BIODEGRADABLE POLYMERS WITH A PHOSPHORYL-CONTAINING BACKBONE:TISSUE ENGINEERING AND CONTROLLED DRUG DELIVERY APPLICATIONS

This review provides a glimpse of the potential of the biodegradable phos-phoryl-containing polymers in medical applications. Undoubtedly these polymerspossess unique properties that are yet to be fully understood. Many areas warrantfurther investigation and much optimization remains to be done. The fascinatingchemistry of phosphorus poses interesting hurdles but at the same time leavesample room for polymer scientists to exercise their creativity in designinginteresting biomaterials. As the mutual understanding between basic and clinicalscientists on the need of medical devices and the capabilities of these newbiomaterials expands, imaginative application of new biomaterials to other medi-cal applications can be expected.

Edaravone-loaded poly(amino acid) nanogel inhibits ferroptosis for neuroprotection in cerebral ischemia injury

Neurological injury caused by ischemic stroke is a major cause of permanent disability and death. The currently available neuroprotective drugs fail to achieve desired therapeutic efficacy mainly due to short circulation half-life and poor blood−brain barrier (BBB) permeability. For that, an edaravone-loaded pH/glutathione (pH/GSH) dual-responsive poly(amino acid) nanogel (NG/EDA) was developed to improve the neuroprotection of EDA. The nanogel was triggered by acidic and EDA-induced high-level GSH microenvironments, which enabled the selective and sustained release of EDA at the site of ischemic injury. NG/EDA exhibited a uniform sub-spherical morphology with a mean hydrodynamic diameter of 112.3 ± 8.2 nm. NG/EDA efficiently accumulated at the cerebral ischemic injury site of permanent middle cerebral artery occlusion (pMCAO) mice, showing an efficient BBB crossing feature. Notably, NG/EDA with 50 µM EDA significantly increased neuron survival (29.3%) following oxygen and glucose deprivation by inhibiting ferroptosis. In addition, administering NG/EDA for 7 d significantly reduced infarct volume to 22.2% ± 7.2% and decreased neurobehavioral scores from 9.0 ± 0.6 to 2.0 ± 0.8. Such a pH/GSH dual-responsive nanoplatform might provide a unique and promising modality for neuroprotection in ischemic stroke and other central nervous system diseases.

Biointerface engineering nanoplatforms for cancer-targeted drug delivery

Over the past decade,nanoparticle-based therapeutic modalities have become promising strategies in cancer therapy.Selective delivery of anticancer drugs to the lesion sites is critical for elimination of the tumor and an improved prognosis.Innovative design and advanced biointerface engineering have promoted the development of various nanocarriers for optimized drug delivery.Keeping in mind the biological framework of the tumormicroenvironment,biomembrane-camouflaged nanoplatforms have been a research focus,reflecting their superiority in cancer targeting.In this review,we summarize the development of various biomimetic cell membrane-camouflaged nanoplatforms for cancertargeted drug delivery,which are classified according to the membranes fromdifferent cells.The challenges and opportunities of the advanced biointerface engineering drug delivery nanosystems in cancer therapy are discussed.

In situ-prepared homogeneous supramolecular organic framework drug delivery systems(sof-DDSs)：Overcoming cancer multidrug resistance and controlled release

Water-soluble three-dimensional porous supramolecular organic frameworks（SOFs） have been demonstrated as a new generation of homogeneous polycationic platforms for anti-cancer drug delivery.The new SOF drug delivery systems（sof-DDSs） can adsorb dianionic pemetrexed（PMX）,a clinically used chemotherapeutic agent instantaneously upon dissolving in water,which is driven by both electrostatic attraction and hydrophobicity.The in situ-prepared PMX@SOFs are highly stable and can avoid important release of the drug during plasm circulation and overcome the multidrug resistance of human breast MCF-7/Adr cancer cells to enter the cancer cells.Acidic microenvironment of cancer cells promotes the release of the drug in cancer cells.Both in vitro and in vivo studies have revealed that sofDDSs considerably improve the treatment efficacy of PMX,leading to 6-12-fold reduction of the IC50 values,as compared with that of PMX alone.The new drug delivery strategy omits the loading process required by most of reported nanoparticle-based delivery systems and thus holds promise for future development of low-cost drug delivery systems

