DNA response element-based smart drug delivery systems for precise drug release

Smart drug delivery systems (DDSs) that respond to, interact with, or are actuated by biological signals or pathological abnormalities (e.g., the tumor microenvironment) for controllable drug release are appealing therapeutic platforms for cancer treatment. Owing to their inherent self-assembled nature, nucleic acids have emerged as programmable materials for the development of multifunctional structures. In response to external environmental stimuli, DNA response elements can serve as switches to trigger conformational changes in DNA structures. Their stimulus-responsive properties make them promising candidates for constructing smart DDSs, and advancements in DNA response element-based DDSs in the field of biomedicine have been made. This review summarizes different types of DNA response elements, including DNA aptamers, DNAzymes, disulfide bond-modified DNA, pH-responsive DNA motifs, and photocleavable DNA building blocks, and highlights the advancements in DNA response element-based smart DDSs for precise drug release. Finally, future challenges and perspectives in this field are discussed.

Poly(phenylalanine) and poly(3,4-dihydroxy-L-phenylalanine): Promising biomedical materials for building stimuli-responsive nanocarriers

Cancer is a serious threat to human health because of its high annual mortality rate. It has attracted significant attention in healthcare, and identifying effective strategies for the treatment and relief of cancer pain requires urgency. Drug delivery systems (DDSs) offer the advantages of excellent efficacy, low cost, and low toxicity for targeting drugs to tumor sites. In recent decades, copolymer carriers based on poly(phenylalanine) (PPhe) and poly(3,4-dihydroxy-L-phenylalanine) (PDopa) have been extensively investigated owing to their good biocompatibility, biodegradability, and controllable stimulus responsiveness, which have resulted in DDSs with loading and targeted delivery capabilities. In this review, we introduce the synthesis of PPhe and PDopa, highlighting the latest proposed synthetic routes and comparing the differences in drug delivery between PPhe and PDopa. Subsequently, we summarize the various applications of PPhe and PDopa in nanoscale-targeted DDSs, providing a comprehensive analysis of the drug release behavior based on different stimulus-responsive carriers using these two materials. In the end, we discuss the challenges and prospects of polypeptide-based DDSs in the field of cancer therapy, aiming to promote their further development to meet the growing demands for treatment.

Biotechnological Effects of Advanced Smart-Bile Acid Cyclodextrin-Based Nanogels for Ear Delivery and Treatment of Hearing Loss

Inner ear delivery requires safe and effective drug delivery vehicles incorporating high-viscosity formulations with permeation enhancers. This study designs novel thermoresponsive-smart polymer-bile acid and cyclodextrin-based nanogels for inner ear delivery. Nanogels are examined for their rheological and physical properties. The biocompatibility studies will be assessed on auditory and macrophage cell lines by investigating the impact of nanogels on cellular viability, mitochondrial respiration, glycolysis, intracellular oxidative stress, inflammatory profile, and macrophage polarization. Novel ther nanogels based on bile acid and beta-cyclodextrin show preserved porous nanogels' inner structure, exhibit non-Newtonian, shear-thinning fluid behavior, have fast gelation at 37 °C and minimal albumin adsorption on the surface. The nanogels have minimal impact on cellular viability, mitochondrial respiration, glycolysis, intracellular oxidative stress, and inflammatory profile of the auditory cell line House Ear Institute-Organ of Corti 1 after 24 h incubation. Nanogel exposure of 24 h to macrophage cell line RAW264.7 leads to decreased viability, mitochondrial dysfunction, and increased intracellular ROS and inflammatory cytokines. However, polarization changes from M2 anti-inflammatory to M1 pro-inflammatory macrophages are minimal, and inflammatory products of RAW264.7 macrophages do not overly disrupt the survivability of HEI-OC1 cells. Based on these results, thermoresponsive bile acid and cyclodextrin nanogels can be potential drug delivery vehicles for inner ear drug delivery.

Co-delivery of carboplatin and doxorubicin using ZIF-8 coated chitosan-poly(N-isopropyl acrylamide) nanoparticles through a dual pH/thermo responsive strategy to breast cancer cells

A dual pH/temperature sensitive core-shell nanoformulation has been developed based on ZIF-8 coated with chitosan-poly(N-isopropyl acrylamide) (CS-PNIPAAm) for co-delivery of doxorubicin (DOX) and carboplatin (CBP) in breast cancer cells. The resulting nanoparticles (NPs) had particle sizes around 200 nm and a zeta potential of about +30 mV. The CBP and DOX loading contents in the final NPs were 11.6 % and 55.54 %, respectively. NPs showed a pH and thermoresponsive drug release profile with a sustained prolonged release under physiological conditions. The in vitro cytotoxicity experiments showed a significant synergism of CBP and DOX to induce the IC50 of 1.96 μg/mL in MCF-7 cells and 4.54 μg/mL in MDA-MB-231 cells. Also, the final NPs were safer than free DOX and CBP on normal cells. The in vitro study confirmed the higher potency of the designed NPs in combination therapy against breast cancer cells with lower side effects than free drugs.

Smart chitosan nanogel for targeted doxorubicin delivery, ensuring precise release, and minimizing side effects in Ehrlich ascites carcinoma-bearing mice

In recent decades, bio-polymeric nanogels have become a forefront in medical research as innovative in-vivo drug carriers. This study introduces a pH-sensitive chitosan nanoparticles/P(N-Isopropylacrylamide-co-Acrylic acid) nanogel (CSNPs/P(NIPAm-co-AAc)), making significant advancements. The nanogel effectively encapsulated doxorubicin hydrochloride (Dx. HCl), a model drug, within its compartments through electrostatic binding. Comparing nano chitosan (CSNPs) before and after integrating copolymerized P(NIPAm-co-AAc), highlighting an improved and adaptable nanogel structure with responsive behaviors. The intraperitoneal delivery of Dx-loaded nanogel (Dx@N.gel) to Ehrlich ascites carcinoma (Eh)-bearing mice at doses equivalent to 1.5 and 3 mg/kg of Dx per day for 14 days exhibited superiority over the administration of free Dx. Dx@N.gel demonstrated heightened anticancer activity, significantly improving mean survival rates in Eh mice. The nanogel's multifaceted defense mechanism mitigated oxidative stress, inhibited lipid peroxidation, and curbed nitric oxide formation induced by free Dx. It effectively countered hepatic DNA deterioration, normalized elevated liver and cardiac enzyme levels, and ameliorated renal complications. This pH-responsive CSNPs/P(NIPAm-co-AAc) nanogel loaded with Dx represents a paradigm shift in antitumor drug delivery. Its efficacy and ability to minimize side effects, contrasting sharply with those of free Dx, offer a promising future where potent cancer therapies seamlessly align with patient well-being.

