Latest advances in glucose-responsive microneedle-based systems for transdermal insulin delivery

The development of a self-regulated minimally invasive system for insulin delivery can be considered as the holy grail in the field of diabetes mellitus. A delivery system capable of releasing insulin in response to blood glucose levels would significantly improve the quality of life of diabetic patients, eliminating the need for frequent finger-prick tests and providing better glycaemic control with lower risk of hypoglycaemia. In this context, the latest advances in glucose-responsive microneedle-based transdermal insulin delivery are here compiled with a thorough analysis of the delivery mechanisms and challenges lying ahead in their clinical translation. Two main groups of microneedle-based systems have been developed so far: glucose oxidase-containing and phenylboronic acid-containing systems. Both strategies in combination have also been tested and two other novel strategies are under development, namely electronic closed-loop and glucose transporter-based systems. Results from preclinical studies conducted using these different types of glucose-triggered release systems are comprehensively discussed. Altogether, this analysis from both a mechanistic and translational perspective will provide rationale and/or guidance for future trends in the research hotspot of glucose-responsive microneedle-based insulin delivery systems.

Targeted cancer treatment using folate-conjugated sponge-like ZIF-8 nanoparticles: a review

ZIF-8 (zeolitic imidazolate framework-8) is a potential drug delivery system because of its unique properties, which include a large surface area, a large pore capacity, a large loading capacity, and outstanding stability under physiological conditions. ZIF-8 nanoparticles may be readily functionalized with targeting ligands for the identification and absorption of particular cancer cells, enhancing the efficacy of chemotherapeutic medicines and reducing adverse effects. ZIF-8 is also pH-responsive, allowing medication release in the acidic milieu of cancer cells. Because of its tunable structure, it can be easily functionalized to design cancer-specific targeted medicines. The delivery of ZIF-8 to cancer cells can be facilitated by folic acid-conjugation. Hence, it can bind to overexpressed folate receptors on the surface of cancer cells, which holds the promise of reducing unwanted deliveries. As a result of its importance in cancer treatment, the folate-conjugated ZIF-8 was the major focus of this review.

TiO2/PEG as smart anticorrosion and drug-eluting platforms in inflammatory conditions

The failure of a titanium implant is often attributed to inflammatory reactions following implantation. This study focuses on the synthesis of a polyethylene glycol (PEG) layer on porous titanium dioxide (TiO2) coatings using plasma electrolytic oxidation (PEO). This PEG layer serves as a foundation for a drug-eluting platform designed to respond to pH stimuli during inflammation. Betamethasone (BET), a widely used anti-inflammatory drug, was loaded onto the pH-responsive functional PEG layers. The application of the PEG-BET layer onto TiO2 coatings through the vacuum dip coating method resulted in a pH-sensitive sustained release of BET over a 30-day period. Notably, the release rates were 81% at pH 5.0 and 55% at pH 7.2. Electrochemical corrosion tests conducted in both normal and acidic inflammatory solutions demonstrated that duplex composite coatings offer superior protection compared to simple oxide coatings. In a pH 5.0 solution, corrosion current density measurements revealed values of 1.75 μA cm-2 (PEO/PEG-BET), 8.87 μA cm-2 (PEO), and 49.17 μA cm-2 (bare titanium). These results highlight the effectiveness of the PEO/PEG-BET layer in sealing pores within PEO coatings, subsequently reducing the infiltration of corrosive ions in inflammatory environments.

