Chitosan coated pH-responsive metal-polyphenol delivery platform for melanoma chemotherapy

Morusin-Cu(II)-indocyanine green nanoassembly ignites mitochondrial dysfunction for chemo-photothermal tumor therapy

Nanoscale drug delivery systems derived from natural bioactive materials accelerate the innovation and evolution of cancer treatment modalities. Morusin (Mor) is a prenylated flavonoid compound with high cancer chemoprevention activity, however, the poor water solubility, low active pharmaceutical ingredient (API) loading content, and instability compromise its bioavailability and therapeutic effectiveness. Herein, a full-API carrier-free nanoparticle is developed based on the self-assembly of indocyanine green (ICG), copper ions (Cu2+) and Mor, termed as IMCNs, via coordination-driven and π-π stacking for synergistic tumor therapy. The IMCNs exhibits a desirable loading content of Mor (58.7 %) and pH/glutathione (GSH)-responsive motif. Moreover, the photothermal stability and photo-heat conversion efficiency (42.8 %) of IMCNs are improved after coordination with Cu2+ and help to achieve photothermal therapy. Afterward, the released Cu2+ depletes intracellular overexpressed GSH and mediates Fenton-like reactions, and further synergizes with ICG at high temperatures to expand oxidative damage. Furthermore, the released Mor elicits cytoplasmic vacuolation, expedites mitochondrial dysfunction, and exerts chemo-photothermal therapy after being combined with ICG to suppress the migration of residual live tumor cells. In vivo experiments demonstrate that IMCNs under laser irradiation could excellently inhibit tumor growth (89.6 %) through the multi-modal therapeutic performance of self-enhanced chemotherapy/coordinated-drugs/ photothermal therapy (PTT), presenting a great potential for cancer therapy.

Enhancing metformin-induced tumor metabolism destruction by glucose oxidase for triple-combination therapy

Despite decades of laboratory and clinical trials, breast cancer remains the main cause of cancer-related disease burden in women. Considering the metabolism destruction effect of metformin (Met) and cancer cell starvation induced by glucose oxidase (GOx), after their efficient delivery to tumor sites, GOx and Met may consume a large amount of glucose and produce sufficient hydrogen peroxide in situ. Herein, a pH-responsive epigallocatechin gallate (EGCG)-conjugated low-molecular-weight chitosan (LC-EGCG, LE) nanoparticle (Met-GOx/Fe@LE NPs) was constructed. The coordination between iron ions (Fe3+) and EGCG in this nanoplatform can enhance the efficacy of chemodynamic therapy via the Fenton reaction. Met-GOx/Fe@LE NPs allow GOx to retain its enzymatic activity while simultaneously improving its stability. Moreover, this pH-responsive nanoplatform presents controllable drug release behavior. An in vivo biodistribution study showed that the intracranial accumulation of GOx delivered by this nanoplatform was 3.6-fold higher than that of the free drug. The in vivo anticancer results indicated that this metabolism destruction/starvation/chemodynamic triple-combination therapy could induce increased apoptosis/death of tumor cells and reduce their proliferation. This triple-combination therapy approach is promising for efficient and targeted cancer treatment.

Advanced manufacturing of nanoparticle formulations of drugs and biologics using microfluidics

Numerous innovative nanoparticle formulations of drugs and biologics, named nano-formulations, have been developed in the last two decades. However, methods for their scaled-up production are still lagging, as the amount needed for large animal tests and clinical trials is typically orders of magnitude larger. This manufacturing challenge poses a critical barrier to successfully translating various nano-formulations. This review focuses on how microfluidics technology has become a powerful tool to overcome this challenge by synthesizing various nano-formulations with improved particle properties and product purity in large quantities. This microfluidic-based manufacturing is enabled by microfluidic mixing, which is capable of the precise and continuous control of the synthesis of nano-formulations. We further discuss the specific applications of hydrodynamic flow focusing, a staggered herringbone micromixer, a T-junction mixer, a micro-droplet generator, and a glass capillary on various types of nano-formulations of polymeric, lipid, inorganic, and nanocrystals. Various separation and purification microfluidic methods to enhance the product purity are reviewed, including acoustofluidics, hydrodynamics, and dielectrophoresis. We further discuss the challenges of microfluidics being used by broader research and industrial communities. We also provide future outlooks of its enormous potential as a decentralized approach for manufacturing nano-formulations.

