A Study on the Multi-Compartment Linear Circulation Pharmacokinetic Model for the Targeting Drug Delivery System

By analyzing the observed phenomena and the data collected in the study, a multi-compartment linear circulation model for targeting drug delivery system was developed and the function formulas of the drug concentration-time in blood and target organ by computing were figured out. The drug concentration-time curve for target organ can be plotted with reference to the data of drug concentration in blood according to the model. The pharmacokinetic parameters of the drug in target organ could also be obtained. The practicability of the model was further checked by the curves of drug concentration-time in blood and target organ(liver) of liver-targeting nanoparticles in animal tests. Based on the liver drug concentration-time curves calculated by the function formula of the drug in target organ, the pharmacokinetic behavior of the drug in target organ(liver) was analyzed by statistical moment, and its pharmacokinetic parameters in liver were obtained. It is suggested that the (relative targeting index( can be used for quantitative evaluation of the targeting drug delivery systems.

Recent advances in lymphatic targeted drug delivery system for tumor metastasis

The lymphatic system has an important defensive role in the human body. The metastasis of most tumors initially spreads through the surrounding lymphatic tissue and eventually forms lymphatic metastatic tumors; the tumor cells may even transfer to other organs to form other types of tumors. Clinically, lymphatic metastatic tumors develop rapidly. Given the limitations of surgical resection and the low effectiveness of radiotherapy and chemotherapy, the treatment of lymphatic metastatic tumors remains a great challenge. Lymph node metastasis may lead to the further spread of tumors and may be predictive of the endpoint event. Under these circumstances, novel and effective lymphatic targeted drug delivery systems have been explored to improve the specificity of anticancer drugs to tumor cells in lymph nodes. In this review, we summarize the principles of lymphatic targeted drug delivery and discuss recent advances in the development of lymphatic targeted carriers.

Design and preparation of a new multi-targeted drug delivery system using multifunctional nanoparticles for co-delivery of siRNA and paclitaxel

Drug resistance is a great challenge in cancer therapy using chemotherapeutic agents. Administration of these drugs with siRNA is an efficacious strategy in this battle. Here, the present study tried to incorporate siRNA and paclitaxel(PTX) simultaneously into a novel nanocarrier. The selectivity of carrier to target cancer tissues was optimized through conjugation of folic acid(FA) and glucose(Glu) onto its surface. The structure of nanocarrier was formed from ternary magnetic copolymers based on FeCopolyethyleneimine(FeCo-PEI) nanoparticles and polylactic acid-polyethylene glycol(PLA-PEG) gene delivery system. Biocompatibility of FeCo-PEI-PLA-PEG-FA(NPsA), FeCo-PEI-PLA-PEG-Glu(NPsB) and FeCo-PEI-PLA-PEG-FA/Glu(NPsAB) nanoparticles and also influence of PTX-loaded nanoparticles on in vitro cytotoxicity were examined using MTT assay. Besides, siRNA-FAM internalization was investigated by fluorescence microscopy. The results showed the blank nanoparticles were significantly less cytotoxic at various concentrations. Meanwhile, siRNA-FAM/PTX encapsulated nanoparticles exhibited significant anticancer activity against MCF-7 and BT-474 cell lines. NPsAB/siRNA/PTX nanoparticles showed greater effects on MCF-7 and BT-474 cells viability than NPsA/siRNA/PTX and NPsB/siRNA/PTX.Also, they induced significantly higher anticancer effects on cancer cells compared with NPsA/siRNA/PTX and NPsB/siRNA/PTX due to their multi-targeted properties using FA and Glu. We concluded that NPsAB nanoparticles have a great potential for co-delivery of both drugs and genes for use in gene therapy and chemotherapy.

