Functional Particles
Supporting Diagnostics
We develop, manufacture and supply raw materials for in vitro diagnostic reagents, handled in-house from development through to manufacturing and sales.
Products
We supply polymer particles designed around particle size, surface charge and function to meet the performance required of in vitro diagnostic reagents.
Latex particles
Polystyrene nanoparticles for immunoturbidimetry. Particle size and COOH charge density are designed for each application.
Magnetic particles
Magnetic particles for chemiluminescent immunoassay, supporting direct antibody coupling and streptavidin (SA) immobilisation.
Coloured and fluorescent particles
Coloured and fluorescent latex particles for POCT and lateral flow assays.
Why ZOKK
Particle design for each application
We design and develop particles with appropriate sizes and surface characteristics, taking into account the intended application, assay principle and instrument characteristics of in vitro diagnostic and research reagents.
Integrated support from development to mass production
Product design, synthesis, performance evaluation, process development, quality assessment and scale-up are all handled in house, from early development through commercial production.
Experience in in vitro diagnostics
We bring practical knowledge and experience in developing and manufacturing raw materials for latex immunoturbidimetry, chemiluminescence and POCT.
Custom development and OEM
Alongside our standard products, we welcome enquiries about custom development, prototyping and OEM based on your application and specifications.
Company
We provide consistent quality built on proven technology, together with flexible development support tailored to each application, at a competitive price. Through the development, manufacture and sale of raw materials used in in vitro diagnostic and research reagents, we contribute to progress in healthcare and research.
As diagnostics and research move further towards automation, the performance and quality demanded of reagents and their raw materials continue to rise. We respond to these varied requirements through product design and technical development that reflect each application and instrument.
| Company name | ZOKK Co., Ltd. / ゾック株式会社 |
|---|---|
| Founded | 3 June 2024 |
| Capital | JPY 10 million |
| Employees | 8 (as of July 2026) |
| Business | Development, manufacture and sale of raw materials for in vitro diagnostic reagents; OEM |
| Address | Room 601, Tokatsu Techno Plaza, 5-4-6 Kashiwanoha, Kashiwa, Chiba, Japan |
Careers
We are hiring R&D and manufacturing engineers, as well as support and administrative staff. If you are interested, please send us your CV by email.
Open positionsContact
We welcome enquiries about product specifications and technical questions, samples and quotations, OEM and custom development, and new business relationships.
Contact usCompany
Consistent quality built on proven technology, with flexible development support, at a competitive price.
Message
Since its establishment in 2024, ZOKK Co., Ltd. has focused on the development of nanoparticle raw materials for in vitro diagnostics.
Building on our polymerisation technology, we are engaged in the integrated research, development and mass production of carrier materials used in medical diagnostics, including latex particles, magnetic beads and filler particles. We provide IVD companies in Japan and abroad with raw material solutions that combine consistent quality with strong cost competitiveness.
Medical diagnostics play an important role in protecting human life and health. Carrier materials form the foundation for the development of high-quality diagnostic reagents.
At our approximately 280 m² research and development facility, we strictly control particle size, surface functional groups and batch-to-batch consistency through established polymerisation processes and a comprehensive performance verification system. Through these quality control measures, ZOKK’s magnetic beads and latex particles deliver consistent quality and performance across a range of clinical testing applications, including chemiluminescence immunoassays, immunoturbidimetry and point-of-care testing.
We aim to be more than a raw material supplier — a technology partner that works closely with our customers. In response to the performance requirements of various diagnostic kits, we provide customised particle modification services as well as OEM reagent development and manufacturing services, while continuously improving our manufacturing processes and optimising product performance.
Looking ahead, ZOKK will continue to advance its nano-biomaterial technologies and expand their applications, developing more reliable and versatile raw materials for diagnostic use.