Sodium alginate-based smart gastro-retentive drug delivery system of revaprazan loaded SLNs; Formulation and characterization

Revaprazan (REV), a novel reversible Proton Pump Inhibitor (PPI) used to treat peptic ulcers, faces challenges in therapeutic efficacy due to its poor dissolution properties and a short half-life. Solid lipid nanoparticles (SLNs) have emerged as a drug delivery system capable of enhancing dissolution and bioavailability of lipid soluble drugs. Here, we report on the development and optimization of a smart gastro-retentive raft system of REV-loaded SLNs (GRS/REV-SLNs) to enhance drug bioavailability and gastric retention. The optimized REV-SLNs had a particle size of 120 nm, a Polydispersity Index (PDI) of 0.313, a zeta potential of -20.7 mV, and efficient drug incorporation of 88 %. Transmission Electron Microscopy (TEM) affirmed the spherical morphology of these REV-SLNs, while Fourier Transform Infrared Spectroscopy (FTIR) revealed no chemical interactions among components. In-vitro assessment of the final GRS/REV-SLNs demonstrated sustained gelation and buoyancy for over 12 h, which would significantly enhance REV retention and its release within the stomach. Further assessments in rats confirmed successful gel transformation within the stomach, resulting in the improved bioavailability of REV. Thus, the development of GRS/REV-SLNs significantly improved the delivery and bioavailability of REV within the stomach, and offers a potentially improved method of treating peptic ulcers.

Light and pH responsive catanionic vesicles based on a chalcone/flavylium photoswitch for smart drug delivery: From molecular design to the controlled release of doxorubicin

Spatially and temporally localized delivery is a promising strategy to circumvent adverse effects of traditional drug therapy such as drug toxicity and prolonged treatments. Stimuli-responsive colloidal nanocarriers can be crucial to attain such goals. Here, we develop a delivery system based on dual light and pH responsive vesicles having a cationic bis-quat gemini surfactant, 12-2-12, and a negatively charged amphiphilic chalcone, C4SCh. The premise is to exploit the chalcone/flavylium interconversion to elicit a morphological change of the vesicles leading to the controlled release of an encapsulated drug. First, the phase behavior of the catanionic system is studied and the desirable composition yielding stable unilamellar vesicles identified and selected for further studies. The solutions containing vesicles (Dh ≈ 200 nm, ζ-potential ≈ 80 mV) are in-depth characterized by light microscopy, cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and surface tension measurements. Upon subjecting the vesicles to UV irradiation (λ = 365 nm) at near neutral pH (≈ 6.0), no morphological effects are observed, yet when irradiation is coupled with pH = 3.0, the majority of the vesicles are disrupted into bilayer fragments. The anticancer drug doxorubicin (DOX) is successfully entrapped in the non-irradiated vesicles, yielding an encapsulation efficiency of ≈ 25% and a loading capacity of ≈ 3%. The release profile of the drug-loaded vesicles is then studied in vitro in four conditions: i) no stimuli (pH = 6.0); ii) irradiation, pH = 6.0; iii) no irradiation and adjusted pH = 3.0; iv) irradiation and adjusted pH = 3.0 Crucially, irradiation at pH = 3.0 leads to a sustained release of DOX to ca. 80% (within 4 h), whereas cases i) and ii) lead to only ≈ 25 % release and case iii) to 50% release but precipitation of the vesicles. Thus, our initial hypothesis is confirmed: we present a proof of concept delivery system where light and pH act as inputs of an AND logic gate mechanism for the controlled release of a relevant biomedical drug (output). This may prove useful if the irradiated nanocarriers meet acidified physiological environments such as tumors sites, endosomes or lysosomes.

Localised Delivery of Cisplatin from Chitosan-Coated Titania Nanotube Array Nanosystems Targeting Nasopharyngeal Carcinoma

