Sono-assembly of folate-decorated curcumins/alginate core-shell microcomplex and its targeted delivery and pH/reduction dual-triggered release

In this study,sodium alginate(SA),a non-toxic natural polysaccharide with good biocompatibility and biodegradability,was developed for targeted delivery of curcumin(CUR)in tumor therapy.The strategy is to sulfhydrylate the folic acid(FA)modified SA,and the CUR dissolved in ethyl acetate(EAC)phase is coated in microcapsules by a quick,efficient and environment-friendly sonochemical method.The EAC in the microcapsule core is volatile,which can be recycled and reused to reduce cost.The prepared mi-crocapsules(FA-RSMCs@CUR)exhibited similar toxicity to free curcumin in anti-tumour evaluation in vitro.FA-RSMCs@CUR also exhibited effective antibacterial properties in the antibacterial evaluation in vitro.It is expected to become a low-cost tumor targeting vector in the future,and has the potential to be promoted in clinical application.

A food-grade and senescent cell-targeted fisetin delivery system based on whey protein isolate-galactooligosaccharides Maillard conjugate

Cellular senescence is the results of aging and age-related diseases,and the development of anti-aging methods may improve health and extend longevity.The natural flavonol fisetin has been shown to antagonize senescence in vitro and increases longevity in vivo,but has poor water solubility and limited bioavailability.In this study,a food-grade and senescent cell-targeted delivery system for fisetin was developed based on whey protein isolate-galactooligosaccharides(WPI-GOS)Maillard conjugate,which could recognize senescence associatedβ-galactosidase in senescent cells.The fisetin nanoparticles possessed a high encapsulation efficiency,excellent dispersibility in water,good storage stability and well biocompatibility.Moreover,they could effectively accumulate and retain in senescent cells with excellent senescent cell-targeting efficacy,and inhibit the oxidative stress-induced cellular senescence in vitro.Thus,this novel nanoparticle system based on WPI-GOS Maillard conjugate showed promise to deliver hydrophobic bioactive ingredients like fisetin to senescent cells to improve their bioavailability and anti-senescence effect.

Targeted delivery of RNAi to cancer cells using RNA-ligand displaying exosome

Exosome is an excellent vesicle for in vivo delivery of therapeutics,including RNAi and chemical drugs.The extremely high efficiency in cancer regression can partly be attributed to its fusion mechanism in delivering therapeutics to cytosol without endosome trapping.However,being composed of a lipidbilayer membrane without specific recognition capacity for aimed-cells,the entry into nonspecific cells can lead to potential side-effects and toxicity.Applying engineering approaches for targeting-capacity to deliver therapeutics to specific cells is desirable.Techniques with chemical modification in vitro and genetic engineering in cells have been reported to decorate exosomes with targeting ligands.RNA nanoparticles have been used to harbor tumor-specific ligands displayed on exosome surface.The negative charge reduces nonspecific binding to vital cells with negatively charged lipid-membrane due to the electrostatic repulsion,thus lowering the side-effect and toxicity.In this review,we focus on the uniqueness of RNA nanoparticles for exosome surface display of chemical ligands,small peptides or RNA aptamers,for specific cancer targeting to deliver anticancer therapeutics,highlighting recent advances in targeted delivery of siRNA and miRNA that overcomes the previous RNAi delivery roadblocks.Proper understanding of exosome engineering with RNA nanotechnology promises efficient therapies for a wide range of cancer subtypes.

