Recent Progress in Stimuli-Responsive Intelligent Nano Scale Drug Delivery Systems: A Special Focus Towards pH-Sensitive Systems

Targeted delivery of quercetin using gelatin/starch/Fe3O4 nanocarrier to suppress the growth of liver cancer HepG2 cells

To suppress HepG2 liver cancer cells, a nanocarrier (NC) consisting of Fe3O4, Gelatin (G), and Starch (S) was synthesized and characterized for targeted delivery of Quercetin (QC) drug. The spectra obtained from X-ray diffraction (XRD) and Fourier transform infrared (FTIR) demonstrated that the nanoparticles (NP) in the NC are well-interconnected to each other and have formed a regular structure. Also, field emission scanning electron microscopy (FE-SEM) indicates a smooth and homogeneous surface of the synthesized NC. The results of the vibrating sample magnetometer (VSM) also corroborated the correctness of the synthesis of Fe3O4 NPs and Gelatin/Starch/Fe3O4@Quercetin NC (G/S/Fe3O4@QC) because the magnetic properties of Fe3O4 decreased with the addition of G/S@QC. Stability and particle size were determined by zeta potential and Dynamic light scattering (DLS). The percentage of drug loading and encapsulation efficiency of QC in the NC was 46.25 % and 87 %, respectively. QC profile release in acidic and natural environments showed controlled release and pH sensitivity of the NC. Cytotoxicity of L929 and HepG2 treated cells with the G/S/Fe3O4@QC was investigated by MTT staining, which agreed with the flow cytometry result. The results of Flowcytometry and MTT showed 43.5 % apoptosis and 42 % cytotoxicity in treated HepG2 cells by G/S/Fe3O4@QC, while it was not toxic to L929 normal cells. According to the results, G/S/Fe3O4@QC is a suitable NC for the targeted delivery of QC as a drug against HepG2 cancer cells.

Nitrogen-doped carbon dots as fluorescent probes for sensitive and selective determination of Fe3

At present, the contamination of water resources by heavy metal ions has posed a significant threat to human survival. Therefore, it is particularly critical to develop low-cost, easy-to-use, and highly efficient heavy metal detection technologies. In this work, a fast and cost-effective fluorescent probe for nitrogen-doped carbon dots (N-CDs) was prepared using one-step hydrothermal method with citric acid (CA) as carbon source, and melamine as nitrogen source. The structural and optical characterizations of the resulting N-CDs were investigated in details. The results showed that the quantum yield of the prepared fluorescent probe was as high as 45 %, and an average fluorescence lifetime was about 7.80 ns. N-CDs have excellent water solubility and dispersibility, with an average size of 2.58 nm. N-CDs exhibited excellent specific responsiveness to Fe3+ and can be used as an effective method for detecting Fe3+ at low-concentrations (the concentrations of N-CDs as low as 0.24 μg/mL) using fluorescent probes. The linear response of the fluorescent probe N-CDs to Fe3+ was formed in the concentration range of 20-80 μM, and the detection limit was 3.18 μM. In addition, in the actual water samples analysis, the recovery rate reached 97.05-100.58 %. The prepared of N-CDs provide available Fe3+ fluorescent probes in the environment.

Design and Application of pH-Responsive Liposomes for Site-Specific Delivery of Cytotoxin from Cobra Venom

Background

Current immunotherapies with unexpected severe side effects and treatment resistance have not resulted in the desired outcomes for patients with melanoma, and there is a need to discover more effective medications. Cytotoxin (CTX) from Cobra Venom has been established to have favorable cytolytic activity and antitumor efficacy and is regarded as a promising novel anticancer agent. However, amphiphilic CTX with excellent anionic phosphatidylserine lipid-binding ability may also damage normal cells.

Methods

We developed pH-responsive liposomes with a high CTX load (CTX@PSL) for targeted acidic-stimuli release of drugs in the tumor microenvironment. The morphology, size, zeta potential, drug-release kinetics, and preservation stability were characterized. Cell uptake, apoptosis-promoting effects, and cytotoxicity were assessed using MTT assay and flow cytometry. Finally, the tissue distribution and antitumor effects of CTX@PSL were systematically assessed using an in vivo imaging system.

Results

CTX@PSL exhibited high drug entrapment efficiency, drug loading, stability, and a rapid release profile under acidic conditions. These nanoparticles, irregularly spherical in shape and small in size, can effectively accumulate at tumor sites (six times higher than free CTX) and are rapidly internalized into cancer cells (2.5-fold higher cell uptake efficiency). CTX@PSL displayed significantly stronger cytotoxicity (IC50 0.25 μg/mL) and increased apoptosis in than the other formulations (apoptosis rate 71.78±1.70%). CTX@PSL showed considerably better tumor inhibition efficacy than free CTX or conventional liposomes (tumor inhibition rate 79.78±5.93%).

