Design and evaluation of antibacterials crosslinked chitosan nanoparticle as a novel carrier for the delivery of metronidazole to treat bacterial vaginosis.

Bacterial vaginosis (BV) is a recurring, chronic infection that is difficult to treat due to the limited bioavailability of antimicrobials within vaginal epithelial cells. Vaginal administration, because of lower dosing and systemic exposure offers a viable option for treating vaginal infections. In this study, Metronidazole-loaded chitosan nanoparticles were synthesised employing borax (BX) or tannic acid (TA) as an antimicrobial crosslinking agent for treating BV. The prepared NPs were characterized for various physical, physicochemical, pharmaceutical, thermal and antibacterial properties. Morphological investigation revealed that nanoparticles prepared from 0.5 % w/v chitosan, 1.2 % w/v BX, and 0.4 % w/v metronidazole (MTZ) were non-spherical, with particle sizes of 377.4 ± 37.3 nm and a zeta potential of 34 ± 2.1 mV. The optimised formulation has MIC values of 24 ± 0.5 and 59 ± 0.5 µg/mL, against Escherichia coli (E.coli) and Candida albicans (C.albicans) respectively. The results of DSC and XRD demonstrated no change in the physical state of the drug in the finished formulation. Under simulated vaginal fluid, the optimised formulation demonstrates a cumulative drug release of about 90 % within 6h. The prepared borax crosslinked NPs exhibit anti-fungal activities by inhibiting ergosterol synthesis. The in-vivo antibacterial data indicated a comparable reduction in bacterial count compared to the marketed formulation in female Swiss albino mice treated with optimised nanoparticles. According to histopathological findings, the prepared nanoparticle was safe for vaginal use. Based on the experimental findings, it was concluded that MBCSNPs, due to their good physiochemical and antimicrobial properties, could serve as a potential topical alternative for treating BV and reducing fungal infection.

Development of Betulin-Loaded Nanostructured Lipid Carriers for the Management of Imiquimod-Induced Psoriasis.

Psoriasis is a complex and persistent autoimmune skin disease. The present research focused on the therapeutic evaluation of betulin-loaded nanostructured lipid carriers (BE-NLCs) towards managing psoriasis. The BE-NLCs were synthesized using the emulsification cum solidification method, exhibiting a spherical shape with a particle size of 183.5±1.82nm and a narrow size distribution window (PDI: 0.142±0.05). A high zeta potential -38.64±0.05mV signifies the relative stability of the nano-dispersion system. BE-NLCs show a drug loading and entrapment efficiency of 47.35±3.25% and 87.8±7.86%, respectively. In vitro release study, BE NLCs show a cumulative percentage release of 90.667±5.507% over BE-sol (57.334±5.03%) and BD-oint (42±4.58%) for 720min. In an ex vivo 24-h permeation study, % cumulative amount permeated per cm2 was found to be 55.667±3.33% from BE-NLCs and 32.012±3.26% from BE-sol, demonstrating a better permeability of 21.66% when compared to the standard formulation BD-oint. The in vivo anti-psoriatic activity in the IMQ-induced model shows topical application of BE-sol, BE-NLCs, and BD-oint resulted in recovery rates of 56%, 82%, and 65%, respectively, based on PASI (Psoriasis Area and Severity Index) score. Notably, BE-NLCs demonstrated a more significant reduction in spleen mass, indicating attenuation of the local innate immune system in psoriatic mice. Reductions in TNF-α, IL-6, and IL-17 levels were observed in both BE-sol and BE-NLCs groups compared to the disease control (DC) group, with BE-NLCs exhibiting superior outcomes (74.05%, 44.76%, and 49.26% reduction, respectively). Soy lecithin and squalene-based NLCs could be better carrier system for the improvement of the therapeutic potential of BE towards management of psoriasis.

Novel Drug Delivery Approaches for the Localized Treatment of Cervical Cancer.