Recent advances in zwitterionic nanoscale drug delivery systems to overcome biological barriers

Nanoscale drug delivery systems(nDDS)have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects.Although several nDDS have been successfully approved for clinical use up to now,biological barriers between the administration site and the target site hinder the wider clinical adoption of nDDS in disease treatment.Polyethylene glycol(PEG)-modification(or PEGylation)has been regarded as the gold standard for stabilising nDDS in complex biological environment.However,the accelerated blood clearance(ABC)of PEGylated nDDS after repeated injections becomes great challenges for their clinical applications.Zwitterionic polymer,a novel family of antifouling materials,have evolved as an alternative to PEG due to their super-hydrophilicity and biocompatibility.Zwitterionic nDDS could avoid the generation of ABC phenomenon and exhibit longer blood circulation time than the PEGylated analogues.More impressively,zwitterionic nDDS have recently been shown to overcome multiple biological barriers such as nonspecific organ distribution,pressure gradients,impermeable cell membranes and lysosomal degradation without the need of any complex chemical modifications.The realization of overcoming multiple biological barriers by zwitterionic nDDS may simplify the current overly complex design of nDDS,which could facilitate their better clinical translation.Herein,we summarise the recent progress of zwitterionic nDDS at overcoming various biological barriers and analyse their underlyingmechanisms.Finally,prospects and challenges are introduced to guide the rational design of zwitterionic nDDS for disease treatment.

Macrophage membrane-mediated targeted drug delivery for treatment of spinal cord injury regardless of the macrophage polarization states

Targeted delivery of therapeutics for spinal cord injury(SCI)has been a long-term challenge due to the complexity of the pathological procession.Macrophage,as an immune cell,can selectively accumulate at the trauma site after SCI.This intrinsic targeting,coupled with good immune-escaping capacity makes macrophages an ideal source of biomimetic delivery carrier for SCI.Worth mentioning,macrophages have multiple polarization states,which may not be ignored when designing macrophage-based delivery systems.Herein,we fabricated macrophage membrane-camouflaged liposomes(RM-LIPs)and evaluated their abilities to extend drug circulation time and target the injured spinal cord.Specially,we detected the expression levels of the two main targeted receptors Mac-1 and integrinα4 in three macrophage subtypes,including unactivated(M0)macrophages,classically activated(M1)macrophages and alternatively activated(M2)macrophages,and compared targeting of these macrophage membrane-coated nanoparticles for SCI.The macrophage membrane camouflage decreased cellular uptake of liposomes in RAW264.7 immune cells and strengthened binding of the nanoparticle to the damaged endothelial cells in vitro.RM-LIPs can prolong drug circulation time and actively accumulate at the trauma site of the spinal cord in vivo.Besides,RM-LIPs loaded with minocycline(RM-LIP/MC)showed a comprehensive therapeutic effect on SCI mice,and the anti-pyroptosis was found to be a novel mechanism of RM-LIP/MC treatment of SCI.Moreover,the levels of Mac-1 and integrinα4 in macrophages and the targeting of RM-LIP for SCI were found to be independent of macrophage polarization states.Our study provided a biomimetic strategy via the biological properties of macrophages for SCI targeting and treatment.

Glycyrrhizic Acid-Targeted Carbon Nanotube Nanocomposites with Polyethylenimines-Mediated for Cancer Drug Delivery

In order to enhance the efficiency and specificity of anticancer drug delivery and realize intelligently controlled release,a new multi-functional nanoparticle drug carrier was synthesized.The drug carrier was prepared by functionalizing multi-walled carbon nanotubes(MWCNTs) with polyethylenimines(PEI),fluorescein isothiocyanate(FITC) and glycyrrhizic acid(GL).After detailed characterization,doxorubicin(DOX) was loaded onto the obtained MWCNT composites through π-π stacking interactions.The drug loading capacity of the GL-functionalized material was up to 92%,and the release behavior was significantly pH-sensitive.Release at pH = 5.8(typical of the tumor cell microenvironment) was much more rapid and reached a greater extent than release under normal physiological conditions(pH = 7.4).The modified MWCNTs had high biocompatibility with the liver cancer cell line SMMC-7721,but were able to induce cell death after 24 h incubation if loaded with DOX.Tests with shorter incubation time(2 h) were undertaken to investigate the selectivity of the MWCNT composites,showed that the nanocomposites could specifically target cancer cells.The above results suggest that the functionalized carbon nanotubes-based material has potential applications for targeted delivery and controlled release of anticancer drug.