We remain committed to providing products that earn the trust of our customers and, together with IVD industry partners in Japan and abroad, to contributing to the advancement of clinical testing technologies and the improvement of human health.
| Company name | ZOKK Co., Ltd. / ゾック株式会社 |
|---|---|
| Founded | 3 June 2024 |
| Capital | JPY 10 million |
| Employees | 8 (as of July 2026) |
| Business | Development, manufacture and sale of raw materials for in vitro diagnostic reagents; OEM |
| Technology | Polymerisation technology and reagent development know-how |
| Address | Room 601, Tokatsu Techno Plaza 5-4-6 Kashiwanoha, Kashiwa Chiba 277-0882, Japan |
| Phone | +81-4-7128-7017 |
| zokk@zokkbio.com |
Technology
We occupy approximately 280 m² at Tokatsu Techno Plaza, comprising office space and areas for R&D and production. With the equipment required for aqueous polymerisation and experienced engineers on site, we cover the full path from development through manufacturing and evaluation.
Emulsion polymerisation (batch, incremental and seed) is our core technology. Aqueous solution polymerisation is used for water-soluble polymers, while two-step swelling and suspension polymerisation are used to design and produce polymer particles with the size and size distribution each application requires.
Access
- Address
- Room 601, Tokatsu Techno Plaza, 5-4-6 Kashiwanoha, Kashiwa, Chiba 277-0882, Japan
- Nearest station
- Kashiwanoha-campus Station (Tsukuba Express)
- Getting here
- About 20 minutes on foot from Kashiwanoha-campus Station, or about 6 minutes by Tobu bus
About 3 minutes on foot from the “National Cancer Center” bus stop
View on Google Maps (opens in a new tab)
Tokatsu Techno Plaza official site (opens in a new tab)
By train and bus
- From the west exit of Kashiwanoha-campus Station (Tsukuba Express), take the Tobu bus towards the National Cancer Center
- Get off at the “National Cancer Center” bus stop; about 3 minutes on foot
- Buses bound for the National Cancer Center also run from the west exit of JR Kashiwa Station
- Buses are also available from the east exit of Edogawadai Station (Tobu Urban Park Line)
By car
- About 5 minutes from the Kashiwa IC on the Joban Expressway
- About 3 minutes from the “Toyofuta Industrial Park Entrance” on National Route 16
- Visitor parking available
Products
We supply polymer particles designed around particle size, surface charge and function to meet the performance required of in vitro diagnostic reagents.
Latex particles (polystyrene)
Polystyrene nanoparticles for immunoturbidimetry (latex agglutination). The line-up covers particle sizes from 70 to 440 nm across a wide range of COOH charge densities, so that a grade can be selected to suit the antibody sensitisation conditions.
| No | Product | Typ. size (µm) | Typ. COOH charge density (mmol/g) |
|---|---|---|---|
| 1 | C080N | 0.08 | 0.18 |
| 2 | C090A | 0.09 | 0.31 |
| 3 | C090N | 0.09 | 0.16 |
| 4 | C100A | 0.10 | 0.14 |
| 5 | C150N | 0.15 | 0.10 |
| 6 | C150L | 0.16 | 0.07 |
| 7 | C180N | 0.19 | 0.08 |
| 8 | C190N | 0.19 | 0.08 |
| 9 | C200A | 0.20 | 0.08 |
| 10 | C270N | 0.27 | 0.05 |
| 11 | C400N | 0.42 | 0.03 |
| 12 | B120Z | 0.11 | — |
B120Z: “—” indicates a physical adsorption type.
Magnetic particles
Magnetic particles for chemiluminescent immunoassay (CLIA). They carry carboxyl groups and support direct antibody coupling as well as streptavidin (SA) immobilisation.
| Product | Surface | Typ. size (µm) | Typ. COOH charge density (µmol/g) | Typ. magnetic separation time (sec) | Typ. magnetic material content (%) |
|---|---|---|---|---|---|
| FS300C | Hydrophilic | 3.0 | 9 | 25 | 28 |
| FF240C | Hydrophobic | 2.4 | 15 | 30 | 34 |
| FS150C | Hydrophilic | 1.6 | 28 | 70 | 33 |
Coloured and fluorescent particles
Coloured and fluorescent latex particles for POCT and immunochromatography (lateral flow). They are designed to match the required colour or emission wavelength.