Conclusion

Our results suggest that CTX@PSL improves tumor-site accumulation and intracellular uptake for sustained and targeted CTX release. By combining the advantages of CTX and stimuli-responsive nanotechnology, the novel CTX@PSL nanoformulation is a promising therapeutic candidate for cancer treatment.

Biomaterial-Based Responsive Nanomedicines for Targeting Solid Tumor Microenvironments

Solid tumors are composed of a highly complex and heterogenic microenvironment, with increasing metabolic status. This environment plays a crucial role in the clinical therapeutic outcome of conventional treatments and innovative antitumor nanomedicines. Scientists have devoted great efforts to conquering the challenges of the tumor microenvironment (TME), in respect of effective drug accumulation and activity at the tumor site. The main focus is to overcome the obstacles of abnormal vasculature, dense stroma, extracellular matrix, hypoxia, and pH gradient acidosis. In this endeavor, nanomedicines that are targeting distinct features of TME have flourished; these aim to increase site specificity and achieve deep tumor penetration. Recently, research efforts have focused on the immune reprograming of TME in order to promote suppression of cancer stem cells and prevention of metastasis. Thereby, several nanomedicine therapeutics which have shown promise in preclinical studies have entered clinical trials or are already in clinical practice. Various novel strategies were employed in preclinical studies and clinical trials. Among them, nanomedicines based on biomaterials show great promise in improving the therapeutic efficacy, reducing side effects, and promoting synergistic activity for TME responsive targeting. In this review, we focused on the targeting mechanisms of nanomedicines in response to the microenvironment of solid tumors. We describe responsive nanomedicines which take advantage of biomaterials' properties to exploit the features of TME or overcome the obstacles posed by TME. The development of such systems has significantly advanced the application of biomaterials in combinational therapies and in immunotherapies for improved anticancer effectiveness.

Advance in placenta drug delivery: concern for placenta-originated disease therapy

In the therapy of placenta-originated diseases during pregnancy, the main challenges are fetal exposure to drugs, which can pass through the placenta and cause safety concerns for fetal development. The design of placenta-resident drug delivery system is an advantageous method to minimize fetal exposure as well as reduce adverse maternal off-target effects. By utilizing the placenta as a biological barrier, the placenta-resident nanodrugs could be trapped in the local placenta to concentrate on the treatment of this abnormal originated tissue. Therefore, the success of such systems largely depends on the placental retention capacity. This paper expounds on the transport mechanism of nanodrugs in the placenta, analyzes the factors that affect the placental retention of nanodrugs, and summarizes the advantages and concerns of current nanoplatforms in the treatment of placenta-originated diseases. In general, this review aims to provide a theoretical basis for the construction of placenta-resident drug delivery systems, which will potentially enable safe and efficient clinical treatment for placenta-originated diseases in the future.

Nanoparticle-based drug delivery systems to enhance cancer immunotherapy in solid tumors

Immunotherapy has developed rapidly in solid tumors, especially in the areas of blocking inhibitory immune checkpoints and adoptive T-cell transfer for immune regulation. Many patients benefit from immunotherapy. However, the response rate of immunotherapy in the overall population are relatively low, which depends on the characteristics of the tumor and individualized patient differences. Moreover, the occurrence of drug resistance and adverse reactions largely limit the development of immunotherapy. Recently, the emergence of nanodrug delivery systems (NDDS) seems to improve the efficacy of immunotherapy by encapsulating drug carriers in nanoparticles to precisely reach the tumor site with high stability and biocompatibility, prolonging the drug cycle of action and greatly reducing the occurrence of toxic side effects. In this paper, we mainly review the advantages of NDDS and the mechanisms that enhance conventional immunotherapy in solid tumors, and summarize the recent advances in NDDS-based therapeutic strategies, which will provide valuable ideas for the development of novel tumor immunotherapy regimen.