Molecularly engineered truncated tissue factor with therapeutic aptamers for tumor-targeted delivery and vascular infarction

Selective occlusion of tumor vasculature has proven to be an effective strategy for cancer therapy.Among vascular coagulation agents,the extracellular domain of coagulation-inducing protein tissue factor,truncated tissue factor(tTF),is the most widely used.Since the truncated protein exhibits no coagulation activity and is rapidly cleared in the circulation,free tTF cannot be used for cancer treatment on its own but must be combined with other moieties.We here developed a novel,tumor-specific tTF delivery system through coupling tTF with the DNA aptamer,AS1411,which selectively binds to nucleolin receptors overexpressing on the surface of tumor vascular endothelial cells and is specifically cytotoxic to target cells.Systemic administration of the tTF-AS1411 conjugates into tumor-bearing animals induced intravascular thrombosis solely in tumors,thus reducing tumor blood supply and inducing tumor necrosis without apparent side effects.This conjugate represents a uniquely attractive candidate for the clinical translation of vessel occlusion agent for cancer therapy.

Insights on drug and gene delivery systems in liver fibrosis

Complications of the liver are amongst the world’s worst diseases.Liver fibrosis is the first stage of liver problems,while cirrhosis is the last stage,which can lead to death.The creation of effective anti-fibrotic drug delivery methods appears critical due to the liver’s metabolic capacity for drugs and the presence of insurmountable physiological impediments in the way of targeting.Recent breakthroughs in anti-fibrotic agents have substantially assisted in fibrosis;nevertheless,the working mechanism of anti-fibrotic medications is not fully understood,and there is a need to design delivery systems that are well-understood and can aid in cirrhosis.Nanotechnology-based delivery systems are regarded to be effective but they have not been adequately researched for liver delivery.As a result,the capability of nanoparticles in hepatic delivery was explored.Another approach is targeted drug delivery,which can considerably improve efficacy if delivery systems are designed to target hepatic stellate cells(HSCs).We have addressed numerous delivery strategies that target HSCs,which can eventually aid in fibrosis.Recently genetics have proved to be useful,and methods for delivering genetic material to the target place have also been investigated where different techniques are depicted.To summarize,this review paper sheds light on themost recent breakthroughs in drug and gene-based nano and targeted delivery systems that have lately shown useful for the treatment of liver fibrosis and cirrhosis.

In Vitro Targeted Magnetic Delivery and Tracking of Superparamagnetic Iron Oxide Particles Labeled Stem Cells for Articular Cartilage Defect Repair

To assess a novel cell manipulation technique of tissue engineering with respect to its ability to augment superparamagnetic iron oxide particles （SPIO） labeled mesenchymal stem cells （MSCs） density at a localized cartilage defect site in an in vitro phantom by applying magnetic force. Meanwhile, non-invasive imaging techniques were use to track SPIO-labeled MSCs by magnetic resonance imaging （MRI）. Human bone marrow MSCs were cultured and labeled with SPIO. Fresh degenerated human osteochondral fragments were obtained during total knee arthroplasty and a cartilage defect was created at the center. Then, the osteochondral fragments were attached to the sidewalls of culture flasks filled with phosphate-buffered saline （PBS） to mimic the human joint cavity. The SPIO-labeled MSCs were injected into the culture flasks in the presence of a 0.57 Tesla （T） magnetic force. Before and 90 min after cell targeting, the specimens underwent T2-weighted turbo spin-echo （SET2WI） sequence of 3.0 T MRI. MRI results were compared with histological findings. Macroscopic observation showed that SPIO-labeled MSCs were steered to the target region of cartilage defect. MRI revealed significant changes in signal intensity （P0.01）. HE staining exibited that a great number of MSCs formed a three-dimensional （3D） cell ＂sheet＂ structure at the chondral defect site. It was concluded that 0.57 T magnetic force permits spatial delivery of magnetically labeled MSCs to the target region in vitro. High-field MRI can serve as an very sensitive non-invasive technique for the visualization of SPIO-labeled MSCs.