Pupose: Cisplatin (CDDP), while amongst the recognised chemotherapeutic drugs currently available, is known to have limitations; the lack of a single treatment approach and non-specific targeted therapies. Therefore, the development of an innovative strategy that could achieve localised CDDP treatment is an urgent undertaking. Recent advances in titania nanotube arrays (TNAs) technology have demonstrated promising applications for localised chemotherapeutic drug treatment. The present work investigated the efficiency of a TNA nanosystem for the localised CDDP treatment of nasopharyngeal carcinoma (NPC). Methods: Two models of the TNA nanosystem were prepared: CDDP loaded onto the TNA nanosystem surface (CDDP-TNA) and the other consisted of chitosan-coated CDDP-TNA. CDDP release from these two nanosystems was comprehensively tested on the NPC cells NPC/HK-1 and C666-1. The NPC cytotoxicity profile of the two CDDP-TNA nanosystems was evaluated after incubation for 24, 48 and 72 hours. Intracellular damage profiles were studied using fluorescence microscopy analysis with Hoechst 33342, acridine orange and propidium iodide. Results: The half-maximal inhibitory concentrations (IC₅₀) of CDDP at 24 hours were 0.50 mM for NPC/HK-1 and 0.05 mM for C666-1. CDDP in the CDDP-TNA and chitosan-coated CDDPTNA models presented a significant degree of NPC inhibition (P<0.05) after 24, 48 and 72 hours of exposure. The outcome revealed cellular damage and shrinkage of the cell membranes after 48 hours of exposure to CDDP-TNA. Conclusion: This in vitro work demonstrated the effectiveness of TNA nanosystems for the localised CDDP treatment of NPC cells. Further in vivo studies are needed to support the findings.

Clickable and smart drug delivery vehicles accelerate the healing of infected diabetic wounds

In this study, an adipic acid dihydrazide (ADH)/ tannic acid (TA)-grafted hyaluronic acid (HA)-based multifunctional hydrogel was synthesized through a spontaneous amino-yne click reaction and used to promote the improved healing of infected diabetic wounds. This hydrogel exhibited a range of beneficial properties such as tunable gelation time, adjustable mechanical properties, pH-sensitive response characteristics, excellent injectability, the ability to readily adhere to tissue, and ultra-intimate contact capabilities. Following the encapsulation of ultrasmall Ag nanoclusters (AgNCs) and deferoxamine loaded polydopamine/ hollow mesoporous manganese dioxide (PHMD, PDA/H-mMnO₂@DFO) nanoparticles, the prepared hydrogel presented with robust antibacterial, anti-inflammatory, and pro-angiogenic properties and a desirable smart drug release profile. In this fabricated platform, PHMD was able to effectively alleviate localized oxidative stress and prolonged oxygen deprivation via the decomposition of endogenous H₂O₂ to produce O₂. Further in vivo assays revealed that this hydrogel was capable of facilitating the healing of infected wounds through the sequential engagement of antibacterial, anti-inflammatory, and pro-angiogenic activities. Together, this synthesized clickable environmentally-responsive hydrogel offers great promise as a tool that can be applied to aid in the healing of chronically infected diabetic wounds and other inflammatory conditions.

Nanocarrier cancer therapeutics with functional stimuli-responsive mechanisms

Presently, nanocarriers (NCs) have gained huge attention for their structural ability, good biocompatibility, and biodegradability. The development of effective NCs with stimuli-responsive properties has acquired a huge interest among scientists. When developing drug delivery NCs, the fundamental goal is to tackle the delivery-related problems associated with standard chemotherapy and to carry medicines to the intended sites of action while avoiding undesirable side effects. These nanocarriers were able of delivering drugs to tumors through regulating their pH, temperature, enzyme responsiveness. With the use of nanocarriers, chemotherapeutic drugs could be supplied to tumors more accurately that can equally encapsulate and deliver them. Material carriers for chemotherapeutic medicines are discussed in this review keeping in viewpoint of the structural properties and targeting methods that make these carriers more therapeutically effective, in addition to metabolic pathways triggered by drug-loaded NCs. Largely, the development of NCs countering to endogenous and exogenous stimuli in tumor regions and understanding of mechanisms would encourage the progress for tumor therapy and precision diagnosis in future.