Cervical cancer (CC) is the fourth leading cancer type in females globally. Being an ailment of the birth canal, primitive treatment strategies, including surgery, radiation, or laser therapy, bring along the risk of infertility, neonate mortality, premature parturition, etc. Systemic chemotherapy led to systemic toxicity. Therefore, delivering a smaller cargo of therapeutics to the local site is more beneficial in terms of efficacy as well as safety. Due to the regeneration of cervicovaginal mucus, conventional dosage forms come with the limitations of leaking, the requirement of repeated administration, and compromised vaginal retention. Therefore, these days novel strategies are being investigated with the ability to combat the limitations of conventional formulations. Novel carriers can be engineered to manipulate bioadhesive properties and sustained release patterns can be obtained thus leading to the maintenance of actives at therapeutic level locally for a longer period. Other than the purpose of CC treatment, these delivery systems also have been designed as postoperative care where a certain dose of antitumor agent will be maintained in the cervix postsurgical removal of the tumor. Herein, the most explored localized delivery systems for the treatment of CC, namely, nanofibers, nanoparticles, in situ gel, liposome, and hydrogel, have been discussed in detail. These carriers have exceptional properties that have been further modified with the aid of a wide range of polymers in order to serve the required purpose of therapeutic effect, safety, and stability. Further, the safety of these delivery systems toward vital organs has also been discussed.

Spray-Dried Mucoadhesive Re-dispersible Gargle of Chlorhexidine for Improved Response Against Throat Infection: Formulation Development, In Vitro and In Vivo Evaluation.

Drug delivery to the buccal mucosa is one of the most convenient ways to treat common mouth problems. Here, we propose a spray-dried re-dispersible mucoadhesive controlled release gargle formulation to improve the efficacy of chlorhexidine. The present investigation portrays an approach to get stable and free-flowing spray-dried porous aggregates of chlorhexidine-loaded sodium alginate nanoparticles. The ionic gelation technique aided with the chlorhexidine's positive surface charge-based crosslinking, followed by spray drying of the nanoparticle's dispersion in the presence of lactose- and leucine-yielded nano-aggregates with good flow properties and with a size range of about 120-350 nm. Provided with the high entrapment efficiency (87%), the particles showed sustained drug release behaviors over a duration of 10 h, where 87% of the released drug got permeated within 12 h. The antimicrobial activity of the prepared formulation was tested on S. aureus, provided with a higher zone of growth inhibition than the marketed formulation. Aided with an appropriate mucoadhesive strength, this product exhibited extended retention of nanoparticles in the throat region, as shown by in vivo imaging results. In conclusion, the technology, provided with high drug retention and extended effect, could be a potential candidate for treating several types of throat infections.

Exploring the Biofilm Inhibition Potential of a Novel Phytic Acid-Crosslinked Chitosan Nanoparticle: In Vitro and In Vivo Investigations.

The primary factor underlying the virulence of Candida albicans is its capacity to form biofilms, which in turn leads to recurrent complications. Over-the-counter antifungal treatments have proven ineffective in eliminating fungal biofilms and the inflammatory cytokines produced during fungal infections. Chitosan nanoparticles offer broad and versatile therapeutic potential as both antifungal agents and carriers for antifungal drugs to combat biofilm-associated Candida infections. In our study, we endeavoured to develop chitosan nanoparticles utilising chitosan and the antifungal crosslinker phytic acid targeting C. albicans. Phytic acid, known for its potent antifungal and anti-inflammatory properties, efficiently crosslinks with chitosan. The nanoparticles were synthesised using the ionic gelation technique and subjected to analyses including Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential analysis. The synthesised nanoparticles exhibited dimensions with a diameter (Dh) of 103 ± 3.9 nm, polydispersity index (PDI) of 0.33, and zeta potential (ZP) of 37 ± 2.5 mV. These nanoparticles demonstrated an antifungal effect with a minimum inhibitory concentration (MIC) of 140 ± 2.2 µg/mL, maintaining cell viability at approximately 90% of the MIC value and reducing cytokine levels. Additionally, the nanoparticles reduced ergosterol content and exhibited a 62% ± 1.2 reduction in biofilm susceptibility, as supported by colony-forming unit (CFU) and XTT assays-furthermore, treatment with nanoparticles reduced exopolysaccharide production and decreased secretion of aspartyl protease by C. albicans. Our findings suggest that the synthesised nanoparticles effectively combat Candida albicans infections. In vivo studies conducted on a mouse model of vaginal candidiasis confirmed the efficacy of the nanoparticles in combating fungal infections in vivo.