Engineering aspects of lipid-based delivery systems: In vivo gene delivery, safety criteria, and translation strategies

Defects in the genome cause genetic diseases and can be treated with gene therapy. Due to the limitations encountered in gene delivery, lipid-based supramolecular colloidal materials have emerged as promising gene carrier systems. In their non-functionalized form, lipid nanoparticles often demonstrate lower transgene expression efficiency, leading to suboptimal therapeutic outcomes, specifically through reduced percentages of cells expressing the transgene. Due to chemically active substituents, the engineering of delivery systems for genetic drugs with specific chemical ligands steps forward as an innovative strategy to tackle the drawbacks and enhance their therapeutic efficacy. Despite intense investigations into functionalization strategies, the clinical outcome of such therapies still needs to be improved. Here, we highlight and comprehensively review engineering aspects for functionalizing lipid-based delivery systems and their therapeutic efficacy for developing novel genetic cargoes to provide a full snapshot of the translation from the bench to the clinics. We outline existing challenges in the delivery and internalization processes and narrate recent advances in the functionalization of lipid-based delivery systems for nucleic acids to enhance their therapeutic efficacy and safety. Moreover, we address clinical trials using these vectors to expand their clinical use and principal safety concerns.

ON/OFF based synergetic plasmonic photothermal drug release approach through core-satellite like mussel-inspired polydopamine nanoparticles

One of the studies on new drug delivery and release systems that has increased in recent years is the study using plasmonic nanoparticles. In this study, polydopamine nanoparticles (PDOP NPs), which contribute to photothermal drug release by near infrared radiation (NIR), were decorated with gold nanoparticles (AuNPs) to utilize their plasmonic properties, and a core-satellite-like system was formed. With this approach, epirubicin (EPI)-loaded PDOP NPs were prepared by utilizing the plasmonic properties of AuNPs. Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) methods were used to evaluate the structural properties of these particles. The release behavior of the prepared structures in acidic (pH 5.0) and neutral (pH 7.4) environments based on the ON/OFF approach was also examined. The biocompatibility properties of the particles were evaluated on mouse fibroblast (L929) and anticancer activities on neuroblastoma (SH-SY5Y) cells. The effects of prepared EPI-loaded particles and laser-controlled drug release on ROS production, genotoxicity, and apoptosis were also investigated in SH-SY5Y cells. With the calculated combination index (CI) value, it was shown that the activity of EPI-loaded AuNP@PDOP NPs increased synergistically with the ON/OFF-based approach. The developed combination approach is considered to be remarkable and promising for further evaluation before clinical use.

Neutron reflectometry as a powerful tool to elucidate membrane interactions of drug delivery systems

The last couple of decades have seen an explosion of novel colloidal drug delivery systems, which have been demonstrated to increase drug efficacy, reduce side-effects, and provide various other advantages for both small-molecule and biomacromolecular drugs. The interactions of delivery systems with biomembranes are increasingly recognized to play a key role for efficient eradication of pathogens and cancer cells, as well as for intracellular delivery of protein and nucleic acid drugs. In parallel, there has been a broadening of methodologies for investigating such systems. For example, advanced microscopy, mass-spectroscopic "omic"-techniques, as well as small-angle X-ray and neutron scattering techniques, which only a few years ago were largely restricted to rather specialized areas within basic research, are currently seeing increased interest from researchers within wide application fields. In the present discussion, focus is placed on the use of neutron reflectometry to investigate membrane interactions of colloidal drug delivery systems. Although the technique is still less extensively employed for investigations of drug delivery systems than, e.g., X-ray scattering, such studies may provide key mechanistic information regarding membrane binding, re-modelling, translocation, and permeation, of key importance for efficacy and toxicity of antimicrobial, cancer, and other therapeutics. In the following, examples of this are discussed and gaps/opportunities in the research field identified.

pH-Activatable Ruthenium(II) Fluorescein Salphen Schiff Base Photosensitizers for Theranostic Applications

Ruthenium(II) polypyridyl complexes exhibit a lack of selectivity toward cancer tissues despite extensive studies as photosensitizers for photodynamic therapy (PDT). Here, we report pH-activatable RuII photosensitizers for molecularly targeted PDT by exploiting the higher acidity of tumoral tissue. The fluorescein moiety, well known for its high pH sensitivity, was connected to a RuII center to yield novel photosensitizers for pH-sensitive 1O2 photogeneration. Their ability to photosensitize molecular dioxygen was studied at various pHs and revealed a drastic enhancement from 0.07 to 0.66 of the 1O2 quantum yield under acidic conditions (pH 7.5 to pH 5.5). Their photocytotoxicity against U2OS osteosarcoma cells was also investigated at pH 5.5 and 7.5 through IC50 determination. A strong enhancement of the photocytotoxicity reaching 930 nM was observed at pH 5.5, which showed the potential of such photosensitizers for pH-activatable PDT.

Biomaterial-Based Responsive Nanomedicines for Targeting Solid Tumor Microenvironments

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

Single-, Dual-, and Multi-Stimuli-Responsive Nanogels for Biomedical Applications

In recent years, stimuli-responsive nanogels that can undergo suitable transitions under endogenous (e.g., pH, enzymes and reduction) or exogenous stimuli (e.g., temperature, light, and magnetic fields) for on-demand drug delivery, have received significant interest in biomedical fields, including drug delivery, tissue engineering, wound healing, and gene therapy due to their unique environment-sensitive properties. Furthermore, these nanogels have become very popular due to some of their special properties such as good hydrophilicity, high drug loading efficiency, flexibility, and excellent biocompatibility and biodegradability. In this article, the authors discuss current developments in the synthesis, properties, and biomedical applications of stimulus-responsive nanogels. In addition, the opportunities and challenges of nanogels for biomedical applications are also briefly predicted.

