ClassID:

20074

A61K9/141 - CPC Classification

Classification description:

Medicinal preparations characterised by special physical form; Particulate form, e.g. powders, Processes for size reducing of pure drugs or the resulting products, Pure drug nanoparticles Intimate drug-carrier mixtures characterised by the carrier, e.g. ordered mixtures, adsorbates, solid solutions, eutectica, co-dried, co-solubilised, co-kneaded, co-milled, co-ground products, co-precipitates, co-evaporates, co-extrudates, co-melts; Drug nanoparticles with adsorbed surface modifiers

Sub-classes:
Recent Application in this class:
#1
20260048031
2026-02-19

POLYMORPHS OF CO-CRYSTALS OF ITANAPRACED AND NICOTINAMIDE

#2
20250352538
2025-11-20

PHARMACEUTICAL RESINATE COMPOSITIONS AND METHODS OF MAKING AND USING THEREOF

#3
20250276002
2025-09-04

Particles with RNA Cleaving Nucleobase Polymers and Uses for Managing Inflammatory Disorders

#4
20250195435
2025-06-19

Oral Rapamycin Nanoparticle Preparations and Use

#5
20250114484
2025-04-10

ULTRASMALL NANOPARTICLES AND METHODS OF MAKING AND USING SAME

#6
20250057855
2025-02-20

PHARMACEUTICAL COMPOSITIONS OF MIFEPRISTONE

#7
20250025435
2025-01-23

CO-CRYSTALS OF NONSTEROIDAL ANTI-INFLAMMATORY DRUGS, LYSINE AND GABAPENTIN, PHARMACEUTICAL COMPOSITIONS AND THEIR MEDICAL USE

#8
20250025419
2025-01-23

PROCESS OF PREPARING MRNA-LOADED LIPID NANO PARTICLES

#9
20240408021
2024-12-12

PHARMACEUTICAL FORMULATION

#10
20240358641
2024-10-31

PROCESSES FOR MAKING CYCLIC LIPID IMPLANTS FOR INTRAOCULAR USE

#11
20240293374
2024-09-05

Anticancer compositions

#12
20240293321
2024-09-05

ANTICANCER COMPOSITIONS

#13
20240285819
2024-08-29

COMPOSITION OF RADIOACTIVE AND NON-RADIOACTIVE MICROPARTICLES

#14
20240216382
2024-07-04

PEDIATRIC POWDER FOR ORAL SUSPENSION CONTAINING ANTIVIRAL AGENT AND METHOD FOR THE PREPARATION THEREOF

#15
20240141342
2024-05-02

RNA INTERFERENCE DELIVERY FORMULATION AND METHODS FOR MALIGNANT TUMORS

#16
20240122944
2024-04-18

Pharmaceutical compositions of mifepristone

#17
20240100361
2024-03-28

METHODS OF USE OF ULTRA-HIGH DOSE RATE RADIATION AND THERAPEUTIC AGENT

#18
20230381121
2023-11-30

N-PALMITOYLETHANOLAMIDE AND MELATONIN FOR USE IN THE TREATMENT OF AUTISM SPECTRUM DISORDER AND OTHER NEUROBEHAVIORAL DISORDERS SIMILARLY ACCOMPANIED BY RESTLESSNESS, IRRITABILITY, SLEEP DISORDERS, AND POTENTIALLY STEREOTYPIES

#19
20230293696
2023-09-21

CURCUMINOID COMPOSITES

#20
20230241229
2023-08-03

A SAPOGENIN POLYETHYLENE GLYCOL ESTER COMPLEX OF FORMULA-I, A COMPOSITION, PROCESS OF PREPARATION, AND APPLICATIONS THEREOF

#21
20230233529
2023-07-27

ANTICANCER COMPOSITIONS

#22
20230227806
2023-07-20

SYSTEMS AND METHODS FOR GROWING A BIOFILM OF PROBIOTIC BACTERIA ON SOLID PARTICLES FOR COLONIZATION OF BACTERIA IN THE GUT