Layered Double Hydroxide Modified by PEGylated Hyaluronic Acid as a Hybrid Nanocarrier for Targeted Drug Delivery

In recent years, organic-inorganic hybrid nanocarriers are explored for effective drug delivery and preferable disease treatments. In this study, using 5-fluorouracil(5-FU)as electronegative model drug, a new type of organic-inorganic hybrid drug delivery system(LDH/HA-PEG/5-FU)was conceived and manufactured by the adsorption of PEGylated hyaluronic acid(HA-PEG)on the surface of layered double hydroxide(LDH, prepared via hydrothermal method)and the intercalation of 5-FU in the interlamination of LDH via ion exchange strategy. The drug loading amount of LDH/HA-PEG/5-FU achieved as high as 34.2%. LDH, LDH/5-FU and LDH/HA-PEG/5-FU were characterized by FT-IR, XRD, TGA, laser particle size analyzer and SEM. With the benefit of p Hdegradable feature of LDH and enzyme-degradable feature of HA, LDH/HA-PEG/5-FU showed p H-degradable and enzyme-degradable capacity in in vitro drug release. Moreover, the drug carrier LDH/HA-PEG contained biocompatible PEG and tumor-targeted HA, resulting in lower cytotoxicity and better endocytosis compared with LDH in vitro. It was suggested that the organic-inorganic hybrid drug delivery system, which was endowed with the properties of controlled release, low toxicity and tumor-targeting delivery for ameliorative cancer therapy, was advisable and might be applied further to fulfill other treatments.

Process Modeling of Ferrofluids Flow for Magnetic Targeting Drug Delivery

Among the proposed techniques for delivering drugs to specific sites within the human body, magnetic targeting drug delivery surpasses due to its non-invasive character and its high targeting efficiency. Although there have been some analyses theoretically for magnetic drug targeting, very few researchers have addressed the hydrodynamic models of magnetic fluids in the blood vessel of human body. This paper presents a mathematical model to describe the hydrodynamics of ferrofluids as drug carriers flowing in a blood vessel under the applied magnetic field. A 3D flow field of magnetic particles in a blood vessel model is numerically simulated in order to further understand clinical application of magnetic targeting drug delivery. Simulation results show that magnetic nanoparticles can be enriched in a target region depending on the applied magnetic field intensity. Magnetic resonance imaging confirms the enrichment of ferrofluids in a desired body tissue of Sprague-Dawley rats. The simulation results coincide with those animal experiments. Results of the analysis provide the important information and can suggest strategies for improving delivery in favor of the clinical application.

Hydrodynamic modeling of ferrofluid flow in magnetic targeting drug delivery

Among the proposed techniques for delivering drugs to specific locations within human body, magnetic drug targeting prevails due to its non-invasive character and its high targeting efficiency. Magnetic targeting drug delivery is a method of carrying drug-loaded magnetic nanoparticles to a target tissue target under the applied magnetic field. This method increases the drug concentration in the target while reducing the adverse side-effects. Although there have been some theoretical analyses for magnetic drug targeting, very few researchers have addressed the hydrodynamic models of magnetic fluids in the blood vessel. A mathematical model is presented to describe the hydrodynamics of ferrofiuids as drug carriers flowing in a blood vessel under the applied magnetic field. In this model, magnetic force and asymmetrical force are added, and an angular momentum equation of magnetic nanoparticles in the applied magnetic field is modeled. Engineering approximations are achieved by retaining the physically most significant items in the model due to the mathematical complexity of the motion equations. Numerical simulations are performed to obtain better insight into the theoretical model with computational fluid dynamics. Simulation results demonstrate the important parameters leading to adequate drug delivery to the target site depending on the magnetic field intensity, which coincident with those of animal experiments. Results of the analysis provide important information and suggest strategies for improving delivery in clinical application.

Performance Analysis of Magnetic Nanoparticles during Targeted Drug Delivery:Application of OHAM