Tuning the 1O2 Oxidation of a Phenol at the Air/Solid Interface of a Nanoparticle: Hydrophobic Surface Increases Oxophilicity.

Although silica surfaces have been used in organic oxidations for the production of peroxides, studies of airborne singlet oxygen at interfaces are limited and have not found widespread advantages. Here, with prenyl phenol-coated silica and delivery of singlet oxygen (1O2) through the gas phase, we uncover significant selectivity for dihydrofuran formation over allylic hydroperoxide formation. The hydrophobic particle causes prenyl phenol to produce an iso-hydroperoxide intermediate with an internally protonated oxygen atom, which leads to dihydrofuran formation as well as O atom transfer. In contrast, hydrophilic particles cause prenyl phenol to produce allylic hydroperoxide, due to phenol OH hydrogen bonding with SiOH surface groups. Mechanistic insight is provided by air/nanoparticle interfaces coated with the prenyl phenol, in which product yield was 6-fold greater on the hydrophobic nanoparticles compared to the hydrophilic nanoparticles and total rate constants (ASI-kT) of 1O2 were 13-fold greater on the hydrophobic vs hydrophilic nanoparticles. A slope intersection method was also developed that uses the airborne 1O2 lifetime (τairborne) and surface-associated 1O2 lifetime (τsurf) to quantitate 1O2 transitioning from volatile to non-volatile and surface boundary (surface···1O2). Further mechanistic insights on the selectivity of the reaction of prenyl phenol with 1O2 was provided by density functional theory calculations.

Low-volume plasma sampling for determination of dextromethorphan and dextrorphan in rat plasma: LC-MS/MS method and its application in pharmacokinetic study.

Dextromethorphan (DM) and its metabolite dextrorphan (DX) continue to draw the attention of researchers owing to their diverse pharmacodynamics. Thus, there are possibilities for repurposing DM. Most of the pharmacodynamics of DM needs further validation in different preclinical models. Also, it is necessary to correlate the pharmacodynamics with relevant pharmacokinetics data. Multiple bioanalytical techniques developed for this purpose primarily use a high sample processing volume. Since sample volume is a limiting factor for many preclinical models, an effort was taken to develop an alternative method suitable for handling low sample processing volumes. An efficient solid-phase extraction technique, robust liquid chromatographic (LC) separation and highly sensitive tandem mass spectrometric detection (MS/MS) showed suitability for use of a 30 µl sample processing volume. This led to the development of a highly specific, selective, accurate and precise-bio-analytical method for simultaneous quantification of DM and DX in rat plasma. The validated method was linear in the range of 0.196-403.356 ng/ml for DM and 0.102-209.017 ng/ml for DX. The application of the method was demonstrated through the estimation of pharmacokinetic parameters that showed good congruence with earlier studies.

Chitosan as a potential biomaterial for the management of oral mucositis, a common complication of cancer treatment.