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.

Phytoestrogen-derived multifunctional ligands for targeted therapy of breast cancer

Nano-targeted delivery systems have been widely used for breast tumor drug delivery.Estrogen receptors are considered to be significant drug delivery target receptors due to their overexpression in a variety of tumor cells.However,targeted ligands have a significant impact on the safety and effectiveness of active delivery systems,limiting the clinical transformation of nanoparticles.Phytoestrogens have shown good biosafety characteristics and some affinity with the estrogen receptor.In the present study,molecular docking was used to select tanshinone IIA(Tan IIA)among phytoestrogens as a target ligand to be used in nanodelivery systems with somemodifications.Modified Tan IIA(Tan-NH2)showed a good biosafety profile and demonstrated tumor-targeting,anti-tumor and anti-tumor metastasis effects.Moreover,the ligand was utilized with the anti-tumor drug Dox-loaded mesoporous silica nanoparticles via chemical modification to generate a nanocomposite Tan-Dox-MSN.Tan-Dox-MSN had a uniform particle size,good dispersibility and high drug loading capacity.Validation experiments in vivo and in vitro showed that it also had a better targeting ability,anti-tumor effect and lower toxicity in normal organs.These results supported the idea that phytoestrogens with high affinity for the estrogen receptor could improve the therapeutic efficacy of nano-targeted delivery systems in breast tumors.

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.

Liposome based drug delivery as a potential treatment option for Alzheimer’s disease

Alzheimer’s disease is a neurodegenerative condition leading to atrophy of the brain and robbing nearly 5.8 million individuals in the United States age 65 and older of their cognitive functions.Alzheimer’s disease is associated with dementia and a progressive decline in memory,thinking,and social skills,eventually leading to a point that the individual can no longer perform daily activities independently.Currently available drugs on the market temporarily alleviate the symptoms,however,they are not successful in slowing down the progression of Alzheimer’s disease.Treatment and cures have been constricted due to the difficulty of drug delivery to the blood-brain barrier.Several studies have led to identification of vesicles to transport the necessary drugs through the blood-brain barrier that would typically not achieve the targeted area through systemic delivered medications.Recently,liposomes have emerged as a viable drug delivery agent to transport drugs that are not able to cross the blood-brain barrier.Liposomes are being used as a component of nanoparticle drug delivery;due to their biocompatible nature;and possessing the capability to carry both lipophilic and hydrophilic therapeutic agents across the blood brain barrier into the brain cells.Studies indicate the importance of liposomal based drug delivery in treatment of neurodegenerative disorders.The idea is to encapsulate the drugs inside the properly engineered liposome to generate a response of treatment.Liposomes are engineered to target specific diseased moieties and also several surface modifications of liposomes are under research to create a clinical path to the management of Alzheimer’s disease.This review deals with Alzheimer’s disease and emphasize on challenges associated with drug delivery to the brain,and how liposomal drug delivery can play an important role as a drug delivery method for the treatment of Alzheimer’s disease.This review also sheds some light on variation of liposomes.Additionally,it emphasizes on the liposomal formulations which are currently researched or used for treatment of Alzheimer’s disease and also discusses the future prospect of liposomal based drug delivery in Alzheimer’s disease.