In recent years,the emergence of nanotechnology experienced incredible development in the field of medical sciences.During the past decade,investigating the characteristics of nanoparticles during fluid flow has been one of the intriguing issues.Nanoparticle distribution and uniformity have emerged as substantial criteria in both medical and engineering applications.Adverse effects of chemotherapy on healthy tissues are known to be a significant concern during cancer therapy.A novel treatment method of magnetic drug targeting(MDT)has emerged as a promising topical cancer treatment along with some attractive advantages of improving efficacy,fewer side effects,and reduce drug dose.During magnetic drug targeting,the appropriate movement of nanoparticles(magnetic)as carriers is essential for the therapeutic process in the blood clot removal,infection treatment,and tumor cell treatment.In this study,we have numerically investigated the behavior of an unsteady blood flowinfused with magnetic nanoparticles during MDT under the influence of a uniform external magnetic field in a microtube.An optimal homotopy asymptotic method(OHAM)is employed to compute the governing equation for unsteady electromagnetohydrodynamics flow.The influence of Hartmann number(Ha),particle mass parameter(G),particle concentration parameter(R),and electro-osmotic parameter(k)is investigated on the velocity of magnetic nanoparticles and blood flow.Results obtained show that the electro-osmotic parameter,along with Hartmann’s number,dramatically affects the velocity of magnetic nanoparticles,blood flow velocity,and flow rate.Moreover,results also reveal that at a higher Hartman number,homogeneity in nanoparticles distribution improved considerably.The particle concentration andmass parameters effectively influence the capturing effect on nanoparticles in the blood flow using a micro-tube for magnetic drug targeting.Lastly,investigation also indicates that the OHAM analysis is efficient and quick to handle the system of nonlinear equations.

MOF-based magnetic microrobot swarms for pH-responsive targeted drug delivery

Metal-organic frameworks(MOFs)hold significant potential as vehicles for drug delivery due to their expansive specific surface area,biocompatibility,and versatile attributes.Concurrently,magnetically actuated micro/nano-robots(MNRs)offer distinct advantages,such as untethered and precise manipulation.The fusion of these technologies presents a promising avenue for achieving non-invasive targeted drug delivery.Here,we report a MOF-based magnetic microrobot swarm(MMRS)for targeted therapy.Our approach overcomes limitations associated with a single MNR,including limited drug loading and the risk of loss during manipulation.We select Zeolitic Imidazolate Framework-8(ZIF-8)as the drug vehicle for its superior loading potential and p H-sensitive decomposition.Our design incorporates magnetic responsive components into the one-pot synthesis of Fe@ZIF-8,enabling collective behaviors under actuation.Tuning the yaw angle of alternating magnetic fields and nanoparticles'amount,the MMRSs with controllable size achieve instantaneous transformation among different configurations,including vortex-like swarms,chain-like swarms,and elliptical swarms,facilitating adaptation to environmental variations.Transported to the subcutaneous T24 tumor site,the MMRSs with encapsulated doxorubicin(DOX)automatically degrade and release the drug,leading to a dramatic reduction of the tumor in vivo.Our investigation signifies a significant advancement in the integration of biodegradable MOFs into microrobot swarms,ushering in new avenues for accurate and non-invasive targeted drug delivery.

Anti-cancer drugs targeting using nanocarrier niosomes-a review

In the last few decades numbers of review and research articles have been published on niosomes. This shows the relevant interest of academias & researchers in niosomes because of the advantages sponsored by them over other colloidal drug delivery systems. Niosomes formation occurs when non-ionic surfactant vesicles assemble themselves. Various antineoplastic agents are used in chemotherapy, but they have some drawbacks that these agents cause cell death in normal tissues as well. There are two approaches to overcome this limitation. First, to modify the structure of existing drugs, but this will not possible because it changes the properties of drugs. Second, the development of nano-carriers like liposomes, dendrimers, nanoparticles, niosomes et al. Among all, niosomes (non-ionic surfactant vesicles) have more advantages besides all nano-carriers. Drugs either hydrophilic in nature or hydrophobic in nature, both can be incorporated in niosomes. And by embedding specific ligands over vesicular surface enables us to target the drug to specific cancer cells.