Novel carboxymethyl cellulose-halloysite-polyethylene glycol nanocomposite for improved 5-FU delivery

Drug nano-carriers are crucial for achieving targeted treatment against cancer disorders with minimal side effects. In this study, a pH-responsive nanocomposite based on halloysite nanotube (HNT) coated with carboxymethyl cellulose (CMC)/polyethylene glycol (PEG) hydrogel for controlled delivery of 5-Fluorouracil (5-FU), a hydrophobic chemotherapy drug prescribed for different types of cancers was synthesized for the first time using the water-in-oil-in-water (W/O/W) technique. The developed CMC/PEG/HNT/5-FU nanocomposite was characterized by dynamic light scattering (DLS), zeta potential, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Field emission scanning electron microscope (FE-SEM) to get information about the particle size, surface charge, interactions between functional groups, crystalline structure and morphology, respectively. High efficiencies in terms of drug entrapment and loading (46 % and 87 %, respectively) were attained. In-vitro drug release results revealed an improved and sustained 5-FU delivery in an acid environment compared to the physiological medium, corroborating the pH-sensitivity of the developed nano-carrier. Flow cytometry and MTT assays demonstrated that the 5-FU loaded nanocomposite had considerable cytotoxicity on MCF-7 breast cancer cells while it is not toxic against L929 fibroblast cells. The nanocomposite synthesized herein could serve as a platform for the pH-sensitive release of anti-cancer drugs.

Exploring the Application of Micellar Drug Delivery Systems in Cancer Nanomedicine

Various formulations of polymeric micelles, tiny spherical structures made of polymeric materials, are currently being investigated in preclinical and clinical settings for their potential as nanomedicines. They target specific tissues and prolong circulation in the body, making them promising cancer treatment options. This review focuses on the different types of polymeric materials available to synthesize micelles, as well as the different ways that micelles can be tailored to be responsive to different stimuli. The selection of stimuli-sensitive polymers used in micelle preparation is based on the specific conditions found in the tumor microenvironment. Additionally, clinical trends in using micelles to treat cancer are presented, including what happens to micelles after they are administered. Finally, various cancer drug delivery applications involving micelles are discussed along with their regulatory aspects and future outlooks. As part of this discussion, we will examine current research and development in this field. The challenges and barriers they may have to overcome before they can be widely adopted in clinics will also be discussed.

Recent advances in magnetic nanocarriers for tumor treatment

Magnetic nanocarriers are nano-platforms that integrate multiple moieties based on magnetic nanoparticles for diagnostic and therapeutic purposes. In recent years, they have become an advanced platform for tumor treatment due to their wide application in magnetic resonance imaging (MRI), biocatalysis, magneto-thermal therapy (MHT), and photoresponsive therapy. Drugs loaded into magnetic nanocarriers can efficiently be directed to targeted areas by precisely reshaping their structural properties. Magnetic nanocarriers allow us to track the location of the therapeutic agent, continuously control the therapeutic process and eventually assess the efficacy of the treatment. They are typically used in synergistic therapeutic applications to achieve precise and effective tumor treatment. Here we review their latest applications in tumor treatment, including stimuli-responsive drug delivery, MHT, photoresponsive therapy, immunotherapy, gene therapy, and synergistic therapy. We consider reducing toxicity, improving antitumor efficacy, and the targeting accuracy of magnetic nanocarriers. The challenges of their clinical translation and prospects in cancer therapy are also discussed.

Novel Carboxymethyl Cellulose-Based Hydrogel with Core-Shell Fe3O4@SiO2 Nanoparticles for Quercetin Delivery

A nanocomposite composed of carboxymethyl cellulose (CMC) and core-shell nanoparticles of Fe₃O₄@SiO₂ was prepared as a pH-responsive nanocarrier for quercetin (QC) delivery. The nanoparticles were further entrapped in a water-in-oil-in-water emulsion system for a sustained release profile. The CMC/Fe₃O₄@SiO₂/QC nanoparticles were characterized using dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), a field emission scanning electron microscope (FE-SEM), and a vibrating sample magnetometer (VSM) to obtain insights into their size, stability, functional groups/chemical bonds, crystalline structure, morphology, and magnetic properties, respectively. The entrapment and loading efficiency were slightly improved after the incorporation of Fe₃O₄@SiO₂ NPs within the hydrogel network. The dialysis method was applied for drug release studies. It was found that the amount of QC released increased with the decrease in pH from 7.4 to 5.4, while the sustained-release pattern was preserved. The A549 cell line was chosen to assess the anticancer activity of the CMC/Fe₃O₄@SiO₂/QC nanoemulsion and its components for lung cancer treatment via an MTT assay. The L929 cell line was used in the MTT assay to determine the possible side effects of the nanoemulsion. Moreover, a flow cytometry test was performed to measure the level of apoptosis and necrosis. Based on the obtained results, CMC/Fe₃O₄@SiO₂ can be regarded as a novel promising system for cancer therapy.

