Search results

Search for "photosensitizer" in Full Text gives 39 result(s) in Beilstein Journal of Nanotechnology.

Prospects of nanotechnology and natural products for cancer and immunotherapy

  • Jan Filipe Andrade Santos,
  • Marcela Bernardes Brasileiro,
  • Pamela Danielle Cavalcante Barreto,
  • Ligiane Aranha Rocha and
  • José Adão Carvalho Nascimento Júnior

Beilstein J. Nanotechnol. 2025, 16, 1644–1667, doi:10.3762/bjnano.16.116

Graphical Abstract
  • , significantly improved blood indicators compared to paclitaxel injection (p < 0.01), extended circulation, improved targeting to tumor sites, and reduced toxic side effects [65]. CN109846857 (2019) describes the development of a natural photosensitizer derived from chlorophyllin e6 (Ce6). Self-assembled
PDF
Album
Review
Published 22 Sep 2025

Laser processing in liquids: insights into nanocolloid generation and thin film integration for energy, photonic, and sensing applications

  • Akshana Parameswaran Sreekala,
  • Pooja Raveendran Nair,
  • Jithin Kundalam Kadavath,
  • Bindu Krishnan,
  • David Avellaneda Avellaneda,
  • M. R. Anantharaman and
  • Sadasivan Shaji

Beilstein J. Nanotechnol. 2025, 16, 1428–1498, doi:10.3762/bjnano.16.104

Graphical Abstract
PDF
Album
Review
Published 27 Aug 2025

Enhancing the therapeutical potential of metalloantibiotics using nano-based delivery systems

  • Alejandro Llamedo,
  • Marina Cano,
  • Raquel G. Soengas and
  • Francisco J. García-Alonso

Beilstein J. Nanotechnol. 2025, 16, 1350–1366, doi:10.3762/bjnano.16.98

Graphical Abstract
  • highly selective and efficient photosensitizer delivery systems. Ir(III) complexes are excellent photosensitizers due to their highly sensitive excited-state properties in response to the surrounding environment, high photostability, and unique intracellular localization [137][138]. However, the
PDF
Album
Review
Published 15 Aug 2025

Better together: biomimetic nanomedicines for high performance tumor therapy

  • Imran Shair Mohammad,
  • Gizem Kursunluoglu,
  • Anup Kumar Patel,
  • Hafiz Muhammad Ishaq,
  • Cansu Umran Tunc,
  • Dilek Kanarya,
  • Mubashar Rehman,
  • Omer Aydin and
  • Yin Lifang

Beilstein J. Nanotechnol. 2025, 16, 1246–1276, doi:10.3762/bjnano.16.92

Graphical Abstract
  • membrane, the IR780 (NIR) fluorescence dye was loaded as a photosensitizer for PTT to generate biomimetic “IR780-rRBC” NPs. The antitumor effect of IR780-rRBC was also evaluated. After laser treatment, the tumor temperatures in mice treated with IR780-rRBC and IR780-rRBC NPs increased up to 60 and 70 °C
PDF
Album
Review
Published 05 Aug 2025

Investigation of the solubility of protoporphyrin IX in aqueous and hydroalcoholic solvent systems

  • Michelly de Sá Matsuoka,
  • Giovanna Carla Cadini Ruiz,
  • Marcos Luciano Bruschi and
  • Jéssica Bassi da Silva

Beilstein J. Nanotechnol. 2025, 16, 1209–1215, doi:10.3762/bjnano.16.89

Graphical Abstract
  • Michelly de Sa Matsuoka Giovanna Carla Cadini Ruiz Marcos Luciano Bruschi Jessica Bassi da Silva Department of Pharmacy, State University of Maringa, Maringa, PR, Brazil 10.3762/bjnano.16.89 Abstract Photodynamic therapy (PDT) is a non-invasive treatment involving a photosensitizer (PS), light
  • ; protoporphyrin IX; shake-flask; solubility test; Introduction Photodynamic therapy (PDT) is a promising therapeutic modality that has raised keen interest in the treatment of various conditions including cancer and microbial infections [1][2]. This non-invasive treatment combines a photosensitizer (PS), a
  • , the findings observed at 0.4 mg/mL PpIX are not in line. While spectrophotometric readings indicated high solubility, the visual inspection revealed turbidity, suggesting incomplete dissolution of the photosensitizer. This discrepancy may be attributed to the filtration step performed prior to UV–vis
PDF
Album
Letter
Published 29 Jul 2025