Influence of unsaturated fatty acids on the antitumor activity of polymeric conjugates grafted with cabazitaxel against prostate cancer

Cabazitaxel (CTX) is a medication used for treating metastatic prostate cancer. However, its effectiveness is majorly limited by its poor water solubility and lack of tumor targeting. In this study, three unsaturated fatty acids, GLA, ALA and DHA, were separately connected with CTX and then covalently attached to bifunctionalized dextran through a linker to produce three dual drug conjugates named dextran-GLA-CTX, dextran-ALA-CTX and dextran-DHA-CTX. The three conjugates displayed enhanced solubility of CTX in water and improved antitumor effects compared to the conventional CTX formulation. The results also confirmed that dextran-GLA-CTX exhibited the strongest antitumor activity, while dextran-DHA-CTX displayed less efficacy, as evaluated through xenografted nude mice bearing PC-3 and DU145 prostate cancer cells. Additionally, dextran-GLA-CTX showed greater inhibition of tumor growth than dextran-CTX. Moreover, the dextran-GLA-CTX conjugate was found to prolong the half-life of CTX in plasma and selectively accumulate in tumors. This study revealed that unsaturated fatty acids can enhance the antitumor activity of dextran-based conjugates grafted with CTX.

Optimized DOX Drug Deliveries via Chitosan-Mediated Nanoparticles and Stimuli Responses in Cancer Chemotherapy: A Review

Chitosan nanoparticles (NPs) serve as useful multidrug delivery carriers in cancer chemotherapy. Chitosan has considerable potential in drug delivery systems (DDSs) for targeting tumor cells. Doxorubicin (DOX) has limited application due to its resistance and lack of specificity. Chitosan NPs have been used for DOX delivery because of their biocompatibility, biodegradability, drug encapsulation efficiency, and target specificity. In this review, various types of chitosan derivatives are discussed in DDSs to enhance the effectiveness of cancer treatments. Modified chitosan-DOX NP drug deliveries with other compounds also increase the penetration and efficiency of DOX against tumor cells. We also highlight the endogenous stimuli (pH, redox, enzyme) and exogenous stimuli (light, magnetic, ultrasound), and their positive effect on DOX drug delivery via chitosan NPs. Our study sheds light on the importance of chitosan NPs for DOX drug delivery in cancer treatment and may inspire the development of more effective approaches for cancer chemotherapy.

Polyphenol-Based Nanosystems for Next-Generation Cancer Therapy: Multifunctionality, Design, and Challenges

With the continuous updating of cancer treatment methods and the rapid development of precision medicine in recent years, there are higher demands for advanced and versatile drug delivery systems. Scientists are committed to create greener and more effective nanomedicines where the carrier is no longer limited to a single function of drug delivery. Polyphenols, which can act as both active ingredients and fundamental building blocks, are being explored as potential multifunctional carriers that are efficient and safe for design purposes. Due to their intrinsic anticancer activity, phenolic compounds have shown surprising expressiveness in ablation of tumor cells, overcoming cancer multidrug resistance (MDR), and enhancing immunotherapeutic efficacy. This review provides an overview of recent advances in the design, synthesis, and application of versatile polyphenol-based nanosystems for cancer therapy in various modes. Moreover, the merits of polyphenols and the challenges for their clinical translation are also discussed, and it is pointed out that the novel polyphenol delivery system requires further optimization and validation.