Oral mucositis is a serious issue in patients receiving oncological therapies. Mucosal protectants considered to be one of the preferred choices used in the management of mucositis. However, the protective efficacy of currently available mucosal protectants has been significantly compromised due to poor retention, lack of lubrication, poor biodegradability, and inability to manage secondary complications. Chitosan is a promising material for mucosal applications due to its beneficial biomedical properties. Chitosan is also anti-inflammatory, anti-microbial, and capable of scavenging free radicals, makes it a good candidate for the treatment of oral mucositis. Additionally, chitosan's amino polysaccharide skeleton permits a number of chemical alterations with better bioactive performance. This article provides a summary of key biological properties of chitosan and its derivatives that are useful for treating oral mucositis. Current literature evidence shows that Chitosan has superior mucosal protective properties when utilised alone or as delivery systems for co-encapsulated drugs.

Nanofibers of Glycyrrhizin/Hydroxypropyl-ß-Cyclodextrin Inclusion Complex: Enhanced Solubility Profile and Anti-inflammatory Effect of Glycyrrhizin.

Despite having a wide range of therapeutic advantages, glycyrrhizin (GL) has few commercial applications due to its poor aqueous solubility. In this study, we combined the benefits of hydroxypropyl ß-cyclodextrin (HP-ßCD) supramolecular inclusion complexes and electrospun nanofibers to improve the solubility and therapeutic potential of GL. A molecular inclusion complex containing GL and HP-ßCD was prepared by lyophilization at a 1:2 molar ratio. GL and hydroxypropyl ß-cyclodextrin inclusion complexes were also incorporated into hyaluronic acid (HA) nanofibers. Prepared NF was analyzed for physical, chemical, thermal, and pharmaceutical properties. Additionally, a rat model of carrageenan-induced hind paw edema and macrophage cell lines was used to evaluate the anti-inflammatory activity of GL-HP-ßCD NF. The DSC and XRD analyses clearly showed the amorphous state of GL in nanofibers. In comparison to pure GL, GL-HP-ßCD NF displayed improved release (46.6 ± 2.16% in 5 min) and dissolution profiles (water dissolvability ≤ 6 s). Phase solubility results showed a four-fold increase in GL solubility in GL-HP-ßCD NF. In vitro experiments on cell lines showed that inflammatory markers like IL-1ß, TNF-α, and IL-6 were significantly lower in GL-HP-ßCD NF compared to pure GL (p < 0.01 and p < 0.05). According to in vivo results, the prepared nanofiber exhibits a better anti-inflammatory effect than pure GL (63.4% inhibition vs 53.7% inhibition). The findings presented here suggested that GL-HP-ßCD NF could serve as a useful strategy for improving the therapeutic effects of GL.

Anticooperative Supramolecular Oligomerization Mediated by V-Shaped Monomer Design and Unconventional Hydrogen Bonds.

After more than three decades of extensive investigations on supramolecular polymers, strategies for self-limiting growth still remain challenging. Herein, we exploit a new V-shaped monomer design to achieve anticooperatively formed oligomers with superior robustness and high luminescence. In toluene, the monomer-oligomer equilibrium is shifted to the monomer side, enabling the elucidation of the molecular packing modes and the resulting (weak) anticooperativity. Steric effects associated with an antiparallel staircase organization of the dyes are proposed to outcompete aromatic and unconventional B-F⋅⋅⋅H-N/C interactions, restricting the growth at the stage of oligomers. In methylcyclohexane (MCH), the packing modes and the anticooperativity are preserved; however, pronounced solvophobic and chain-enwrapping effects lead to thermally ultrastable oligomers. Our results shed light on understanding anticooperative effects and restricted growth in self-assembly.

Direct Participation of Solvent Molecules in the Formation of Supramolecular Polymers.