Co-biopolymer of chitosan/carboxymethyl cellulose hydrogel improved by zinc oxide and graphene quantum dots nanoparticles as pH-sensitive nanocomposite for quercetin delivery to brain cancer treatment

Brain cancer is the major reason of cancer-relevant deaths every year, as it is the most challenging cancer to treat and drug delivery. Quercetin (QUR), as a flavonoid substance found in plants and fruits, has good anticancer and medicinal effects on brain tumors, but its low stability and bioavailability as well as the blood-brain barrier (BBB), prevent it from reaching brain tumors. This research has introduced a nanocomposite made of biocompatible polymers, chitosan, and carboxymethyl cellulose. This co- biopolymer's mechanical and chemical properties and drug-loading capacity have been improved by adding zinc oxide nanoparticles (ZnO NPs). In addition, graphene quantum dots (GQDs) were used to improve the chemical properties as well as the ability to penetrate the BBB. The CS/CMC/GQDs/ZnO@QUR nanocomposites have nanoneedle structures with an average size of 219.38 ± 5.21 nm and a zeta potential of -53 mV. The morphology, chemical bonds, and crystallinity of the nanocomposite were examined by FE-SEM, FTIR, and XRD analyses, respectively. By examining the release of QUR, it became apparent that the half-drug release takes about 72 h, which has a much more controlled release than other QUR carriers. Further, the MTT test on U-87 MG and L929 cell lines suggested that this nanocomposite has good anticancer properties and low cytotoxicity compared to the free QUR.

Hybrid nanogels by direct mixing of chitosan, tannic acid and magnetite nanoparticles: processes involved in their formation and potential catalytic properties

Magnetite (Fe3O4) nanoparticles (MNPs) as nanocatalysts have drawn considerable attention because of their unique properties such as peroxidase-like activity. However, their biodistribution and availability for specific treatments still need to be improved. In this study, a simple and convenient strategy for the synthesis of hybrid nanogels (NGs) is described, which involves direct mixing of biomaterials such as chitosan (Ch) and tannic acid (TA), with the incorporation of MNPs, under oxidising conditions, using the inverse nanoemulsion method. The different processes involved in the formation of these hybrid nanosystems as well as their morphological and chemical structure are investigated using optical, spectroscopic, and electron microscopic techniques (DLS, UV-VIS, FT-IR, XPS, TEM, and SEM-EDS). It is demonstrated that ∼11 nm synthesized MNPs, post-functionalized with oxidised TA, act as covalent crosslinkers. As a proof of concept, the potential use of these materials in nanocatalytic medicine was evaluated using a colorimetric method based on the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in hydrogen peroxide. The results show that these hybrid nanogels have the same peroxidase-like activity as bare MNPs, indicating that the organic nanostructure stabilises the inorganic nanoparticles without any significant change in the catalytic properties. Therefore, this kind of nanomaterial has promising potential for use in nanocatalytic medicine with improved biocompatibility and biodistribution.

Novel chitosan/γ-alumina/carbon quantum dot hydrogel nanocarrier for targeted drug delivery

Curcumin (CUR) is among the most natural and effective antitumor drugs for cancer treatment. These drugs have low solubility and short half-lives that reduce their effectiveness in drug release systems. Herein, a hydrogel nanocarrier containing chitosan (CS), alumina (γ-Al2O3), and carbon quantum dots (CQDs) was prepared by the water-in-oil-in-water (W/O/W) double nanoemulsion method. DLS revealed a nanocarrier size of 227 nm, with a zeta potential of -37.8 mV, which corroborates its stability. FE-SEM showed its quasi-spherical shape, FT-IR and XRD confirmed the presence of all the components in the nanocomposite and gave information about the intermolecular interactions between them and the crystalline nature of the nanocarrier, respectively. The drug loading (48 %) and entrapment efficiency (86 %) were higher than those reported previously for other CUR nanocarriers. The drug release profile revealed a controlled and stable release, and a pH-sensitive behavior, with faster CUR release in an acid environment. The breast cancer cell line was examined by cytotoxicity and cell apoptosis analyses. The results showed that the slow release over time and the programmed cell death were due to interactions between CUR and the nanocarrier. Considering the results obtained herein, CS/γAl2O3/CQDs/CUR can be considered as a promising new nanosystem for tumor treatment.

Targeted co-delivery of methotrexate and chloroquine via a pH/enzyme-responsive biocompatible polymeric nanohydrogel for colorectal cancer treatment

Application of conventional chemotherapy regardless of its unique effectiveness have been gradually being edged aside due to limited targeting capability, lack of selectivity and chemotherapy-associated side effects. To this end, colon-targeted nanoparticles via combination therapy have shown great therapeutic potential against cancer. Herein, pH/enzyme-responsive biocompatible polymeric nanohydrogels based on poly(methacrylic acid) (PMAA) containing methotrexate (MTX) and chloroquine (CQ) were fabricated. PMAA-MTX-CQ exhibited high drug loading capacity of which MTX was 4.99% and was CQ 25.01% and displayed pH/enzyme-triggered drug release behavior. Higher CQ release rate (76%) under simulated acidic microenvironment of tumor tissue whereas 39% of CQ was released under normal physiological conditions. Intestinally, MTX release was facilitated in the presence of proteinase K enzyme. TEM image demonstrated spherical morphology with particle size of less than 50 nm. In vitro and in vivo toxicity assessments indicated that developed nanoplatforms possessed great biocompatibility. These nanohydrogels did not cause any adverse effects against Artemia Salina and HFF2 cells (around 100% cell viability) which highlight the safety of prepared nanohydrogels. There was no death in mice received different concentrations of nanohydrogel through oral administration and less than 5% hemolysis was found in red blood cells incubated with PMAA nanohydrogels. In vitro anti-cancer results showed that combination therapy based on PMAA-MTX-CQ can effectively suppress the growth of SW480 colon cancer cells (29% cell viability) compared to monotherapy. Altogether, these findings suggest that pH/enzyme-responsive PMAA-MTX-CQ could effectively inhibit cancer cell growth and progression via site-specific delivery of its cargo in a safe and controlled manner.

Mucoadhesive, Fluconazole-Loaded Nanogels Complexed with Sulfhydryl-β-cyclodextrin for Oral Thrush Treatment

The objective of this study was to generate fluconazole-loaded mucoadhesive nanogels to address the problem of hydrophobicity of fluconazole (FL). An inclusion complex was formulated with sulfhydryl-β-CD (SH-β-CD) followed by nanogels formation by a Schiff base reaction of carbopol 940 (CA-940) and gelatin (GE). For characterization, PXRD, FT-IR analysis, drug content, and phase solubility studies were performed. Similarly, nanogels were assessed for particle size, zeta potential, organoleptic, and spreadability studies. Moreover, drug contents, rheological, in vitro drug permeation, release kinetics, toxicity, and stability studies of nanogels were performed. Furthermore, mucoadhesive characteristics over the buccal mucosal membrane of the goat were evaluated. The nanogels formulated with a higher amount of CA-940 and subsequently loaded with the inclusion complexes of FL showed promising results. PXRD and FT-IR analysis confirmed the physical complexes by displaying a reduction in the intensity of peaks of FL. The average particle size of nanogels was in the range of 257 to 361 nm. The highest drug content of 88% was encapsulated within the FL-SH-β-CD complex. All formulations at 0.5-1% concentration displayed no toxicity to the Caco-2 cell lines. Nanogels loaded with FL-SH-β-CD complexes showed 18-fold improved mucoadhesion on the buccal mucous membrane of the goat when compared to simple nanogels. The in vitro permeation study exhibited significantly enhanced permeation and first-order concentration-dependent drug release was observed. On the bases of these findings, we can conclude that a mucoadhesive nanogel-based drug delivery system can be an ideal therapy for candidiasis.