Smart stimuli-responsive drug delivery systems in spotlight of COVID-19

The world has been dealing with a novel severe acute respiratory syndrome (SARS-CoV-2) since the end of 2019, which threatens the lives of many people worldwide. COVID-19 causes respiratory infection with different symptoms, from sneezing and coughing to pneumonia and sometimes gastric symptoms. Researchers worldwide are actively developing novel drug delivery systems (DDSs), such as stimuli-responsive DDSs. The ability of these carriers to respond to external/internal and even multiple stimuli is essential in creating "smart" DDS that can effectively control dosage, sustained release, individual variations, and targeted delivery. To conduct a comprehensive literature survey for this article, the terms "Stimuli-responsive", "COVID-19″ and "Drug delivery" were searched on databases/search engines like "Google Scholar", "NCBI", "PubMed", and "Science Direct". Many different types of DDSs have been proposed, including those responsive to various exogenous (light, heat, ultrasound and magnetic field) or endogenous (microenvironmental changes in pH, ROS and enzymes) stimuli. Despite significant progress in DDS research, several challenging issues must be addressed to fill the gaps in the literature. Therefore, this study reviews the drug release mechanisms and applications of endogenous/exogenous stimuli-responsive DDSs while also exploring their potential with respect to COVID-19.

Dipole moment as the underlying mechanism for enhancing the immobilization of glucose oxidase by ferrocene-chitosan for superior specificity non-invasive glucose sensing

Non-invasive methods for sensing glucose levels are highly desirable due to the comfortableness, simplicity, and lack of infection risk. However, the insufficient accuracy and ease of interference limit their practical medical applications. Here, we develop a non-invasive salivary glucose biosensor based on a ferrocene-chitosan (Fc-Chit) modified carbon nanotube (CNT) electrode through a simple drop-casting method. Compared with previous studies that relied mainly on trial and error for evaluation, this is the first time that dipole moment was proposed to optimize the electron-mediated Fc-Chit, demonstrating sturdy immobilization of glucose oxidase (GOx) on the electrode and improving the electron transfer process. Thus, the superior sensing sensitivity of the biosensor can achieve 119.97 μA mM-1 cm-2 in phosphate buffered saline (PBS) solution over a wide sensing range of 20-800 μM. Additionally, the biosensor exhibited high stability (retaining 95.0% after three weeks) and high specificity toward glucose in the presence of various interferents, attributed to the specific sites enabling GOx to be sturdily immobilized on the electrode. The results not only provide a facile solution for accurate and regular screening of blood glucose levels via saliva tests but also pave the way for designing enzymatic biosensors with specific enzyme immobilization through fundamental quantum calculations.

Multi-functional chitosan-based nanoparticles for drug delivery: Recent advanced insight into cancer therapy

Cancer therapy continues to be a major global concern, with conventional treatments suffering from low efficacy, untargeted drug delivery, and severe side effects. Recent research in nanomedicine suggests that nanoparticles' unique physicochemical properties can be leveraged to surmount the limitations of conventional cancer treatment. Chitosan-based nanoparticles have gained significant attention due to their high drug-carrying capacity, non-toxicity, biocompatibility, and long circulation time. Chitosan is utilized in cancer therapies as a carrier to accurately deliver active ingredients to tumor sites. This review focuses on clinical studies and current market offerings of anticancer drugs. The unique nature of tumor microenvironments presents new opportunities for the development of smart drug delivery systems, and this review explores the design and preparation of chitosan-based smart nanoparticles. Further, we discuss the therapeutic efficacies of these nanoparticles based on various in vitro and in vivo findings. Finally, we present a forward-looking perspective on the challenges and prospects of chitosan-based nanoparticles in cancer therapy, intending to provide fresh ideas for advancing cancer treatment strategies.

Recent Advances of Metal-Polyphenol Coordination Polymers for Biomedical Applications

Nanomedicine has provided cutting-edge technologies and innovative methods for modern biomedical research, offering unprecedented opportunities to tackle crucial biomedical issues. Nanomaterials with unique structures and properties can integrate multiple functions to achieve more precise diagnosis and treatment, making up for the shortcomings of traditional treatment methods. Among them, metal-polyphenol coordination polymers (MPCPs), composed of metal ions and phenolic ligands, are considered as ideal nanoplatforms for disease diagnosis and treatment. Recently, MPCPs have been extensively investigated in the field of biomedicine due to their facile synthesis, adjustable structures, and excellent biocompatibility, as well as pH-responsiveness. In this review, the classification of various MPCPs and their fabrication strategies are firstly summarized. Then, their significant achievements in the biomedical field such as biosensing, drug delivery, bioimaging, tumor therapy, and antibacterial applications are highlighted. Finally, the main limitations and outlooks regarding MPCPs are discussed.