Poly(β-cyclodextrin)-mediated Polylactide-cholesterol Stereocomplex Micelles for Controlled Drug Delivery

A series of host-guest interaction-adjusted polylactide stereocomplex micelles was prepared via the self-assembly of 4-armed poly（ethylene glycol）-block-poly（L-lactide/D-lactide）-cholesterol （4-armed PEG-b-PLLA/PDLA-CHOL） and poly（β-cyclodextrin） （PCD） with the molar ratios of CHOL/β-CD at 1：0.5, 1 ：l, and 1：2 in an aqueous environment. The hydrodynamic diameters of the micelles ranged from 84.1 nm to 107 nm depending on the molar ratio of CHOL/β-CD. It was shown that the micelle with the largest proportion of PCD possessed excellent abilities in drug release, cell internalization as well as proliferation inhibitory effect toward human A549 lung cancer cells. The results demonstrated that the stereocomplex and host-guest interactions-mediated PLA micelles exhibited great potential in sustained drug delivery.

Silk fibroin/poly (vinyl alcohol) blend scaffolds for controlled delivery of curcumin

A silk fibroin/poly(vinyl alcohol)porous scaffold with a water vapor transmission rate of 21256464 g/m^(2)/day has been developed via thermally induced phase separation(gelation)and freeze-drying process.A hierarchical architecture of micropores and nanofibers was observed inside the scaffolds,and the related structures were analyzed.The viability and proliferation of 3T3 fibroblasts were examined,which indicated that the scaffolds exerted low cytotoxicity.After loading curcumin,the scaffolds can suppress the growth of 3T3 fibroblasts.The release behavior of curcumin from the scaffolds was investigated.At pH=7.2,the release profiles showed no significant difference for the loading amounts of 0.5mg and 0.25mg per sample.Meanwhile,the cumulative amount of released drug at pH=5.7 was significantly more than that in neutral solution due to more degradation of the scaffolds.It was suggested that the silk fibroin/poly(vinyl alcohol)blend scaffolds could be potentially used as wound dressing materials.

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

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

Graphene-incorporated hyaluronic acid-based hydrogel as a controlled Senexin A delivery system

Perivascular delivery of therapeutic agents against established aetiologies for occlusive vascular remodelling has great therapeutic potential for vein graft failure.However,none of the perivascular drug delivery systems tested experimentally have been translated into clinical practice.In this study,we established a novel strategy to locally and sustainably deliver the cyclin-dependent kinase 8/19 inhibitor Senexin A(SenA),an emerging drug candidate to treat occlusive vascular disease,using graphene oxide-hybridised hyaluronic acid-based hydrogels.We demonstrated an approach to accommodate SenA in hyaluronic acid-based hydrogels through utilising graphene oxide nanosheets allowing for non-covalent interaction with SenA.The resulting hydrogels produced sustained delivery of SenA over 21 days with tunable release kinetics.In vitro assays also demonstrated that the hydrogels were biocompatible.This novel graphene oxide-incorporated hyaluronic acid hydrogel offers an optimistic outlook as a perivascular drug delivery system for treating occlusive vascular diseases,such as vein graft failure.

Targeted nanostrategies eliminate pre-metastatic niche of cancer

Establishing a pre-metastatic niche(PMN)in secondary organs is a prerequisite for cancer metastases.Despite advances in cancer therapy,the efficient inhibition of PMN formation remains a clinical challenge.Recent advances in understanding the specific characteristics of PMN and advances in nanotechnology have provided hope for manipulating their microenvironments.A series of nanostrategies have been designed to eliminate the PMN,including the removal of pro-metastatic exosomes from the bloodstream for excretion via the intestines,the targeting and scavenging of myeloid-derived suppressor cells,fibroblasts,and critical extracellular matrix components,and the elimination of circulating tumor cells prior to colonization in distant organs.This review summarizes the underlying mechanisms of PMN formation,highlights the anti-PMN efficacy of currently reported nanostrategies,and underlines the unresolved questions.