Responsive shape-shifting nanoarchitectonics and its application in tumor diagnosis and therapy

Nanodrug delivery system has a great application in the treatment of solid tumors by virtue of EPR effect, though its success in clinics is still limited by its poor extravasation, small intratumoral accumulation, and weak tumor penetration. The shape of nanoparticles (NPs) greatly affects their circulation time, flow behavior, intratumoral amassing, cell internalization as well as tumor tissue penetration. Generally, short nanorods and 100-200 nm spherical nanocarriers possess nice circulation behaviors, nanorods and nanofibers with a large aspect ratio (AR) cumulate well at tumor sites, and tiny nanospheres/disks (< 50 nm) and short nanorods with a low AR achieve a favorable tumor tissue penetration. The AR and surface evenness of NPs also tune their cell contact, cell ingestion, and drug accumulation at tumor sites. Therefore, adopting stimulus-responsive shape-switching (namely, shape-shifting nanoarchitectonics) can not only ensure a good circulation and extravasation for NPs, but also and more importantly, promote their amassing, retention, and penetration in tumor tissues to maximize therapeutic efficacy. Here we review the recently developed shape-switching nanoarchitectonics of antitumoral NPs based on stimulus-responsiveness, demonstrate how successful they are in tumor shrinking and elimination, and provide new ideas for the optimization of anticancer nanotherapeutics.

Neural Differentiation Potential of Mesenchymal Stem Cells Enhanced by Biocompatible Chitosan-Gold Nanocomposites

Chitosan (Chi) is a natural polymer that has been demonstrated to have potential as a promoter of neural regeneration. In this study, Chi was prepared with various amounts (25, 50, and 100 ppm) of gold (Au) nanoparticles for use in in vitro and in vivo assessments. Each as-prepared material was first characterized by UV-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), and Dynamic Light Scattering (DLS). Through the in vitro experiments, Chi combined with 50 ppm of Au nanoparticles demonstrated better biocompatibility. The platelet activation, monocyte conversion, and intracellular ROS generation was remarkably decreased by Chi–Au 50 pm treatment. Furthermore, Chi–Au 50 ppm could facilitate colony formation and strengthen matrix metalloproteinase (MMP) activation in mesenchymal stem cells (MSCs). The lower expression of CD44 in Chi–Au 50 ppm treatment demonstrated that the nanocomposites could enhance the MSCs undergoing differentiation. Chi–Au 50 ppm was discovered to significantly induce the expression of GFAP, β-Tubulin, and nestin protein in MSCs for neural differentiation, which was verified by real-time PCR analysis and immunostaining assays. Additionally, a rat model involving subcutaneous implantation was used to evaluate the superior anti-inflammatory and endothelialization abilities of a Chi–Au 50 ppm treatment. Capsule formation and collagen deposition were decreased. The CD86 expression (M1 macrophage polarization) and leukocyte filtration (CD45) were remarkably reduced as well. In summary, a Chi polymer combined with 50 ppm of Au nanoparticles was proven to enhance the neural differentiation of MSCs and showed potential as a biosafe nanomaterial for neural tissue engineering.

Perspectives of using microRNA-loaded nanocarriers for epigenetic reprogramming of drug resistant colorectal cancers

Epigenetic regulation by microRNAs (miRs) demonstrated a promising therapeutic potential of these molecules to regulate genetic activity in different cancers, including colorectal cancers (CRCs). The RNA-based therapy does not change genetic codes in tumor cells but can silence oncogenes and/or reactivate inhibited tumor suppressor genes. In many cancers, specific miRs were shown to promote or stop tumor progression. Among confirmed and powerful epigenetic regulators of colon carcinogenesis and development of resistance are onco-miRs, which include let-7, miR-21, miR-22, miR-23a, miR-27a, miR-34, miR-92, miR-96, miR-125b, miR-135b, miR-182, miR-200c, miR-203, miR-221, miR-421, miR-451, and others. Moreover, various tumor-suppressor miRs (miR-15b-5b, miR-18a, miR-20b, miR-22, miR-96, miR-139-5p, miR-145, miR-149, miR-197, miR-199b, miR-203, miR-214, miR-218, miR-320, miR-375-3p, miR-409-3p, miR-450b-5p, miR-494, miR-577, miR-874, and others) were found silenced in drug-resistant CRCs. Re-expression of tumor suppressor miR is complicated by the chemical nature of miRs that are not long-lasting compounds and require protection from the enzymatic degradation. Several recent studies explored application of miRs using nanocarrier complexes. This study critically describes the most successfully tested nanoparticle complexes used for intracellular delivery of nuclear acids and miRs, including micelles, liposomes, inorganic and polymeric NPs, dendrimers, and aptamers. Nanocarriers shield incorporated miRs and improve the agent stability in circulation. Attachment of antibodies and/or specific peptide or ligands facilitates cell-targeted miR delivery. Addressing in vivo challenges, a broad spectrum of non-toxic materials has been tested and indicated reliable advantages of lipid-based (lipoplexes) and polymer-based liposomes. Recent cutting-edge developments indicated that lipid-based complexes with multiple cargo, including several miRs, are the most effective approach to eradicate drug-resistant tumors. Focusing on CRC-specific miRs, this review provides a guidance and insights towards the most promising direction to achieve dramatic reduction in tumor growth and metastasis using miR-nanocarrier complexes.