Bifunctional alginate/chitosan stabilized perfluorohexane nanodroplets as smart vehicles for ultrasound and pH responsive delivery of anticancer agents

The combination of ultrasound and chemotherapy has been proposed as a promising strategy to achieve a better anticancer therapeutic efficacy. Here we present a facile strategy to construct novel bifunctional nanodroplets as smart vehicles for ultrasound and pH responsive delivery of anticancer agents. PFH is used as core and chitosan/alginate complexes are used as the stable shells of the nanodroplets. The effects of alginate/chitosan ratio, and the amount of surfactant as well as PFH on the size, size distribution, and encapsulation efficiency of nanodroplets are systematically investigated with the optimized formulation identified. The release of the encapsulated doxorubicin hydrochloride can be triggered by changing the pH value of the surrounding environment and the exposure to ultrasound. The nanodroplets also show strong ultrasound contrast via droplet-to-bubble transition as demonstrated by B-mode ultrasound imaging. The hemolytic activity and cytotoxicity are further studied, revealing the biocompatibility of the nanodroplets. The in vivo antitumor results demonstrate that the prepared droplets show excellent antitumor therapeutic efficacy and outstanding tumor-targeting ability. The proposed alginate/chitosan stabilized PFH nanodroplets represent an important advance in fabricating multifunctional therapeutic materials with great promises in the applications of combined antitumor therapies.

Advances in amphiphilic polylactide/vinyl polymer based nano-assemblies for drug delivery

Micelles from self-assembled amphiphilic copolymers are highly attractive in drug delivery, due to their small size and hydrophilic stealth corona allowing prolonged lifetimes in the bloodstream and thus improved drug bioavailability. Polylactide (PLA)-based amphiphilic copolymer micelles are key candidates in this field, owing to the well-established biodegradability and biocompatibility of PLA. While PLA-b-poly(ethylene glycol) (PEG) block copolymer micelles can be seen as the "gold standard" in drug delivery research so far, the progresses in controlled radical polymerizations (Atom Transfer Radical Polymerization, Reversible Addition-Fragmentation Transfer and Nitroxide Mediated Polymerization) have offered new opportunities in the design of advanced amphiphilic copolymers for drug delivery due to their flexibility in many regards: (i) they can be easily combined with ring-opening polymerization (ROP) of lactide, with a diversity in types of architectures (e.g., block, graft, star), (ii) they allow (co)polymerization of a wide range of vinyl monomers, possibly circumventing PEG limitations, (iii) functionalization (with biomolecules or stimuli-cleavable moieties) is versatile due to end-group fidelity and copolymerization ability with reactive/functional comonomers. In this review, we report on the advances in the past decade of such amphiphilic PLA/vinyl polymer based nano-carriers, regarding key properties such as stealth character, cell targeting and stimuli-responsiveness.

Injectable supramolecular hydrogels based on custom-made poly(ether urethane)s and α-cyclodextrins as efficient delivery vehicles of curcumin

A strategy to enhance drug effectiveness while minimizing controversial effects consists in exploiting host-guest interactions. Moreover, these phenomena can induce the self-assembly of physical hydrogels as effective tools to treat various pathologies (e.g., chronic wounds or cancer). Here, two Poloxamers®/Pluronics® (P407/F127 and P188/F68) were utilized to synthesize various LEGO-like poly(ether urethane)s (PEUs) to develop a library of tunable and injectable supramolecular hydrogels for drug delivery. Three PEUs were synthesized by chain extending Poloxamer/Pluronic with 1,6-cyclohexanedimethanol or N-Boc serinol. Other two amino-functionalized and highly responsive polymers were obtained thorough Boc-group cleavage. For hydrogel design, the spontaneous self-assembly of the poly(ethylene oxide) domains of PEUs with α-cyclodextrins was exploited to form poly(pseudo)rotaxanes (PPRs). PPR-derived channel-like crystals were characterized by X-Ray powder diffraction, Infra-Red and Proton Nuclear Magnetic Resonance spectroscopies. Cytocompatible hydrogel formulations were designed at PEU concentrations between 1% and 5% w/v and α-cyclodextrin at 10% w/v. Supramolecular gels showed good mechanical performances (storage modulus up to 20 kPa) coupled with marked thixotropic and self-healing properties (mechanical recovery over 80% within 30 s after cyclic rupture) as assessed through rheology. Hydrogels exhibited stability and high responsiveness in watery environment up to 5 days: the release of less stable components as suitable drug carriers was coupled with high swelling (doubling the content of fluids with respect to their dry mass) and shape retention. Curcumin was encapsulated into the hydrogels at high concentration (80 μg ml^-1) through its complexation with α-cyclodextrins and delivery tests showed controllable and progressive release profiles up to four days.