Contract development of qualitative and quantitative reagents
Contract development of qualitative and quantitative reagents using our own latex and magnetic particles. Drawing on our know-how in particle design, surface modification and reagent development, we propose a reagent design suited to your requirements.
Careers
We are hiring engineers to work on polymer particles for in vitro diagnostic reagents, from development through to commercial production.
Position
R&D and manufacturing — experienced professionals
Requirements
- Bachelor’s degree or above (Master’s or Ph.D. welcome)
- R&D experience in either ① or ② below
① Chemistry
- R&D experience with products related to polymer chemistry, organic synthesis or colloid chemistry
② Life sciences
- R&D experience with products related to biomolecules such as proteins or DNA
Preferred
- Research experience in polymerisation, particle design, or conjugation of particles with biomolecules
- Experience developing qualitative or quantitative reagents (ELISA, LIA, CLEIA and similar)
- Basic office software skills (Excel, Word)
The work
① Chemistry: development and manufacture of polymer particles
You will be responsible for the development, manufacture and evaluation of polymer particles used in in vitro diagnostic reagents and related fields.
The role covers the whole path from product design and synthesis to process development, quality assessment and scale-up.
Main responsibilities
- Design, synthesis, evaluation and improvement of polymer latex, magnetic particles and particles for chromatography columns
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
② Life sciences: conjugation technology for particles and biomolecules
You will develop and improve processes for conjugating our particles with biomolecules such as proteins and DNA, and develop research reagents.
The role spans the study of conjugation conditions, performance evaluation, process development and scale-up.
Main responsibilities
- Study and optimisation of conjugation conditions between our particles and biomolecules
- Design, evaluation and improvement of conjugation technology
- Development and performance evaluation of research reagents
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
Conditions
| Employment type | Permanent, full-time |
|---|---|
| Working hours | 9:00–18:00 (8 hours plus a 60-minute break; some flexibility) |
| Holidays | 120 days per year (two days off every week, Japanese public holidays, year-end / New Year period) |
| Paid leave | 10 days granted after six months of service, increasing to a maximum of 20 days |
| Salary review / bonus | Salary review once a year (April); bonus twice a year |
| Insurance | Health insurance, employees’ pension, employment insurance and workers’ compensation insurance |
| Overtime | Average overtime is approximately 10 hours per month. Overtime pay is paid in full. |
| Allowances | Commuting allowance and housing allowance (in accordance with company rules) |
| Probation | Three months in principle |
Position
R&D and manufacturing — entry-level / early-career
Requirements
- Bachelor’s degree or above (Master’s or Ph.D. welcome)
- An academic background in either ① or ② below
① Chemistry
- A major in polymer chemistry, organic synthesis or colloid chemistry
② Life sciences
- A major in biology, life science, agriculture, pharmaceutical science or a related field
Preferred
- University research in polymerisation, particle design, or conjugation of particles with biomolecules
- Basic knowledge of, or laboratory experience with, qualitative or quantitative reagents (ELISA, LIA, CLEIA and similar), including at university
- Basic office software skills (Excel, Word)
The work
① Chemistry: development and manufacture of polymer particles
You will be responsible for the development, manufacture and evaluation of polymer particles used in in vitro diagnostic reagents and related fields.
The role covers the whole path from product design and synthesis to process development, quality assessment and scale-up.
After joining, you will learn the work mainly through on-the-job training, supported by experienced colleagues.
Main responsibilities
- Design, synthesis, evaluation and improvement of polymer latex
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
② Life sciences: conjugation technology for particles and biomolecules
You will develop and improve processes for conjugating our particles with biomolecules such as proteins and DNA, and develop research reagents.
The role spans the study of conjugation conditions, performance evaluation, process development and scale-up.
After joining, you will learn the work mainly through on-the-job training, supported by experienced colleagues.