#23
20230212282
2023-07-06

METHODS AND COMPOSITIONS FOR TREATING, PREVENTING THE ONSET AND/OR SLOWING PROGRESSION OF OSTEOARTHRITIS

#24
20230181794
2023-06-15

PARTICLE SUITABLE FOR THE MANUFACTURE OF AN IMPLANTABLE SOFT TISSUE ENGINEERING MATERIAL

#25
20230181695
2023-06-15

MULTIPARTICULATE GRANULATE COMPRISING INSULIN

#26
20230172875
2023-06-08

EXTENDED RELEASE LIQUID COMPOSITIONS OF GUAIFENESIN

#27
20230172847
2023-06-08

PROCESS FOR PRODUCING AN ORAL THIN FILM COMPRISING MICROPARTICLES

#28
20230157967
2023-05-25

Nanoparticle vaccine adjuvant and methods of use thereof

#29
20230140770
2023-05-04

Ultrasmall nanoparticles and methods of making and using same

#30
20230125208
2023-04-27

PHARMACEUTICAL RESINATE COMPOSITIONS AND METHODS OF MAKING AND USING THEREOF

#31
20230119567
2023-04-20

PHARMACEUTICAL FORMULATION

#32
20230111793
2023-04-13

ANTIMALARIAL COMPOSITIONS AND USES THEREOF

#33
20230085008
2023-03-16

Pharmaceutical compositions of mifepristone

#34
20220395459
2022-12-15

Process of preparing mRNA-loaded lipid nanoparticles

#35
20220339159
2022-10-27

PEDIATRIC POWDER FOR ORAL SUSPENSION CONTAINING ANTIVIRAL AGENT AND METHOD FOR THE PREPARATION THEREOF

#36
20220313611
2022-10-06

METHODS TO PREPARE DRY POWDERS USING SUSPENSION BASED THIN FILM FREEZING

#37
20220211887
2022-07-07

Composition of radioactive and non-radioactive microparticles

#38
20220151931
2022-05-19

ANTICANCER COMPOSITIONS

#39
20220096657
2022-03-31

COMPOSITIONS FOR THE TREATMENT OF DISEASE

#40
20220031679
2022-02-03

PHARMACEUTICAL COMPOSITIONS OF 3-(6-(1-(2,2-DIFLUOROBENZO[D][1,3]DIOXOL-5-YL) CYCLOPROPANECARBOXAMIDO)-3-METHYLPYRIDIN-2-YL) BENZOIC ACID AND ADMINISTRATION THEREOF

#41
20220008750
2022-01-13

Methods of use of ultra-high dose rate radiation and therapeutic agent

#42
20210386672
2021-12-16

Oral rapamycin nanoparticle preparations and use

#43
20210330591
2021-10-28

Curcuminoid composites

#44
20210322318
2021-10-21

PROCESSES FOR MAKING CYCLIC LIPID IMPLANTS FOR INTRAOCULAR USE

#45
20210315953
2021-10-14

Composition for preventing, ameliorating or treating acne symptoms using natural extracts as active ingredients

#46
20210290733
2021-09-23

INJECTABLE MICRONIZED HUMAN INSULIN

#47
20210267897
2021-09-02

Therapeutic Nanoparticles and Related Compositions, Methods and Systems

#48
20210179524
2021-06-17

Antimalarial compositions and uses thereof

#49
20210093655
2021-04-01

Particles with RNA Cleaving Nucleobase Polymers and Uses for Managing Inflammatory Disorders

#50
20210085611
2021-03-25

Pharmaceutical formulation

#51
20210030784
2021-02-04

Compact gyroplane employing torque compensated main rotor and hybrid power train

#52
20210009985
2021-01-14

Systems and methods for growing a biofilm of probiotic bacteria on solid particles for colonization of bacteria in the gut

#53
20210008171
2021-01-14

MULTIPARTICULATE GRANULATE COMPRISING INSULIN

#54
20210002627
2021-01-07

Systems and methods for growing a biofilm of probiotic bacteria on solid particles for colonization of bacteria in the gut

#55
20200384152
2020-12-10

Particle suitable for the manufacture of an implantable soft tissue engineering material

#56
20200331986
2020-10-22

Vascular endothelial growth factor receptor targeting peptide-elastin fusion polypeptides

#57
20200316093
2020-10-08

ABIRATERONE ACETATE LIPID FORMULATIONS

#58
20200197380
2020-06-25

Pharmaceutical compositions of 3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl) cyclopropanecarboxamido)-3-methylpyridin-2-yl) benzoic acid and administration thereof