Current Status and Emerging Trend of Nanoshuttle in Biological Applications

Nanoshuttles are unique structures that resemble double-headed arrows or a nanorod with sharp tips for better penetration into the tumor cells, reduction of toxicity and minimization of off-targeting effect. These biologically- inspired multimetallic or bimetallic nano swimmers are capable of transporting cargoes from one end to another via self-propulsion in an efficient manner. Encapsulation with pH- and heat-sensitive polymers allows nanoshuttles to release cargos at the targeted site in a controlled fashion. This review article focuses on the methods of preparation and characterization of nanoshuttles with applications in the field of antineoplastic, antibacterial, erectile dysfunction, electrochemical biosensing, anticounterfeiting, on-demand and targeted delivery system for imaging as well as cell ablation therapy. Magnetic nanoshuttles exhibit modified optical properties for utilization in diagnostic imaging for sensitive and early diagnosis of diseases. Smart drug delivery is achieved when nanoshuttles are combined with nanomotors to exhibit distinctive, rapid and unidirectional movement in the bloodstream. Cost-effective synthesis of nanoshuttles will extend their applications in the commercial sectors by overcoming the limitations like scale-up and regulatory approval. In the near future, nanoshuttles will diversify in the fields of energy conversion, energy storage, 3D printing, stem cell fabrication and theranostics.

Amphiphilic copolymers in biomedical applications: Synthesis routes and property control

The request of new materials, matching strict requirements to be applied in precision and patient-specific medicine, is pushing for the synthesis of more and more complex block copolymers. Amphiphilic block copolymers are emerging in the biomedical field due to their great potential in terms of stimuli responsiveness, drug loading capabilities and reversible thermal gelation. Amphiphilicity guarantees self-assembly and thermoreversibility, while grafting polymers offers the possibility of combining blocks with various properties in one single material. These features make amphiphilic block copolymers excellent candidates for fine tuning drug delivery, gene therapy and for designing injectable hydrogels for tissue engineering. This manuscript revises the main techniques developed in the last decade for the synthesis of amphiphilic block copolymers for biomedical application. Strategies for fine tuning the properties of these novel materials during synthesis are discussed. A deep knowledge of the synthesis techniques and their effect on the performance and the biocompatibility of these polymers is the first step to move them from the lab to the bench. Current results predict a bright future for these materials in paving the way towards a smarter, less invasive, while more effective, medicine.

Novel pH-responsive nanohybrid for simultaneous delivery of doxorubicin and paclitaxel: an in-silico insight

BACKGROUND

The distribution of drugs could not be controlled in the conventional delivery systems. This has led to the developing of a specific nanoparticle-based delivery system, called smart drug delivery systems. In cancer therapy, innovative biocompatible nanocarriers have received much attention for various ranges of anti-cancer drugs. In this work, the effect of an interesting and novel copolymer named "dimethyl acrylamide-trimethyl chitosan" was investigated on delivery of paclitaxel and doxorubicin applying carboxylated fullerene nanohybrid. The current study was run via molecular dynamics simulation and quantum calculations based on the acidic pH differences between cancerous microenvironment and normal tissues. Furthermore, hydrogen bonds, radius of gyration, and nanoparticle interaction energies were studied here. Stimulatingly, a simultaneous pH and temperature-responsive system were proposed for paclitaxel and doxorubicin for a co-polymer. A pH-responsive and thermal responsive copolymer were utilized based on trimethyl chitosan and dimethyl acrylamide, respectively. In such a dualistic approach, co-polymer makes an excellent system to possess two simultaneous properties in one bio-polymer.