Endoplasmic reticulum-targeted delivery of celastrol and PD-L1 siRNA for reinforcing immunogenic cell death and potentiating cancer immunotherapy

The prospect of employing chemoimmunotherapy targeted towards the endoplasmic reticulum(ER)presents an opportunity to amplify the synergistic effects of chemotherapy and immunotherapy.In this study,we initially validated celastrol(CEL)as an inducer of immunogenic cell death(ICD)by promoting ER stress and autophagy in colorectal cancer(CRC)cells.Subsequently,an ER-targeted strategy was posited,involving the codelivery of CEL with PD-L1 small interfering RNAs(siRNA)using KDEL peptide-modified exosomes derived from milk(KME),to enhance chemoimmunotherapy outcomes.Our findings demonstrate the efficient transportation of KME to the ER via the Golgi-to-ER pathway.Compared to their non-targeting counterparts,KME exhibited a significant augmentation of the CEL-induced ICD effect.Additionally,it facilitated the release of danger signaling molecules(DAMPs),thereby stimulating the antigen-presenting function of dendritic cells and promoting the infiltration of T cells into the tumor.Concurrently,the ER-targeted delivery of PD-L1 siRNA resulted in the downregulation of both intracellular and membrane PD-L1 protein expression,consequently fostering the proliferation and activity of CD8^(+)T cells.Ultimately,the ER-targeted formulation exhibited enhanced anti-tumor efficacy and provoked anti-tumor immune responses against orthotopic colorectal tumors in vivo.Collectively,a robust ER-targeted delivery strategy provides an encouraging approach for achieving potent cancer chemoimmunotherapy.

Macrophage membrane-coated nanovesicles for dual-targeted drug delivery to inhibit tumor and induce macrophage polarization

Background:Immunosuppressive M2 macrophages in the tumor microenvironment(TME)can mediate the therapeutic resistance of tumors,and seriously affect the clinical efficacy and prognosis of tumor patients.This study aims to develop a novel drug delivery system for dual-targeting tumor and macrophages to inhibit tumor and induce macrophage polarization.Methods:The anti-tumor effects of methyltransferase like 14(METTL14)were investigated both in vitro and in vivo.The underlying mechanisms of METTL14 regulating macrophages were also explored in this study.We further constructed the cyclic(Arg-Gly-Asp)(cRGD)peptide modified macrophage membrane-coated nanovesicles to co-deliver METTL14 and the TLR4 agonist.Results:We found that METTL14 significantly inhibits the growth of tumor in vitro.METTL14 might downregulate TICAM2 and inhibit the Toll-like receptor 4(TLR4)pathway of macrophages,meanwhile,the combination of METTL14 and the TLR4 agonist could induce M1 polarization of macrophages.Macrophage membrane-coated nanovesicles are characterized by easy modification,drug loading,and dual-targeting tumor and macrophages,and cRGD modification can further enhance its targeting ability.It showed that the nanovesicles could improve the in vivo stability of METTL14,and dual-target tumor and macrophages to inhibit tumor and induce M1 polarization of macrophages.Conclusions:This study anticipates achieving the dual purposes of tumor inhibition and macrophage polarization,and providing a new therapeutic strategy for tumors.

Targeting Effect Study of ￣(3) H-Mitoxantrone Nanosphereson Hepatocellular Carcinoma(HCC) Model in Nude Mice

The distribution of ￣(3)H-mitoxantrone polybutyl cyanoacrylate nanospheres(￣(3)H-DHAQ-PBCA-NS)in the viscera,muscle and tumors of human hepatocellular carcinoma (HCC)model in nude mice was studied with liquid scintillation counting techniique. The results showed that the ￣(3)H-DHAQ-PBCA-NS had remarkable liver targeting effect. The content of ￣(3)H-DHAQ-PBCA-NSin liver and heterotopic liver tumor was found to be 71.31±10. 49% of total amount of drug in animal body. It was also found that the content of ￣(3)H-DHAQ-PBCA-NS in liver was higher than that in liver tissue, and the content of ￣(3)H-DHAQ-PBCA-NS in annpit tumor was higher than that in armpit muscle tissue,but had no significant difference;It provides an ideal preparation for the DHAQ admini-stration.

The feasibility of oral targeted drug delivery: Gut immune to particulates?