#59
20200157540
2020-05-21

RNA interference delivery formulation and methods for malignant tumors

#60
20200121602
2020-04-23

THERAPEUTIC NANOPARTICLES AND RELATED COMPOSITIONS, METHODS AND SYSTEMS

#61
20200113977
2020-04-16

MULTIPARTICULATE GRANULATE COMPRISING INSULIN

#62
20200085949
2020-03-19

Microcapsule having a microcapsule shell material that is rupturable via a retro-dimerization reaction

#63
20200085756
2020-03-19

Nanoparticle vaccine adjuvant and methods of use thereof

#64
20200085745
2020-03-19

Process of preparing mRNA-loaded lipid nanoparticles

#65
20200038432
2020-02-06

HYALURONIC ACID COATED CHIMERIC VIRAL/NONVIRAL NANOPARTICLES

#66
20200038326
2020-02-06

PROCESSES FOR MAKING CYCLIC LIPID IMPLANTS FOR INTRAOCULAR USE

#67
20190350856
2019-11-21

Oral rapamycin nanoparticle preparations and use

#68
20190330317
2019-10-31

ANTI-GUANOSINE ANTIBODY AS A MOLECULAR DELIVERY VEHICLE

#69
20190307895
2019-10-10

PVP Coated Tellurium Nanorods with Antibacterial and Anticancer Properties

#70
20190282614
2019-09-19

Composition in powder form comprising iron and probiotic bacteria

#71
20190274961
2019-09-12

CONTROLLED RELEASE TABLET BASED ON POLYVINYL ALCOHOL AND ITS MANUFACTURING

#72
20190262472
2019-08-29

Isolated composite drug and carrier nanoparticles

#73
20190262334
2019-08-29

Pharmaceutical resinate compositions and methods of making and using thereof

#74
20190224339
2019-07-25

COMPOSITIONS FOR THE TREATMENT OF DISEASE

#75
20190202766
2019-07-04

Antimalarial compositions and uses thereof

#76
20190192550
2019-06-27

Particles with RNA cleaving nucleobase polymers and uses for managing inflammatory disorders

#77
20190142865
2019-05-16

Modified metal nanoparticle comprising cyclic polyether and pharmaceutical composition

#78
20190142857
2019-05-16

Methods for promoting entry of an agent into a cell

#79
20190133945
2019-05-09

Method and System for Killing Cancer Cells Using a Virus

#80
20190117793
2019-04-25

MODULAR NANODEVICES FOR SMART ADAPTABLE VACCINES

#81
20190105286
2019-04-11

Curcuminoid compositions and preparation methods

#82
20190104757
2019-04-11

Powder formulation having a function of enhancing immunity and method for preparing the same

#83
20190076360
2019-03-14

Method of production of inhalable composite particles using a three-fluid nozzle

#84
20190075763
2019-03-14

Device, method, and system for distributing pesticide in a fish pen

#85
20190060486
2019-02-28

Continuous complexation of active pharmaceutical ingredients

#86
20190046468
2019-02-14

EXTENDED RELEASE LIQUID COMPOSITIONS OF GUAIFENESIN

#87
20190022411
2019-01-24

Methods of use of ultra-high dose rate radiation and therapeutic agent

#88
20180355343
2018-12-13

Systems and methods for growing a biofilm of probiotic bacteria on solid particles for colonization of bacteria in the gut

#89
20180353502
2018-12-13

CONTROLLED RELEASE HYDROCODONE FORMULATIONS

#90
20180296514
2018-10-18

NOVEL FORMULATION OF DICLOFENAC

#91
20180243283
2018-08-30

Pharmaceutical composition capable of the incorporation of lenalidomide in various crystalline modifications

#92
20180208642
2018-07-26

Vascular endothelial growth factor receptor targeting peptide-elastin fusion polypeptides

#93
20180169270
2018-06-21

Self-assembled ribonucleoprotein nanoparticles

#94
20180153835
2018-06-07

COMPOSITIONS OF DICLOFENAC ACID

#95
20180133346
2018-05-17

Ultrasmall nanoparticles and methods of making and using same

#96
20180125863
2018-05-10

Abiraterone acetate lipid formulations

#97
20180085420
2018-03-29

Ezetimibe-associated ApoA-I mimetic peptides showing enhanced synergism

#98
20180071314
2018-03-15

Dehydroandrosterol and methods of using the same

#99
20180071208
2018-03-15

Soluble microneedle for delivering poorly-soluble drug

#100
20180064812
2018-03-08

Microcapsule having a microcapsule shell material that is rupturable via a retro-dimerization reaction