RESULTS

The simulation results proposed dramatic and indisputable effects of the copolymer in the release of drugs in cancerous tissues, as well as increased biocompatibility and drug uptake in healthy tissues. Repeated simulations of a similar article performed for the validation test. The results are very close to those of the reference paper.

CONCLUSIONS

Overall, conjugated modified fullerene and dimethyl acrylamide-trimethyl chitosan (DMAA-TMC) as nanohybrid can be an appropriate proposition for drug loading, drug delivery, and drug release on dual responsive smart drug delivery system.

A novel multifunctional NCQDs-based injectable self-crosslinking and in situ forming hydrogel as an innovative stimuli responsive smart drug delivery system for cancer therapy

In this work, we offer an easy approach to develop a novel injectable, pH sensitive and in situ smart drug delivery system for use in cancer treatments. The developed hydrogels containing nitrogen doped carbon quantum dots (NCQD), doxorubicin (Dox) and hydroxyapatite (HA) were obtained by in situ self-crosslinking. Characterization of the synthesized nanomaterials, interactions between NCQD/Dox/HA hydrogel structure were carried out by TEM, FESEM, EDS, FTIR, XPS, XRD, Zeta potential, DLS, UV-Vis, SEM, gelation time, injectability and DIST measurements. In addition, antibacterial evaluation which was performed against Staphylococcus aureus realized that HA compound significantly increased the antibacterial activity of the hybrid hydrogel. The anticancer drug release to the tumor cell microenvironment with a pH of 5.5 was found to be higher compared to the release in the normal physiological range of pH 6.5 and 7.4. MTT and live/dead assays were also performed using L929 fibroblastic cell lines to investigate the cytotoxic behavior of NCQDs, and NCQDs/Dox/HA hydrogels. Furthermore, the NCQDs/Dox/HA hydrogel could transport Dox within a MCF-7 cancerous cell at specifically acidic pH. Additionally, imaging of cell line was observed using NCQDs and their use in imaging applications and multicolor features in the living cell system were evaluated. The overall study showed that in situ formed NCQDs/Dox/HA hydrogel represented a novel and multifunctional smart injectable controlled-release drug delivery system with great potential, which may be considered as an attractive minimal invasive smart material for future intelligent delivery of chemotherapeutic drug and disease therapy applications.

Chemotaxis-based smart drug delivery of epirubicin using a 3D printed microfluidic chip

Recent developments on self-propelled microdroplets, moving controllably in response to an external stimulus like chemical, electrical, or magnetic field, have opened a new horizon for smart drug delivery investigations. On the other hand, the new achievements in 3D printing technology has provided a promising option for the fabrication of microfluidic devices, which is an unrivalled platform for in-vitro drug delivery studies. By synergizing the features of chemotaxis, 3D printing, and microfluidic techniques a new approach was introduced to deliver the drug to targeted sites with a well-controlled method and a reasonable speed. A self-propelled ionic liquid ([P_6,6,6,14][Cl]) microdroplet, as the drug carrier, was utilised for the targeted delivery of epirubicin anticancer drug within an integrated drug delivery microfluidic system. The asymmetric diffusion of [P_6,6,6,14]⁺ ion from the microdroplet into an aqueous solution with chloride gradient concentration (created under an external electrical field) caused the microdroplet to move. The spatial and temporal position of the moving microdroplet could be controlled by changing the magnitude and polarity of the external electrical field. A piece of hollow-fiber, fixed next to the anode, was filled with phosphate buffer (as the receptor) and used to remove the drug from the carrier. The receptor solution was then taken and injected into a HPLC system for quantification of the released drug. After one-at-a-time optimization of the channel geometry and electrolyte concentration, the experimental variables affecting the drug loading including contact time, pH, and volume of carrier were optimized via a central composite design (CCD) approach.

pH-bioresponsive poly(ε-caprolactone)-based polymersome for effective drug delivery in cancer and protein glycoxidation prevention