Targeted drug delivery is constantly updated with a better understanding of the physiological and pathological features of various diseases. Depending on high safety, good compliance and many other undeniable advantages, attempts have been undertaken to complete an intravenous-to-oral conversion of targeted drug delivery. However, oral delivery of particulates to systemic circulation is highly challenging due to the biochemical aggressivity and immune exclusion in the gut that restrain absorption and access to the bloodstream. Little is known about the feasibility of targeted drug delivery via oral administration(oral targeting) to a remote site beyond the gastrointestinal tract. To this end, this review proactively contributes to a special dissection on the feasibility of oral targeting. We discussed the theoretical basis of oral targeting, the biological barriers of absorption, the in vivo fate and transport mechanisms of drug vehicles, and the effect of structural evolution of vehicles on oral targeting as well. At last, a feasibility analysis on oral targeting was performed based on the integration of currently available information. The innate defense of intestinal epithelium does not allow influx of more particulates into the peripheral blood through enterocytes. Therefore, limited evidence and lacking exact quantification of systemically exposed particles fail to support much success with oral targeting. Nevertheless, the lymphatic pathway may serve as a potentially alternative portal of peroral particles into the remote target sites via M-cell uptake.

Functionalized liposomes for targeted breast cancer drug delivery

Despite the exceptional progress in breast cancer pathogenesis,prognosis,diagnosis,and treatment strategies,it remains a prominent cause of female mortality worldwide.Additionally,although chemotherapies are effective,they are associated with critical limitations,most notably their lack of specificity resulting in systemic toxicity and the eventual development of multi-drug resistance(MDR)cancer cells.Liposomes have proven to be an invaluable drug delivery system but of the multitudes of liposomal systems developed every year only a few have been approved for clinical use,none of which employ active targeting.In this review,we summarize the most recent strategies in development for actively targeted liposomal drug delivery systems for surface,transmembrane and internal cell receptors,enzymes,direct cell targeting and dual-targeting of breast cancer and breast cancer-associated cells,e.g.,cancer stem cells,cells associated with the tumor microenvironment,etc.

Brain delivering RNA-based therapeutic strategies by targeting mTOR pathway for axon regeneration after central nervous system injury

Injuries to the central nervous system(CNS)such as stroke,brain,and spinal cord trauma often result in permanent disabilities because adult CNS neurons only exhibit limited axon regeneration.The brain has a surprising intrinsic capability of recovering itself after injury.However,the hostile extrinsic microenvironment significantly hinders axon regeneration.Recent advances have indicated that the inactivation of intrinsic regenerative pathways plays a pivotal role in the failure of most adult CNS neuronal regeneration.Particularly,substantial evidence has convincingly demonstrated that the mechanistic target of rapamycin(mTOR)signaling is one of the most crucial intrinsic regenerative pathways that drive axonal regeneration and sprouting in various CNS injuries.In this review,we will discuss the recent findings and highlight the critical roles of mTOR pathway in axon regeneration in different types of CNS injury.Importantly,we will demonstrate that the reactivation of this regenerative pathway can be achieved by blocking the key mTOR signaling components such as phosphatase and tensin homolog(PTEN).Given that multiple mTOR signaling components are endogenous inhibitory factors of this pathway,we will discuss the promising potential of RNA-based therapeutics which are particularly suitable for this purpose,and the fact that they have attracted substantial attention recently after the success of coronavirus disease 2019 vaccination.To specifically tackle the blood-brain barrier issue,we will review the current technology to deliver these RNA therapeutics into the brain with a focus on nanoparticle technology.We will propose the clinical application of these RNA-mediated therapies in combination with the brain-targeted drug delivery approach against mTOR signaling components as an effective and feasible therapeutic strategy aiming to enhance axonal regeneration for functional recovery after CNS injury.