Fabrication of metal complex phthalocyanine and porphyrin nanoparticle aqueous colloids by pulsed laser fragmentation in liquid and their potential application to a photosensitizer for photodynamic therapy

  • Taisei Himeda,
  • Risako Kunitomi,
  • Ryosuke Nabeya,
  • Tamotsu Zako and
  • Tsuyoshi Asahi

Beilstein J. Nanotechnol. 2025, 16, 1088–1096, doi:10.3762/bjnano.16.80

Graphical Abstract
  • generation of reactive oxygen species by AlClPc, ZnPc, and PtOEP nanoparticles and the photocytotoxicity for PC12 and HeLa cells, and demonstrated that the nanoparticles can be used as photosensitizers for photodynamic therapy. Keywords: aqueous colloid; photosensitizer; phthalocyanine; pulsed laser
  • generation with a conventional water-soluble photosensitizer, Zn(II) meso-tetra(4-sulfonatophenyl)porphine tetrasodium salt (ZnTPPS), and demonstrated that the PtOEP nanoparticles acted as photosensitizers with greater efficiency than ZnTPPS (Figure S8, Supporting Information File 1). The decays of DPBF
  • strongly supports that cellular phototoxicity is due to photosensitized ROS generation by the nanoparticles. Therefore, it is concluded that the MPc and PtOEP nanoparticles fabricated by PLAL could be used as a new potential photosensitizer for PDT. The efficiency for PDT in acting as a sensitizer cannot
PDF
Album
Supp Info
Full Research Paper
Published 11 Jul 2025

Nanotechnological approaches for efficient N2B delivery: from small-molecule drugs to biopharmaceuticals

  • Selin Akpinar Adscheid,
  • Akif E. Türeli,
  • Nazende Günday-Türeli and
  • Marc Schneider

Beilstein J. Nanotechnol. 2024, 15, 1400–1414, doi:10.3762/bjnano.15.113

Graphical Abstract
  • another widely used complex vector, polyplexes. They took the approach one step further and combined these polyplexes formed by a cationic polymer and anionic mRNA with a photosensitizer for photochemical internalization and subsequent enhancement in delivery to the cytoplasm. They showed that laser
PDF
Album
Review
Published 12 Nov 2024

Entry of nanoparticles into cells and tissues: status and challenges

  • Kirsten Sandvig,
  • Tore Geir Iversen and
  • Tore Skotland

Beilstein J. Nanotechnol. 2024, 15, 1017–1029, doi:10.3762/bjnano.15.83

Graphical Abstract
  • CC BY 4.0. SIM image showing photosensitizer–chitosan conjugate polymeric NPs within lysosomes. MDA-MB-231 cells were incubated with the NPs (red) for 2 h, followed by a washout and chasing for 2 h at 37 °C. Then, the cells were fixed and stained with an antibody against the lysosomal marker LAMP-1
PDF
Album
Perspective
Published 12 Aug 2024

Therapeutic effect of F127-folate@PLGA/CHL/IR780 nanoparticles on folate receptor-expressing cancer cells

  • Thi Ngoc Han Pham,
  • Phuong-Thao Dang-Luong,
  • Hong-Phuc Nguyen,
  • Loc Le-Tuan,
  • Xuan Thang Cao,
  • Thanh-Danh Nguyen,
  • Vy Tran Anh and
  • Hieu Vu_Quang

Beilstein J. Nanotechnol. 2024, 15, 954–964, doi:10.3762/bjnano.15.78

Graphical Abstract
  • nanoparticles to follow the targeting of nanoparticles as well as using it as a photosensitizer [23][48][49][50][51][52]. First, IR780 has an excitation wavelength of 777–780 nm and an emission wavelength of 798–823 nm, which is suitable for obtaining noninvasive near-infrared fluorescence images for clinical
PDF
Album
Supp Info
Full Research Paper
Published 31 Jul 2024

Cyclodextrins as eminent constituents in nanoarchitectonics for drug delivery systems