Phenylboronic Ester-Bridged Chitosan/Myricetin Nanomicelle for Penetrating the Endothelial Barrier and Regulating Macrophage Polarization and Inflammation against Ischemic Diseases

The brain and liver are more susceptible to ischemia and reperfusion (IR) injury (IRI), which triggers the reactive oxygen species (ROS) burst and inflammatory cascade and results in severe neuronal damage or hepatic injury. Moreover, the damaged endothelial barrier contributes to proinflammatory activity and limits the delivery of therapeutic agents such as some macromolecules and nanomedicine despite the integrity being disrupted after IRI. Herein, we constructed a phenylboronic-decorated chitosan-based nanoplatform to deliver myricetin, a multifunctional polyphenol molecule for the treatment of cerebral and hepatic ischemia. The chitosan-based nanostructures are widely studied cationic carriers for endothelium penetration such as the blood-brain barrier (BBB) and sinusoidal endothelial barrier (SEB). The phenylboronic ester was chosen as the ROS-responsive bridging segment for conjugation and selective release of myricetin molecules, which meanwhile scavenged the overexpressed ROS in the inflammatory environment. The released myricetin molecules fulfill a variety of roles including antioxidation through multiple phenolic hydroxyl groups, inhibition of the inflammatory cascade by regulation of the macrophage polarization from M1 to M2, and endothelial injury repairment. Taken together, our present study provides valuable insight into the development of efficient antioxidant and anti-inflammatory platforms for potential application against ischemic disease.

Responsive Microneedles as a New Platform for Precision Immunotherapy

Microneedles are a well-known transdermal or transdermal drug delivery system. Different from intramuscular injection, intravenous injection, etc., the microneedle delivery system provides unique characteristics for immunotherapy administration. Microneedles can deliver immunotherapeutic agents to the epidermis and dermis, where immune cells are abundant, unlike conventional vaccine systems. Furthermore, microneedle devices can be designed to respond to certain endogenous or exogenous stimuli including pH, reactive oxygen species (ROS), enzyme, light, temperature, or mechanical force, thereby allowing controlled release of active compounds in the epidermis and dermis. In this way, multifunctional or stimuli-responsive microneedles for immunotherapy could enhance the efficacy of immune responses to prevent or mitigate disease progression and lessen systemic adverse effects on healthy tissues and organs. Since microneedles are a promising drug delivery system for accurate delivery and controlled drug release, this review focuses on the progress of using reactive microneedles for immunotherapy, especially for tumors. Limitations of current microneedle system are summarized, and the controllable administration and targeting of reactive microneedle systems are examined.

A timescale-guided microfluidic synthesis of tannic acid-FeIII network nanocapsules of hydrophobic drugs

Many drugs are poorly water-soluble and suffer from low bioavailability. Metal-phenolic network (MPN), a hydrophilic thin layer such as tannic acid (TA)-FeIII network, has been recently used to encapsulate hydrophobic drugs to improve their bioavailability. However, it remains challenging to synthesize nanocapsules of a wide variety of hydrophobic drugs and to scale up the production in a continuous manner. Here, we present a microfluidic synthesis method to continuously produce TA-FeIII network nanocapsules of hydrophobic drugs. We hypothesize that nanocapsules can continuously be formed only when the microfluidic mixing timescale is shorter than the drug's nucleation timescale. The hypothesis was tested on three hydrophobic drugs - paclitaxel, curcumin, and vitamin D with varying solubility and nucleation timescale. The proposed mechanism was validated by successfully predicting the synthesis outcomes. The microfluidically-synthesized nanocapsules had well-controlled sizes of 100-200 nm, high drug loadings of 40-70%, and a throughput of up to 70 mg hr-1 per channel. The release kinetics, cellular uptake, and cytotoxicity were further evaluated. The effect of coating constituents on nanocapsule properties were characterized. Fe content of nanocapsules was reported. The stability of nanocapsules at different temperatures and pHs were also tested. The results suggest that the present method can provide a quantitative guideline to predictively design a continuous synthesis scheme for hydrophobic drug encapsulation via MPN nanocapsules with scaled-up capability.