Noninvasive remote-controlled nanomedicine by using electric field stimulation for in vivo effective cancer therapy

Precision therapy has developed as an important strategy for cancer treatment. We have developed an external electric field (EF) controlled targeting drug delivery nanosystem (TDDS) for precision cancer therapy. The electric field responsive targeting drug delivery nanosystem (EFTDDS) is synthesized by functionalizing mesoporous silica with polynitrophenyl-methacrylamide-folate (PNMAFA). The functional molecules grafted in the mesopores effectively encapsulate the drugs in the EFTDDS and control the drug release by nitrylphenyl dipolar responding to electric field. The EFTDDS has achieved high electric field control as demonstrated by the promoted EF-responsive release and the low nonspecific leakage of the doxorubicin. Furthermore, when breast cancer xenograft models on nude mice were treated with EF-stimulated nanomedicine, the tumor-inhibition rate increases to 75%, which is 2.7 times as high as that without electric field stimulation. The EFTDDS is demonstrated biodegradable, biocompatible, and EF remotely controllable, represents excellent inhibiting effect on tumor in vivo, and might become a promising nanomedicine platform for electrodynamic therapy (EDT) in the potential clinical applications.

In-vitro pH-responsive release of imatinib from iron-supplement coated anatase TiO2 nanoparticles

Targeted drug delivery is one such precision method of delivering medication inside the human body which can vanquish all the limitations of the conventional chemotherapeutic techniques. In the present study, two types of nanoparticles (NPs) were chosen for the in-vitro pH-responsive release study of the drug, Imatinib, namely anatase Titanium Dioxide nanoparticles (TiO₂ NPs) and iron-capped TiO₂ NPs, designated as Fe@TiO₂ NPs. The novelty of this work lies behind the use of commercially available iron supplement ‘Autrin’ meant for human consumption, as the material to coat the TiO₂ NPs to synthesize Fe@TiO₂ NPs. The synthesized NPs were analyzed by XRD, HR‐TEM, SAED, EDX and VSM. UV–Vis spectroscopy was performed for absorption studies. Fe@TiO₂ NPs showed superparamagnetic behavior and thus they are able to ensure the facile transfer of Imatinib via external magnetic fields. The results obtained from in-vitro drug release studies depicted that both TiO₂ NPs and Fe@TiO₂ NPs showed a controlled pH-sensitive delivery of the loaded Imatinib molecules. Moreover, both types of NPs do not result in the formation of ROS under human physiological conditions. These results can lay the foundation to the development of efficacious targeted drug delivery systems in the healthcare sector.

Light-Responsive Micelles Loaded With Doxorubicin for Osteosarcoma Suppression

The enhancement of tumor targeting and cellular uptake of drugs are significant factors in maximizing anticancer therapy and minimizing the side effects of chemotherapeutic drugs. A key challenge remains to explore stimulus-responsive polymeric nanoparticles to achieve efficient drug delivery. In this study, doxorubicin conjugated polymer (Poly-Dox) with light-responsiveness was synthesized, which can self-assemble to form polymeric micelles (Poly-Dox-M) in water. As an inert structure, the polyethylene glycol (PEG) can shield the adsorption of protein and avoid becoming a protein crown in the blood circulation, improving the tumor targeting of drugs and reducing the cardiotoxicity of doxorubicin (Dox). Besides, after ultraviolet irradiation, the amide bond connecting Dox with PEG can be broken, which induced the responsive detachment of PEG and enhanced cellular uptake of Dox. Notably, the results of immunohistochemistry in vivo showed that Poly-Dox-M had no significant damage to normal organs. Meanwhile, they showed efficient tumor-suppressive effects. This nano-delivery system with the light-responsive feature might hold great promises for the targeted therapy for osteosarcoma.