  • Makoto Komiyama

Beilstein J. Nanotechnol. 2023, 14, 218–232, doi:10.3762/bjnano.14.21

Graphical Abstract
  • therapy (PDT) employs a light-sensitive medicine (photosensitizer) and a light source to destroy abnormal cells [72][73]. The photosensitizer absorbs the light and is activated to kill target tissue. In many cases, reactive oxygen species (ROSs) such as singlet oxygen (1O2) generated from 3O2 by a
  • accomplish PDT using NIR light irradiation, adamantane-modified phthalocyanine was connected to upconversion nanoparticles using carboxymethyl-β-CyD [76]. Furthermore, boron-dipyrromethene (BODIPY) photosensitizer was complexed with amphiphilic α-CyD bearing oligo(ethylene glycol) chains [77]. By
  • encapsulating (a part of) the photosensitizer in the cavities, its self-aggregation was suppressed to accomplish a high quantum yield of 1O2 production. The aggregation of porphyrin was photocontrolled by using complex formation of β-CyD with photoresponsive azobenzene [78]. By delivering nitrogen oxide (NO
PDF
Album
Review
Published 09 Feb 2023

Recent advances in green carbon dots (2015–2022): synthesis, metal ion sensing, and biological applications

  • Aisha Kanwal,
  • Naheed Bibi,
  • Sajjad Hyder,
  • Arif Muhammad,
  • Hao Ren,
  • Jiangtao Liu and
  • Zhongli Lei

Beilstein J. Nanotechnol. 2022, 13, 1068–1107, doi:10.3762/bjnano.13.93

Graphical Abstract
PDF
Album
Review
Published 05 Oct 2022

Engineered titania nanomaterials in advanced clinical applications

  • Padmavati Sahare,
  • Paulina Govea Alvarez,
  • Juan Manual Sanchez Yanez,
  • Gabriel Luna-Bárcenas,
  • Samik Chakraborty,
  • Sujay Paul and
  • Miriam Estevez

Beilstein J. Nanotechnol. 2022, 13, 201–218, doi:10.3762/bjnano.13.15

Graphical Abstract
  • become superhydrophilic under UV light, function well as photosensitizer. Subsequently, another study established the use of nanoscale TiO2 as a redox coating of in implants [9]. Titanium and its alloys are considered the most promising materials for implants due to their superior properties, which
  • cells containing TiO2 nps undergo oxidative degeneration upon light irradiation under the influence of generated ROS and, therefore, these nps are considered as a potent photosensitizer in anticancer photodynamic therapy and the photodynamic inactivation of antibiotic-resistant bacteria [15]. TiO2
  • drawback of using TiO2 as photosensitizer is the shallow penetration depth in tissues as it gets activated only by UV light; however, for deep penetration of light into tissues, the wavelength should be in the near-infrared (NIR) window (700–1100 nm) [111]. TiO2 nps can be retained in the body for more
PDF
Album
Review
Published 14 Feb 2022

Self-assembly of amino acids toward functional biomaterials

  • Huan Ren,
  • Lifang Wu,
  • Lina Tan,
  • Yanni Bao,
  • Yuchen Ma,
  • Yong Jin and
  • Qianli Zou

Beilstein J. Nanotechnol. 2021, 12, 1140–1150, doi:10.3762/bjnano.12.85

Graphical Abstract
  • acid and functional molecule self-assembly (drug, photosensitizer) (Figure 1). In this paper, the self-assembly of single amino acids is discussed first. We then discuss the co-assembly of amino acids and their derivatives with functional components including metal ions, photosensitizers (PS), and
  • PS to tumor tissues [76]. Liu et al. [78] designed photosensitizer delivery systems by self-assembling cationic diphenylalanine (H-Phe-Phe-NH2 HCl, CDP) or 9-fluorenylmethoxycarbonyl-ʟ-lysine (Fmoc-ʟ-Lys) with Ce6 into nanoparticles (CCNPs and FCNPs, respectively). Intermolecular hydrophobic and π–π
  • ) melanin through a Schiff base reaction to form an adhesive layer, and Fmoc-ʟ-Lys/DOPA fiber simulated an antenna to capture light. As a photosensitizer, Sn(IV)tetrakis(4-pyridyl)porphyrin (SnTPyP) was combined with the photocatalyst Co3O4 NPs by coordination bonds and electrostatic interaction onto the
PDF
Album
Review
Published 12 Oct 2021