#101
20180011346
2018-01-11

PROBE FOR TARGETING AND MANIPULATING MITOCHONDRIAL FUNCTION USING QUANTUM DOTS

#102
20180008601
2018-01-11

Nanoparticulate compositions and formulations of piperazine compounds

#103
20170367981
2017-12-28

Biomimetic drug delivery of an immunomodulatory agent for the treatment of ocular conditions

#104
20170360707
2017-12-21

ANTICANCER COMPOSITIONS

#105
20170319504
2017-11-09

Statin-encapsulated nanoparticle preparation for enhancing stem cell function, stem cell with enhanced function containing statin-encapsulated nanoparticle, and method for producing same

#106
20170273975
2017-09-28

Pharmaceutical composition having abuse deterrent properties

#107
20170202843
2017-07-20

Pediatric powder for oral suspension containing antiviral agent and method for the preparation thereof

#108
20170189408
2017-07-06

NOVEL PHARMACEUTICAL COMPOSITION

#109
20170172924
2017-06-22

Tyrosine derivatives and compositions comprising them

#110
20170158860
2017-06-08

Surface-modified calcium oxide

#111
20170151229
2017-06-01

Methods of manufacturing oral formulations

#112
20170105966
2017-04-20

PHARMACEUTICAL COMPOSITION CONTAINING INDOMETACIN AND/OR ACEMETACIN

#113
20170007678
2017-01-12

Compositions and methods to promote wound healing

#114
20160374940
2016-12-29

Oral delivery compositions for treating dermatitis disorders in mammals

#115
20160369065
2016-12-22

Functional Nanoparticle Composite Comprising Chitosan

#116
20160324782
2016-11-10

Oral rapamycin nanoparticle preparations and use

#117
20160158224
2016-06-09

Controlled release hydrocodone formulations

#118
20160158223
2016-06-09

Controlled release hydrocodone formulations

#119
20160151361
2016-06-02

Controlled release hydrocodone formulations

#120
20160151292
2016-06-02

Controlled release hydrocodone formulations

#121
20160151288
2016-06-02

Controlled release hydrocodone formulations

#122
20160128940
2016-05-12

Docetaxel nano-polymer micelle lyophilized preparation and preparation method thereof

#123
20160074530
2016-03-17

Nanoparticles for drug delivery comprising albumin having a polymer chain coupled thereto

#124
20160058707
2016-03-03

NOVEL FORMULATION OF DICLOFENAC

#125
20160058706
2016-03-03

Therapeutic nanoparticles and related compositions, methods and systems

#126
20160032480
2016-02-04

Porous particles and methods of making thereof

#127
20160022707
2016-01-28

Chelated drug delivery systems

#128
20160022581
2016-01-28

Processes for making cyclic lipid implants for intraocular use

#129
20160000711
2016-01-07

Stabilized granules containing glyceryl trinitrate

#130
20150359742
2015-12-17

COMPOSITIONS AND METHODS FOR ENHANCING THE TOPICAL APPLICATION OF A BENEFIT AGENT INCLUDING POWDER TO LIQUID PARTICLES AND A SECOND POWDER

#131
20150337136
2015-11-26

Surface-modified calcium oxide

#132
20150297521
2015-10-22

Pharmaceutical core-shell composite powder and processes for making the same

#133
20150290275
2015-10-15

Application of composition in preparing health care product or medicine for preventing and treating leukopenia caused by radiotherapy and chemotherapy

#134
20150273008
2015-10-01

Heavy metals defense

#135
20150265537
2015-09-24

Controlled release hydrocodone formulations

#136
20150258090
2015-09-17

Controlled release hydrocodone formulations

#137
20150258089
2015-09-17

Controlled release hydrocodone formulations

#138
20150238418
2015-08-27

Controlled release hydrocodone formulations

#139
20150166949
2015-06-18

Process for producing cell culture media

#140
20150150928
2015-06-04

Composition for preventing and treating aids and preparation method thereof

#141
20150147396
2015-05-28

Nanoparticle delivery vehicle for S-nitroso-N-acetyl cysteine and uses thereof

#142
20150147351
2015-05-28

Use of composition in preparing health care products or medicines for preventing and treating allergic diseases