Chitosan-Biotin-Conjugated pH-Responsive Ru(II) Glucose Nanogel: A Dual Pathway of Targeting Cancer Cells and Self-Drug Delivery

The current study paves the way for improved chemotherapy by creating pH-responsive nanogels (NGs) (GC1 and GC2) loaded with synthetic ruthenium(II) arene complexes to increase biological potency. NGs are fabricated by the conjugation of chitosan (CTS)-biotin biopolymers that selectively target the cancer cells as CTS has the pH-responsive property, which helps in releasing the drug in cancer cells having pH ∼ 5.5, and biotin provides the way to target the cancer cells selectively due to the overexpression of integrin. The synthesized compounds and NGs were thoroughly characterized using various spectroscopic and analytical techniques such as NMR, electrospray ionization-mass spectrometry, Fourier transform infrared, UV-vis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, rheology, Brunauer-Emmett-Teller, and others. NGs displayed exceptional increased efficacy toward cancerous cells with IC50 values ranging from 7.50 to 18.86 μM via induced apoptosis in three human cancer cell lines. Apart from its potency, NGs were found to be highly selective toward cancer cells. Moreover, based on the results of immunoblot analysis, it was observed that the synthesized compounds exhibit a significant increase in the expression of cleaved caspase-3 and a decrease in the expression of the antiapoptotic protein BCL-XL. Interestingly, the complexes were discovered to have the additional capability of catalyzing the conversion of NADH to NAD+, leading to the generation of radical oxygen species within the cells. Additionally, it was discovered that NG-induced apoptosis depends on ROS production and DNA binding. A narrower range of LD50 values (1185.93 and 823.03 μM) was seen after administering NGs to zebrafish embryos in vivo. The results support the use of drug-loaded NGs as potential chemotherapeutic and chemopreventive agents for human cancer cells.

Peptide Amphiphilic Supramolecular Nanogels: Competent Host for Notably Efficient Lipase-Catalyzed Hydrolysis of Water-Insoluble Substrates

The present work depicts the development of stable nanogels in an aqueous medium that were exploited for efficient surface-active lipase-catalyzed hydrolysis of water-insoluble substrates. Surfactant-coated gel nanoparticles (neutral NG1, anionic NG2, and cationic NG3) were prepared from peptide amphiphilic hydrogelator (G1, G2, and G3, respectively) at different hydrophilic and lipophilic balance (HLB). Chromobacterium viscosum (CV) lipase activity towards hydrolysis of water-insoluble substrates (p-nitrophyenyl-n-alkanoates (C4-C10)) in the presence of nanogels got remarkably improved by ~1.7-8.0 fold in comparison to that in aqueous buffer and other self-aggregates. An increase in hydrophobicity of the substrate led to a notable improvement in lipase activity in the hydrophilic domain (HLB>8.0) of nanogels. The micro-heterogeneous interface of small-sized (10-65 nm) nanogel was found to be an appropriate scaffold for immobilizing surface-active lipase to exhibit superior catalytic efficiency. Concurrently, the flexible conformation of lipase immobilized in nanogels was reflected in its secondary structure having the highest α-helix content from the circular dichroism spectra.

pH stimuli-responsive hydrogels from non-cellulosic biopolymers for drug delivery

Over the past several decades, there has been significant growth in the design and development of more efficient and advanced biomaterials based on non-cellulosic biological macromolecules. In this context, hydrogels based on stimuli-responsive non-cellulosic biological macromolecules have garnered significant attention because of their intrinsic physicochemical properties, biological characteristics, and sustainability. Due to their capacity to adapt to physiological pHs with rapid and reversible changes, several researchers have investigated pH-responsive-based non-cellulosic polymers from various materials. pH-responsive hydrogels release therapeutic substances in response to pH changes, providing tailored administration, fewer side effects, and improved treatment efficacy while reducing tissue damage. Because of these qualities, they have been shown to be useful in a wide variety of applications, including the administration of chemotherapeutic drugs, biological material, and natural components. The pH-sensitive biopolymers that are utilized most frequently include chitosan, alginate, hyaluronic acid, guar gum, and dextran. In this review article, the emphasis is placed on pH stimuli-responsive materials that are based on biological macromolecules for the purposes of drug administration.

Polymeric Nanoparticles and Nanogels: How Do They Interact with Proteins?

Polymeric nanomaterials, nanogels, and solid nanoparticles can be fabricated using single or double emulsion methods. These materials hold great promise for various biomedical applications due to their biocompatibility, biodegradability, and their ability to control interactions with body fluids and cells. Despite the increasing use of nanoparticles in biomedicine and the plethora of publications on the topic, the biological behavior and efficacy of polymeric nanoparticles (PNPs) have not been as extensively studied as those of other nanoparticles. The gap between the potential of PNPs and their applications can mainly be attributed to the incomplete understanding of their biological identity. Under physiological conditions, such as specific temperatures and adequate protein concentrations, PNPs become coated with a "protein corona" (PC), rendering them potent tools for proteomics studies. In this review, we initially investigate the synthesis routes and chemical composition of conventional PNPs to better comprehend how they interact with proteins. Subsequently, we comprehensively explore the effects of material and biological parameters on the interactions between nanoparticles and proteins, encompassing reactions such as hydrophobic bonding and electrostatic interactions. Moreover, we delve into recent advances in PNP-based models that can be applied to nanoproteomics, discussing the new opportunities they offer for the clinical translation of nanoparticles and early prediction of diseases. By addressing these essential aspects, we aim to shed light on the potential of polymeric nanoparticles for biomedical applications and foster further research in this critical area.