This article reports supramolecular polymerization of two bis-amide functionalized naphthalene-diimide (NDI) building blocks (NDI-L and NDI-C) in two solvents, namely n-heptane (Hep) and methylcyclohexane (MCH). NDI-L and NDI-C differ only by the peripheral hydrocarbon wedges, consisting of linear C7 chains or cyclic methylcyclohexane rings, respectively. UV/Vis and FTIR spectroscopy studies reveal distinct internal order and H-bonding pattern for NDI-L and NDI-C aggregates irrespective of the solvent system, indicating the dominant role of the intrinsic packing parameters of the individual building block, possibly influenced by the peripheral steric crowding. However, NDI-L produces a significantly stronger gel in Hep compared to MCH as evident from the rheological and thermal properties. In contrast, NDI-C exhibits a clear preference for MCH, producing gel with moderate strength but in Hep it fails to produce 1D morphology or gelation. All-atom molecular dynamics (MD) simulation studies corroborate with the experimental observation and provide the rationale for the observed solvent-shape effect by revealing a quantitative estimate regarding the thermodynamics of self-assembly in these four combinations. Such clear-cut shape-matching effect (between the peripheral hydrocarbon wedge and the solvent system) unambiguously support a direct participation of the solvent molecules during supramolecular polymerization and presence of a closely-adhered solvent shell around the supramolecular polymers, similar to the first layer of water molecules around the protein surface. Solvent induced CD experiments support this hypothesis as induced CD band was observed only from a chiral co-solvent of matching shape. This is reconfirmed by the higher de-solvation temperature of the shape-matching NDI/solvent system combination compared to the shape mis-match combination in variable temperature UV/Vis experiments, revealing transformation to a different aggregate at higher temperatures rather than disassembly to the monomer for all four combinations.

Nanotherapeutics approaches to overcome P-glycoprotein-mediated multi-drug resistance in cancer.

Multidrug resistance (MDR) in cancer chemotherapy is a growing concern for medical practitioners. P-glycoprotein (P-gp) overexpression is one of the major reasons for multidrug resistance in cancer chemotherapy. The P-gp overexpression in cancer cells depends on several factors like adenosine triphosphate (ATP) hydrolysis, hypoxia-inducible factor 1 alpha (HIF-1α), and drug physicochemical properties such as lipophilicity, molecular weight, and molecular size. Further multiple exposures of anticancer drugs to the P-gp efflux protein cause acquired P-gp overexpression. Unique structural and functional characteristics of nanotechnology-based drug delivery systems provide opportunities to circumvent P-gp mediated MDR. The primary mechanism behind the nanocarrier systems in P-gp inhibition includes: bypassing or inhibiting the P-gp efflux pump to combat MDR. In this review, we discuss the role of P-gp in MDR and highlight the recent progress in different nanocarriers to overcome P-gp mediated MDR in terms of their limitations and potentials.

Control over Multiple Nano- and Secondary Structures in Peptide Self-Assembly.

Herein, we report the rich morphological and conformational versatility of a biologically active peptide (PEP-1), which follows diverse self-assembly pathways to form up to six distinct nanostructures and up to four different secondary structures through subtle modulation in pH, concentration and temperature. PEP-1 forms twisted ß-sheet secondary structures and nanofibers at pH 7.4, which transform into fractal-like structures with strong ß-sheet conformations at pH 13.0 or short disorganized elliptical aggregates at pH 5.5. Upon dilution at pH 7.4, the nanofibers with twisted ß-sheet secondary structural elements convert into nanoparticles with random coil conformations. Interestingly, these two self-assembled states at pH 7.4 and room temperature are kinetically controlled and undergo a further transformation into thermodynamically stable states upon thermal annealing: whereas the twisted ß-sheet structures and corresponding nanofibers transform into 2D sheets with well-defined ß-sheet domains, the nanoparticles with random coil structures convert into short nanorods with α-helix conformations. Notably, PEP-1 also showed high biocompatibility, low hemolytic activity and marked antibacterial activity, rendering our system a promising candidate for multiple bio-applications.

Protein-nanoparticle interactions and a new insight.