#143
20150125384
2015-05-07

Modular nanodevices for smart adaptable vaccines

#144
20150112116
2015-04-23

Tyrosine derivatives and compositions comprising them

#145
20150094371
2015-04-02

Solid pharmaceutical compositions containing pregabalin

#146
20150087709
2015-03-26

Novel Formulation of Naproxen

#147
20150004234
2015-01-01

Nanoparticulate compositions and formulations of piperazine compounds

#148
20140370109
2014-12-18

Stabilized granules containing glyceryl trinitrate

#149
20140364494
2014-12-11

Processes for making cyclic lipid implants for intraocular use

#150
20140328763
2014-11-06

Bioactive amphiphilic polymer stabilized nanoparticles with enhanced stability and activity

#151
20140255311
2014-09-11

Biocompatible polymeric nanoparticles degrade and release cargo in response to biologically relevant levels of hydrogen peroxide

#152
20140248360
2014-09-04

NANOPARTICLE TUMOUR VACCINES

#153
20140242097
2014-08-28

Methods for promoting entry of an agent into a cell

#154
20140105989
2014-04-17

Treatment Methods with Low-Dose, Longer-Acting Formulations of Local Anesthetics and Other Agents

#155
20140065061
2014-03-06

Curcumin-ER, a liposomal-PLGA sustained release nanocurcumin for minimizing QT prolongation for cancer therapy

#156
20130337058
2013-12-19

Micronized Tanaproget and Compositions Containing Same

#157
20130309311
2013-11-21

Pellet formulation for the treatment of the intestinal tract

#158
20130189356
2013-07-25

Pellet formulation for the treatment of the intestinal tract

#159
20130177650
2013-07-11

Pellet formulation for the treatment of the intestinal tract

#160
20130136696
2013-05-30

METALLIC NANOPARTICLES WITH COATED SHELLS AND APPLICATIONS OF SAME

#161
20130095181
2013-04-18

PHARMACEUTICAL COMPOSITIONS OF 3-(6-(1-(2,2-DIFLUOROBENZO[D][1,3]DIOXOL-5-YL) CYCLOPROPANECARBOXAMIDO)-3-METHYLPYRIODIN-2-YL)BENZOIC ACID AND ADMINISTRATION THEREOF

#162
20130078282
2013-03-28

Formulations decreasing particle exhalation

#163
20130004592
2013-01-03

Pharmaceutical compositions for parenteral administration

#164
20120309809
2012-12-06

Ingredients for inhalation and methods for making the same

#165
20120308659
2012-12-06

Pellet formulation for the treatment of the intenstinal tract

#166
20120263788
2012-10-18

Controlled release hydrocodone formulations

#167
20120232149
2012-09-13

SOLID PHARMACEUTICAL COMPOSITIONS CONTAINING PREGABALIN

#168
20120202283
2012-08-09

Freeze-dried product for introducing nucleic acid, oligonucleic acid or derivative thereof

#169
20120148634
2012-06-14

NOVEL FORMULATION OF NAPROXEN

#170
20120135047
2012-05-31

Formulation of diclofenac

#171
20120128740
2012-05-24

NANOSTRUCTURED SILDENAFIL BASE, ITS PHARMACEUTICALLY ACCEPTABLE SALTS AND CO-CRYSTALS, COMPOSITIONS OF THEM, PROCESS FOR THE PREPARATION THEREOF AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM

#172
20120128728
2012-05-24

Compositions Comprising Amphotericin B

#173
20120121708
2012-05-17

Acetazolamide Microparticle And Its Preparation Method And Use

#174
20120095067
2012-04-19

PHARMACEUTICAL COMPOSITION CONTAINING CARBOXYLOSARTAN AND A PRODUCTION METHOD THEREFOR

#175
20120077980
2012-03-29

METHOD FOR PRODUCING A SOLID PREPARATION

#176
20120029081
2012-02-02

Solid Pharmaceutical Compositions Containing Pregabalin

#177
20110257236
2011-10-20

SOLID SOLUTION OF VALINE, ISOLEUCINE, LEUCINE AND ITS MANUFACTURING METHOD

#178
20110256220
2011-10-20

Pharmaceutical compositions of 3-(6-(1-(2,2-difluorobenzo[d][1,3]dioxol-5-yl) cyclopropanecarboxamido)-3-methylpyridin-2-yl)benzoic acid and administration thereof