Liver-specific drug delivery platforms: Applications for the treatment of alcohol-associated liver disease

Alcohol-associated liver disease(ALD)is a common chronic liver disease and major contributor to liver disease-related deaths worldwide.Despite its prevalence,there are few effective pharmacological options for the severe stages of this disease.While much pre-clinical research attention is paid to drug development in ALD,many of these experimental therapeutics have limitations such as poor pharmacokinetics,poor efficacy,or off-target side effects due to systemic administration.One means of addressing these limitations is through liver-targeted drug delivery,which can be accomplished with different platforms including liposomes,polymeric nanoparticles,exosomes,bacteria,and adenoassociated viruses,among others.These platforms allow drugs to target the liver passively or actively,thereby reducing systemic circulation and increasing the‘effective dose’in the liver.While many studies,some clinical,have applied targeted delivery systems to other liver diseases such as viral hepatitis or hepatocellular carcinoma,only few have investigated their efficacy in ALD.This review provides basic information on these liver-targeting drug delivery platforms,including their benefits and limitations,and summarizes the current research efforts to apply them to the treatment of ALD in rodent models.We also discuss gaps in knowledge in the field,which when addressed,may help to increase the efficacy of novel therapies and better translate them to humans.

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.

Ex vivo cartilage explant model for the evaluation of chondrocyte-targeted exosomes

There is no efficient tracking system available for the therapeutic molecules delivered to cartilage.The dense matrix covering the cartilage surface is the main biological barrier that the therapeutic molecules must overcome.In this study,we aimed to establish a system that can dynamically and effectively track the therapeutic molecules delivered to cartilage.To this aim,we adopted bovine and human cartilage explants as ex vivo models for chondrocyte-targeted exosome dispersion.The efficiency of drug delivery was evaluated using frozen sections.The results of this study showed that the penetration and distribution of chondrocyte-targeted exosomes in cartilage explants can be tracked dynamically.Thus,ex vivo cartilage explants provide an effective and economic system to evaluate therapeutic drugs encapsulated in chondrocyte-targeted exosomes in preclinical studies.

Nanoemulsion for delivery of anticancer drugs

Cancer refers to a collection of diseases that have abnormal cell growth as their hallmark.This inability of cytotoxic agents to distinguish between rapidly dividing healthy cells and rapidly multiplying cancerous cells produces the most notorious adverse effects of cytotoxic anticancer agents.As an essential tool in nanotechnology,nanoemulsions have therapeutic and clinical applications.Currently,nanoemulsions are considered to be one of the most feasible nano-carriers for delivering lipophilic antineoplastic agents with targeted delivery.In addition to solving water-solubilization issues,these formulations deliver specific targeting to cancer cells and might even be developed to overcome multi-drug resistance.Nanoemulsions overcome the problems associated with conventional drug delivery systems,such as low bioavailability and noncompliance.A review of nanoemulsion in cancer therapeutics is presented here to shed light on the current position of this technology.

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.

pH-sensitive polymeric nanocarriers for antitumor biotherapeutic molecules targeting delivery

pH-sensitive smart polymeric nanocarriers have been under development in the field ofbiomedicine due to permeabilization the physiological barriers readily to address the limitation of conventional chemotherapeutics delivery systems of low intracellular transport and targeting efficiency.Where traditional polymers kept stable under physiological neutral or acidic conditions,pH-sensitive polymeric nanocarriers underwent rapid degradation with a labile group in tumor acidic environment(around 5.0-6.0),allowing these biomaterials to achieve controlled drug release,drug pharmacokinetics improvement and antitumor biotherapeutic molecules efficiency enhancement compared with traditional polymers.This review mainly concentrated on properties of pH-sensitive polymers for biomedical purposes to construct the smart drug delivery system based on acid liable linkers which were categorized into pH-sensitive polymeric prodrugs composed of antitumor drugs(doxorubicin and paclitaxel)bounded to the polymer via acid liable linkers and pH-sensitive copolymeric nanocarriers prepared by block copolymers containing polymer blocks linked with acid-cleavable groups.Besides,advanced platforms in biomedicine for special biotherapeutic molecules delivery were reviewed in the article.Furthermore,several acid-sensitive linkages were reviewed to study the mechanism of the controlled pH-responsive drug delivery,such as hydrazone,acetal,cis-aconityl linker and β-thioether ester,as well as improvement of drug pharmacokinetics.

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.