducibility. Moreover, due to the versatility of microfluidic devices, it is possible to generate and customize endless platforms for rapid and efficient in vitro and in vivo screening of NPs' performance. Indeed, microfluidic devices show great potential as advanced systems for small organism manipulation and immobilization. In this review, first we summarize the major microfluidic platforms that allow for controlled NPs synthesis. Next, we will discuss the most innovative microfluidic platforms that enable mimicking in vitro environments as well as give insights into organism-on-a-chip and their promising application for NPs screening. We conclude this review with a critical assessment of the current challenges and possible future directions of microfluidic systems in NPs synthesis and screening to impact the field of nanomedicine.

Size-Dependent Polymeric Nanoparticle Distribution in a Static versus Dynamic Microfluidic Blood Vessel Model: Implications for Nanoparticle-Based Drug Delivery

Nanoparticles (NPs) have been widely investigated in the nanomedicine field. One of the main challenges is to accurately predict the NP distribution and fate after administration. Microfluidic platforms acquired huge importance as tools to model the in vivo environment. In this study, we leveraged a microfluidic platform to produce FITC-labeled poly(lactide-co-glycolide)-block-poly(ethylene glycol) (PLGA-PEG) NPs with defined sizes of 30, 50, and 70 nm. The study aimed to compare the ability of NPs with differences of 20 nm in size to cross an endothelial barrier using static (Transwell inserts) and dynamic (microfluidic perfusion device) in vitro models. Our results evidence a size-dependent NP crossing in both models (30 > 50 > 70 nm) and highlight the bias deriving from the static model, which does not involve shear stresses. The permeation of each NP size was significantly higher in the static system than in the dynamic model at the earliest stages. However, it gradually decreased to levels comparable with those of the dynamic model. Overall, this work highlights clear differences in NP distribution over time in static versus dynamic conditions and distinct size-dependent patterns. These findings reinforce the need for accurate in vitro screening models that allow for more accurate predictions of in vivo performance.