Recent progress in actuation technologies of micro/nanorobots

  • Ke Xu and
  • Bing Liu

Beilstein J. Nanotechnol. 2021, 12, 756–765, doi:10.3762/bjnano.12.59

Graphical Abstract
  • dual-mode fluorescence and magnetic resonance imaging. Using magnetic targeting, the micro/nanorobot broke through complex physiological barriers and entered tumors while carrying a photosensitizer. After that, local high temperature was generated by a near-infrared laser, and observable and accurate
PDF
Album
Review
Published 20 Jul 2021

Photothermally active nanoparticles as a promising tool for eliminating bacteria and biofilms

  • Mykola Borzenkov,
  • Piersandro Pallavicini,
  • Angelo Taglietti,
  • Laura D’Alfonso,
  • Maddalena Collini and
  • Giuseppe Chirico

Beilstein J. Nanotechnol. 2020, 11, 1134–1146, doi:10.3762/bjnano.11.98

Graphical Abstract
  • of a NaYF4:Mn/Yb/Er@photosensitizer doped with SiO2 This allowed for the integration of photodynamic and photothermic therapy to improve the treatment against multidrug-resistant bacteria [82]. It was demonstrated that such nanodevices exhibited superior antibacterial activity towards drug-resistant
PDF
Album
Review
Published 31 Jul 2020

A few-layer graphene/chlorin e6 hybrid nanomaterial and its application in photodynamic therapy against Candida albicans

  • Selene Acosta,
  • Carlos Moreno-Aguilar,
  • Dania Hernández-Sánchez,
  • Beatriz Morales-Cruzado,
  • Erick Sarmiento-Gomez,
  • Carla Bittencourt,
  • Luis Octavio Sánchez-Vargas and
  • Mildred Quintana

Beilstein J. Nanotechnol. 2020, 11, 1054–1061, doi:10.3762/bjnano.11.90

Graphical Abstract
  • ; few-layer graphene (FLG); hybrid nanomaterial; photodynamic therapy (PDT); photosensitizer; Introduction The frequency of fungal infections has notably increased in the last decades; for instance, Candida albicans is now reported as the fourth cause of nosocomial septicemia in the United States [1
  • Paramecia [5]. PDT consists of the interaction of visible-light photons with a photosensitizer located inside the cell or in close proximity to it. In this interaction, the photosensitizer produces highly reactive oxygen species (ROS) by reacting in the excited state with molecular oxygen present in the
  • environment. ROS refer to molecules like singlet oxygen, superoxide anion, and radicals, which are responsible for producing oxidative stress in cells followed by cell death [4]. Photosensitizer molecules must be nontoxic before irradiated with light, must produce high amounts of ROS when irradiated with
PDF
Album
Full Research Paper
Published 17 Jul 2020

Rational design of block copolymer self-assemblies in photodynamic therapy

  • Maxime Demazeau,
  • Laure Gibot,
  • Anne-Françoise Mingotaud,
  • Patricia Vicendo,
  • Clément Roux and
  • Barbara Lonetti

Beilstein J. Nanotechnol. 2020, 11, 180–212, doi:10.3762/bjnano.11.15

Graphical Abstract
  • therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years
  • , regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic
  • photosensitizer formulation, light dosimetry, to planning and monitoring the treatment [15][18][19][20][21][22]. Some of these points have been recently reviewed: ideal photosensitizers [23], challenges in formulating photosensitizers, and choosing the right light dosimetry [24], as well as monitoring the
PDF
Album
Review
Published 15 Jan 2020

Air oxidation of sulfur mustard gas simulants using a pyrene-based metal–organic framework photocatalyst

  • Ghada Ayoub,
  • Mihails Arhangelskis,
  • Xuan Zhang,
  • Florencia Son,
  • Timur Islamoglu,
  • Tomislav Friščić and
  • Omar K. Farha