The study of protein-nanoparticle interactions provides knowledge about the bio-reactivity of nanoparticles, and creates a database of nanoparticles for applications in nanomedicine, nanodiagnosis, and nanotherapy. The problem arises when nanoparticles come in contact with physiological fluids such as plasma or serum, wherein they interact with the proteins (or other biomolecules). This interaction leads to the coating of proteins on the nanoparticle surface, mostly due to the electrostatic interaction, called 'corona'. These proteins are usually partially unfolded. The protein corona can deter nanoparticles from their targeted functionalities, such as drug/DNA delivery at the site and fluorescence tagging of diseased tissues. The protein corona also has many repercussions on cellular intake, inflammation, accumulation, degradation, and clearance of the nanoparticles from the body depending on the exposed part of the proteins. Hence, the protein-nanoparticle interaction and the configuration of the bound-proteins on the nanosurface need thorough investigation and understanding. Several techniques such as DLS and zeta potential measurement, UV-vis spectroscopy, fluorescence spectroscopy, circular dichroism, FTIR, and DSC provide valuable information in the protein-nanoparticle interaction study. Besides, theoretical simulations also provide additional understanding. Despite a lot of research publications, the fundamental question remained unresolved. Can we aim for the application of functional nanoparticles in medicine? A new insight, given by us, in this article assumes a reasonable solution to this crucial question.

Implications of relaxation dynamics of collapsed conjugated polymeric nanoparticles for light-harvesting applications.

Conjugated polymer-based nanostructures have been explored extensively from energy harvesting to healthcare applications due to their unique photophysical properties. This perspective includes the mechanism of the formation of polymer nanoparticles from linear chain polymers by utilizing experimental and theoretical studies. Conjugated polymer nanoparticles lead to changes in excitonic absorption bands, photoluminescence (PL) bands, and relaxation kinetics due to the inter-chain interactions between the chromophoric sub-units and the formation of the low-lying delocalized collective state. Here, we have illustrated the current understanding of the ultrafast relaxation dynamics of π-conjugated polymer-based nanostructured materials using global and target analysis. We have shown the impacts of the photoinduced carrier dynamics of polymer nanoparticles on the energy and charge transfer processes. Polymer nanoparticles found promising applications in bio-imaging, photothermal and photodynamic therapeutic agents, photocatalysis, and lasing materials. Finally, we have given the future perspectives of luminescent polymer nanoparticles.

Compositional heterogeneity of different biochar: Effect of pyrolysis temperature and feedstocks.

We have quantified the influence of different pyrolysis temperature and feedstocks types on thirty six compositional characteristics of biochar. The properties of biochar were principally influenced more by the feedstocks type than pyrolytic temperature. Higher porosity and surface area illustrated its soil structural modification and nutrient retention capacity along with their utilization for wastewater adsorbents. The total carbon content in all the biochar increased upto 10.14% with the increase in pyrolysis temperature. The produced biochar can replace the conventional fossil fuels due to their high fixed carbon. The cation exchange capacity of biochar augmented with rise in pyrolysis temperature. But the dissolved organic carbon reduced exponentially with increase in temperature. At low temperature pyrolysis the polarity index tends to increase and vice-versa. All the biochar has a potential to alleviate soil boron deficiency due to its higher concentration. Therefore, dissimilar properties of biochar can be produced by selecting the right feedstock type and standardizing specific pyrolytic temperature, depending on the necessity for environmental application in a specific crisis.

Recent Advancement in Nanotechnology-Based Drug Delivery System Against Viral Infections.