Biochemical hallmarks-targeting antineoplastic nanotherapeutics

Tumor microenvironments(TMEs)have received increasing attention in recent years as they play pivotal roles in tumorigenesis,progression,metastases,and resistance to the traditional modalities of cancer therapy like chemotherapy.With the rapid development of nanotechnology,effective antineoplastic nanotherapeutics targeting the aberrant hallmarks of TMEs have been proposed.The appropriate design and fabrication endow nanomedicines with the abilities for active targeting,TMEs-responsiveness,and optimization of physicochemical properties of tumors,thereby overcoming transport barriers and significantly improving antineoplastic therapeutic benefits.This review begins with the origins and characteristics of TMEs and discusses the latest strategies for modulating the TMEs by focusing on the regulation of biochemical microenvironments,such as tumor acidosis,hypoxia,and dysregulated metabolism.Finally,this review summarizes the challenges in the development of smart anti-cancer nanotherapeutics for TME modulation and examines the promising strategies for combination therapies with traditional treatments for further clinical translation.

In situ bone regeneration with sequential delivery of aptamer and BMP2 from an ECM-based scaffold fabricated by cryogenic free-form extrusion

In situ tissue engineering is a powerful strategy for the treatment of bone defects.It could overcome the limitations of traditional bone tissue engineering,which typically involves extensive cell expansion steps,low cell survival rates upon transplantation,and a risk of immuno-rejection.Here,a porous scaffold polycaprolactone(PCL)/decellularized small intestine submucosa(SIS)was fabricated via cryogenic free-form extrusion,followed by surface modification with aptamer and PlGF-2_(123-144)*-fused BMP2(pBMP2).The two bioactive molecules were delivered sequentially.The aptamer Apt19s,which exhibited binding affinity to bone marrow-derived mesenchymal stem cells(BMSCs),was quickly released,facilitating the mobilization and recruitment of host BMSCs.BMP2 fused with a PlGF-2_(123-144)peptide,which showed“super-affinity”to the ECM matrix,was released in a slow and sustained manner,inducing BMSC osteogenic differentiation.In vitro results showed that the sequential release of PCL/SIS-pBMP2-Apt19s promoted cell migration,proliferation,alkaline phosphatase activity,and mRNA expression of osteogenesis-related genes.The in vivo results demonstrated that the sequential release system of PCL/SIS-pBMP2-Apt19s evidently increased bone formation in rat calvarial critical-sized defects compared to the sequential release system of PCL/SIS-BMP2-Apt19s.Thus,the novel delivery system shows potential as an ideal alternative for achieving cell-free scaffold-based bone regeneration in situ.

Biomaterial scaffold-based local drug delivery systems for cancer immunotherapy

Immunotherapy has attracted tremendous attention due to the remarkable clinical successes for treating a broad spectrum of tumors. One challenge for cancer immunotherapy is the inability to control localization and sustain concentrations of therapeutics at tumor sites. Local drug delivery systems(LDDSs) like the biomaterial scaffold-based drug delivery systems have emerged as a promising approach for delivering immunotherapeutic agents facilely and intensively in situ with reduced systemic toxicity. In this review, recent advances in biomaterial scaffold-based LDDSs for the administration of immunotherapeutic agents including vaccines, immunomodulators, and immune cells are summarized. Moreover, codelivery systems are also evaluated for local immunotherapy-involving combination anti-tumor therapy,including chemotherapy-immunotherapy, photothermal-immunotherapy, and other combination therapies. Finally, the current challenges and future perspectives on the development of next-generation LDDSs for cancer immunotherapy are discussed.

Sustained delivery of rhMG53 promotes diabetic wound healing and hair follicle development

MG53 is an essential component of the cell membrane repair machinery,participating in the healing of dermal wounds.Here we develop a novel delivery system using recombinant human MG53(rhMG53)protein and a reactive oxygen species(ROS)-scavenging gel to treat diabetic wounds.Mice with ablation of MG53 display defective hair follicle structure,and topical application of rhMG53 can promote hair growth in the mg53/mice.Cell lineage tracing studies reveal a physiological function of MG53 in modulating the proliferation of hair follicle stem cells(HFSCs).We find that rhMG53 protects HFSCs from oxidative stress-induced apoptosis and stimulates differentiation of HSFCs into keratinocytes.The cytoprotective function of MG53 is mediated by STATs and MAPK signaling in HFSCs.The thermosensitive ROS-scavenging gel encapsulated with rhMG53 allows for sustained release of rhMG53 and promotes healing of chronic cutaneous wounds and hair follicle development in the db/db mice.These findings support the potential therapeutic value of using rhMG53 in combination with ROS-scavenging gel to treat diabetic wounds.