Targeted Drug Delivery Systems for Curcumin in Breast Cancer Therapy

Breast cancer (BC) is the most prevalent type of cancer in the world and the main reason women die from cancer. Due to the significant side effects of conventional treatments such as chemotherapy and radiotherapy, the search for supplemental and alternative natural drugs with lower toxicity and side effects is of interest to researchers. Curcumin (CUR) is a natural polyphenol extracted from turmeric. Numerous studies have demonstrated that CUR is an effective anticancer drug that works by modifying different intracellular signaling pathways. CUR's therapeutic utility is severely constrained by its short half-life in vivo, low water solubility, poor stability, quick metabolism, low oral bioavailability, and potential for gastrointestinal discomfort with high oral doses. One of the most practical solutions to the aforementioned issues is the development of targeted drug delivery systems (TDDSs) based on nanomaterials. To improve drug targeting and efficacy and to serve as a reference for the development and use of CUR TDDSs in the clinical setting, this review describes the physicochemical properties and bioavailability of CUR and its mechanism of action on BC, with emphasis on recent studies on TDDSs for BC in combination with CUR, including passive TDDSs, active TDDSs and physicochemical TDDSs.

DNA hydrogels and nanogels for diagnostics, therapeutics, and theragnostics of various cancers

As an efficient class of hydrogel-based therapeutic drug delivery systems, deoxyribonucleic acid (DNA) hydrogels (particularly DNA nanogels) have attracted massive attention in the last five years. The main contributor to this is the programmability of these 3-dimensional (3D) scaffolds that creates fundamental effects, especially in treating cancer diseases. Like other active biological ingredients (ABIs), DNA hydrogels can be functionalized with other active agents that play a role in targeting drug delivery and modifying the half-life of the therapeutic cargoes in the body's internal environment. Considering the brilliant advantages of DNA hydrogels, in this survey, we intend to submit an informative collection of feasible methods for the design and preparation of DNA hydrogels and nanogels, and the responsivity of the immune system to these therapeutic cargoes. Moreover, the interactions of DNA hydrogels with cancer biomarkers are discussed in this account. Theragnostic DNA nanogels as an advanced species for both detection and therapeutic purposes are also briefly reviewed.

Current Principles, Challenges, and New Metrics in pH-Responsive Drug Delivery Systems for Systemic Cancer Therapy

The paradigm of drug delivery via particulate formulations is one of the leading ideas that enable overcoming limitations of traditional chemotherapeutic agents. The trend toward more complex multifunctional drug carriers is well-traced in the literature. Nowadays, the prospectiveness of stimuli-responsive systems capable of controlled cargo release in the lesion nidus is widely accepted. Both endogenous and exogenous stimuli are employed for this purpose; however, endogenous pH is the most common trigger. Unfortunately, scientists encounter multiple challenges on the way to the implementation of this idea related to the vehicles' accumulation in off-target tissues, their immunogenicity, the complexity of drug delivery to intracellular targets, and finally, the difficulties in the fabrication of carriers matching all imposed requirements. Here, we discuss fundamental strategies for pH-responsive drug delivery, as well as limitations related to such carriers' application, and reveal the main problems, weaknesses, and reasons for poor clinical results. Moreover, we attempted to formulate the profiles of an "ideal" drug carrier in the frame of different strategies drawing on the example of metal-comprising materials and considered recently published studies through the lens of these profiles. We believe that this approach will facilitate the formulation of the main challenges facing researchers and the identification of the most promising trends in technology development.

pH-Responsive Nano-transferosomes of Purpurin-18 Sodium Salt and Doxorubicin for Enhanced Anticancer Efficiency by Photodynamic and Chemo Combination Therapy

Cancer is a devastating disease and a major human health concern. Various combination treatments have been developed to combat cancer. To obtain superior cancer therapy, the objective of this study was to synthesize purpurin-18 sodium salt (P18Na) and design P18Na- and doxorubicin hydrochloride (DOX)-loaded nano-transferosomes as a combination of photodynamic therapy (PDT) and chemotherapy for cancer. The characteristics of P18Na- and DOX-loaded nano-transferosomes were assessed, and the pharmacological efficacy of P18Na and DOX was determined using the HeLa and A549 cell lines. The nanodrug delivery system characteristics of the product were found to range from 98.38 to 217.50 nm and -23.63 to -41.10 mV, respectively. Further, the release of P18Na and DOX from nano-transferosomes exhibited a sustained pH-responsive behavior and burst in physiological and acidic environments, respectively. Accordingly, the nano-transferosomes effectively delivered P18Na and DOX into cancer cells, with less leakage in the body, and exhibited pH-responsive release in cancer cells. A photo-cytotoxicity study to HeLa and A549 cell lines revealed a size-dependent anti-cancer effect. These results suggest that the combined nano-transferosomes of P18Na and DOX are effective in the combination of PDT and chemotherapy for cancer.

Improved anticancer efficacy of methyl pyropheophorbide-a-incorporated solid lipid nanoparticles in photodynamic therapy

Photodynamic therapy (PDT) is a promising anticancer treatment because it is patient-friendly and non-invasive. Methyl pyropheophorbide-a (MPPa), one of the chlorin class photosensitizers, is a drug with poor aqueous solubility. The purpose of this study was to synthesize MPPa and develop MPPa-loaded solid lipid nanoparticles (SLNs) with improved solubility and PDT efficacy. The synthesized MPPa was confirmed ¹H nuclear magnetic resonance (¹H-NMR) spectroscopy and UV-Vis spectroscopy. MPPa was encapsulated in SLN via a hot homogenization with sonication. Particle characterization was performed using particle size and zeta potential measurements. The pharmacological effect of MPPa was evaluated using the 1,3-diphenylisobenzofuran (DPBF) assay and anti-cancer effect against HeLa and A549 cell lines. The particle size and zeta potential ranged from 231.37 to 424.07 nm and - 17.37 to - 24.20 mV, respectively. MPPa showed sustained release from MPPa-loaded SLNs. All formulations improved the photostability of MPPa. The DPBF assay showed that SLNs enhanced the ¹O₂ generation from MPPa. In the photocytotoxicity analysis, MPPa-loaded SLNs demonstrated cytotoxicity upon photoirradiation but not in the dark. The PDT efficacy of MPPa improved following its entrapment in SLNs. This observation suggests that MPPa-loaded SLNs are suitable for the enhanced permeability and retention effect. Together, these results demonstrate that the developed MPPa-loaded SLNs are promising candidates for cancer treatment using PDT.