#179
20110201814
2011-08-18

METHOD FOR PRODUCING SOLID PREPARATION

#180
20110091539
2011-04-21

Micronized tanaproget and compositions containing same

#181
20110038927
2011-02-17

Controlled release hydrocodone formulations

#182
20100310621
2010-12-09

Controlled Iodine Release Particle Micro-Biocide

#183
20100166847
2010-07-01

Fine particles coated with lipid membrane

#184
20100136129
2010-06-03

Nanoparticles comprising a cyclodextrin and a biologically active molecule and uses thereof

#185
20100136091
2010-06-03

Extracellular matrix production from nanoscale substrate

#186
20100119611
2010-05-13

Delivery of a bioactive material

#187
20100113861
2010-05-06

METALLIC NANOPARTICLES WITH COATED SHELLS AND APPLICATIONS OF SAME

#188
20100004473
2010-01-07

Method for producing coenzyme Q10 particle

#189
20090269328
2009-10-29

Dry composition for oral ingestion and gel composition prepared just before use for oral ingestion

#190
20090202629
2009-08-13

Controlled release hydrocodone formulations

#191
20090176877
2009-07-09

Oseltamivir phosphate granule and preparation method thereof

#192
20090130761
2009-05-21

Freeze-Dried Product for Introducing Nucleic Acid, Oligonucleic Acid or Derivative Thereof

#193
20090087389
2009-04-02

DEHYDROEPIANDROSTERONE SULFATE DIHYDRATE INHALATION COMPOSITIONS AND METHODS

#194
20090081303
2009-03-26

Pharmaceutical formulation for contraception and hormone-replacement therapy

#195
20090074858
2009-03-19

Sustained-release formulation

#196
20090017117
2009-01-15

Pellet formulation for the treatment of the intestinal tract

#197
20080317807
2008-12-25

STRONTIUM FORTIFIED CALCIUM NANO-AND MICROPARTICLE COMPOSITIONS AND METHODS OF MAKING AND USING THEREOF

#198
20080286362
2008-11-20

Compositions exhibiting improved flowability

#199
20080280140
2008-11-13

Electrochemical method of making porous particles using a constant current density

#200
20080145403
2008-06-19

Low temperature processes for making cyclic lipid implants for intraocular use

#201
20080124386
2008-05-29

APOPTOSIS-MIMICKING SYNTHETIC ENTITIES AND USE THEREOF IN MEDICAL TREATMENT

#202
20070270502
2007-11-22

Formulations decreasing particle exhalation

#203
20070269511
2007-11-22

SOLID PHARMACEUTICAL COMPOSITIONS CONTAINING PREGABALIN

#204
20070224256
2007-09-27

Apoptosis-mimicking synthetic entities and use thereof in medical treatment

#205
20070178152
2007-08-02

Carboxyalkylcellulose esters for administration of poorly soluble pharmaceutically active agents

#206
20070178151
2007-08-02

Spray dried pharmaceutical compositions

#207
20070082055
2007-04-12

Stable micronized candesartan cilexetil and methods for preparing thereof

#208
20060246128
2006-11-02

Micronized tanaproget and compositions containing same

#209
20060062853
2006-03-23

Treating neuromuscular disorders with an oral formulation of creatine derivatives

#210
20050258288
2005-11-24

High pressure media milling system and process of forming particles

#211
20050207983
2005-09-22

Formulations decreasing particle exhalation

#212
20050169993
2005-08-04

Sustained-release formulation

#213
20050123598
2005-06-09

Apoptosis-mimicking synthetic entities and use thereof in medical treatment

#214
20050119340
2005-06-02

Treatment methods with low-dose, longer-acting formulations of local anesthetics and other agents

#215
20050025827
2005-02-03

Pharmaceutical formulation for contraception and hormone-replacement therapy

#216
15705196
2018-03-06

Biomimetic synthesis of antihyperglycemic silver nanoparticles

#217
15611768
2018-07-24

Synthesis of nanoparticles