pH- and H_(2)O_(2)-sensitive drug delivery system based on sodium xanthate:Dual-responsive supramolecular vesicles from one functional group

Nano-drug delivery systems with multiple stimulus-responsive capabilities have superior response performance and efficient drug release.Nevertheless,it is sophisticated to construct multiple stimulus-responsive systems where the two or more functional groups need to be introduced simultaneously.Xanthate,one functional group with pH and H2O2 stimulus responsiveness,has significant potential applications for building dual-responsive drug delivery system.Herein,we present a novel dual stimuli-responsive supramolecular drug delivery system by using sodium xanthate derivative(SXD)as guest molecule and quaternary ammonium capped pillar[5]arene(QAP5)as host molecule through host-guest interaction on the basis of electrostatic interaction.The amphiphile QAP5⊃SXD could self-assemble into vesicles to efficiently load the anti-cancer drug DOX.The experimental results showed that QAP5⊃SXD nanoparticles could achieve efficient drug delivery and controlled release in the tumor microenvironment.Cytotoxicity experiments proved that DOX@QAP5⊃SXD nanoparticles could significantly improve the anticancer efficiency of free DOX on cancer cells.The present study provides an efficient strategy to develop supramolecular nanocarriers with dual-responsiveness in one functional group for controlled drug release.

Loading-free supramolecular organic framework drug delivery systems(sof-DDSs) for doxorubicin:normal plasm and multidrug resistant cancer cell-adaptive delivery and release

Four water-soluble porous supramolecular organic framework drug delivery systems（sof-DDSs） have been used to adsorb doxorubicin（DOX） in water at physiological pH of 7.4,which is driven exclusively by hydrophobicity.The resulting complexes DOX@SOFs are formed instantaneously upon dissolving the components in water.The drug-adsorbed sof-DDSs can undergo plasm circulation with important maintenance of the drug and overcome the multidrug resistance of human breast MCF-7/Adr cancer cells.DOX is released readily in the cancer cells due to the protonation of its amino group in the acidic medium of cancer cells.In vitro and in vivo experiments reveal that the delivery of SOF-a-d remarkably improve the cytotoxicity of DOX for the MCF-7/Adr cells and tumors,leading to 13-19-fold reduction of the 1C_（50）values as compared with that of DOX.This new sof-DDSs strategy omits the indispensable loading process required by most of reported nano-scaled carriers for neutral hydrophobic chemotherapeutic agents,and thus should be highly valuable for future development of low-cost delivery systems.

Preparation of monolithic osmotic tablet of quercetin loaded by solid dispersion

The objective of this study was to prepare monolithic osmotic tablet of quercetin for controlled drug release. Quercetin-PVP solid dispersion was prepared to enhance its solubility and dissolution rate. Solid dispersion, suspending agents, osmotic agents and other conventional excipients were used as tablet core composition and cellulose acetate （CA） with plasticizer as release controlling membrane. Different formulation variables, the amounts of PEO （polyethylene oxide）, NaC1, plasticizer, and coating weight gain were optimized to gain the optimum formulation. The mechanism of drug release from monolithic osmotic tablet was also discussed. The optimal monolithic osmotic pump tablet could deliver quercetin at the rate of approximate zero-order up to 12 h, and the cumulative release was 90.74%. The developed monolithic osmotic system for quercetin loaded by solid dispersion was found to be a promising approach for controlled release of poorly-water soluble drug candidates.

Ultrasound-triggered noninvasive regulation of blood glucose levels using microgels integrated with insulin nanocapsules

Diabetes is a serious public health problem affecting 422 million people worldwide. Traditional diabetes management often requires multiple daily insulin injections, associated with pain and inadequate glycemia control. Herein, we have developed an ultrasound-triggered insulin delivery system capable of pulsatile insulin release that can provide both long-term sustained and fast on-demand responses. In this system, insulin-loaded poly（lactic-co-glycolic acid） （PLGA） nanocapsules are encapsulated within chitosan microgels. The encapsulated insulin in nanocapsules can passively diffuse from the nanoparticle but remain restricted within the microgel. Upon ultrasound treatment, the stored insulin in microgels can be rapidly released to regulate blood glucose levels. In a chemically-induced type I diabetic mouse model, we demonstrated that this system, when activated by 30 s ultrasound administration, could effectively achieve glycemic control for up to one week in a noninvasive, localized, and pulsatile manner.