Carboxymethyl cellulose/starch/reduced graphene oxide composite as a pH-sensitive nanocarrier for curcumin drug delivery

Nanocomposites are promising drug carriers to treat terminal cancers with few adverse effects. Herein, nanocomposite hydrogels composed of carboxymethyl cellulose (CMC)/starch/reduced graphene oxide (RGO) were synthesized via a green chemistry approach and then encapsulated in double nanoemulsions to act as pH-responsive delivery systems for curcumin, a potential antitumor drug. A water/oil/water nanoemulsion containing bitter almond oil served as a membrane surrounding the nanocarrier to control drug release. DLS and zeta potential measurements were used to estimate the size and confirm the stability of curcumin-loaded nanocarriers. The intermolecular interactions, crystalline structure and morphology of the nanocarriers were analyzed through FTIR spectroscopy, XRD and FESEM, respectively. The drug loading and entrapment efficiencies were significantly improved compared to previously reported curcumin delivery systems. In vitro release experiments demonstrated the pH-responsiveness of the nanocarriers and the faster curcumin release at a lower pH. The MTT assay revealed the increased toxicity of the nanocomposites against MCF-7 cancer cells compared to CMC, CMC/RGO or free curcumin. Apoptosis was detected in MCF-7 cells via flow cytometry tests. The results obtained herein support that the developed nanocarriers are stable, uniform and effective delivery systems for a sustained and pH-sensitive curcumin release.

Recent Advances in Hydrogel-Based Phototherapy for Tumor Treatment

Phototherapeutic agent-based phototherapies activated by light have proven to be safe modalities for the treatment of various malignant tumor indications. The two main modalities of phototherapies include photothermal therapy, which causes localized thermal damage to target lesions, and photodynamic therapy, which causes localized chemical damage by generated reactive oxygen species (ROS). Conventional phototherapies suffer a major shortcoming in their clinical application due to their phototoxicity, which primarily arises from the uncontrolled distribution of phototherapeutic agents in vivo. For successful antitumor phototherapy, it is essential to ensure the generation of heat or ROS specifically occurs at the tumor site. To minimize the reverse side effects of phototherapy while improving its therapeutic performance, extensive research has focused on developing hydrogel-based phototherapy for tumor treatment. The utilization of hydrogels as drug carriers allows for the sustained delivery of phototherapeutic agents to tumor sites, thereby limiting their adverse effects. Herein, we summarize the recent advancements in the design of hydrogels for antitumor phototherapy, offer a comprehensive overview of the latest advances in hydrogel-based phototherapy and its combination with other therapeutic modalities for tumor treatment, and discuss the current clinical status of hydrogel-based antitumor phototherapy.

Recent strategies to develop pH-sensitive injectable hydrogels

"Smart" biomaterials that are responsive to pathological abnormalities are an appealing class of therapeutic platforms for the development of personalized medications. The development of such therapeutic platforms requires novel techniques that could precisely deliver therapeutic agents to the diseased tissues, resulting in enhanced therapeutic effects without harming normal tissues. Among various therapeutic platforms, injectable pH-responsive biomaterials are promising biomaterials that respond to the change in environmental pH. Aqueous solutions of injectable pH-responsive biomaterials exhibit a phase transition from sol-to-gel in response to environmental pH changes. The injectable pH-responsive hydrogel depot can provide spatially and temporally controlled release of various bioactive agents including chemotherapeutic drugs, peptides, and proteins. Therapeutic agents are imbibed into hydrogels by simple mixing without the use of toxic solvents and used for long-term storage or in situ injection using a syringe or catheter that could form a stable gel and acts as a controlled release depot in a minimally invasive manner. Tunable physicochemical properties of the hydrogels, such as biodegradability, ability to interact with drugs and mechanical properties, can control the release of the therapeutic agent. This review highlights the advances in the design and development of biodegradable and in situ forming injectable pH-responsive biomaterials that respond to the physiological conditions. Special attention has been paid to the development of amphoteric pH-responsive biomaterials and their utilization in biomedical applications. We also highlight key challenges and future directions of pH-responsive biomaterials in clinical translation.

Past, present and future of biomedical applications of dextran-based hydrogels: A review

This review extensively surveys the biomedical applications of hydrogels containing dextran. Dextran has gained much attention as a biomaterial due to its distinctive properties such as biocompatibility, non-toxicity, water solubility and biodegradability. It has emerged as a critical constituent of hydrogels for biomedical applications including drug delivery devices, tissue engineering scaffolds and biosensor materials. The benefits, challenges and potential prospects of dextran-based hydrogels as biomaterials are highlighted in this review.

Biodegradable porous polymeric drug as a drug delivery system: alleviation of doxorubicin-induced cardiotoxicity via passive targeted release

Doxorubicin (DOX) is an effective chemotherapeutic drug developed against a broad range of cancers, and its clinical applications are greatly restricted by the side effects of severe cardiotoxicity during tumour treatment. Herein, the DOX-loaded biodegradable porous polymeric drug, namely, Fc-Ma-DOX, which was stable in the circulation, but easy to compose in the acidic medium, was used as the drug delivery system avoiding the indiscriminate release of DOX. Fc-Ma was constructed via the copolymerization of 1,1'-ferrocenecarbaldehyde with d-mannitol (Ma) through the pH-sensitive acetal bonds. Echocardiography, biochemical parameters, pathological examination, and western blot results showed that DOX treatment caused increased myocardial injury and oxidative stress damage. In contrast, treatment with Fc-Ma-DOX significantly reduced myocardial injury and oxidative stress by DOX treatment. Notably, in the Fc-Ma-DOX treatment group, we observed a significant decrease in the uptake of DOX by H9C2 cells and a significant decrease in reactive oxygen species (ROS) production.

Chemical, physical, and biological stimuli-responsive nanogels for biomedical applications (mechanisms, concepts, and advancements): A review

The development of nanotechnology has influenced the advancements in biomedical and pharmaceutical fields. The design and formulation of stimuli-responsive nano-drug delivery systems, also called smart drug delivery systems, have attracted significant research worldwide and have been seen as a breakthrough in nanomedicines. The ability of these nanocarriers to respond to external and internal stimuli, such as pH, temperature, redox, electric and magnetic fields, enzymes, etc., has allowed them to deliver the cargo at targeted sites in a controlled fashion. The targeted drug delivery systems limit the harmful side effects on healthy tissue by toxic drugs and furnish spatial and temporal control drug delivery, improved patient compliance, and treatment efficiency. The polymeric nanogels (hydrogel nanoparticles) with stimuli-responsive characteristics have shown great potential in various biomedical, tissue engineering, and pharmaceutical fields. It is primarily because of their small size, biocompatibility, biodegradability, stimuli-triggered drug deliverability, high payload capacity, and tailored functionality. This comprehensive review deals distinctively with polymeric nanogels, their chemical, physical, and biological stimuli, the concepts of nanogels response to different stimuli, and recent advancements. This document will further improve the current understanding of stimuli-responsive materials and drug delivery systems and assist in exploring advanced potential applications of these intelligent materials.