Beilstein J. Nanotechnol. 2019, 10, 2422–2427, doi:10.3762/bjnano.10.232

Graphical Abstract
  • photosensitizer for generating singlet oxygen and subsequent oxidative degradation of chemical warfare agents (CWAs). The high activity of NU-400 permits photocatalytic conversion of the 2-chloroethyl ethyl sulfide (CEES) mustard gas simulant into a benign sulfoxide derivative, in air, with less than 15 minutes
  • nerve gas agents [37][38][39][40][41][42]. Here, we describe the preparation of NU-400 [43], a zirconium-based MOF based on a judiciously chosen pyrene-based linker and utilized it as a photosensitizer for the efficient production of 1O2 and hence photocatalytic conversion of the sulfur mustard simulant
  • 2-chloroethyl ethyl sulfide (CEES) into a benign sulfoxide product, using ambient air as the oxygen source. We selected a Zr6-based MOF because of its outstanding stability under a wide range of thermal and chemical conditions. As pyrene has been known as an efficient photosensitizer that is capable
PDF
Album
Supp Info
Full Research Paper
Published 09 Dec 2019

Photoactive nanoarchitectures based on clays incorporating TiO2 and ZnO nanoparticles

  • Eduardo Ruiz-Hitzky,
  • Pilar Aranda,
  • Marwa Akkari,
  • Nithima Khaorapapong and
  • Makoto Ogawa

Beilstein J. Nanotechnol. 2019, 10, 1140–1156, doi:10.3762/bjnano.10.114

Graphical Abstract
  • transformation and for improved overall reaction efficiency. This article tries also to present new steps towards more sophisticated but efficient and highly selective functional nanoarchitectures incorporating photosensitizer elements for tuning the semiconductor–clay photoactivity. Keywords: clays
  • represents an additional improvement of the photoactivity tuning of semiconductor–clay nanoarchitectures. For instance, tris(2,2′-bipyridine)ruthenium(II) has been used as photosensitizer for titania, being further applied to TiO2@clay nanoarchitectures. In this way, a synthetic saponite containing tris(2,2
  • ′-bipyridine)ruthenium(II) intercalated in the interlayer space was complexed with TiO2 NPs [166]. The resulting material shows enhanced stability toward visible-light irradiation, if compared with the TiO2 (P25) standard material photosensitized by an analogous commercially available photosensitizer (tris(2,2
PDF
Album
Review
Published 31 May 2019

The nanoscaled metal-organic framework ICR-2 as a carrier of porphyrins for photodynamic therapy

  • Jan Hynek,
  • Sebastian Jurík,
  • Martina Koncošová,
  • Jaroslav Zelenka,
  • Ivana Křížová,
  • Tomáš Ruml,
  • Kaplan Kirakci,
  • Ivo Jakubec,
  • František Kovanda,
  • Kamil Lang and
  • Jan Demel

Beilstein J. Nanotechnol. 2018, 9, 2960–2967, doi:10.3762/bjnano.9.275

Graphical Abstract
  • ) to and the excited O2(1∆g) from the solid photosensitizer [14][15][16]. In our recent work we have shown that microcrystalline porphyrin containing MOFs are poor O2(1∆g) photosensitizers [17], due to the combined effect of the quenching of excited states in tightly stacked porphyrin units and strong
  • photosensitizer loading of the nanoparticles. The porphyrins retain part of their photophysical properties including production of singlet oxygen. Interestingly, the photodynamic activity on HeLa cells strongly depends on the R substituent at the P atom, i.e., only the phenyl substituent (TPPPi(Ph)) ensured high
PDF
Album
Supp Info
Full Research Paper
Published 30 Nov 2018

Droplet-based synthesis of homogeneous magnetic iron oxide nanoparticles

  • Christian D. Ahrberg,
  • Ji Wook Choi and
  • Bong Geun Chung

Beilstein J. Nanotechnol. 2018, 9, 2413–2420, doi:10.3762/bjnano.9.226

Graphical Abstract
  • healthcare significantly [5]. For example, a composite nanomaterial has been developed as a photosensitizer in photothermal therapy (PTT), while also acting as a contrast agent for magnetic resonance imaging (MRI) [6]. Magnetic materials are of particular interest here, as they can be used for targeting [7
PDF
Album
Supp Info
Full Research Paper
Published 10 Sep 2018