In the last few decades, the exponential rise in the incidence of viral infections sets a global health emergency across the world. The biomimetic architecture, the ability to hijack host immune responses, continuous antigen shifting, and drafting are the major critical factors that are responsible for the unavailability of a concrete therapeutic regimen against viral infections. Further, inappropriate pharmacodynamic physicochemical and biological parameters such as low aqueous solubility, poor permeability, high affinity for plasm proteins, short biological half-lives, and fast elimination from the systemic circulation are the major critical factors that govern the suboptimal drug concentration at the target site that leads to the development of drug resistance. To address this issue, nanotechnology-based drug delivery approach is emerged as an altering method to attain the optimal drug concentration at the target site for a prolonged period by integrating the nanoengineering tools in the synthesis of nanoparticles. Nanodimensional configuration with enhanced permeability and retention effect, increased surface-area-to-volume ratio, provision for surface functionalization, etc., are the privileged aspects that make it an effective drug delivery system for dispensing the antiviral therapeutics. However, size, shape, charge, and surface topology of nanoparticles are the greater influential factors that determine target-specific drug delivery, optimum cellular uptake, degree of opsonization by the host immune cells, drug retention time, transcytosis, the extension of biological half-life, in vivo stability, and cytotoxicity. The review will enlighten the elaborative role of nanotechnology-based drug delivery and the major challenging aspect of clinical safety and efficacy.

Recent Advancement in Topical Nanocarriers for the Treatment of Psoriasis.

Psoriasis is a life-threatening autoimmune inflammatory skin disease, triggered by T lymphocyte. Recently, the drugs most commonly used for the treatment of psoriasis include methotrexate (MTX), cyclosporine (CsA), acitretin, dexamethasone, and salicylic acid. However, conventional formulations due to poor absorptive capacity, inconsistent drug release characteristics, poor capability of selective targeting, poor retention of drug molecules in target tissue, and unintended skin reactions restrict the clinical efficacy of drugs. Advances in topical nanocarriers allow the development of prominent drug delivery platforms can be employed to address the critical issues associated with conventional formulations. Advances in nanocarriers design, nano-dimensional configuration, and surface functionalization allow formulation scientists to develop formulations for a more effective treatment of psoriasis. Moreover, interventions in the size distribution, shape, agglomeration/aggregation potential, and surface chemistry are the significant aspects need to be critically evaluated for better therapeutic results. This review attempted to explore the opportunities and challenges of current revelations in the nano carrier-based topical drug delivery approach used for the treatment of psoriasis.

Pathway and Length Control of Supramolecular Polymers in Aqueous Media via a Hydrogen Bonding Lock.

Programming the organization of π-conjugated systems into nanostructures of defined dimensions is a requirement for the preparation of functional materials. Herein, we have achieved high-precision control over the self-assembly pathways and fiber length of an amphiphilic BODIPY dye in aqueous media by exploiting a programmable hydrogen bonding lock. The presence of a (2-hydroxyethyl)amide group in the target BODIPY enables different types of intra- vs. intermolecular hydrogen bonding, leading to a competition between kinetically controlled discoidal H-type aggregates and thermodynamically controlled 1D J-type fibers in water. The high stability of the kinetic state, which is dominated by the hydrophobic effect, is reflected in the slow transformation to the thermodynamic product (several weeks at room temperature). However, this lag time can be suppressed by the addition of seeds from the thermodynamic species, enabling us to obtain supramolecular polymers of tuneable length in water for multiple cycles.

Global and target analysis of relaxation processes of the collapsed state of P3HT polymer nanoparticles.

Organic-inorganic heterostructure materials have received significant research interest for designing light harvesting devices because of their efficient charge separation. Here, we design organic and inorganic nano-heterostructures using conjugated polymer nanoparticles (PNPs) [poly(3-hexylthiophene-2,5-diyl), P3HT] and Au nanoparticles. We investigate the carrier relaxation processes of this heterostructure at different time scales by ultrafast transient absorption spectroscopy. The lifetime of the singlet state (S1) of the pristine polymer shortens from 480.7 ps to 2.8 ps due to the formation of nanoparticles, and the formation of a delocalized collective state (CLS) is obtained in polymer nanoparticles whose lifetime is found to be 384.6 ps. The hot and ultrafast electron transfers occur from P3HT polymer nanoparticles to Au nanoparticles and the time constants are 253 fs and 37.7 ps, respectively, which are responsible for the efficient charge separation in such heterostructures. Such a fundamental study of relaxation processes of organic-inorganic nano heterostructures is very significant for designing light harvesting systems.