Main responsibilities
- Study and optimisation of conjugation conditions between our particles and biomolecules
- Design, evaluation and improvement of conjugation technology
- Development and performance evaluation of research reagents
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
Conditions
| Employment type | Permanent, full-time |
|---|---|
| Working hours | 9:00–18:00 (8 hours plus a 60-minute break; some flexibility) |
| Holidays | 120 days per year (two days off every week, Japanese public holidays, year-end / New Year period) |
| Paid leave | 10 days granted after six months of service, increasing to a maximum of 20 days |
| Salary review / bonus | Salary review once a year (April); bonus twice a year |
| Insurance | Health insurance, employees’ pension, employment insurance and workers’ compensation insurance |
| Overtime | Average overtime is approximately 10 hours per month. Overtime pay is paid in full. |
| Allowances | Commuting allowance and housing allowance (in accordance with company rules) |
| Probation | Three months in principle |
R&D and production support
The work
- Support for R&D and production activities
- Quality testing and recording of experimental data
- Preparation and management of tools, equipment and materials
- Other work related to R&D and production
Preferred
- Knowledge of, or laboratory experience in, chemistry or the life sciences
- Basic office software skills (Excel, Word)
Administrative positions
The work
- Accounting, general affairs, HR, purchasing and sales administration
- Preparation and management of documents and data
- Handling telephone calls, email and visitors
- Other administrative work supporting company operations
Preferred
- Practical experience in accounting or other administrative work
- Basic office software skills (Excel, Word)
Conditions
Working days, hours, salary and other conditions are agreed individually, based on the role, your experience and your preferences.
Selection process
After reviewing your application, we will contact you with the outcome and, where applicable, an invitation to the first interview.
How to apply
Please send your CV and work history to the email address below. Japanese applicants are welcome to submit the standard Japanese resume (rirekisho) and work history (shokumu-keirekisho); a CV in the usual international format is equally acceptable. After reviewing your application, we will contact you about an interview.
Contact for recruitment: Tamori
Contact
We welcome enquiries about product specifications and technical questions, samples and quotations, OEM and custom development, purchasing and new business relationships, and recruitment.
Business hours: 9:00–18:00, Monday to Friday (Japan time). Closed on Japanese public holidays and during the year-end / New Year period.
For information on how we handle personal information, please see our Privacy Policy.
Privacy Policy
How we handle personal information.
ZOKK Co., Ltd. (“the Company”) recognises the importance of the personal information entrusted to us through enquiries and job applications, and handles it appropriately in accordance with the following policy.
1. Information we collect
Your name, company or organisation name, email address, telephone number, the content of your enquiry, and information contained in application documents such as a CV or work history. This website does not use web forms; such information is provided by you directly, by telephone or email.
2. Purpose of use
- Responding to enquiries
- Providing information about our products and services
- Communication regarding business transactions and the performance of contracts
- Recruitment screening and related communication
3. Disclosure to third parties
Except as required by law, we do not provide personal information to third parties without the prior consent of the individual concerned.
4. Security measures
We take the necessary and appropriate measures to prevent unauthorised access to, and the loss, destruction, alteration or leakage of, personal information.
5. Retention period
We retain personal information only for as long as it is needed for the purposes set out above, and thereafter delete or dispose of it by appropriate means. Application documents are disposed of after the period defined by the Company following the end of the selection process.
6. Cookies and analytics
This website does not use cookies to identify visitors, and no web analytics tools are installed.
7. Links to external services
This website contains links to external services, including Google Maps. The handling of personal information on linked sites is governed by the terms of each service, and the Company accepts no responsibility for it.
8. Disclosure, correction and deletion
Upon request by the individual concerned, we respond to requests for the disclosure, correction, suspension of use or deletion of personal information in accordance with applicable law. Please contact us using the details below.
9. Contact
ZOKK Co., Ltd.
Room 601, Tokatsu Techno Plaza, 5-4-6 Kashiwanoha, Kashiwa, Chiba 277-0882, Japan
TEL +81-4-7128-7017
MAIL zokk@zokkbio.com
10. Changes to this policy
We may revise this policy without prior notice in response to changes in legislation or in our business. Any revised policy takes effect once published on this website.
Established: 1 July 2026
Last revised: 24 July 2026