Cr(VI) remediation from aqueous environment through modified-TiO2-mediated photocatalytic reduction

  • Rashmi Acharya,
  • Brundabana Naik and
  • Kulamani Parida

Beilstein J. Nanotechnol. 2018, 9, 1448–1470, doi:10.3762/bjnano.9.137

Graphical Abstract
  • the later prevents the former from photocorroding [197]. In addition, CdS acts as a photosensitizer to absorb visible radiation and transfers eCB− to the CB of TiO2 by retaining hVB+ at its VB. As a result, the recombination of photoinduced species is appreciably inhibited [70]. Therefore, it is often
PDF
Album
Review
Published 16 May 2018

Sugarcane juice derived carbon dot–graphitic carbon nitride composites for bisphenol A degradation under sunlight irradiation

  • Lan Ching Sim,
  • Jing Lin Wong,
  • Chen Hong Hak,
  • Jun Yan Tai,
  • Kah Hon Leong and
  • Pichiah Saravanan

Beilstein J. Nanotechnol. 2018, 9, 353–363, doi:10.3762/bjnano.9.35

Graphical Abstract
  • diffuse reflectance spectra (UV–vis DRS) results. Although the CDs did not display upconversion photoluminescence (UCPL) properties, the π-conjugated CDs served as a photosensitizer (like organic dyes) to sensitize g-C3N4 and injected electrons to the conduction band (CB) of g-C3N4, resulting in the
  • was attributed to the dual functionality of CDs as electron trapper and photosensitizer. Although some works have been carried out in this field, several insights have yet to be explored to fill the gaps of previous works, including (i) the utilization of harmless solar energy as a resource to
  • irradiate photocatalytic degradation of organic pollutant (since CDs could act as a photosensitizer over the entire solar spectrum) and (ii) acknowledgement that the most reported bioprecursor-derived CDs and g-C3N4 composite are limited to the photocatalytic generation of H2 (instead limited attempts have
PDF
Album
Supp Info
Full Research Paper
Published 30 Jan 2018

Application of visible-light photosensitization to form alkyl-radical-derived thin films on gold

  • Rashanique D. Quarels,
  • Xianglin Zhai,
  • Neepa Kuruppu,
  • Jenny K. Hedlund,
  • Ashley A. Ellsworth,
  • Amy V. Walker,
  • Jayne C. Garno and
  • Justin R. Ragains

Beilstein J. Nanotechnol. 2017, 8, 1863–1877, doi:10.3762/bjnano.8.187

Graphical Abstract
  • Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA Department of Materials Science, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA 10.3762/bjnano.8.187 Abstract Visible-light irradiation of phthalimide esters in the presence of the photosensitizer [Ru(bpy)3]2+ and
  • ), species that are synthesized in one step from carboxylic acids [33][34][35][36][37][38][39][40] and which have been used to address a number of difficult problems in organic synthesis [36][37][38][39][40]. Therefore (Scheme 1), visible-light irradiation (e.g., with blue LEDs) of the photosensitizer [Ru
  • turns over the photosensitizer (Equation 2) [39]. The fate of 7 is protonation, possibly by BNAH∙+ (4), to generate phthalimide [39]. Alkyl radical R∙ would then be subject to processes including reduction to alkane RH with generation of benzyl nicotinamide radical (BNA∙, 8, Equation 3) or fully
PDF
Album
Supp Info
Full Research Paper
Published 06 Sep 2017

Three-in-one approach towards efficient organic dye-sensitized solar cells: aggregation suppression, panchromatic absorption and resonance energy transfer

  • Jayita Patwari,
  • Samim Sardar,
  • Bo Liu,
  • Peter Lemmens and
  • Samir Kumar Pal

Beilstein J. Nanotechnol. 2017, 8, 1705–1713, doi:10.3762/bjnano.8.171

Graphical Abstract
  • being used to sensitize the photoanodes [13]. Organic dyes are attractive as a photosensitizer because of their high molar extinction coefficient, tunable absorption wavelength, and easy design and synthesis strategies. Still, the efficiency of organic dye-sensitized solar cells is not comparable to
PDF
Album
Full Research Paper
Published 17 Aug 2017
Other Beilstein-Institut Open Science Activities