Artificial nanostructures using polymers to produce polymeric vesicles are inspired by the many intricate structures found in living organisms. Polymersomes are a class of self-assembled vesicles known for their great stability and application in drug delivery. They can be tuned according to their intended use by changing their components and introducing activable block copolymers that transform these polymersomes into smart nanocarriers. In this study, we propose the synthesis of a poly (ethylene oxide)-poly (ε-caprolactone)-based polymersome (PEO-PCL) loaded with GSH as a pH-responsive drug delivery molecule for cancer and protein alteration inhibition. Initially, the nanocarrier was synthesized and characterized by DLS, TEM/SEM microscopy as well as gel permeation chromatography (GPC) and ¹H NMR. Their CMC formation, encapsulation efficiency, and pH responsiveness were analyzed. In addition, empty and GSH-loaded PEO-PCL polymersomes were tested for their toxicity and therapeutic effect on normal and cancer cells via an MTT test. Subsequently, protein alteration models (aggregation, glycation, and oxidation) were performed in vitro where the polymersomes were tested. Results showed that other than being non-toxic and able to highly encapsulate and release the GSH in response to acidic conditions, the nanocomposites do not hinder its content's ameliorative effects on cancer cells and protein alterations. This infers that polymeric nanocarriers can be a base for future smart biomedicine applications and theranostics.

Smart Drug Delivery Systems in Cancer Therapy

BACKGROUND

Smart nanocarriers have been designed for tissue-specific targeted drug delivery, sustained or triggered drug release and co-delivery of synergistic drug combinations to develop safer and more efficient therapeutics.

OBJECTIVE

Advances in drug delivery systems provide reduced side effects, longer circulation half-life and improved pharmacokinetics.

RESULTS

Smart drug delivery systems have been achieved successfully in the case of cancer. These nanocarriers can serve as an intelligent system by considering the differences of tumor microenvironment from healthy tissue, such as low pH, low oxygen level, or high enzymatic activity of matrix metalloproteinases.

CONCLUSION

The performance of anti-cancer agents used in cancer diagnosis and therapy is improved by enhanced cellular internalization of smart nanocarriers and controlled drug release. Here, we review targeting, cellular internalization; controlled drug release and toxicity of smart drug delivery systems. We are also emphasizing the stimulus responsive controlled drug release from smart nanocarriers.

Smart nanocarrier-based drug delivery systems for cancer therapy and toxicity studies: A review

Nonspecific distribution and uncontrollable release of drugs in conventional drug delivery systems (CDDSs) have led to the development of smart nanocarrier-based drug delivery systems, which are also known as Smart Drug Delivery Systems (SDDSs). SDDSs can deliver drugs to the target sites with reduced dosage frequency and in a spatially controlled manner to mitigate the side effects experienced in CDDSs. Chemotherapy is widely used to treat cancer, which is the second leading cause of death worldwide. Site-specific drug delivery led to a keen interest in the SDDSs as an alternative to chemotherapy. Smart nanocarriers, nanoparticles used to carry drugs, are at the focus of SDDSs. A smart drug delivery system consists of smart nanocarriers, targeting mechanisms, and stimulus techniques. This review highlights the recent development of SDDSs for a number of smart nanocarriers, including liposomes, micelles, dendrimers, meso-porous silica nanoparticles, gold nanoparticles, super paramagnetic iron-oxide nanoparticles, carbon nanotubes, and quantum dots. The nanocarriers are described in terms of their structures, classification, synthesis and degree of smartness. Even though SDDSs feature a number of advantages over chemotherapy, there are major concerns about the toxicity of smart nanocarriers; therefore, a substantial study on the toxicity and biocompatibility of the nanocarriers has been reported. Finally, the challenges and future research scope in the field of SDDSs are also presented. It is expected that this review will be widely useful for those who have been seeking new research directions in this field and for those who are about to start their studies in smart nanocarrier-based drug delivery.