Preparation of Conotoxin-Encapsulated Chitosan Nanoparticles and Evaluation of Their Skin Permeability

μ-Conotoxin CnIIIC (conotoxin, CTX)-loaded chitosan nanoparticles (CTX-NPs) were prepared using the ionic cross-linking method. The CTX-NPs were spherical and well with a polydispersity index of 0.292 ± 0.039, drug loading efficiency of 25.9 ± 1.2%, and encapsulation efficiency of 95.6 ± 1.3%. In vitro release studies showed that the release behavior of CTX-NPs in a pH 5.0 acetate buffer followed zero-order kinetics. In vitro transdermal experiments using Franz diffusion cells mounted with mouse abdominal skin demonstrated that the cumulative intradermal deposition amount of CTX per unit area in 8 h (D₈) and permeability coefficient (P_f) of CTX loaded on CTX-NPs were 2.30- and 7.71-times that of the CTX solution. In vivo transdermal experiments in mice showed that the amount of CTX deposited in the skin after 8 h of CTX saline administration was significantly lower than that of CTX deposited in the skin after administration of CTX-NPs. In vitro fluorescence labeling transdermal studies through Franz diffusion cells mounted with mouse abdominal skin indicated that CTX-NPs aggregated at hair follicles. Skin irritation tests in mice indicated that the irritation due to CTX-NPs was negligible. The cytotoxicity experiment showed that the viability of Balb/c 3T3 cells with CTX-NPs containing 230 μg/mL (0.08 μM) CTX was greater than 75%. CTX-NPs increase intradermal deposition of CTX by accumulating in hair follicles, which has positive implications for transdermal penetration of CTX.

Boosting ferroptosis and microtubule inhibition for antitumor therapy via a carrier-free supermolecule nanoreactor

Traditional microtubule inhibitors fail to significantly enhance the effect of colorectal cancer; hence, new and efficient strategies are necessary. In this study, a supramolecular nanoreactor (DOC@TA-Fe³⁺) based on tannic acid (TA), iron ion (Fe³⁺), and docetaxel (DOC) with microtubule inhibition, reactive oxygen species (ROS) generation, and glutathione peroxidase 4 (GPX4) inhibition, is prepared for ferroptosis/apoptosis treatment. After internalization by CT26 cells, the DOC@TA-Fe³⁺ nanoreactor escapes from the lysosomes to release payloads. The subsequent Fe³⁺/Fe²⁺ conversion mediated by TA reducibility can trigger the Fenton reaction to enhance the ROS concentration. Additionally, Fe³⁺ can consume glutathione to repress the activity of GPX4 to induce ferroptosis. Meanwhile, the released DOC controls microtubule dynamics to activate the apoptosis pathway. The superior in vivo antitumor efficacy of DOC@TA-Fe³⁺ nanoreactor in terms of tumor growth inhibition and improved survival is verified in CT26 tumor-bearing mouse model. Therefore, the nanoreactor can act as an effective apoptosis and ferroptosis inducer for application in colorectal cancer therapy.

Critical Evaluation of Multifunctional Betaxolol Hydrochloride Nanoformulations for Effective Sustained Intraocular Pressure Reduction

Introduction

Glaucoma is a chronic disease that requires long-term adherence to treatment. Topical application of conventional eye drops results in substantial drug loss due to rapid tear turnover, with poor drug bioavailability being a major challenge for efficient glaucoma treatment. We aimed to prepare the anti-glaucoma drug betaxolol hydrochloride (BH) as a novel nano-delivery system that prolonged the retention time at the ocular surface and improved bioavailability.

Methods

We constructed multifunctional nanoparticles (MMt-BH-HA/CS-ED NPs) by ion cross-linking-solvent evaporation method. The particle size, zeta potential, encapsulation efficiency and drug loading of MMt-BH-HA/CS-ED NPs were physicochemically characterized. The structure of the preparations was characterized by microscopic techniques of SEM, TEM, XPS, XRD, FTIR and TGA, and evaluated for their in vitro release performance as well as adhesion properties. Its safety was investigated using irritation assays of hemolysis experiment, Draize test and histopathology examination. Precorneal retention was examined by in vivo fluorescence tracer method and pharmacokinetics in tear fluid was studied. A model of high IOP successfully induced by injection of compound carbomer solution was used to assess the IOP-lowering efficacy of the formulation, and it was proposed that micro-interactions between the formulation and the tear film would be used to analyze the behavior at the ocular surface.