Tumor microenvironment-responsive hyaluronate-calcium carbonate hybrid nanoparticle enables effective chemo-therapy for primary and advanced osteosarcomas

Osteosarcoma is the most common malignancy in the bone. Current chemotherapy offers limited efficacy with significant side effects, especially for advanced and relapsed osteosarcomas. Nanoparticle-formulated chemotherapeutic drugs may be used to resolve these issues, but several aspects of these formulations remain unsatisfactory, such as how to improve their stability in the bloodstream, prevent undesirable drug leakage, and enhance targeted drug accumulation in the tumor. In this study, a tumor microenvironment-responsive calcium carbonate （CaCO3）- crosslinked hyaluronate （HA） nanopartide was prepared via a ＂green＂ process to effectively deliver doxorubicin （DOX） for the treatment of various stages of osteosarcoma. The DOX-loaded hyaluronate-calcium carbonate hybrid nanoparfide （HA-DOX/CaCO3） demonstrated superior stability both in vitro and in vivo, and rapidly released DOX at the tumor site when triggered by the acidic tumor microenvironment. Compared with free DOX and a non-crosslinked nanoparficle （HA-DOX）, HA-DOX]CaCO3 exhibited the most potent inhibition efficacy toward both primary and advanced models of routine osteosarcoma, resulting in effective tumor inhibition, improved survival time, and reduced adverse effects. Most importantly, in the advanced osteosarcoma model, HA-DOX/CaCO3 potently suppressed tumor growth by 84.6%, which indicates the potential of this platform for osteosarcoma treatment, particularly for advanced and relapsed cases. The proposed polysaccharide nanopartide would be a promising drug delivery platform to advance osteosarcoma nanomedicine.

Cystine proportion regulates fate of polypeptide nanogel as nanocarrier for chemotherapeutics

The physicochemical characteristics of nanoparticles are closely related to their drug delivery performances in vitro and in vivo.A well-designed nanocarrier can prolong the drug half-life in the blood circulation,upregulate the drug accumulation at the target site,and enhance the treatment efficacy.To elucidate the impact of physicochemical properties on the fate of nanogel as a nanocarrier of chemotherapeutics,three methoxy poly(ethylene glycol)-poly(L-phenylalanine-co-L-cystine)(mPEG-P(LP-coLC))nanogels with different L-cystine proportions were developed,namely mPEG-P(LP10-co-LC5)(NG10-5),mPEG-P(LP10-coLC10)(NG10-10),and mPEG-P(LP10-co-LC15)(NG10-15).The three nanogels shared similar surface charge and reductionresponsive behavior,but they had distinct diameters and different drug release profiles.Among them,NG10-5,which has the smallest diameter,was preferentially internalized by tumor cells in vitro and showed rapid migration to the tumor site in vivo.Using doxorubicin(DOX)as a model chemotherapeutic agent,NG10-5/DOX had the most prolonged blood circulation period and highest tumor accumulation after intravenous administration.NG10-5/DOX also had the most potent antitumor effect of all three drug-loaded nanogels.Accordingly,adjusting physicochemical characteristics by changing the amino acid composition might improve the therapeutic efficacies of nanogels and enhance their potential for clinical application.

Bioinspired Andrias davidianus-Derived wound dressings for localized drug-elution

Local drug delivery has received increasing attention in recent years.However,the therapeutic efficacy of local delivery of drugs is still limited under certain scenarios,such as in the oral cavity or in wound beds after resection of tumors.In this study,we introduce a bioinspired adhesive hydrogel derived from the skin secretions of Andrias davidianus(SSAD)as a wound dressing for localized drug elution.The hydrogel was loaded with aminoguanidine or doxorubicin,and its controlled drug release and healing-promoting properties were verified in a diabetic rat palatal mucosal defect model and a C57BL/6 mouse melanoma-bearing model,respectively.The results showed that SSAD hydrogels with different pore sizes could release drugs in a controllable manner and accelerate wound healing.Transcriptome analyses of the palatal mucosa suggested that SSAD could significantly upregulate pathways linked to cell adhesion and extracellular matrix deposition and had the ability to recruit keratinocyte stem cells to defect sites.Taken together,these findings indicate that property-controllable SSAD hydrogels could be a promising biofunctional wound dressing for local drug delivery and promotion of wound healing.