Synthesis and modification of crystalline SBA-15 nanowhiskers as a pH-sensitive metronidazole nanocarrier system

Clinical resistance to drugs and diminution in their side effects have become great issues for pharmacologists. In veterinary medicine, parasites like Trichomonas gallinae are of veterinary, hygienic and economic importance and can be treated by metronidazole. Unfortunately, scientific evidence has been reported about its resistance and serious side effects in trichomoniasis. In this research, it was attempted to introduce a new procedure to lower side effects of the drug molecules and also, enhance the treatment of disease. Whisker-formed SBA-15 nanoparticles were utilized for the first time in this issue. They had mesoporous structures which metronidazole molecules could be trapped in them. Additionally, these crystalline nanowhiskers were modified with tannic acid to make the release process better. The branches of tannic acid covered the opening of pores in crystalline SBA-15 nanowhiskers and restricted the drug from fast release. It caused a controlled metronidazole release in the smart drug delivery. These nanocarriers were completely tested by several experiments. Whisker-like SBA-15 nanocrystals had a mesopore volume of 0.5931 cm³/g, pore diameter of 6.06 nm and surface area of 491.38 m²/g. Based on TGA analysis, 10% of tannic acid was coated on the crystalline nanowhiskers during the modification. The metronidazole content and entrapment efficiency of final nanocarriers was 28.56% and 71.40%, respectively. The decomposition of tannic acid in lower pHs made whisker-like SBA-15@tannic acid nanocrystals be pH-responsive which can be used for other applications in the pharmacology. In-vitro study revealed that the minimal lethal concentration of nanocarriers was 0.5 mg/mL for 180 min.

Smart gated magnetic silica mesoporous particles for targeted colon drug delivery: New approaches for inflammatory bowel diseases treatment

Magnetic mesoporous silica microparticles were loaded with safranin O (S1) and with hydrocortisone (S2) and the outer surface functionalized with a bulky azo derivative bearing urea moieties. Aqueous suspensions of both solids at pH 7.4 showed negligible payload release whereas a marked delivery was observed in the presence of sodium dithionite due to the rupture of the azo bonds. Besides, a moderate cargo release was observed at acidic pH due to the hydrolysis of the urea bonds that linked the azo derivative onto the external surface of the inorganic scaffolds. In vitro digestion models showed that S1 and S2 microparticles could be used for the controlled release of payload in the reducing colon environment (in which azoreductase enzymes are present). On the other hand, in vivo pharmacokinetic studies in rats showed that safranine O release from S1 microparticles was concentrated in colon. The performance of S2 microparticles for the treatment of colitis in rats (induced by oral administration of a 2,4,6-trinitrobenzenesulfonic acid solution) was tested. The controlled release of hydrocortisone from S2 in the colon of injured rats induced marked reduction in colon/body weight ratio and in clinical activity score. Also, histological studies showed a marked decrease in inflammation followed by intensive regeneration and almost normal mucosal structure of the individuals treated with S2. Besides, the use of a magnetic belt increased the therapeutic performances of S2 due to an enhanced retention time of the particles in the colon.

Dual pH/redox responsive and CD44 receptor targeting hybrid nano-chrysalis based on new oligosaccharides of hyaluronan conjugates

A smart hybrid microenvironment-mediated dual pH/redox-responsive polymeric nanoparticles combined with inorganic calcium phosphate (CaP) was fabricated, which we term as armored nano-chrysalis inspired by butterfly pupa. The nano-chrysalis has an inner core composed of specially designed oligosaccharides of hyaluronan (oHA) targeting CD44 receptor. The inner core has two functions, i.e., the dual pH/redox responsive polymeric conjugate and the fluorescent curcumin-prodrug function. The prepared nano-chrysalis possessed a smaller size (102.5±4.6nm) than the unarmored nano-chrysalis (122.5±6.6nm). Interestingly, while the nano-chrysalis were stable under pH 7.4, when incubated under the tumor acidic conditions (pH 6.5) the outer CaP armor would dissolve in a pH-dependent, sustained manner. Moreover, nano-chrysalis was demonstrated to present the most effective antitumor efficacy than other formulations. This study provides a promising smart nano-carrier platform to enhance the stability, decrease the side effects, and improve the therapeutic efficacy of anticancer drugs.