Results

The positively charged MMt-BH-HA/CS-ED NPs were successfully prepared with good two-step release properties, higher viscosity, and slower pre-corneal diffusion rate along with longer precorneal retention time compared to BH solution. The micro-interactions between nanoparticles and tear film converted the drug clearance from being controlled by fast aqueous layer turnover to slow mucin layer turnover, resulting in higher drug concentration on the ocular surface, providing more durable and stable IOP-lowering efficacy.

Conclusion

The novel multifunctional MMt-BH-HA/CS-ED NPs can effectively reduce IOP and are suitable for the treatment of chronic disease glaucoma.

Preparation and characterization of high embedding efficiency epigallocatechin-3-gallate glycosylated nanocomposites

Glycosylated protein nano encapsulation was an efficient encapsulation technology, but its embedding rate for EGCG was not high, and the research on the embedding mechanism was relatively weak. Based on this, this study compared the embedding effect of glycosylated peanut globulin and glycosylated casein on EGCG. The embedding mechanism of EGCG with glycosylated protein was discussed by ultraviolet, fluorescence, infrared and fluorescence microscopy. Results revealed that the highest encapsulation efficiency of EGCG was 93.89 ± 1.11%. The neutral pH value and 0.3 mg/mL EGCG addition amount were suitable for EGCG glycosylated nanocomposites. The hydrogen bond between EGCG hydroxyl group and tyrosine and tryptophan of glycosylated protein is mainly non covalent. The encapsulation effect of EGCG glycosylated nanocomposites could be quenched by changing the polar environment and spatial structure of the group. The fluorescence characteristic and dispersibility of EGCG glycosylated peanut globin were higher than EGCG glycosylated casein. This study might provide a theoretical basis for EGCG microencapsulation technology and EGCG application in tea beverage and liquid tea food systems.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

Making waves: how ultrasound-targeted drug delivery is changing pharmaceutical approaches

Administration of drugs through oral and intravenous routes is a mainstay of modern medicine, but this approach suffers from limitations associated with off-target side effects and narrow therapeutic windows. It is often apparent that a controlled delivery of drugs, either localized to a specific site or during a specific time, can increase efficacy and bypass problems with systemic toxicity and insufficient local availability. To overcome some of these issues, local delivery systems have been devised, but most are still restricted in terms of elution kinetics, duration, and temporal control. Ultrasound-targeted drug delivery offers a powerful approach to increase delivery, therapeutic efficacy, and temporal release of drugs ranging from chemotherapeutics to antibiotics. The use of ultrasound can focus on increasing tissue sensitivity to the drug or actually be a critical component of the drug delivery. The high spatial and temporal resolution of ultrasound enables precise location, targeting, and timing of drug delivery and tissue sensitization. Thus, this noninvasive, non-ionizing, and relatively inexpensive modality makes the implementation of ultrasound-mediated drug delivery a powerful method that can be readily translated into the clinical arena. This review covers key concepts and areas applied in the design of different ultrasound-mediated drug delivery systems across a variety of clinical applications.

Silk Nanocarrier Size Optimization for Enhanced Tumor Cell Penetration and Cytotoxicity In Vitro

Silk nanofibers are versatile carriers for hydrophobic and hydrophilic drugs, but fall short in terms of effective delivery to cells, which is essential for therapeutic benefits. Here, the size of silk nanofibers was tuned by ultrasonic treatment to improve the cell penetration features without impacting the structural features. The gradual decrease in silk nanofiber length from 1700 to 40 nm resulted in improved cell uptake. The internalized silk nanofiber carriers evaded lysosomes, which facilitated retention in cancer cells in vitro. The smaller sizes also facilitated enhanced penetration of tumor spheroids for improved delivery in vitro. The cytotoxicity of paclitaxel (PTX)-laden nanocarriers increased when the length of the silk nanocarriers decreased. Both the drug loading capacity and delivery of silk nanocarriers with optimized sizes suggest potential utility in cell treatments.