Self-assembled Nanoparticles based on Folic Acid Modifi ed Carboxymethyl Chitosan Conjugated with Targeting Antibody

Nanoparticles conjugated with antibody were designed as active drug delivery system to reduce the toxicity and side effects of drugs for acute myeloid leukemia（AML）.Moreover,methotrexate（MTX）was chosen as modeldrug and encapsulate within folic acid modified carboxymethylchitosan（FACMCS）nanoparticles through self-assembling.The chemicalstructure,morphology,release and targeting of nanoparticles were characterized by routine detection.It is demonstrated that the mean diameter is about 150 nm,the release rate increases with the decreasing of p H,the binding rate of CD33 antibody and FA-CMCS nanoparticles is about 5：2,and nanoparticles can effectively bind onto HL60 cells in vitro.The experimentalresults indicate that the FA-CMCS nanoparticles conjugated with antibody may be used as a potentialp Hsensitive drug delivery system with leukemic targeting properties.

Tumor specifically internalizing peptide ‘HN-1’: Targeting the putative receptor retinoblastoma-regulated discoidin domain receptor 1 involved in metastasis

BACKGROUND Less than 0.5%of intravenously injected drugs reach tumors,contributing to side effects.To limit damage to healthy cells,various delivery vectors have been formulated;yet,previously developed vectors suffer from poor penetration into solid tumors.This issue was resolved by the discovery of HN-1 peptide isolated via biopanning a phage-display library.HN-1 targets human head and neck squamous cell carcinoma(HNSCC)(breast,thyroid;potentially lung,cervix,uterine,colon cancer),translocates across the cell membrane,and efficiently infiltrates solid tumors.HN-1 peptide has been conjugated to various anticancer drugs and imaging agents though the identity of its receptor remained enigmatic.AIM To decipher the clues that pointed to retinoblastoma(Rb)-regulated discoidindomain receptor 1 as the putative receptor for HN-1 is described.METHODS HN-1 peptide was synthesized and purified using reverse-phase highperformance liquid chromatography and gel electrophoresis.The predicted mass was confirmed by mass spectroscopy.To image the 3-dimensional structure of HN-1 peptide,PyMOL was used.Molecular modeling was also performed with PEP-FOLD3 software via RPBS bioinformatics web portal(INSERM,France).The immunohistochemistry results of discoidin domain receptor 1(DDR1)protein were obtained from the publicly accessible database in the Human Protein Atlas portal,which contained the images of immunohistochemically labeled human cancers and the corresponding normal tissues.RESULTS The clues that led to DDR1 involved in metastasis as the putative receptor mediating HN-1 endocytosis are the following:(1)HN-1 is internalized in phosphate-buffered saline and its uptake is competitively inhibited;(2)HN-1(TSPLNIHNGQKL)exhibits similarity with a stretch of amino acids in alpha5 beta3 integrin(KLLITIHDRKEF).Aside from two identical residues(Ile-His)in the middle,the overall distribution of polar and nonpolar residues throughout the sequences is nearly identical.As HN-1 sequence lacks the Arg-Gly-Asp motif recognized by integrins,HN-1 may interact with an"integrin-like"molecule.The tertiary structure of both peptides showed similarity at the 3-dimensional level;(3)HN-1 is internalized by attached cells but not by suspended cells.As culture plates are typically coated with collagen,collagen-binding receptor(expressed by adherent but not suspended cells)may represent the receptor for HN-1;(4)DDR1 is highly expressed in head and neck cancer(or breast cancer)targeted by HN-1;(5)Upon activation by collagen,DDR1 becomes internalized and compartmentalized in endosomes consistent with the determination of’energy-dependent clathrin-mediated endocytosis’as the HN-1 entry route and the identification of HN-1 entrapped vesicles as endosomes;and(6)DDR1 is essential for the development of mammary glands consistent with the common embryonic lineage rationale used to identify breast cancer as an additional target of HN-1.In summary,collagenactivated tyrosine kinase receptor DDR1 overexpressed in HNSCC assumes a critical role in metastasis.Further studies are warranted to assess HN-1 peptide’s interaction with DDR1 and the therapeutic potential of treating metastatic cancer.Additionally,advances in delivery(conformation,endocytic mechanism,repertoire of targeted cancers of HN-1 peptide),tracking(HN-1 conjugated imaging agents),and activity(HN-1 conjugated therapeutic agents)are described.CONCLUSION The discovery of DDR1 as HN-1 peptide’s putative receptor represents a significant advance as it enables identification of metastatic cancers or clinical application of previously developed therapeutics to block metastasis.