Amplifying the efficacy of ALA-based prodrugs for photodynamic therapy using nanotechnology

5-aminolevulinic acid (ALA) is a clinically approved prodrug involved in intracellular Heme biosynthesis to produce the natural photosensitizer (PS) Protoporphyrin IX (PpIX). ALA based photodynamic therapy (PDT) has been used to treat various malignant and non-malignant diseases. However, natural ALA has disadvantages such as weak lipophilicity, low stability and poor bioavailability, greatly reducing its clinical performance. The emerging nanotechnology is expected to address these limitations and thus improve the therapeutic outcomes. Herein, we summarized important recent advances in the design of ALA-based prodrugs using nanotechnology to improve the efficacy of PDT. The potential limitations and future perspectives of ALA-based nanomedicines are also briefly presented and discussed.

Novel Tumor-Targeted Self-Nanostructured and Compartmentalized Water-in-Oil-in-Water Polyurethane-Polyurea Nanocapsules for Cancer Theragnosis

Encapsulation of water-soluble bioactive compounds for enabling specific accumulation in tumor locations, while avoiding premature clearance and/or degradation in the bloodstream, is one of the main hallmarks in nanomedicine, especially that of NIR fluorescent probes for cancer theragnosis. The herein reported technology furnishes water-dispersible double-walled polyurethane-polyurea hybrid nanocapsules (NCs) loaded with indocyanine green (ICG-NCs), using a versatile and highly efficient one-pot and industrially scalable synthetic process based on the use of two different prepolymers to set up the NCs walls. Flow cytometry and confocal microscopy confirmed that both ICG-loaded NCs internalized in monocyte-derived dendritic cells (moDCs). The in vivo analysis of xenograft A375 mouse melanoma model revealed that amphoteric functionalization of NCs' surface promotes the selective accumulation of ICG-NCs in tumor tissues, making them promising agents for a less-invasive theragnosis of cancer.

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

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

Review targeted drug delivery systems for norcantharidin in cancer therapy

Norcantharidin (NCTD) is a demethylated derivative of cantharidin (CTD), the main anticancer active ingredient isolated from traditional Chinese medicine Mylabris. NCTD has been approved by the State Food and Drug Administration for the treatment of various solid tumors, especially liver cancer. Although NCTD greatly reduces the toxicity of CTD, there is still a certain degree of urinary toxicity and organ toxicity, and the poor solubility, short half-life, fast metabolism, as well as high venous irritation and weak tumor targeting ability limit its widespread application in the clinic. To reduce its toxicity and improve its efficacy, design of targeted drug delivery systems based on biomaterials and nanomaterials is one of the most feasible strategies. Therefore, this review focused on the studies of targeted drug delivery systems combined with NCTD in recent years, including passive and active targeted drug delivery systems, and physicochemical targeted drug delivery systems for improving drug bioavailability and enhancing its efficacy, as well as increasing drug targeting ability and reducing its adverse effects.

Graphical Abstract

A pH-responsive complex based on supramolecular organic framework for drug-resistant breast cancer therapy

Chemotherapy is one of the main ways to treat breast cancer clinically. However, the multidrug resistance to anti-tumor drugs limits their clinical use. To overcome these drawbacks, the development of drug delivery systems (DDSs) has attracted more and more attention in cancer therapy. At present, the preparation and purification process are complicated for many reported DDSs, while the clinic calls for new DDSs that are more convenient for preparation. Here a new pH-responsive supramolecular organic framework drug delivery complex loading doxorubicin (DOX) is fabricated. Anti-tumor activity of the system in vitro was investigated by cell cytotoxicity, uptake assay, and cell apoptosis analysis. The anti-tumor activity in vivo was investigated by inspecting nude mice body weight, tumor volume and weight, also a preliminary mechanism probe was conducted by HE and TUNEL staining. The DOX@SOF displayed high stability, good biocompatibility and pH-regulated drug release. At acid condition, the hydrazone bonds would be broken, which result in the dissociation of SOF, and then the drugs would be released from the system. Furthermore, DOX@SOF enhanced cellular internalization. Both in vitro and in vivo experiments reflected that DOX@SOF could enhance the anti-tumor activity of DOX. for the MCF-7/ADR tumor cells and tumors. This study provides a highly efficient strategy to prepare a stimulus-responsive supramolecular drug delivery complex for the treatment of drug-resistant cancer, the results presented inspiring scientific interests in exploring new drug delivery strategies and reversing multi-drug resistance for clinical chemotherapy.

Synthesis and Characterization of a Novel Dual-Responsive Nanogel for Anticancer Drug Delivery

In this study, to reduce the side effects of anticancer drugs and also to increase the efficiency of current drug delivery systems, a pH and temperature-responsive polymeric nanogel was synthesized by copolymerization of N-vinylcaprolactam (VCL) and acrylic acid (AA) monomers (P(VCL-co-AA)) with a novel cross-linker, triethylene glycol dimethacrylate (TEGDMA), as a biocompatible and nontoxic component. The structural and physicochemical features of the P(VCL-co-AA) nanogel were characterized by FT-IR, DLS/Zeta potential, FE-SEM, and 1HNMR techniques. The results indicated that spherical polymeric nanogel was successfully synthesized with a 182 nm diameter. The results showed that the polymerization process continues with the opening of the carbon-carbon double bond of monomers, which was approved by C-C band removing located at 1600 cm-1. Doxorubicin (Dox) as a chemotherapeutic agent was loaded into the P(VCL-co-AA), whit a significant loading of Dox (83%), and the drug release profile was investigated in the physiological and cancerous site simulated conditions. P(VCL-co-AA) exhibited a pH and temperature-responsive behavior, with an enhanced release rate in the cancerous site condition. The biocompatibility and nontoxicity of P(VCL-co-AA) were approved by MTT assay on the normal human foreskin fibroblasts-2 (HFF-2) cell line. Also, Dox-loaded P(VCL-co-AA) had excellent toxic behavior on the Michigan Cancer Foundation-7 (MCF-7) cell line as model cancerous cells. Moreover, Dox-loaded P(VCL-co-AA) had higher toxicity in comparison with free Dox, which would be a vast advantage in reducing Dox side effects in the clinical cancer treatment applications.

Tumor acidity: From hallmark of cancer to target of treatment

Tumor acidity is one of the cancer hallmarks and is associated with metabolic reprogramming and the use of glycolysis, which results in a high intracellular lactic acid concentration. Cancer cells avoid acid stress major by the activation and expression of proton and lactate transporters and exchangers and have an inverted pH gradient (extracellular and intracellular pHs are acid and alkaline, respectively). The shift in the tumor acid–base balance promotes proliferation, apoptosis avoidance, invasiveness, metastatic potential, aggressiveness, immune evasion, and treatment resistance. For example, weak-base chemotherapeutic agents may have a substantially reduced cellular uptake capacity due to “ion trapping”. Lactic acid negatively affects the functions of activated effector T cells, stimulates regulatory T cells, and promotes them to express programmed cell death receptor 1. On the other hand, the inversion of pH gradient could be a cancer weakness that will allow the development of new promising therapies, such as tumor-targeted pH-sensitive antibodies and pH-responsible nanoparticle conjugates with anticancer drugs. The regulation of tumor pH levels by pharmacological inhibition of pH-responsible proteins (monocarboxylate transporters, H⁺-ATPase, etc.) and lactate dehydrogenase A is also a promising anticancer strategy. Another idea is the oral or parenteral use of buffer systems, such as sodium bicarbonate, to neutralize tumor acidity. Buffering therapy does not counteract standard treatment methods and can be used in combination to increase effectiveness. However, the mechanisms of the anticancer effect of buffering therapy are still unclear, and more research is needed. We have attempted to summarize the basic knowledge about tumor acidity.

Phenylboronic acid conjugated multifunctional nanogels with 131I-labeling for targeted SPECT imaging and radiotherapy of breast adenocarcinoma

We report a new 131I-labeling functional platform for targeted single-photon emission computed tomography (SPECT) imaging and radiotherapy of breast adenocarcinoma. In this study, polyethyleneimine (PEI) based nanogels (P.NH2 NGs) were prepared by water/oil polymerization, modified with targeted agent phenylboronic acid (PBA), and labeled with radionuclide 131I. The NGs without 131I-labeling own a spherical structure, uniform size distribution, and good cell viability. After 131I-labeling, the obtained 131I-PBA-PHP NGs displayed much higher cellular uptake than the non-targeted NGs due to the good softness and fluidity of NGs and the PBA targeting. The in vivo results demonstrated that 131I-PBA-PHP NGs could specifically target breast cancer cells and efficiently aggregate into xenograft breast adenocarcinoma for tumor SPECT imaging and specific radiotherapy. The developed 131I-labeling NGs may be used as a promising platform for efficient radioactive theranostic nanoplatform of tumor.

Unravelling the Supramolecular Driving Forces in the Formation of CO2-Responsive Pseudopeptidic Low-Molecular-Weight Hydrogelators

A new family of C₂-symmetric pseudopeptides with a high functional density for supramolecular interactions has been synthetized through the attachment of four amino acid subunits to a diamino aliphatic spacer. The resulting open-chain compounds present remarkable properties as low-molecular-weight hydrogelators. The self-assembled 3D networks were characterized by SEM analyses, observing regular nanofibres with 80–100 nm diameters. Spectroscopic and molecular modelling experiments revealed the presence of strong synergic effects between the H-bonding and π–π interactions, with the best results obtained for the homoleptic tetra-pseudopeptide derived from l-Phe. In addition, these bioinspired hydrogels possessed pH- and CO₂-responsive sol–gel transitions. The formation of ammonium carbamate derivatives in the presence of carbon dioxide led to a detrimental change in its adequate self-assembly. CO₂ desorption temperatures of ca. 70 °C were assigned to the thermodynamically favoured recovery of the supramolecular gel.

Temperature/pH-responsive carmofur-loaded nanogels rapidly prepared via one-pot laser-induced emulsion polymerization

Tumor microenvironment-responsive nanogels loading antitumor drugs can improve the chemotherapy efficiency due to their suitable size, great hydrophilicity, excellent biocompatibility, and sensitivity to specific stimulation. Herein, a simple and effective strategy of one-pot laser-induced emulsion polymerization at 532 nm was developed to prepare carmofur-loaded nanogels based on biocompatible and temperature/pH-sensitive monomers including polyethylene glycol diacrylate (PEGDA), N-vinylcaprolactam (NVCL), and 2-(dimethylamino) ethyl methacrylate (DMAEMA). The nanogels loading carmofur with dual-stimuli responsive drug release properties were rapidly obtained under laser irradiation (beam diameter 2.5 mm, laser power 60 mW) for only 100 s. These nanogels exhibited an average hydrodynamic diameter of 195.9 nm and a low polydispersity index of 0.115. The effect of monomer ratio on the size, morphology, double-bond conversion, and thermo/pH-sensitivity of nanogels was investigated. The cumulative carmofur release from nanogels at pH 5.0 within 48 h was nearly three times that at pH 7.4, while the release amount at 42 °C was twice that at 25 °C, showing the controlled and sustainable release with the change of pH and temperature. The in vitro release kinetics of carmofur was in accord with first-order release model.

Preparation and application of pH-responsive drug delivery systems

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

A fluorescent, chirality-responsive, and water-soluble cage as a multifunctional molecular container for drug delivery

In recent years, the rational design and construction of drug delivery systems (DDSs) via a supramolecular approach for improving chemical therapeutics have gained significant attention. Here, we report a host-guest DDS formed from a fluorescent, chirality-responsive, and water-soluble tetraphenylethene-based octacationic cage as a fluorescent/chiral probe, solubilizer, and molecular cargo, which can recognize chiral nucleoside drugs, enhance the solubility of insoluble drugs, and protect drugs from the outside environment by forming host-guest complexes in aqueous solution. Given the fluorescence properties and dynamically rotational conformation of tetraphenylethene (TPE) units, this fluorescent and chirality-responsive cage exhibits different responses including turn-on/turn-off fluorescence and negative/positive circular dichroism (CD) when binding with different chiral nucleoside drugs in water, resulting in multiple-responsive photophysical behaviors for these chiral drugs. Furthermore, this water-soluble cationic cage with a hydrophobic cavity can improve the water solubility of insoluble drugs (e.g., CPT) by forming host-guest complexes in water. More importantly, this multifunctional cage exhibits a low toxicity to both human colon and breast cancer cell lines in vitro, and drugs encapsulated by the cage are more effective in killing cancer cells than drugs alone. Finally, the on-off-on fluorescence responses in the formation and dissociation processes of the cage⊃drug complexes have been successfully used to monitor drug release and track drug delivery by fluorescence microscopy in vitro. Therefore, this fluorescent, chirality-responsive, and water-soluble cage as a multifunctional molecular container can be used to construct a smart drug delivery system with several functions of fluorescence and CD detection, water solubilization, real-time monitoring, and chemotherapy.