Cancer chemotherapy and beyond:Current status,drug candidates,associated risks and progress in targeted therapeutics

Cancer is an abnormal state of cells where they undergo uncontrolled proliferation and produce aggressive malignancies that causes millions of deaths every year.With the new understanding of the molecular mechanism(s)of disease progression,our knowledge about the disease is snowballing,leading to the evolution of many new therapeutic regimes and their successive trials.In the past few decades,various combinations of therapies have been pro-posed and are presently employed in the treatment of diverse cancers.Targeted drug therapy,immunotherapy,and personalized medicines are now largely being employed,which were not common a few years back.The field of cancer discoveries and therapeutics are evolving fast as cancer type-specific biomarkers are progressively being identified and several types of cancers are nowadays undergoing systematic therapies,extending patients’disease-free survival thereafter.Although growing evidence shows that a systematic and targeted approach could be the future of cancer medicine,chemotherapy remains a largely opted therapeutic option despite its known side effects on the patient’s physical and psychological health.Chemother-apeutic agents/pharmaceuticals served a great purpose over the past few decades and have remained the frontline choice for advanced-stage malignancies where surgery and/or radiation therapy cannot be prescribed due to specific reasons.The present report succinctly reviews the existing and contemporary advancements in chemotherapy and assesses the status of the enrolled drugs/pharmaceuticals;it also comprehensively discusses the emerging role of specific/targeted therapeutic strategies that are presently being employed to achieve better clinical success/survival rate in cancer patients.

Brain tumor-targeted drug delivery strategies

Despite the application of aggressive surgery,radiotherapy and chemotherapy in clinics,brain tumors are still a difficult health challenge due to their fast development and poor prognosis.Brain tumor-targeted drug delivery systems,which increase drug accumulation in the tumor region and reduce toxicity in normal brain and peripheral tissue,are a promising new approach to brain tumor treatments.Since brain tumors exhibit many distinctive characteristics relative to tumors growing in peripheral tissues,potential targets based on continuously changing vascular characteristics and the microenvironment can be utilized to facilitate effective brain tumor-targeted drug delivery.In this review,we briefly describe the physiological characteristics of brain tumors,including blood–brain/brain tumor barriers,the tumor microenvironment,and tumor stem cells.We also review targeted delivery strategies and introduce a systematic targeted drug delivery strategy to overcome the challenges.

Cadmium nanoclusters in a protein matrix： Synthesis, characterization, and application in targeted drug delivery and cellular imaging

Biotemplated metal nanoclusters have garnered much attention owing to their wide range of potential applications in biosensing, bioimaging, catalysis, and nanomedicine. Here, we report the synthesis of stable, biocompatible, watersoluble, and highly fluorescent bovine serum albumin-templated cadmium nanoclusters （CdNcs） through a facile one-pot green method. We covalently conjugated hyaluronic acid （HA） to the CdNcs to form a pH-responsive, tumor- targeting theranostic nanocarrier with a sustained release profile for doxorubicin （DOX）, a model anticancer drug. The nanocarrier showed a DOX encapsulation efficiency of about 75.6%. DOX release profiles revealed that 74% of DOX was released at pH 5.3, while less than 26% of DOX was released at pH 7.4 within the same 24-h period. The nanocarrier selectively recognized MCF-7 breast cancer cells expressing CD44, a cell surface receptor for HA, whereas no such recognition was observed with HA receptor-negative HEK293 cells. Biocompatibility of the nanocarrier was evaluated through cytotoxicity assays with HEK293 and MCF-7 ceils. The nanocarrier exhibited very low to no cytotoxicity, whereas the DOX-loaded nanocarrier showed considerable cellular uptake and enhanced MCF-7 breast cancer cell-killing ability. We also confirmed the feasibility of using the highly fluorescent nanoconjugate for bioimaging of MCF-7 and HeLa cells. The superior targeted drug delivery efficacy, cellular imaging capability, and low cytotoxicity position this nanoconjugate as an exciting new nanoplatform with promising biomedical applications.